CN100369323C - Ultra Wideband Trapezoidal Floor Printed Monopole Antenna - Google Patents

Abstract

The invention relates to an ultra-wideband planar monopole antenna, which is composed of a monopole antenna plate printed on a dielectric board, a coplanar metal floor and an embedded feeder line. The monopole antenna plate is an oval patch or a circular Patch, or circular patch; the embedded feeder is a coplanar waveguide strip patch; the coplanar metal floor is a trapezoidal metal patch, which is divided into left and right pieces and attached to the coplanar waveguide On both sides of the conduction band patch; this antenna has good broadband characteristics and can achieve a standing wave bandwidth of more than 15 multipliers, and the gain in the ultra-wideband range is about -2-5db. The antenna has simple and compact structure, small volume, convenient processing and low cost.

Description

Ultra Wideband Trapezoidal Floor Printed Monopole Antenna

Technical field:

The invention relates to an ultra-wideband planar monopole antenna, which can be used for both receiving and transmitting radio waves. In military terms, it can be used as a terminal antenna for ultra-wideband radio equipment such as electronic reconnaissance and electronic interference, electromagnetic protection and ground penetrating radar. In terms of civil use, it can be used as a base station antenna for short-range ultra-wideband (UWB) communication, and an ultra-wideband antenna for home wireless communication.

technical background:

UWB antennas are more and more widely used in military and civilian fields. Especially after the U.S. Federal Communications Commission (FCC) approved the use of UWB (3.1-10.6GHz) for short-distance wireless communication, people put forward higher and higher requirements for ultra-wideband antennas, such as frequency bandwidth, small size, and simple structure. wait.

Traditional ultra-wideband monopole antennas mainly include single-cone antennas and disc-cone antennas, etc. Edited by Wang Yuankun and Li Yuquan, Broadband Technology of Wire Antenna, Xidian University Press, 1995), but its volume is relatively large. In order to reduce the size of the antenna, G.Dubost and S.Zisler first proposed the planar monopole antenna in 1976. Subsequently, scientific and technological workers at home and abroad have done a lot of research on the ultra-wideband planar monopole antenna. Literature (N.P.Agrawal, G.Kumar, and K.P.Ray, "Wideband Planar Monopole Antenna", IEEE Trans. Antennas Propagat., vol.46, pp.294-295, Feb.1998) uses a disc or elliptical disc-shaped plate As a monopole antenna, the coaxial line is used to feed power below it, and the maximum impedance bandwidth reaches 10.7:1. The literature (M.J.Ammann and Z.N.Chen, "A Broadband Short-Circuit Cut Angle Planar Monopole Antenna", IEEE Trans. Antennas Propagat., vol.51, pp.901-903, April 2003) is an improvement of the planar square monopole antenna type structure, the impedance bandwidth of the antenna also reaches 10 octaves. Literature (S.-Y.Suh, W.L. Stutaman, and W.A.Davis, "A New Ultra-Wideband Printed Monopole Antenna: Planar Inverted Conical Antenna (PICA)", IEEE Trans. Antenna and Propagat., Vol.52, pp .1361-1365, May 2004.) is another planar monopole antenna, whose basic principle is similar to that of the monoconical antenna, and also achieves an impedance bandwidth of more than 10 octaves. However, the above antennas all need a floor perpendicular to them, which increases the structure of the antenna and is not easy to integrate with active circuits. Recently, a novel structure of planar printed monopole antenna consists of an inverted triangular patch and a coplanar “T” shaped floor, and the inverted triangular patch is fed by a coplanar waveguide in the center of the floor (N. Fortino, G. Kossiavas, J.Y. Dauvignac and R. Staraj, "Novel ultra-wideband communication antennas", Microwave Opt. Tech. Lett., Vol.41, no.3, pp.166-169, May 2004.). The antenna does not require an additional vertical floor, but its impedance bandwidth is only about 5 octaves.

Invention content:

The purpose of the present invention is to provide a novel ultra-wideband printed monopole antenna, which not only has good ultra-wideband characteristics, but also has a planar structure, simple processing, and easy integration with active circuits.

The idea of the present invention is as follows: the present invention can be regarded as a planarization of the stereo dish cone antenna. The dish cone antenna is composed of a conductor cone with a conductor disk on top of it. It is fed by a coaxial line. The outer conductor of the coaxial line is connected to the top of the cone, and its inner conductor is connected to the disk. The antenna has good broadband characteristics and a simple structure, but its volume is too large, which greatly limits its application range. The invention adopts the printed antenna structure, so that the three-dimensional structure of the dish cone antenna is compressed into an approximately two-dimensional planar antenna structure (very thin), which greatly reduces the volume and weight of the antenna, and is convenient for integration with active circuits.

In order to adopt a single planar printed antenna structure and have good ultra-wideband characteristics, the following measures are adopted in this design:

1. Replace the disk of the dish cone antenna with a monopole antenna plate;

2. Replace the cone of the dish cone antenna with a trapezoidal coplanar metal floor;

3. Replace the coaxial line feed of the disk cone with the coplanar waveguide feed;

4. The coplanar waveguide adopts a gradual change form to achieve impedance matching with the coaxial connector of the antenna port in the ultra-wide frequency range.

There are several advantages to using a coplanar waveguide feed:

a. The coplanar metal floor can just be used as the floor of the coplanar waveguide;

b. The loss of the coplanar waveguide is small, which is beneficial to improve the efficiency of the antenna;

c. Easy to achieve impedance matching;

d. Easy to integrate with active circuits.

According to above-mentioned inventive concept, the present invention adopts following technical scheme:

An ultra-broadband trapezoidal floor printed monopole antenna, which is composed of a monopole antenna plate printed on a dielectric substrate, a coplanar metal floor and an embedded feeder, is characterized in that:

a. The monopole antenna board is an oval patch, or a circular patch, or a circular patch;

b. The coplanar metal floor is a trapezoidal metal patch, which is divided into left and right pieces and placed on both sides of the coplanar waveguide tape patch;

c. The embedded feeder is a coplanar waveguide, which is a conductive strip patch located in the center of two trapezoidal metal floors.

The above-mentioned coplanar waveguide is a tapered patch with a small top and a large bottom.

When the above-mentioned monopole antenna board is an elliptical patch, its elliptical transverse axis a is less than or equal to the width D _max of the trapezoidal bottom of the coplanar metal floor, and the elliptical axis ratio generally ranges from a/b=0.3 to 6 (for When the bandwidth requirement is not very wide, the value range of a/b can be larger).

The height H of the above-mentioned coplanar metal floor is determined by the following formula: H=0.2λ _l , λ _l =c/f _l , where c is the speed of light in free space, and f _l is the lowest operating frequency.

The lower bottom width D _max of the coplanar metal floor is 0.8 to 1.5 times its height H; and the top width D _min is determined by the following formula: D _min /λ _h =0.2 to 0.4, λ _h =c/f _h , where f _h is the highest operating frequency.

The distance t between the above-mentioned elliptical patch and the coplanar metal floor patch is determined by the following formula: t/λ _h =0.05˜0.08.

The relative dielectric constant of the above-mentioned dielectric plate is 2-11, and its dielectric loss tangent is not greater than 10 ^-3 .

Compared with the prior art, the present invention has the following obvious substantive outstanding features and significant advantages: the present invention can realize the impedance bandwidth (voltage standing wave ratio VSWR≤2: 1) exceeding 15 frequency multiplications; The coplanar monopole antenna patch, trapezoidal metal floor and coplanar waveguide strip are printed on the same surface of the dielectric substrate, which has a simple structure and is easy to integrate with active circuits; the gradual coplanar waveguide feed is used to facilitate the realization of ultra-wideband impedance Matching, and the loss is small, which is conducive to improving the efficiency of the antenna. The gain of this antenna is about -2~5dB in its ultra-wideband range. The antenna has simple and compact structure, small volume, convenient processing and low cost.

Description of drawings

Figure 1 Antenna Structure Front View

Figure 2 The measured standing wave ratio diagram of the antenna

Figure 3 Measured pattern at 1.0GHz frequency point

Figure 4 Measured pattern at 3.0GHz frequency point

Figure 5 Measured pattern at 6.0GHz frequency point

Figure 6 The measured pattern at the 8.0GHz frequency point

Detailed ways

A preferred embodiment of the present invention is shown in FIG. 1 . The structure of the antenna is shown in Figure 1. It consists of a monopole antenna plate 1 printed on a dielectric substrate 4 and a coplanar metal floor 3. The monopole antenna plate 1 is an oval patch, and the coplanar metal floor 3 is trapezoidal. The metal floor is fed by the embedded feeder 2 in the middle of the coplanar metal floor 3, and the embedded feeder 2 is a coplanar waveguide. The lower end of the coplanar waveguide is connected with a coaxial connector 5 , the inner conductor of the coaxial connector is connected with the coplanar waveguide strip, and the outer conductor of the connector is connected with the coplanar metal floor 3 . The elliptical patch can also be replaced by a circular patch and a circular patch; the design parameters of the antenna shown in Figure 1 are D _max , D _min , H, b, a, t and the thickness of the dielectric plate h, relative Permittivity ε _r . Using the structure in Figure 1, as long as the parameters are selected reasonably, the input impedance of the entire antenna can be kept small with frequency, so as to realize the ultra-wideband monopole antenna characteristics.

It is usually required to give certain indicators to design the antenna. The indicators of the general ultra-wideband monopole antenna are impedance bandwidth, pattern and gain. The following will describe how to design this form of antenna according to the requirements of the indicators. Assume that the given frequency range is f _l ~ f _h , and the corresponding wavelengths are λ _l and λ _h respectively.

1. Determination of parameters:

The values of design parameters D _max , D _min , H, b, a, t are determined according to theoretical analysis and experimental test experience. The radiation mechanism of the antenna of the present invention is mainly realized by the elliptical patch 1 and the coplanar metal floor 3, and the coplanar metal floor 3 is also an important part of radiation, and the value of the parameter H should be determined first during design. Since the coplanar metal floor 3 is radiated by two hypotenuses, the optimal value of the height H is: H≈0.2λ _l . Next, the parameter D _max is determined. The change of D _max has a great influence on the input impedance of the low-frequency end of the antenna. Increasing D _max can properly reduce the operating frequency of the antenna, but the increase of D _max value will increase the cross-polarization level of the antenna and affect the antenna pattern. Therefore, D _max is generally taken as: D _max /H=0.8～1.5. Next, determine the parameters a and b. The parameter a will affect the low-end impedance of the antenna. Increasing a can usually reduce the operating frequency of the antenna appropriately. However, in order to make the antenna compact, a should not be too large. Generally, a≤D _max , and the parameter b is mainly determined according to a. The ratio between a and b mainly affects the input impedance of the elliptical patch. Generally, a/b is 0.3 to 6, which is more appropriate (if the required bandwidth range is not large, then a/b The value range of b can be larger). Then determine the parameter D _min , the selection of D _min is mainly determined by the highest frequency of the antenna, generally take D _min /λ _h ≈0.2～0.4. Finally, determine the value of the parameter t, which mainly affects the coupling between the elliptical patch and the coplanar metal floor 3 patch. The input impedance of the whole antenna at the upper port of the coplanar waveguide can be considered as the input impedance of the elliptical patch, the coupling impedance between the elliptical patch and the coplanar metal floor 3, and the self-impedance of the coplanar metal floor 3. Therefore, the change of t has obvious influence on the impedance bandwidth of the whole antenna. The optimal value range of t is: t/ _λh = 0.05～0.08 (if the required bandwidth range is not large, the value of t/ _λh The value range can be larger).

2. Design of coplanar waveguide:

The input impedance of the entire antenna at the upper port of the coplanar waveguide is about 100 ohms, while the lower port of the coplanar waveguide is connected to a coaxial connector, and its characteristic impedance is usually 50 ohms. Therefore, the characteristic impedance of the coplanar waveguide needs to be gradually changed from more than 100 ohms to 50 ohms. The characteristic impedance of the coplanar waveguide is related to the width w of the conduction band, the distance g between the coplanar waveguide and the coplanar metal floor 3, and the dielectric constant and thickness of the dielectric substrate 4. It is only necessary to change one parameter and keep the other parameters unchanged. change its characteristic impedance. To this end, a tapered form is used for the width w of the coplanar waveguide strip. Of course, it can also be realized by keeping w constant and changing the interval g. At the same time, in order to ensure a good impedance gradient characteristic at the low frequency end, H needs to be 0.2λ _l or larger.

3. Selection of Dielectric Substrate 4

The relative permittivity of the dielectric substrate 4 generally ranges from ε _r =3 to 6, and ε _r =2 to 11 if the required bandwidth range is not large. At the same time, the dielectric loss tangent should be as small as possible, generally tgδ≤10 ^-3 ; if the efficiency requirement is not high, a larger tgδ value is also acceptable. The selection of the thickness h of the dielectric substrate can be mainly considered in order to ensure the strength of the antenna, such as taking h≥0.8mm.

4. Selection of connector 5:

The connector 5 of the antenna port can be an N-type coaxial connector, an SMA connector or other connectors.

Fig. 2 is the variation curve of the standing wave of the embodiment of the present invention measured by Agilent 8720ES vector network analyzer with frequency. The measured impedance bandwidth (VSWR≤2:1) is 0.41 to 8.8GHz, that is, the specific bandwidth is 21.6:1 (about 22 octaves).

Figures 3 to 6 show the measured direction diagrams at the four frequency points of the antenna. Comparing these groups of curves, it is not difficult to find that the antenna achieves monopole radiation characteristics in a very wide frequency band, and its main polarization has very stable omnidirectional radiation characteristics on the azimuth plane (xy plane).

Claims (7)

1. An ultra-broadband trapezoidal floor printed monopole antenna, consisting of a monopole antenna plate (1), a coplanar metal floor (3) and an embedded feeder (2) printed on a dielectric substrate (4), its characteristics in: a. The monopole antenna plate (1) is an oval patch, or a circular patch, or a circular patch; b. The coplanar metal floor (3) is a trapezoidal metal patch, which is divided into left and right pieces and placed on both sides of the coplanar waveguide strip patch; c. The embedded feeder (2) is a coplanar waveguide, which is a conductive strip patch located in the center of two trapezoidal metal floors. 2. The ultra-wideband trapezoidal floor printed monopole antenna according to claim 1, characterized in that the coplanar waveguide adopts a tapered form. 3. The ultra-broadband trapezoidal floor-printed monopole antenna according to claim 2, characterized in that the coplanar waveguide is a tapered tape-shaped patch with a small top and a large bottom. 4. The ultra-broadband trapezoidal floor printed monopole antenna according to claim 1, wherein when the monopole antenna plate (1) is an elliptical patch, its elliptical transverse axis (a) is less than or equal to the coplanar metal floor (3) The width of the bottom of the trapezoid (D _max ), and the ratio of the horizontal axis (a) to the vertical axis (b) of the ellipse is 0.3-6. 5. The ultra-broadband trapezoidal floor printed monopole antenna according to claim 1, characterized in that the trapezoidal shape of the coplanar metal floor (3) has a size of: its height (H) is 0.2 times the longest operating wavelength, and the following The bottom width (D _max ) is 0.8-1.5 times the height (H); and the top width (D _min ) is 0.2-0.4 times the shortest working wavelength. 6. The ultra-broadband trapezoidal floor printed monopole antenna according to claim 4 or 5, characterized in that the distance (t) between the oval patch and the coplanar metal floor (3) is 0.05 to 0.08 times the shortest operating wavelength . 7. The ultra-broadband trapezoidal floor printing monopole antenna according to claim 1, characterized in that the relative permittivity (ε _r ) of the dielectric substrate (4) is 2～11, and its dielectric loss tangent (tgδ) is not greater than 10 ^-3 .

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