JP2018191034A - Omni-directional small planar antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an omnidirectional small planar antenna device which can be made smaller in diameter than one wavelength of a target matching frequency and can realize omnidirectionality not only in horizontal polarization but also in vertical polarization. SOLUTION: An omnidirectional small planar antenna device 1A has first to fourth conductive layers at the center of four side surfaces of a square dielectric substrate 2 having a first conductive layer 3 and a second conductive layer 4 formed on the upper and lower surfaces thereof. The first to fourth slot antenna regions are formed by providing the connecting portions 61 to 64 and equally dividing the first to fourth dividing lines PL1 to PL4 into four regions. In each region, the upper surface of the first conductive layer 3 is formed. The same shape from the first to fourth slit portions 31 to 34 to the lower surface first to fourth slit portions 41 to 44 of the second conductive layer 4 through the first to fourth side surface slit portions 231 to 234 of the dielectric substrate 2. The first to fourth communication slots 11S to 14S are provided to inject or take out signals from the power supply port 5 provided at the center of the first conductive layer 3. [Selection diagram] Fig. 1

Description

  The present invention relates to a small and planar antenna device having omnidirectionality.

  Miniaturization of the antenna is a theme desired for portable radio terminals and the like from the viewpoint of portability. Further, omnidirectionality is a characteristic desired for a mobile station whose direction changes and a base station which communicates with terminals in all directions. As a small and omnidirectional antenna device, a strip-shaped side conductor is vertically connected to the edge of a flat top conductor and a bottom conductor, and the bottom conductor is passed from the top conductor to the side conductor. An antenna device provided with a communication slot composed of continuous slits leading to a portion, so that a part of the path in the longitudinal direction of the communication slot intersects a TEM wave traveling between the upper surface conductor portion and the lower surface conductor portion Has been proposed (see, for example, Patent Document 1).

  The antenna device described in Patent Document 1 can realize omnidirectionality by horizontal polarization. In addition, the antenna device main body can be configured with a planar structure in which conductors are provided on both surfaces and side surfaces of the dielectric substrate, which is extremely low in comparison with a monopole antenna or the like. In addition, since the communication slot is configured by opening a slit from the upper conductor portion to the lower conductor portion through the side conductor portion, the diameter of the antenna device is reduced to about one wavelength of the matching frequency capable of realizing omnidirectionality. it can.

JP 2009-55543 A

  However, in the invention described in Patent Document 1, since the substrate has a diameter of about one wavelength, further miniaturization is desired in order to improve portability and mountability as a portable wireless terminal. In addition, in order to ensure stable communication even under the influence of multipaths and changes in the orientation of mobile radio terminals, omnidirectionality can be achieved not only by horizontal polarization components but also by vertical polarization components. It is desirable that it can be realized.

  Therefore, the present invention has an object to provide an omnidirectional small planar antenna device that can be made smaller in diameter than one wavelength of a target matching frequency and can realize omnidirectionality not only in horizontal polarization but also in vertical polarization. To do.

  In order to solve the above-mentioned problem, the invention according to claim 1 is formed of a plate-like dielectric substrate whose two opposing surfaces are parallel, and a conductor having a required thickness on the first surface of the dielectric substrate, A first conductive layer provided with a first slit portion of a required shape; a second conductive layer formed of a conductor having a required thickness on the second surface of the dielectric substrate; and a second conductive layer provided with a second slit portion of a required shape; A power supply port provided at a portion where a virtual central axis passing through the center of gravity of the dielectric substrate perpendicular to the first surface and the second surface of the dielectric substrate intersects the first conductive layer or the second conductive layer; and the dielectric A conductive connecting portion that is formed on the outer surface or near the side surface of the substrate and electrically connects the first conductive layer and the second conductive layer, and the side surface of the dielectric substrate is continuous from the conductive connecting portion to the conductive connecting portion. And a side slit portion exposed in the first slit, wherein one end of the side slit portion is the first slit. And connecting the other end of the side slit part to the second slit part to form a long communication slot from the first slit part to the second slit part through the side slit part, It is characterized in that a signal is injected from or taken out of the signal.

  According to a second aspect of the present invention, in the omni-directional small planar antenna device according to the first aspect, the first and second conductive layers and the dielectric substrate are divided into n equal parts through the virtual central axes ( n is a natural number greater than or equal to 2) where the conductive connecting portions are provided at portions where the equally divided surface intersects the side surface of the dielectric substrate, and each of the n slot antenna regions equally divided by the equally divided surface includes A communication slot having the same shape is formed.

  According to a third aspect of the present invention, in the omnidirectional small planar antenna device according to the first or second aspect of the present invention, a second slit provided in the first conductive layer and a second conductive layer provided in the second conductive layer. The slit portions have the same shape and are arranged antisymmetrically with the dielectric substrate interposed therebetween.

  The invention according to claim 4 is the omnidirectional small planar antenna device according to any one of claims 1 to 3, wherein the first slit portion and / or the second slit portion is at least A first end connected to the side slit portion, and a second end connected to the second end of the base end slit in a bent shape, and a second end connected to the second end side in a bent shape. A bent slit having a required width extending in parallel with the side surface of the substrate.

  The invention according to claim 5 is the omnidirectional small planar antenna device according to any one of claims 1 to 4, wherein the shape of the first slit portion and the shape of the second slit portion are provided. In addition, the matching frequency is changed by changing the thickness and / or the dielectric constant of the dielectric substrate without changing the slit length of the side slit portion.

  According to the omnidirectional small planar antenna device according to the present invention, the diameter can be made smaller than one wavelength of the target matching frequency, and omnidirectionality can be realized not only in horizontal polarization but also in vertical polarization.

1 shows a first embodiment of an omnidirectional small planar antenna device according to the present invention, wherein (a) is a perspective view showing a first surface (upper surface) side of the omnidirectional small planar antenna device, and (b) is omnidirectional. FIG. 5C is a perspective view showing a second surface (lower surface) side of the small planar antenna device, and FIG. 5C is an enlarged plan view showing a detailed shape of the first slit portion in the first slot antenna region of the omnidirectional small planar antenna device. It is explanatory drawing which expanded each of the 6 surfaces of the non-directional small planar antenna apparatus of the structure shown in FIG. 1, and showed each shape of the 1st-4th communication slot. It is explanatory drawing which shows the design dimension of the basic composition which formed the omnidirectional small planar antenna apparatus of the structure shown in FIG. 1 so that it may be set as matching frequency fres = 117.6MHz. (A) is a frequency characteristic diagram of a reflection coefficient | S11 | showing a case where the substrate thickness h is changed as a parameter in the basic omnidirectional small planar antenna device. (B) is a frequency characteristic diagram of radiation efficiency ηrad showing a case where the substrate thickness h is changed as a parameter in the omnidirectional small planar antenna device having the basic configuration. It is a dependence characteristic figure with respect to the board | substrate thickness h of the matching frequency fres, the radiation efficiency maximum frequency f ( _eta) , and the radiation efficiency maximum value ( _eta) max in the non-directional small planar antenna apparatus of a basic composition. (A) is a vertical plane pattern characteristic diagram of the absolute gain Ga of the horizontal polarization showing a case where the substrate thickness h is changed as a parameter in the omnidirectional small planar antenna device of the basic configuration. FIG. 5B is a vertical plane pattern characteristic diagram of the absolute gain Ga of the vertical polarization showing a case where the substrate thickness h is changed as a parameter in the omnidirectional small planar antenna device having the basic configuration. (A) is a frequency characteristic diagram of the reflection coefficient | S11 | showing the case where the substrate relative dielectric constant εr is changed as a parameter in the basic omnidirectional small planar antenna device. (B) is a frequency characteristic diagram of radiation efficiency ηrad showing a case where the substrate relative dielectric constant εr is changed as a parameter in the omnidirectional small planar antenna device of the basic configuration. It is a dependence characteristic figure with respect to the board | substrate dielectric constant (epsilon) r of the matching frequency fres, the radiation efficiency maximum frequency f ( _eta) , and the radiation efficiency maximum value ( _eta) max in the omnidirectional small planar antenna apparatus of a basic composition. (A) is a vertical plane pattern characteristic diagram of the absolute gain Ga of horizontal polarization showing a case where the substrate relative dielectric constant εr is changed as a parameter in the omnidirectional small planar antenna device of the basic configuration. (B) is a vertical plane pattern characteristic diagram of the absolute gain Ga of vertical polarization showing a case where the substrate relative dielectric constant εr is changed as a parameter in the omnidirectional small planar antenna device of the basic configuration. It is explanatory drawing which shows the design dimension of the prototype structure formed so that the omnidirectional small planar antenna apparatus of the structure shown in FIG. 1 may be set as matching frequency fres = 169.7MHz. It is an external view by the side of the 1st surface (upper surface) of the omnidirectional small planar antenna device made as an experiment based on the design dimensions of the prototype configuration. FIG. 6 is a frequency characteristic diagram of a reflection coefficient | S11 | showing actual measurement results and simulation results actually obtained with a prototype non-directional small planar antenna device. It is explanatory drawing which shows the arrangement structure of the omnidirectional small planar antenna apparatus of a basic composition, and an electroconductive plate. FIG. 10 is a frequency characteristic diagram of a reflection coefficient | S11 | showing a case where the separation distance Hp with respect to an infinitely large conductive plate is changed as a parameter. It is a dependence characteristic figure with respect to the separation distance Hp of the resonance frequency fres and the reflection coefficient at resonance | S11 | min in the omnidirectional small planar antenna device of the basic configuration. It is a dependence characteristic figure with respect to the separation distance Hp of the radiation efficiency maximum frequency f ( _eta) and the maximum radiation efficiency ( _eta) max in the non-directional small planar antenna apparatus of a basic composition. It is a frequency characteristic diagram of reflection coefficient | S11 | showing a case where the width Wp of the conductive plate is changed as a parameter. It is a dependence characteristic figure with respect to the width Wp of the conductive plate of the resonance frequency fres and the reflection coefficient at resonance | S11 | min in the omnidirectional small planar antenna device of the basic configuration. It is a dependence characteristic figure with respect to the width | variety Wp of the electroconductive plate of the radiation efficiency maximum frequency f ( _eta) and maximum radiation efficiency ( _eta) max in the non-directional small planar antenna apparatus of a basic composition. (A) is an instantaneous electric current vector distribution map in the outer surface of the 1st conductive layer provided in the 1st surface (upper surface) of the non-directional small planar antenna device of basic composition. FIG. 6B is an instantaneous current vector distribution diagram on the inner surface of the first conductive layer provided on the first surface (upper surface) of the basic omnidirectional small planar antenna device. (A) is the 1st modification which changed a part of communication slot in the non-directional small planar antenna device of basic composition. (B) is the 2nd modification which changed a part of communication slot in the non-directional small planar antenna device of basic composition. It is a schematic plan view of the non-directional small planar antenna device according to the second embodiment. It is a schematic plan view of the non-directional small planar antenna device according to the third embodiment. It is a schematic plan view of the omnidirectional small planar antenna device according to the fourth embodiment. (A) is a schematic plan view which shows the 1st structural example of the non-directional small planar antenna device which concerns on 5th Embodiment. (B) is a schematic plan view which shows the 2nd structural example of the omnidirectional small planar antenna apparatus which concerns on 5th Embodiment. (A) is a schematic plan view which shows the 1st structural example of the omnidirectional small planar antenna apparatus which concerns on 6th Embodiment. (B) is a schematic plan view which shows the 2nd structural example of the non-directional small planar antenna apparatus which concerns on 6th Embodiment. It is a schematic plan view of the non-directional small planar antenna device according to the seventh embodiment. It is a schematic plan view of the non-directional small planar antenna device according to the eighth embodiment.

  Next, an embodiment of the omnidirectional small planar antenna device according to the present invention will be described based on the attached drawings.

  1 and 2 show an omnidirectional small planar antenna device 1A according to the first embodiment. The omni-directional small planar antenna device 1A includes a dielectric substrate 2 having a substantially square side of W [mm] and a thickness h [mm], and a first conductive layer formed on the first surface 21 of the dielectric substrate 2. 3 and the second conductive layer 4 formed on the second surface 22 of the dielectric substrate 2.

  The dielectric substrate 2 is composed of a plate-like dielectric plate whose two opposing surfaces are parallel. In the following description, the first surface 21 side is referred to as the upper surface and the second surface 22 side is referred to as the lower surface. There is. In addition, since the dielectric substrate 2 is a regular polygon (square), it always has a center of gravity in the shape of an axis passing through the center of the upper surface and the center of the lower surface. In the following description, an axis passing through the center of gravity perpendicular to the first surface 21 and the second surface 22 of the dielectric substrate 2 is referred to as a virtual central axis CA. A power feeding port 5 is provided at a portion where the virtual central axis CA intersects the first conductive layer 3, and a signal is injected or taken out from the power feeding port 5. When the coaxial cable is connected to the power feeding port 5, the outer conductor of the coaxial cable is electrically connected to the first conductive layer 3 and the central conductor is electrically connected to the second conductive layer 4. Further, the communication port 5 may be provided on the second conductive layer 4 side.

  The first conductive layer 3 is formed of a conductor having a required thickness on the first surface 21 of the dielectric substrate 2, and has an upper surface first slit portion 31, an upper surface second slit portion 32, and an upper surface third in a required shape. The slit portion 33 and the upper surface fourth slit portion 34 are provided. These upper surface first to fourth slit portions 31 to 33 are all in the same shape, and are arranged symmetrically with respect to the center point of the first conductive layer 3 (intersection with the virtual central axis CA).

  The second conductive layer 4 is formed of a conductor having a required thickness on the second surface 22 of the dielectric substrate 2, and has a lower surface first slit portion 41, a lower surface second slit portion 42, and a lower surface third in a required shape. A slit portion 43 and a lower surface fourth slit portion 44 are provided. These upper surface first to fourth slit portions 31 to 33 are all in the same shape, and are arranged symmetrically with respect to the center point of the first conductive layer 3 (intersection with the virtual central axis CA).

  The upper surface first to fourth slit portions 31 to 34 and the lower surface first to fourth slit portions 41 to 44 are formed by removing a part of the first and second conductive layers 3, 4. This is a portion where the outer surface of the dielectric substrate 2 is exposed. Similarly, since the four side surfaces 23 of the dielectric substrate 2 are also exposed to the outside, each side surface has a first side surface slit portion 231, a second side surface slit portion 232, a third side surface slit portion 233, and a fourth side surface slit portion 234. It becomes.

  Furthermore, a first conductive connecting portion 61 and a second conductive connecting portion that electrically connect the first conductive layer 3 and the second conductive layer 4 to the central positions of the first to fourth side slit portions 231 to 234, respectively. 62, a third conductive connecting portion 63, and a fourth conductive connecting portion 64 are formed. Accordingly, the first side slit part 231 is divided into the first side A slit part 231a and the first side B slit part 231b with the first conductive connection part 61 as a boundary, and the second side slit part 232 is the second conductive connection part. The second side A slit part 232a and the second side B slit part 232b are divided with the part 62 as a boundary, and the third side slit part 233 is separated from the third side A slit part 233a with the third conductive connection part 63 as a boundary. The fourth side surface slit portion 234 is divided into a fourth side surface A slit portion 234a and a fourth side surface B slit portion 234b with the fourth conductive connection portion 64 as a boundary.

  In the omni-directional small planar antenna device 1A of the present embodiment, each of the first to fourth conductive connecting portions 61 to 64 has a strip-like conductive layer having a width d [mm] as the four side surfaces 23 of the dielectric substrate 2. However, the structure of the conductive connecting portion is not limited to this, and the first conductive layer 3 and the second conductive layer 4 are connected by through holes formed in the vicinity of the four side surfaces 23 of the dielectric substrate 2. Such a conductive connecting portion may be used.

  In addition, the first to fourth conductive connecting portions 61 to 64 are provided at the center of the first to fourth side slit portions 231 to 234 of the dielectric substrate 2 because the four omnidirectional small planar antenna devices 1A are provided. This is because it is equally divided into two areas. That is, an equally divided surface that divides the first and second conductive layers 3 and 4 and the dielectric substrate 2 into n equal parts (n is a natural number of 2 or more) through the virtual central axis CA intersects the side surface of the dielectric substrate 2. If the conductive connecting portions are respectively provided in the portions, n slot antenna regions equally divided by the equally dividing plane can be formed.

  In the omnidirectional small planar antenna device 1A according to the present embodiment, the equally divided plane that passes through the virtual central axis CA and is orthogonal to the first side slit portion 231 of the dielectric substrate 2 is outside the omnidirectional small planar antenna device 1A. A first dividing line PL1 intersecting with the surface and an equally dividing plane passing through the virtual central axis CA and orthogonal to the second side slit portion 232 of the dielectric substrate 2 intersects the outer surface of the omnidirectional small planar antenna device 1A. A dividing line PL2, and a third dividing line PL3 in which an equal dividing plane passing through the virtual central axis CA and orthogonal to the third side slit portion 233 of the dielectric substrate 2 intersects the outer surface of the omnidirectional small planar antenna device 1A; Four slots are formed by a fourth dividing line PL4 in which an equally dividing plane passing through the virtual central axis CA and orthogonal to the fourth side slit portion 234 of the dielectric substrate 2 intersects the outer surface of the omnidirectional small planar antenna device 1A. To form the antenna area.

  Specifically, the first communication slot 11S is placed in the first slot antenna region 11 defined by the first equal dividing line PL1 and the second equal dividing line PL2, and the second equal dividing line PL2 and the third equal dividing line PL3. The second communication slot 12S is provided in the partitioned second slot antenna region 12, the third communication slot 13S is provided in the third slot antenna region 13 partitioned by the third equal dividing line PL3 and the fourth equal dividing line PL4, and the fourth. A fourth communication slot 14S is provided in each of the fourth slot antenna regions 14 partitioned by the equal dividing line PL4 and the first equal dividing line PL1.

  The first communication slot 11S includes slit portions (upper surface first slit portion 31, first side surface A slit portion 231a, second side surface B slit portion 232b, and lower surface first slit provided in the first slot antenna region 11. Part 41).

  The upper surface first slit portion 31 has a first end 31a1 connected to the dividing end side (formation side of the first conductive connecting portion 61) of the first side surface A slit portion 231a, and the other second end is a first equal dividing line. A base end slit 31a having a width SW1 extending in the center direction along PL1 and a width connected to the second end side of the base end slit 31a in a bent shape and extending in parallel with the first side face A slit portion 231a. A first bent slit 31b of SW2, a second bent slit 31c of width SW3 connected in a bent manner to the extending end side of the first bent slit 31b, and extending in parallel with the second side surface B slit portion 232b; The second bent slit 31c includes a leading end slit 31d having a width SW4 that is bently connected to the extending end side and extends away from the center along the second equal dividing line PL2. Therefore, the upper surface first slit portion 31 has a slit length comparable to the width W of the dielectric substrate 2. As shown in FIG. 1C, the slit length of the base end slit 31a is SL1, the slit length of the first bent slit 31b is SL2, the slit length of the second bent slit 31c is SL3, and the slit length of the distal end slit 31d. Is SL4.

  The lower surface first slit portion 41 has a first end 41a1 connected to a dividing end side (a formation side of the second conductive connecting portion 62) of the second side surface B slit portion 232b, and the other second end is a fourth equal dividing line. A base end slit 41a having a width SW1 extending in the center direction along PL4 and a width connected to the second end side of the base end slit 41a in a bent shape and extending in parallel with the fourth side surface B slit portion 232b. A first bent slit 41b of SW2, a second bent slit 41c of width SW3 connected in a bent manner to the extending end side of the first bent slit 41b, and extending in parallel with the first side surface A slit portion 231a; The second bent slit 41c includes a leading end slit 41d having a width SW4 that is bently connected to the extending end side of the second bent slit 41c and extends away from the center along the first equal dividing line PL1. Therefore, the lower surface first slit portion 41 also has a slit length comparable to the width W of the dielectric substrate 2.

  That is, as shown in FIG. 2, the first slot antenna region 11 has a first side surface extending from the upper surface first slit portion 31 (front end slit 31d → second bent slit 31c → first bent slit 31b → base end slit 31a). A long first communication that reaches the lower surface first slit 41 (base end slit 41a → first bent slit 41b → second bent slit 41c → tip slit 41d) through the A slit 231a and the second side B slit 232b. The slot 11S can be configured.

  Similarly, the second slot antenna region 12 includes an upper surface second slit portion 32 (front end slit 32d → second bent slit 32c → first bent slit 32b → base end slit 32a) to the second side surface A slit portion 232a and the second slit antenna region 232a. A long second communication slot 12S extending from the bottom side second slit portion 42 (base end slit 42a → first bent slit 42b → second bent slit 42c → tip slit 42d) through the three side B slit portions 233b can be configured.

  The third slot antenna region 13 includes a third side surface A slit portion 233a and a fourth side surface B from the upper surface third slit portion 33 (front end slit 33d → second bent slit 33c → first bent slit 33b → base end slit 33a). A long third communication slot 13S extending from the slit portion 234b to the lower surface third slit portion 43 (base end slit 43a → first bent slit 43b → second bent slit 43c → tip slit 43d) can be configured.

  The fourth slot antenna region 14 includes a fourth side surface A slit portion 234a and a first side surface B from the upper surface fourth slit portion 34 (front end slit 34d → second bent slit 34c → first bent slit 34b → base end slit 34a). A long fourth communication slot 14S extending from the slit portion 231b to the lower surface fourth slit portion 44 (base end slit 44a → first bent slit 44b → second bent slit 44c → tip slit 44d) can be configured.

  In the omni-directional small planar antenna device 1A configured as described above, the first to fourth communication slots 11S to 114 each having a long slot length are equally spaced in the first to fourth slot antenna regions 11 to 14, respectively. It will be arranged in. The slot antenna requires a slot length of about half a wavelength of the matching frequency. However, in the omni-directional small planar antenna device 1A of the present embodiment, the four side surfaces 23 of the dielectric substrate 2 are used as slot openings and the top surface Further, the slit formed on the lower surface is appropriately bent to increase the slit length, whereby the substrate diameter can be reduced to about 0.1 wavelength.

  In the omnidirectional small planar antenna device 1 </ b> A according to the present embodiment, the upper surface first to fourth slit portions 31 to 34 provided in the first conductive layer 3 and the lower surface first to fourth provided in the second conductive layer 4. All the slit portions 41 to 44 have the same shape, and are arranged antisymmetrically with respect to the dielectric substrate 2. In this case, as shown in FIG. 2, the first conductive layer 3 in which the upper surface first to fourth slit portions 31 to 34 are formed and the second surface in which the lower surface first to fourth slit portions 41 to 44 are formed. Since the conductive layer 4 has the same shape, there is an advantage that the first conductive layer 3 and the second conductive layer 4 can be formed with the same etching mask. Of course, the shape of the upper surface first to fourth slit portions 31 to 34 and the shape of the lower surface first to fourth slit portions 41 to 44 are not necessarily the same, and the slit width SW and the slit length SL are the upper surface and the lower surface. It does not matter if they are different.

  FIG. 3 shows a substrate number W = 300 [mm], a substrate thickness h = 16 [mm], a dielectric substrate 2 having a substrate relative dielectric constant εr = 2.17, and a division number n = 4. This is an example in which the omni-directional small planar antenna device 1A having a matching frequency fres = 117.6 [MHz] is designed using finite element method simulation software HFSS (Ansys). The total length of the first to fourth communication slots 11S to 114 is about 870 mm, which is about 0.341 times the wavelength λres of the matching frequency. It can be seen that the substrate width W can be suppressed to 0.118 times the wavelength λres of the matching frequency. In the following description, the omnidirectional small planar antenna device 1A based on this design dimension is referred to as a basic configuration.

  The influence of the thickness of the dielectric substrate 2 (substrate thickness h) in the basic omnidirectional small planar antenna device 1A will be described with reference to FIGS.

  FIG. 4 shows antenna characteristics when the substrate thickness h of the basic configuration is changed from 16 mm. FIG. 4A shows the frequency characteristic of the reflection coefficient | S11 |, and FIG. 4B shows the frequency characteristic of the radiation efficiency ηrad. When the substrate thickness h = 16 [mm] in the basic configuration, the frequency ratio band where the reflection coefficient | S11 | is equal to or less than −10 dB is a narrow band of about 0.42%. It can be seen that the matching frequency band becomes narrower as the substrate thickness h of the dielectric substrate 2 becomes thinner. However, when the substrate thickness h is changed, the alignment may be improved by optimizing each dimension. Further, when the substrate thickness h = 16 [mm] in the basic configuration, the matching frequency fres = 117.6 [MHz], and the substrate width W = 300 [mm] of the dielectric substrate 2 is the wavelength λres of the matching frequency. = 0.118 times 2551 [mm]. If the substrate thickness h is reduced to half of 8 mm, the matching frequency fres = 96.3 [MHz] is reduced to 0.82 times, and the substrate width W of the dielectric substrate 2 becomes about 0.96λres. It turns out that deteriorates to -3.0 dB.

From FIG. 4, it can be seen that when the substrate thickness h of the dielectric substrate 2 is changed, the matching frequency fres changes, but a state in which there is always a frequency that can be matched is maintained. Further, it can be seen that the radiation efficiency ηrad is also changed by changing the substrate thickness h. FIG. 5 shows the dependence characteristics of the matching frequency fres, the maximum radiation efficiency frequency f _η , and the maximum radiation efficiency value ηmax on the substrate thickness h in the basic omnidirectional small planar antenna device 1A.

5 that the radiation efficiency maximum frequency f _eta radiation efficiency ηrad is maximized, it can be seen that change remains almost identical to the matching frequency fres. If the substrate thickness h is reduced, the matching frequency fres is lowered, which is effective for downsizing the antenna body. Conversely, in order not to change the matching frequency fres even if the substrate thickness h of the dielectric substrate 2 is reduced, the antenna diameter (the width W of the dielectric substrate 2) has only to be reduced. The planar antenna device 1A is further reduced in size and weight. However, the maximum radiation efficiency ηmax in radiation efficiency maximum frequency f _eta decreases as the substrate thickness h is reduced.

  FIG. 6A is a vertical plane pattern characteristic diagram of the absolute gain Ga of the horizontal polarization when the substrate thickness h of the dielectric substrate 2 is changed as a parameter in the unidirectional small planar antenna device 1A having the basic configuration. FIG. 6B shows a vertical plane of the absolute gain Ga of the vertical polarization when the substrate thickness h of the dielectric substrate 2 is changed as a parameter in the omnidirectional small planar antenna device 1A having the basic configuration. FIG. The omnidirectional small planar antenna device 1A is substantially omnidirectional in both horizontal polarization and vertical polarization in a horizontal plane. However, it can be seen that as the horizontal polarization is about 10 dB stronger than the vertical polarization and the substrate thickness h of the dielectric substrate 2 is reduced, the cross-polarization discrimination increases and the ratio of the vertical polarization decreases.

  Next, the influence of the relative permittivity εr of the dielectric constituting the dielectric substrate 2 in the basic omnidirectional small planar antenna device 1A will be described with reference to FIGS.

  FIG. 7 shows antenna characteristics when the substrate relative dielectric constant εr of the basic configuration is changed from 2.17. 7A shows the frequency characteristic of the reflection coefficient | S11 |, and FIG. 7B shows the frequency characteristic of the radiation efficiency ηrad. From FIG. 7, it can be seen that the matching frequency fres changes by changing the substrate relative permittivity εr, but there is always a frequency at which matching can be obtained.

FIG. 8 shows the dependence characteristics of the matching frequency fres, the maximum radiation efficiency frequency f _η , and the maximum radiation efficiency value ηmax on the substrate relative dielectric constant εr in the basic omnidirectional small planar antenna device 1A. From FIG. 8, it can be seen that the maximum radiation efficiency frequency f _η substantially matches the matching frequency fres and decreases as the substrate relative permittivity εr increases, but the radiation efficiency ηrad also decreases. By using a high dielectric constant material with a substrate relative dielectric constant εr = 6, the matching frequency fres can be lowered from 117.6 [MHz] to 77.2 [MHz], but the radiation efficiency ηrad is also −5.9 [ [dB].

  FIG. 9A shows the vertical plane pattern characteristics of the absolute gain Ga of the horizontal polarization when the substrate relative permittivity εr of the dielectric substrate 2 is changed as a parameter in the unidirectional small planar antenna device 1A having the basic configuration. FIG. 9B is a diagram showing the absolute gain Ga of vertically polarized waves when the substrate relative permittivity εr of the dielectric substrate 2 is changed as a parameter in the omnidirectional small planar antenna device 1A having the basic configuration. It is a vertical surface pattern characteristic view. The omnidirectional small planar antenna device 1A is substantially omnidirectional in both horizontal polarization and vertical polarization in a horizontal plane. It can also be seen that when the substrate relative permittivity εr of the dielectric substrate 2 is increased, the cross-polarization discrimination increases as in the case where the substrate thickness h is reduced.

  As described above, the matching frequency fres can be lowered by reducing the substrate thickness h of the dielectric substrate 2 constituting the omnidirectional small planar antenna device 1A and increasing the substrate relative permittivity εr. Can do. Although the antenna main body can be reduced in size by these design changes, the matching frequency band is narrowed. Note that if the number of divisions n of the slot antenna area in which the communication slot is provided is smaller than 4, the slot length of each communication slot can be made relatively long with respect to the antenna size, so that the matching frequency fres can be lowered. Is considered possible. Therefore, if the division number n of the slot antenna region is reduced, the antenna body can be reduced in size while maintaining the matching frequency fres.

  FIG. 10 shows a dielectric substrate 2 having a substrate width W = 120 [mm], a substrate thickness h = 1.588 [mm], and a substrate relative dielectric constant εr = 2.17. 4 is an example in which the omnidirectional small planar antenna device 1A having a matching frequency fres = 169.7 [MHz] is designed using HFSS. The substrate width W is 0.068 times the wavelength λres of the matching frequency, which is smaller than the basic configuration, and the calculated value of the radiation efficiency ηrad is −4.3 [dB]. In the following description, the omnidirectional small planar antenna device 1A based on this design dimension is referred to as a prototype configuration.

  FIG. 11 shows the external appearance of the first surface (upper surface) side of the omnidirectional small planar antenna device 1A that is prototyped based on the design dimensions of the prototype configuration. The first to fourth conductive connecting portions 61 to 64 are configured by soldering a copper tape having a width of 3 [mm]. FIG. 12 is a frequency characteristic diagram of the reflection coefficient | S11 | showing the actual measurement results actually obtained with this prototype antenna and the simulation results performed by the electromagnetic field analysis simulator HFSS (Ansys) by the finite element method. Although there was some deviation, matching was obtained at almost the design frequency even in the prototype non-directional small planar antenna device 1A, and the matching operation could be confirmed. Although better matching than the calculation is obtained, it is thought that the cause is that the symmetry of n = 4 is broken because the prototype accuracy is low.

  As described above, the omni-directional small planar antenna device 1A according to the present embodiment has a low profile, but includes a communication slot that extends over both the upper surface and the lower surface, so that it contacts a conductor such as an antenna housing case. If the omnidirectional small planar antenna device 1A is installed in such a state, the characteristics are considered to deteriorate. Therefore, assuming the case of being installed close to a housing such as a portable wireless device, the effect of being close to the conductor flat plate will be described. FIG. 13 shows a state in which the omnidirectional small planar antenna device 1A is arranged in parallel by being separated from the conductive plate 7 having a flat width Wp by a separation distance Hp.

First, the antenna characteristics (reflection coefficient | S11) when the width Wp of the conductive plate 7 is set to ∞ and the separation distance Hp from the infinite conductive plate 7 to the basic omnidirectional small planar antenna device 1A is changed. FIG. 14 shows changes in the frequency characteristics of |. FIG. 15 shows a dependence characteristic diagram of the resonance frequency fres and the resonance reflection coefficient | S11 | min with respect to the separation distance Hp in the basic omnidirectional small planar antenna device 1A. The dependency characteristic with respect to separation distance Hp of the radiation efficiency maximum frequency f _eta and maximum radiation efficiency ηmax in omnidirectional small planar antenna device 1A of the basic configuration shown in FIG. 16.

It can be seen that when the omnidirectional small planar antenna device 1A is close to the conductive plate 7, the resonance reflection coefficient | S11 | min first increases and then the resonance frequency fres increases. Even when the separation distance Hp approaches 400 [mm] (about 0.16λres), the matching frequency of | S11 | <−6 dB is maintained at the frequency fres = 117.6 MHz at which matching can be achieved without the conductive plate 7. I understand that. Further, it can be seen that when the omnidirectional small planar antenna device 1A approaches the conductive plate 7, not only the matching is deteriorated but also the radiation efficiency ηrad is deteriorated. When the separation distance Hp is narrowed to 200 mm, the radiation efficiency ηrad deteriorates to −4.7 dB. Further, the separation distance Hp is the narrow below 200 mm, rapidly matching frequency fres and radiation efficiency maximum frequency f _eta changes.

Next, the thickness of the conductive plate 7 is set to 1 mm, the separation distance Hp from the omnidirectional small planar antenna device 1A is fixed to 50 mm (about 0.02λres), and the plate width Wp of the square conductive plate 7 is set. FIG. 17 shows changes in antenna characteristics (frequency characteristics of reflection coefficient | S11 |) when changed. FIG. 18 shows a dependency characteristic diagram of the resonance frequency fres and the reflection coefficient at resonance | S11 | min with respect to the plate width Wp in the basic omnidirectional small planar antenna device 1A. FIG. 19 shows the dependence characteristics of the maximum radiation efficiency frequency _η and the maximum radiation efficiency ηmax on the plate width Wp in the basic omnidirectional small planar antenna device 1A.

  Even if the omnidirectional small planar antenna device 1A is close to the conductive plate 7 (separation distance Hp = 50 mm), there is no conductive plate 7 when the plate width Wp = 150 [mm] (about 0.059λres). It can be seen that the matching of | S11 | <−8 dB can be maintained at the frequency fres = 17.6 [MHz] at which matching can be achieved in the state. When the plate width Wp is increased to 200 [mm], the frequency deteriorates to | S11 |> −3 dB at a frequency fres = 117.6 [MHz] at which matching is achieved without the conductive plate 7. When the plate width Wp is further increased, the matching frequency fres is rapidly increased.

  17 to 19, it can be seen that the deterioration of the antenna characteristics due to the proximity of the conductor is more due to the shift of the matching frequency fres than the deterioration of the reflection coefficient | S11 | and the radiation efficiency ηrad. Therefore, it is considered effective as a countermeasure for the proximity of the conductor to design in advance by shifting the matching frequency to the low frequency side in consideration of the shift of the matching frequency fres due to the proximity of the conductor.

  Here, the current distribution in the basic omnidirectional small planar antenna device 1A (substrate thickness h = 16 [mm], matching frequency fres = 118 [MHz]) is shown in vector form in FIG.

  20A shows the distribution of current flowing on the outer surface of the first conductive layer 3 provided on the first surface (upper surface) of the omnidirectional small planar antenna device 1A, and FIG. 20B shows the omnidirectionality. The current distribution flowing on the inner surface of the first conductive layer 3 provided on the first surface (upper surface) of the small planar antenna device 1A (the surface in contact with the first surface of the dielectric substrate 2) is shown. A strong current flows through the edges of the upper surface first to fourth slit portions 31 to 34 and the outer edge of the first conductive layer 3 on both the outer surface and the inner surface of the first conductive layer 3. On the other hand, a current flows radially at the central portion of the inner surface, and a current flows in the rotational direction at the central portion of the outer surface, and it is considered that the current in the rotational direction is involved in the horizontally polarized radiation. Note that due to the anti-symmetry of the antenna structure, a current flows anti-symmetrically with respect to FIGS. 20A and 20B on the surface side and the inner surface side of the second conductive layer 4.

  As described above, the omnidirectional small planar antenna device 1A according to the present embodiment can be configured with an antenna width of about 0.1 times the wavelength λres of the target matching frequency fres, and has a low attitude and is omnidirectional. Have sex. Therefore, by reducing the thickness of the dielectric substrate 2, the antenna body can be reduced in size and weight, although the radiation efficiency is deteriorated and the band is narrowed. Although the matching frequency band is a narrow band of about 1% or less, the narrow band can be utilized in communication applications that are highly required to suppress interference with adjacent systems.

  In addition, the main polarization of the omni-directional small planar antenna device 1A is horizontal polarization, but has vertical polarization of about −10 dB. Accordingly, the omni-directional small planar antenna device 1A having a certain degree of sensitivity to both polarizations is not limited to a single polarization plane as in a normal loop antenna, and therefore there is a communication application suitable for this characteristic. Conceivable.

  Furthermore, the omni-directional small planar antenna device 1A can maintain the matching of | S11 | <−6 dB even if it is close to the conductive plate 7 up to a separation distance of about 0.16 times the wavelength λres of the matching frequency fres. . Further, since the shift of the matching frequency fres is the main cause of the matching deterioration, the omnidirectional small planar antenna device 1A can be designed by shifting the matching frequency low so as to cancel the increase of the matching frequency due to the adjacent installation. It is considered effective.

  Further, the shape of the communication slot provided in the omnidirectional small planar antenna device 1A may be changed as appropriate according to the required characteristics. For example, the omnidirectional small planar antenna device 1A ′ shown in FIG. 21A is a first modification of the omnidirectional small planar antenna device 1A according to the first embodiment, and is the tip of the upper surface first slit 31 ′. Slit 31d ', tip slit 32d' of upper surface second slit 32 ', tip slit 33d' of upper surface third slit 33 ', tip slit 34d' of upper surface fourth slit 34 ', tip slit 41d of lower surface first slit 41' ', The front end slit 42d' of the lower surface second slit 42 ', the front end slit 43d' of the lower surface third slit 43 ', and the front end slit 44d' of the lower surface fourth slit 44 'are all extended in the center direction. . An omni-directional small planar antenna device 1A ″ shown in FIG. 21 (b) is a second modification of the omni-directional small planar antenna device 1A according to the first embodiment, and is the first modification of the upper surface first slit 31 ′. 2nd bending slit 31c ', second bending slit 32c' of upper surface second slit 32 ', second bending slit 33c' of upper surface third slit 33 ', second bending slit 34c' of upper surface fourth slit 34 ', lower surface second The second bent slit 41c 'of the first slit 41', the second bent slit 42c 'of the lower second slit 42', the second bent slit 43c 'of the lower third slit 43', and the second bent of the lower fourth slit 44 '. All of the slits 44c 'are front ends, and no front end slit provided substantially parallel to the equal dividing line is provided.

  FIG. 22 shows an omnidirectional small planar antenna device 1B according to the second embodiment. Also in the omnidirectional small planar antenna device 1B of the present embodiment, the first to fourth communication slots 11S to 114 having long slot lengths are arranged at equal intervals in the first to fourth slot antenna regions 11 to 14, respectively. Structure. In addition, in the first slot antenna region 11, an upper edge first slit portion 351 that is continuous with the upper edge of the second side surface B slit portion 232b is provided in the first conductive layer 3, and the first side surface A slit portion 231a. A lower edge first slit portion 451 connected to the lower edge is provided. Similarly, in the second slot antenna region 12, an upper edge second slit portion 352 that continues to the upper edge of the third side surface B slit portion 233b is provided in the first conductive layer 3, and the second side surface A slit portion 232a is provided below. A lower edge second slit portion 452 connected to the edge is provided. In the third slot antenna region 13, an upper edge third slit portion 353 that is continuous with the upper edge of the fourth side surface B slit portion 234b is provided in the first conductive layer 3, and is also continuous with the lower edge of the third side surface A slit portion 233a. A lower edge third slit portion 453 is provided. In the fourth slot antenna region 14, an upper edge fourth slit portion 354 that is continuous with the upper edge of the first side surface B slit portion 231b is provided in the first conductive layer 3, and is also continuous with the lower edge of the fourth side surface A slit portion 234a. A lower edge fourth slit 454 is provided.

  FIG. 23 shows an omnidirectional small planar antenna device 1C according to the third embodiment. In the omnidirectional small planar antenna device 1 </ b> C of the present embodiment, the first to fourth conductive connection portions 61 to 64 are provided at the four corners of the dielectric substrate 2, respectively, so that the first to fourth slot antenna regions having a substantially triangular shape are provided. 11 to 14 are formed. In the first slot antenna region 11, the first continuous to the lower surface first slit portion 41 provided in the second conductive layer 4 from the upper surface first slit portion 31 provided in the first conductive layer 3 through the first side surface slit portion 231. A communication slot 11S is formed. Similarly, in the second slot antenna region 12, the upper surface second slit portion 32 provided in the first conductive layer 3 passes through the second side surface slit portion 232 to the lower surface second slit portion 42 provided in the second conductive layer 4. A continuous second communication slot 12S is formed. In the second slot antenna region 12, the second continuous with the lower surface second slit portion 42 provided in the second conductive layer 4 from the upper surface second slit portion 32 provided in the first conductive layer 3 through the second side surface slit portion 232. A communication slot 12S is formed. In the third slot antenna region 13, a third continuous from the upper surface third slit portion 33 provided in the first conductive layer 3 to the lower surface third slit portion 43 provided in the second conductive layer 4 through the third side surface slit portion 233. A communication slot 13S is formed. In the fourth slot antenna region 14, a fourth continuous with the lower surface fourth slit portion 44 provided in the second conductive layer 4 from the upper surface fourth slit portion 34 provided in the first conductive layer 3 through the fourth side surface slit portion 234. A communication slot 14S is formed. Since the first to fourth slot antenna regions 11 to 14 of the omni-directional small planar antenna device 1C have a triangular shape having the four side edges of the dielectric substrate 2 as long sides, the first to fourth upper surfaces are arranged. The slit parts 31 to 34 and the lower surface first to fourth slit parts 41 to 44 have a shape that continues from the proximal slit to the distal slit through the bending slit. In addition, the bent slits of the upper surface first to fourth slit portions 31 to 34 and the lower surface first to fourth slit portions 41 to 44 may have a step structure having different slit widths in the middle thereof.

  FIG. 24 shows an omnidirectional small planar antenna device 1D according to the fourth embodiment. In the omnidirectional small planar antenna device 1D of the present embodiment, a circular dielectric substrate 2D is used, a circular first conductive layer 3D is provided on the upper surface thereof, and a circular second conductive layer 4D is provided on the lower surface thereof. The first to fourth slot antenna regions 11 to 14 are formed. Like the regular polygonal substrate, the circular dielectric substrate 2D always has a center of gravity in the shape of an axis passing through the center of the upper surface and the center of the lower surface, and can be equally divided so as to pass through the virtual central axis. Note that an elliptical substrate with two focal points also has a virtual central axis, but it cannot be equally divided into the same shape, which is considered to be an obstacle to realizing horizontal omnidirectionality. However, if the omni-directional small planar antenna device 1D using the circular dielectric substrate cannot be accommodated due to the size of the terminal case, etc., the elliptical dielectric substrate having a small difference between the long axis and the short axis is not used. If the directional small planar antenna device 1D is made, there is a possibility that characteristics close to omnidirectionality can be obtained.

  In the first slot antenna region 11 of the omnidirectional small planar antenna device 1D, the second conductive layer 4D passes from the upper surface first slit portion 31 provided in the first conductive layer 3D through the arc-shaped first side surface slit portion 231. A first communication slot 11 </ b> S is formed which is continuous with the lower surface first slit portion 41 provided on the lower surface. Similarly, in the second slot antenna region 12, the lower surface second slit provided in the second conductive layer 4D from the upper surface second slit portion 32 provided in the first conductive layer 3D through the arc-shaped second side surface slit portion 232. A second communication slot 12S that is continuous with the unit 42 is formed. In the second slot antenna region 12, from the upper surface second slit portion 32 provided in the first conductive layer 3D to the lower surface second slit portion 42 provided in the second conductive layer 4D via the arc-shaped second side surface slit portion 232. A continuous second communication slot 12S is formed. In the third slot antenna region 13, the upper surface third slit portion 33 provided in the first conductive layer 3 </ b> D passes through the arc-shaped third side surface slit portion 233 to the lower surface third slit portion 43 provided in the second conductive layer 4 </ b> D. A continuous third communication slot 13S is formed. In the fourth slot antenna region 14, the upper surface fourth slit portion 34 provided in the first conductive layer 3D passes through the arc-shaped fourth side surface slit portion 234 to the lower surface fourth slit portion 44 provided in the second conductive layer 4D. A continuous fourth communication slot 14S is formed. Since the first to fourth slot antenna regions 11 to 14 of the omni-directional small planar antenna device 1C are respectively fan-shaped, the upper surface first to fourth slit portions 31 to 34 and the lower surface first to fourth slits. The portions 41 to 44 have a shape that extends from the proximal slit to the distal slit through the bending slit, and each bending slit has an arc shape along the first to fourth side surface slit portions 231 to 234. Moreover, it is good also as a level | step difference structure from which a slit width differs in the middle of each bending slit.

  FIG. 25A shows an omnidirectional small planar antenna device 1E according to the fifth embodiment in which the division number n is six. In the omnidirectional small planar antenna device 1E of the present embodiment, a hexagonal dielectric substrate 2E is used, a hexagonal first conductive layer 3E is provided on the top surface, and a hexagonal second conductive layer 4E is provided on the bottom surface. The first to sixth slot antenna regions 11 to 16 are equally divided by providing the first to sixth conductive connection portions 61 to 66 at the center of each side. The first to sixth slot antenna regions 11 to 16 are provided with first to sixth communication slots 11S to 16S, respectively. However, the slit length of each communication slot cannot be made too long with respect to the antenna diameter. An omnidirectional small planar antenna device 1E ′ shown in FIG. 25 (b) is a modified example of the omnidirectional small planar antenna device 1E according to the fifth embodiment, and the first to sixth conductive connecting portions 61 are provided at the corners. To 66 are equally divided into first to sixth slot antenna regions 11 to 16. Also in this omni-directional small planar antenna device 1E ′, the slit length of each communication slot cannot be made too long with respect to the antenna diameter. For this reason, in the omnidirectional small planar antenna devices 1E and 1E ′ having a division number n larger than 4, the antenna body can be made smaller and lighter than the omnidirectional small planar antenna device 1A according to the first embodiment. It is considered disadvantageous.

  On the other hand, FIG. 26 shows an omnidirectional small planar antenna device 1F according to the sixth embodiment in which the division number n is 3. In the omnidirectional small planar antenna device 1F of the present embodiment, a triangular dielectric substrate 2F is used, a triangular first conductive layer 3F is provided on the upper surface, and a triangular second conductive layer 4F is provided on the lower surface. By providing the first to third conductive connection portions 61 to 63 in the center portion, the first to third slot antenna regions 11 to 13 are equally divided. The first to third slot antenna regions 11 to 13 are provided with first to third communication slots 11S to 13S, respectively, and the slit length of each communication slot can be made longer than the antenna diameter. An omnidirectional small planar antenna device 1F ′ shown in FIG. 26 (b) is a modified example of the omnidirectional small planar antenna device 1F according to the sixth embodiment, and the first to third conductive connecting portions 61 are provided at each corner. To 63 are equally divided into first to third slot antenna regions 11 to 13. Also in this omni-directional small planar antenna device 1F ′, the slit length of each communication slot can be made longer than the antenna diameter. For this reason, in the omnidirectional small planar antenna devices 1F and 1F ′ in which the division number n is smaller than 4, the antenna body can be made smaller and lighter than the omnidirectional small planar antenna device 1A according to the first embodiment. It is considered advantageous.

  FIG. 27 shows a non-directional small planar antenna device 1G according to the seventh embodiment in which the division number n is 2. In the omnidirectional small planar antenna device 1G of the present embodiment, the first and second conductive connecting portions 61 and 62 are provided at the center portions of the two opposing sides using the rectangular dielectric substrate 2, so that the first , Equally divided into second slot antenna regions 11 and 12. The first communication slot 11S provided in the first slot antenna region includes a first side surface A slit portion 231a, a second side surface slit portion 232, and a third side surface B slit from the upper surface first slit portion 31 provided in the first conductive layer 3. It continues to the lower surface first slit portion 41 provided in the second conductive layer 4 through the portion 233b. The second communication slot 12S provided in the second slot antenna region includes the upper side second slit part 32 provided in the first conductive layer 3 to the third side face A slit part 233a, the fourth side face slit part 234, and the first side face B slit. It is continuous with the lower surface second slit portion 42 provided in the second conductive layer 4 via the portion 231b.

  The upper surface first slit portion 31 of the first communication slot 11S has a first end connected to the first side surface A slit portion 231a, and a base end slit 31 having a required width that the other second end extends in the center direction, A first bent slit 31b having a required width connected in a bent manner to the second end side of the proximal end slit 31 and extending in parallel with the first side surface A slit portion 231a, and bent to an extending end of the first bent slit 31b The second bent slit 31c extending in parallel with the second side slit portion 232 and connected to the extending end of the second bent slit 31c in a bent shape and parallel to the third side B slit portion 233b The third bent slit 31d extends, and the tip slit 31e is connected to the extended end side of the third bent slit 31d in a bent shape and extends away from the center. Therefore, the upper surface first slit portion 31 has a slit length close to ½ of the entire circumference of the substrate. The second bent slit 31c is a step structure including a second pre-bend slit 31c1 and a second post-bend slit 31c2 that have different slit widths and separation distances from the second side slit portion 232.

  Since the upper surface second slit portion 32 and the lower surface first and second slit portions 41 and 42, which are not described, are all the same shape as the upper surface first slit portion 31, each has a slit length close to ½ of the entire circumference of the substrate. Therefore, the slot lengths of the first and second communication slots 11S and 12S are respectively the first to fourth communication slots 11S to 14S in the unidirectional small planar antenna device 1A having the basic configuration in which the division number n = 4. This is very long compared to the slot length. Therefore, it is considered that the omnidirectional small planar antenna device 1G with the division number n of 2 can achieve a lower frequency without changing the antenna dimensions, as compared with the omnidirectional small planar antenna device 1A having the basic configuration. .

  Therefore, when a design change in which the n = 4 omni-directional small planar antenna device 1A is changed to the n = 2 omnidirectional small planar antenna device 1G without changing the antenna dimensions is simulated, the omni-directional small planar device is simulated. From the matching frequency fres = 128 MHz in the antenna device 1A, the matching frequency fres = 69 MHz was obtained in the non-directional small planar antenna device 1G. If the number of divisions n is halved from 4 to 2, the matching frequency fres can be lowered to about half.

  If the omnidirectional small planar antenna device 1G is designed so as to obtain the same matching frequency as that of the omnidirectional small planar antenna device 1A, the size is about half the size of the substrate used in the omnidirectional small planar antenna device 1A. Since it is considered that the omni-directional small planar antenna device 1G can be configured with the dielectric substrate 2 having a substrate width of W / 2, the area, volume, and weight can be reduced to about 1/4, and the size and weight can be reduced.

  From the above, it is considered that designing with a small n is effective for miniaturization. FIG. 28 shows an omnidirectional small planar antenna device 1H according to the eighth embodiment in which the division number n = 1. When n = 1, the antenna region is not equally divided into two or more, and therefore only the first slot antenna region 11 in which the first communication slot 11S is formed. However, the side surface of the dielectric substrate 2 is divided by providing the conductive connection portion 6 that electrically connects the first conductive layer 3 and the second conductive layer 4, and the upper surface first slit portion 31 is the conductive connection portion 6. 1 side A slit part 231a is connected in the vicinity of one side, and the lower surface first slit part 41 is connected to the first side B slit part 231b in the vicinity of the other side of the conductive connecting part 6. That is, the first communication slot 11S of the omnidirectional small planar antenna device 1H includes the first side surface A slit portion 231a, the second side surface slit portion 232, the third side surface slit portion 233, and the fourth side surface from the upper surface first slit portion 31. A long slot length that reaches the lower surface first slit portion 41 through the slit portion 234 and the first side surface B slit portion 231b can be obtained.

  In general, it is known that when the antenna is downsized, the radiation efficiency decreases. That is, if the division number n is reduced, the antenna body can be reduced in size, but there is a possibility that practical radiation efficiency may not be obtained. Therefore, it is appropriate to obtain the target matching frequency and sufficient radiation efficiency. It is desirable to select a proper division number n.

  As described above, the omnidirectional small planar antenna device according to the present invention has been described based on the embodiments. However, the present invention is not limited to these embodiments, and the configuration described in the claims is not changed. All omni-directional small planar antenna devices that can be realized in the above are included as a scope of rights.

1A Omnidirectional Small Planar Antenna Device (First Embodiment)
11-14 First to fourth slot antenna regions 11S-14S First to fourth communication slots 2 Dielectric substrate 21 First surface (upper surface)
22 2nd surface (lower surface)
23 Four side surfaces 3 First conductive layers 31 to 34 Upper surface first to fourth slit portions 4 Fourth conductive layers 41 to 44 Lower surface first to fourth slit portions 5 Power supply ports 61 to 64 First to fourth conductive connection portions

Claims (5)

A plate-like dielectric substrate whose two opposing faces are parallel;
A first conductive layer formed of a conductor having a required thickness on the first surface of the dielectric substrate and provided with a first slit portion having a required shape;
A second conductive layer formed of a conductor having a required thickness on the second surface of the dielectric substrate and provided with a second slit portion having a required shape;
A power supply port provided at a portion where a virtual central axis passing through the center of gravity of the dielectric substrate perpendicular to the first surface and the second surface of the dielectric substrate intersects the first conductive layer or the second conductive layer;
A conductive connection part formed on the outer surface or in the vicinity of the side surface of the dielectric substrate and electrically connecting the first conductive layer and the second conductive layer;
A side slit portion where the side surface of the dielectric substrate is continuously exposed from the conductive connection portion to the conductive connection portion;
With
By connecting one end of the side slit part to the first slit part and connecting the other end of the side slit part to the second slit part, the first slit part passes through the side slit part to the second slit part. An omnidirectional small planar antenna device characterized in that a long communication slot is formed and a signal is injected or extracted from the power feeding port. The conductive connecting portion is provided at a portion where an equally divided surface that divides the first and second conductive layers and the dielectric substrate into n equal parts (n is a natural number of 2 or more) through the virtual central axis intersects the side surface of the dielectric substrate. Provided,
2. The omnidirectional small planar antenna device according to claim 1, wherein a communication slot having the same shape is formed in each of the n slot antenna regions equally divided by the equally divided surface.   The first slit portion provided in the first conductive layer and the second slit portion provided in the second conductive layer have the same shape, and are arranged antisymmetrically with the dielectric substrate interposed therebetween. The omnidirectional small planar antenna device according to claim 1 or 2. The first slit portion and / or the second slit portion is at least:
A base end slit having a required width in which the first end is connected to the side slit portion and the other second end extends in the center direction;
A bent slit having a required width connected in a bent manner to the second end side of the base end slit and extending in parallel with the side surface of the dielectric substrate;
The omnidirectional small planar antenna device according to any one of claims 1 to 3, further comprising:   By changing the thickness and / or dielectric constant of the dielectric substrate without changing the shape of the first slit portion, the shape of the second slit portion, and the slit length of the side slit portion, the matching frequency can be changed. The omnidirectional small planar antenna device according to any one of claims 1 to 4, wherein the omnidirectional small planar antenna device is changed.