CN1543011A - Self-tuning multi-band meander line loading antenna - Google Patents

Abstract

An antenna for sending and receiving radio frequency energy. The antenna includes a metal top plate formed in a helical shape. In a particular embodiment, the side wall meander lines extend from the edge of the top plate in the direction of the ground plane. A short circuit meander connects the top plate and the ground plane. The first region of the top plate covers the ground plane. The second area of the top plate extends beyond the ground plane. Tuning is achieved by adjusting the length and other dimensions of the meander.

Description

Self-tuning multi-band meander line loading antenna

This application claims priority to Provisional Application No. 60/420,214, filed October 22,2002.

technical field

The present invention generally relates to an antenna for transmitting and receiving radio frequency signals, in particular to an antenna working in multiple frequency bands.

Background technique

As we all know, the performance of an antenna depends on its size, shape, the material composition of the elements that make up the antenna, and the physical parameters of some antennas (such as the length of the linear antenna and the diameter of the loop antenna) and the wavelength of the signal sent and received by the antenna. relation. The above relationships determine some of the antenna's operating parameters, including input impedance, gain, direction, signal polarization, and radiation pattern. Usually for a working antenna, the minimum physical antenna size (or the smallest size that is electrically effective) must be similar to a quarter wavelength of the operating frequency, which will greatly suppress the energy loss in resistive losses and make the emission and The energy received reaches the maximum value. The most commonly used are quarter-wavelength antennas and half-wavelength antennas.

The rapid development of wireless communication devices and systems has led to the demand for small size, less obtrusive (lessobtrusive), higher efficiency capable of operating in broadband or multi-band, and/or in multi-mode (i.e., selectable radiation pattern or There is a great demand for antennas that work in the state of optional signal polarization direction). State-of-the-art communication devices, such as handhelds, do not provide sufficient space for conventional quarter-wavelength antennas and half-wavelength antenna elements. Antennas of smaller physical size that operate in the desired frequency band and provide other desired operating characteristics (input impedance, radiation pattern, signal polarization direction, etc.) are therefore particularly desirable.

As is known to those skilled in the art, at least for single-element antennas, there is a direct relationship between the physical size of the antenna and the gain of the antenna, the relationship being: Gain = (βR)^2 + 2βR, where R is the The radius of the ball, and β is the propagation factor. An increase in gain therefore requires a physically larger antenna, while users always demand a physically smaller antenna. As another constraint, in order to simplify system design and minimize cost, equipment designers and system operators tend to use antennas that can achieve efficient multi-band and/or wide-band operation, thereby allowing communication equipment to operate in a variety of different Realize various wireless service functions on the frequency band or such services on the broadband. Ultimately, the gain is limited due to the well-known relationship between the operating frequency of the antenna and the effective antenna length (expressed in wavelength) as described above. That is, the antenna gain is constant for all quarter-wavelength antennas having a specific geometry such that the effective antenna length at the operating frequency is a quarter-wavelength of the operating frequency.

A basic antenna commonly used in many applications today is the half-wavelength dipole antenna. Its radiation pattern is a common donut shape, in which most of the energy is radiated in the azimuth direction, and very little energy is radiated in the elevation direction. The expected frequency bands for certain communication devices are 1710 to 1990 MHz and 2110 to 2200 MHz. The half-wavelength dipole antenna is approximately 3.11 inches long at 1900 MHz, 3.45 inches long at 1710 MHz, and approximately 2.68 inches long at 2200 MHz. The characteristic gain value is about 2.15dBi.

A quarter monopole mounted above a ground plane is derived from a half wavelength dipole. The physical size of the antenna is a quarter-wavelength, but the antenna behaves like a half-wavelength dipole antenna because of the ground plane. Therefore, the radiation pattern of a quarter monopole antenna mounted on a ground plane is the same as that of a half-wavelength dipole antenna, and has a characteristic gain value of about 2dBi.

A common free-space (ie not above the ground plane) loop antenna (with a diameter of about one-third of a wavelength) also exhibits the same toroidal radiation pattern along the radiation axis, with a gain value of about 3.1 dBi. At 1900MHz, this antenna has a diameter of approximately 2 inches. A typical loop antenna has an input impedance of 50 ohms, which provides good matching characteristics.

The well known patch antenna provides a directional hemispherical coverage area with a gain of about 4.7dBi. Although smaller than a quarter or half-wave antenna, a patch antenna has a relatively narrow bandwidth.

Due to the favorable performance of quarter antennas and half wavelength antennas, conventional antennas are generally constructed such that the length of the antenna is similar to the quarter wavelength of the radiation frequency, and the antenna operates above a ground plane. These dimensions allow the antenna to be easily excited and operated above or near the resonant frequency, suppressing energy loss in resistive losses and maximizing radiated energy. However, when the operating frequency increases/decreases, the operating wavelength increases/decreases, and thus the size of the antenna increases/decreases proportionally.

Therefore, antenna designers have begun to work on using so-called slow wave structures in which the physical size of the structure is not equal to the effective electrical size. The effective size of the antenna required to eliminate the aforementioned favorable radiation and low loss characteristics requires constraints similar to half wavelength (or quarter wavelength on a ground plane). In general, a slow-wave structure refers to a structure in which the phase velocity of a traveling wave is smaller than the speed of light in free space. The wave speed is the product of wavelength and frequency considering the material permittivity and magnetic permeability, i.e. c/((sqrt(ε _r ) sqrt(μ _r ))=λf. Since the frequency transmitted in the slow wave structure remains unchanged , if the wave velocity is lower (i.e., the phase velocity is lower than) the speed of light, the wavelength in the structure is lower than the wavelength in free space. Thus, for example, a half-wavelength slow-wave structure is faster than a wave propagating at the speed of light (c) The half-wavelength structure is short. The slow-wave structure does not have the traditional relationship between physical size, resonant frequency and wavelength. This slow-wave structure can be used as an antenna element or an antenna radiation structure.

Since the phase velocity of waves propagating in slow-wave structures is lower than the speed of light in free space, the effective electrical length of these structures is greater than that of structures propagating waves at the speed of light. Therefore, the resonant frequency of the slow-wave structure is correspondingly increased. Thus, if two structures operate at the same resonant frequency, eg as half-wavelength dipoles, the structure that transmits slow waves will be physically smaller than the structure that transmits waves at the speed of light.

Contents of the invention

In a specific embodiment, the antenna of the present invention is configured to be connected to a ground plane in a spaced-apart relationship for transmitting and receiving radio frequency energy. The antenna comprises a top plate in the shape of a helix defined by one or more edges; a shorting element (including a meander conductor in a preferred embodiment) extending from the top plate in the direction of the ground plane for electrically connecting the top plate to the ground plane; and sidewalls extending from the edge of the top plate in the direction of the ground plane.

Description of drawings

The foregoing and other features of the invention will be better revealed by the following more detailed description of the invention. As shown in the drawings, wherein like reference numerals refer to like elements in the various drawings. The drawings are not necessarily to size, emphasis instead being placed upon illustrating the principles of the invention.

Figure 1 is a perspective view of an antenna formed in accordance with the teachings of the present invention;

Accompanying drawing 2 and accompanying drawing 3 are respectively the top view and the end view of the antenna formed according to another embodiment of the present invention;

Accompanying drawing 4 shows the sectional view of the zigzag line in the antenna described in accompanying drawing 2,3;

Accompanying drawing 5 is the equivalent circuit diagram of antenna shown in accompanying drawing 2,3;

6-8 are various views of an antenna formed in accordance with a second embodiment of the invention.

Detailed ways

Before proceeding to a detailed description of the specific antenna apparatus of the present invention, it should be clear that the present invention makes an inventive and non-obvious combination of elements. Therefore, elements of the present invention are represented by conventional elements in the drawings, only showing details relevant to the present invention, without showing structural features known to those skilled in the art, so as not to affect the disclosure of the invention.

The antenna of the present invention includes a compact helical radiator to which one or more meander structures are attached, thereby providing optimum operating parameters in a volume smaller than a quarter-wave structure mounted on a ground plane . The antenna can be easily manufactured by printing a blank metal plate. The shape of some specific printed areas can be made as required and the zigzag lines pasted in place. The antenna's small size allows it to be installed in handheld communication devices and other applications where space is at a premium. In another embodiment, the antenna of the present invention may be formed by wiring or etching a conductor layer disposed on a dielectric substrate.

Figure 1 shows a perspective view of an antenna 10 in one embodiment of the present invention. The antenna 10 is made of a relatively thin sheet of conductive material such as copper and includes a top plate 11 further comprising an inner helical segment 12 and an outer helical segment 13 . Alternatively, the top plate 11 comprises a layer of conductive material in which material has been removed from near the center of the sheet to the edges of the sheet of conductive material. In one embodiment, the material is removed to form a helical slot in the top plate 11 .

The antenna 10 is disposed on a dielectric substrate 14 and includes a ground plane 16 extending from an edge 18 to a boundary 20 of the dielectric substrate 14 . Therefore, the ground plane 16 does not extend under the entire antenna 10 . This feature affects the capacitance between the top plate 11 and the dielectric substrate 14, as well as the operating characteristics of the antenna 10 to be mentioned below. In one embodiment, the distance between the top plate 11 and the media base 14 is 5 mm. Adjusting this distance changes the resonant frequency of the antenna 10 .

The antenna 10 also includes a meander element 22 disposed on the dielectric substrate 14 in a region 23 between the boundary 20 and the edge 24 . The meander line element 22 is not electrically connected to the region 23 , but may be mechanically connected thereto to provide support for the antenna 10 .

Antenna 10 is fed and received with signals via feeder trace 30 (formed on dielectric substrate 14 ) and antenna feed 32 . Typically, a feed connector (not shown in FIG. 1 ), which includes feed pins for electrical connection to the feeder trace 30, is physically connected to the dielectric substrate at region 33. , and a ground pin electrically connected to the ground plane 16. The embodiment of Fig. 1 lacks some of the meander line structures of the embodiments described below.

2 and 3 are top and front views, respectively, of another embodiment of antenna 10, including meander line elements 22 and 40 (the latter not shown in FIG. 1). The meander 40 is electrically connected between a region 41 of the top plate 11 and the ground plane 16 . As best illustrated in Figure 3, the meander 22 includes a vertical portion 43 and an arm 44 (arm) extending therefrom and configured to be physically connected to the region 23 of the dielectric substrate; the arm 44 is not in contact with the ground plane 16 electrical connections.

FIG. 4 shows a cross-sectional view of the preferred structure along meander line 40 in plane 4-4 of FIG. 2 . As shown, the top end 42 of the meander line 40 is grounded. In one particular embodiment, distance "d" is about 1 inch.

FIG. 5 shows an equivalent circuit diagram of the antenna 10 . Capacitor 50 represents the capacitance between outer helical segment 13 and ground plane 16 . Capacitor 52 represents the capacitance between inner helical segment 12 and ground plane 16 . Both capacitors 50 and 52 are affected by the distance between top plate 11 and ground plane 16 . At the same time, as boundary 20 (see FIG. 1) is adjusted relative to antenna edge 18 (or edge 24), the values of capacitors 50 and 52 change accordingly. One technique that is often used to vary these capacitances and antenna characteristics is therefore to adjust the distance between boundary 20 and antenna edge 18 (or boundary 24).

Capacitor 54 represents the capacitance between the inner helical segment 12 and the outer helical segment 13 . Reference numeral 56 designates the short-circuit point of meander line 40 to ground. The meander element 22 is indicated by reference numeral 58, which is not connected to ground, but appears to be an open circuit. Generally, as shown in FIG. 5, components to the right of the antenna feed 32 affect low-band performance, while components to the left of the antenna feed 32 affect high-band performance.

In one embodiment, the antenna 10 operates or resonates in the cellular frequency band of approximately 880-960 MHz (low frequency) and in the personal communication system frequency band of 1.710-1.990 Ghz (high frequency). The radiation pattern at low frequencies is omnidirectional (same donut pattern), while at high frequencies it is predominantly horizontal, ie the energy is radiated mainly in the horizontal direction. By adjusting the physical characteristics of the meander 40, such as its length, the tuning of the high frequency band is realized, so as to achieve resonance for a frequency band around 1.5 GHz of the GPS band, for example. The shape and size of the meander line 22 can also be changed to achieve changes in the working characteristics of the antenna 10 including the working frequency.

In one embodiment, the dimensions of the antenna are approximately 0.4 inches long and approximately 0.4 inches wide.

The top view of Fig. 6 shows the resonant state of the antenna 70 in three frequency bands. Generally, the antenna 70 includes the inner helical section 12 and the outer helical section 13 of the antenna 10 shown in FIG. 1 . However, antenna 70 also includes additional and improved meanders compared to antenna 10 .

FIG. 7 shows a front view of the antenna 70 . Antenna 70 includes meander 40 and antenna feed 32 which, together with antenna 10, operate in substantially the same manner as described above. The antenna 70 also includes a meander line element 71 having electrically connected segments 72 and 73 . The segment 72 extends from the top plate 11 , while the segment 73 is disposed on or near the dielectric substrate 14 , but is not electrically connected to the ground plane 16 .

The sectional view of FIG. 8 along plane 8-8 of FIG. 6 further illustrates meander line 71 . As shown, meander line 71 is disposed above dielectric substrate 14 but is not electrically connected to ground plane 16 . In one embodiment the distance dd is about 0.3 inches.

The antenna 70 also has a meander 74 comprising a vertical section 75 and an arm 76 .

When working, the antenna 70 exhibits a resonant state in the cellular frequency band of 820-890 MHz, and in 1.5 GHz for Global Positioning System (GPS) communication and 2.5 GHz for WLAN communication.

Generally, according to the teachings of the present invention, the antenna shown in FIG. 1 can be tuned to work in multiple frequency bands by adding meander elements and/or adjusting the length of the illustrated meander elements. Additional operating frequency bands can be generated by adding meander elements. Operation in one frequency band can be improved without affecting operation in other frequency bands by adjusting certain specific meander elements. The antenna thus provides separate adjustable operating frequencies. Known Antennas in the Prior Art Changing one physical characteristic or dimension of the antenna usually affects all resonant frequencies of the antenna. The antenna of the present invention is not limited thereto. At the same time, scaling the dimensions (eg length, width, height from ground plane) of the antenna of the present invention generally affects all resonant frequencies.

An antenna structure has been described for operation in one or more frequency bands. Specific applications and examples of the invention have also been shown and described, and the principles disclosed herein provide for implementing the principles of the invention in a variety of ways and with a variety of antenna configurations. Various modifications are possible within the scope of the invention. The invention is limited only by the appended claims.

Claims (48)

1. An antenna connected to a ground plane for transmitting and receiving radio frequency energy, comprising: a helical top plate bounded by one or more edges; a shorting element extending from the top plate in the direction of the ground plane for electrically connecting the top plate and the ground plane; and The side wall extending from the edge of the top plate in the direction of the ground plane. 2. The antenna of claim 1, wherein a portion of the top plate is above the ground plane when the antenna is operated with the ground plane. 3. The antenna of claim 2, wherein the area of the portion of the top plate above the ground plane is adjustable to vary the performance of the antenna. 4. The antenna of claim 2, wherein the portion of the top plate above the ground plane includes a first region of the top plate from which the shorting element extends, and wherein said portion of the top plate does not include a sidewall extending therefrom the second area of the top plate. 5. The antenna of claim 1 , wherein the ground plane comprises conductive material disposed on a first region of the substrate, and the conductive material is detached from a second region of the substrate, and the sidewall is disposed between the second region superior. 6. The antenna of claim 1, wherein the top plate has an inner helical section connected to an outer helical section. 7. The antenna of claim 1, wherein the top plate comprises a continuous spiral of conductive material. 8. The antenna of claim 1, wherein the shorting element comprises a meander conductor. 9. The antenna of claim 8, wherein the meander line conductor comprises an elongated transmission line having a meander configuration. 10. The antenna of claim 8, wherein the meander line conductor comprises an elongated transmission line further comprising a first segment and a second segment, wherein the first and second segments are electrically connected and disposed substantially parallel to the top plate . 11. The antenna of claim 10 mounted above a ground plane, wherein the first and second segments are substantially parallel to the ground plane and are disposed between the top plate and the ground plane. 12. The antenna of claim 1, further comprising a feed element connected to the top plate. 13. The antenna of claim 1, further comprising a feed element, wherein the top plate has an inner helical section and an outer helical section, wherein the feed element is disposed at a top end of the outer helical section. 14. The antenna according to claim 13, the antenna is disposed on a dielectric substrate further comprising a ground plane and a metal feed area insulated from the ground plane, wherein the feed area is electrically connected to the feed element. 15. The antenna of claim 14, wherein the feed element comprises a conductor strip extending from the top plate to a conductor feed area on the dielectric substrate. 16. The antenna of claim 1, wherein the side walls form substantially right angles with an edge of the top plate. 17. An antenna comprising: ground plane; a spiral top plate comprising first and second regions, wherein the first region is located above the ground plane; Feed elements in electrical communication with the roof; a first meander conductor extending from the top plate; and A second meander conductor extending from the top plate. 18. The antenna of claim 17, wherein the ground plane comprises a dielectric substrate having a conductive material disposed on a first region of the substrate; and the conductive material is detached from a second region of the substrate; and the first region of the top plate The region is substantially over the first region of the substrate. 19. The antenna of claim 18, wherein the first meander conductor extends from the first region of the top plate and further comprises an elongated meander shaped conductor, wherein the first meander conductor electrically connects the top plate to the ground plane. 20. The antenna of claim 17 , wherein the top plate further includes a second region extending beyond an edge of the ground plane, and the second meander conductor includes a first conductor element extending at an edge of the second region and extending from the edge of the second region. A second conductor element extends from the first conductor element. 21. The antenna of claim 20, wherein the angle formed between the first conductor element and the second region of the top plate is approximately 90°. 22. The antenna of claim 20, wherein the angle between the first conductor element and the second conductor element is approximately 90°. 23. An antenna for transmitting and receiving radio frequency energy connected to a spatially separated ground plane, comprising: a spiral top plate having one or more edges; side walls extending from the edge of the top plate in a direction towards the ground plane; and Wherein, when working together with the ground plane, the first area of the top plate is arranged facing the ground plane, and the second area of the top plate extends beyond the edge of the ground plane. 24. The antenna of claim 23, wherein the sidewall extends beyond an edge of the ground plane. 25. The antenna of claim 24, further comprising a shorting element for electrically connecting the top plate and the ground plane. 26. The antenna of claim 25, wherein the short circuit element comprises a meander line conductor extending from the top plate. 27. The antenna of claim 23, further comprising a dielectric substrate having first and second dielectric regions, wherein the ground plane is disposed over the first dielectric region and the first top plate region faces the first dielectric region set up. 28. The antenna of claim 27, wherein the sidewall is above the second dielectric region. 29. An antenna connected to a ground plane for transmitting and receiving radio frequency energy, comprising: Spiral top plate; a first meander element extending from the top plate in the direction of the ground plane to connect the top plate and the ground plane; a second meander element extending from the top plate; and A side wall extending from the edge of the top panel. 30. The antenna of claim 29, wherein the distance between the top plate and the ground plane is selected to achieve a desired performance parameter of the antenna. 31. The antenna of claim 29, wherein an area of the top plate covers the ground plane when the antenna is designed to operate with the ground plane. 32. The antenna of claim 31, wherein the size of the coverage area is adjusted to change the performance characteristics of the antenna. 33. The antenna of claim 32, wherein a first meander line element is disposed in the coverage area. 34. The antenna of claim 29, wherein the top plate has an inner helical segment electrically connected to an outer helical segment. 35. The antenna of claim 29, wherein the top plate has a continuous spiral of conductive material. 36. The antenna of claim 29, wherein the second meander line element extends from the top plate in the direction of the ground plane and has a substantially L-shaped meander line element. 37. The antenna of claim 36, wherein the second meander line element further comprises a first segment extending from the top plate and a second segment extending from the first segment, wherein the length of the second segment is less than the length and width of the top plate . 38. The antenna of claim 29, wherein the first meander line element comprises an elongated meander transmission line including segments substantially parallel to the top plate. 39. The antenna of claim 29, wherein the first meander line element comprises an elongated transmission line comprising at least two joined segments substantially parallel to the top plate. 40. The antenna of claim 29 arranged to be spaced apart from the ground plane, wherein the first meander line element comprises two substantially parallel elongated segments, the elongated segments being substantially parallel to ground plane and substantially parallel to the top plate. 41. The antenna of claim 29, further comprising a feed element. 42. The antenna according to claim 41 , wherein the feed element extends from the top plate in the direction of a ground plane, wherein the ground plane is provided on a dielectric substrate, wherein the dielectric substrate comprises an electrical connection insulated from the ground plane. Metal feed area to feed element. 43. The antenna of claim 29, wherein the second meander line element is positioned between the sidewall and the first meander line element. 44. The antenna of claim 29, wherein the side wall includes a first segment disposed substantially at right angles to the top plate, and a second segment connected to the first segment and substantially at right angles to the first segment. 45. An antenna connected to a spatially separated ground plane for transmitting and receiving radio frequency energy, comprising: a conductor foil defining an aperture therein, the conductor foil further comprising one or more edges and first and second regions; a side wall extending from the edge of the conductor sheet in a direction towards the ground plane when the antenna is in operation with the ground plane; and Wherein, when working together with the ground plane, the first region is disposed facing the ground plane, and the second region extends beyond the edge of the ground plane. 46. The antenna of claim 45, wherein the sidewall extends from the second region. 47. The antenna of claim 24, further comprising a shorting element extending from the first region to electrically connect the top plate and the ground plane. 48. The antenna of claim 46, wherein the slot forms a helical shape.

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