KR100646850B1 - Planar Array Antenna with Spherical Beam Pattern - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a planar array antenna having a spherical beam pattern.

2. The technical problem to be solved by the invention

According to the present invention, a planar array structure using a passive multi-terminal network has a rectangular pattern so that the beam of the antenna has a spherical pattern, thereby reducing beam interference with adjacent cells, and having a planar array having uniform gain characteristics and low side lobe characteristics within a desired beam directing range. The purpose is to provide an antenna.

3. Summary of Solution to Invention

Input power distribution means for distributing and outputting a signal received from the outside into a signal having the same power and phase; First distributing means for distributing electric power and controlling a phase of the signal received from the input electric power distributing means so as to satisfy a predetermined rectangular beam pattern power supply requirement; Second distributing means for distributing and outputting a signal received from the first distributing means into a signal having the same power and phase; And radiating means for radiating a signal received from the second distribution means to the free space.

4. Important uses of the invention

The present invention is used for a mobile communication base station antenna and the like.

Spherical Beam Pattern, Array Antenna, Microstrip Radiator, 180 Degree Hybrid Ring Combiner, Wilkinson Power Divider

Description

Plane Array Antenna with Flat-Topped Element Pattern             

Figure 1a is an exemplary view showing an embodiment of a planar array antenna having a rectangular sector beam pattern to which the present invention is applied,

1B is an exemplary diagram illustrating beam coverage in the azimuth direction of a planar array antenna having a spherical sector beam pattern as an embodiment to which the present invention is applied;

2A is an exemplary diagram showing another embodiment of a planar array antenna having a spherical sector beam pattern to which the present invention is applied;

2B is an exemplary diagram showing beam coverage of a planar array antenna embodiment having a spherical sector beam pattern to which the present invention is applied;

3 is a graph showing the required amplitude and phase distribution of the 16 antenna array elements arranged in the azimuth direction according to an embodiment of the present invention;

4 is a configuration diagram of an embodiment of a planar array antenna having a spherical beam pattern according to the present invention;

5 is a front view and a cross-sectional view showing a detailed structure of one embodiment of a radiating element having a coaxial feed according to the present invention;

6A is a detailed structural diagram of one embodiment of a row distributor according to the present invention;

Figure 6b is an appearance of the radiating element and the row divider manufactured in accordance with a preferred embodiment of the present invention,

7A is a detailed structural diagram of an embodiment of a heat distributor according to the present invention;

7B illustrates an embodiment of a 180 ^o ring hybrid coupler device in accordance with the present invention;

7C is an external view of a heat distributor manufactured according to one preferred embodiment of the present invention;

8A is a detailed structural diagram of an embodiment of an input power divider according to the present invention;

8b is an external view of an input power divider manufactured according to an embodiment of the present invention;

9 is an experimental correction device for correcting the relative power ratio and phase difference of the planar array antenna according to the present invention,

10A is an exemplary view showing a front surface of an embodiment of a planar array antenna having a 90 ^o spherical beam pattern according to the present invention;

Figure 10b is an exemplary view showing the back of one embodiment of a planar array antenna having a 90 ^o spherical beam pattern according to the present invention,

FIG. 11A is a graph comparing measurement and simulation performance of principal polarization and cross polarization radiation pattern characteristics (frequency is 1.920 GHz) of a planar array antenna having a spherical beam pattern according to an exemplary embodiment of the present invention. FIG.

FIG. 11B is a graph comparing measurement and simulation performances of principal polarization and cross polarization radiation pattern characteristics (frequency is 2.045 GHz) in the azimuth direction of a planar array antenna having a spherical beam pattern according to an embodiment of the present invention;

11C is a graph comparing measurement and simulation performance of principal polarization and cross polarization radiation pattern characteristics (frequency is 2.170 GHz) in azimuth direction of a planar array antenna having a spherical beam pattern according to an embodiment of the present invention;

12A is a graph comparing measurement and simulation performance of a polarization radiation pattern characteristic (frequency is 1.920 GHz) in an elevation angle of a planar array antenna having a spherical beam pattern according to an embodiment of the present invention;

12B is a graph comparing measurement and simulation performance of a polarization radiation pattern characteristic (frequency is 2.045 GHz) in an elevation angle of a planar array antenna having a spherical beam pattern according to an embodiment of the present invention;

12C is a graph comparing measurement and simulation performance of a polarization radiation pattern characteristic (frequency is 2.170 GHz) in an elevation angle of a planar array antenna having a spherical beam pattern according to an exemplary embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

10: coaxial feed microstrip radiating element (RA # 1 to RA # 4)

20: 1-4 row divider (CD # 1 to CD # 8)

30: 1-8 heat splitter block (RD # 1 to RD # 4)

40: 1-4 Input Power Divider (IPD)

RH1 to RH7: 180 ^o ring hybrid coupler element

Z ₁ , Z ₂ : Characteristic impedance of transmission line of hybrid coupler element

E ₁ ~ E ₃ : Electrical length of transmission line of hybrid coupler element

60: 50Ω termination element (T1 # 1 to T1 # 3, T2 # 1 to T2 # 7)

The present invention relates to a planar array antenna having a spherical beam pattern, and more particularly, to a planar array antenna having a spherical beam pattern applicable to a multi-sector base station antenna system.

In the conventional base station antenna system, an array antenna having a general shaped beam pattern is used.

However, when more sector beams than conventional three sector beams 120 ^o are applied to the base station antenna system in order to increase traffic capacity and increase maximum capacity in the future, the conventional array antenna having a general shaped beam pattern becomes narrower. The application is difficult because of the cross-over problem between the width and the adjacent beam.

Thus, the mobile communication base station antenna system can provide many independent beams with various beam shapes and various gains, and has low side lobe characteristics that can provide uniform gain within the beam width and sharp drop off beam edges. Antennas should be applied.

In general, the spherical sector beam pattern shows low antenna aperture efficiency and low side lobe level characteristics in terms of pattern characteristics, and thus is suitable for an antenna system having a multi-sector beam.

Conventional spherical beam pattern implementation techniques include an array structure using passive multi-terminal networks, an array structure using coupled dual-mode waveguides, a passive reaction load element array structure, an array structure using similar optical networks, and an array using protruding dielectric bars. There is also a recently announced multi-layer circular conductor array structure, of which a passive multi-terminal network, which is advantageous when obtaining a relatively large spherical beam pattern such as a spherical beam pattern width of 60 ^o to 90 ^o , has a spherical beam pattern. It is desirable to implement an array antenna.

On the other hand, implementing a two-dimensional power supply circuit with a conventional amplitude control method for distributing the current distribution of the antenna aperture to obtain a spherical beam pattern, the phase component is changed to 0 ^o or 180 ^o and the amplitude component change is relatively severe. Therefore, there is a problem that the power supply circuit becomes complicated.

Therefore, an implementation of an antenna capable of simplifying a power supply circuit by forming a spherical beam pattern by controlling the phase component of the amplitude component among the current distribution of the antenna aperture is performed.

The present invention has been proposed to meet the above requirements, and has a spherical beam pattern through a planar array structure using a passive multi-terminal network to reduce beam interference with adjacent cells and to achieve uniform gain characteristics and low within the desired beam directing range. It is an object to provide a planar array antenna having side lobe characteristics.

It is also an object of the present invention to provide a planar array antenna in which a radiating element has a specific amplitude component in the form of a Gaussian distribution and controls a phase component so that the power supply circuit has a simple spherical beam pattern.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. In addition, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

The present invention for achieving the above object is an array antenna for forming a spherical beam pattern in the azimuth or elevation direction by controlling the phase component to have a constant distribution of the amplitude component of the antenna aperture surface, the same as the signal received from the outside Input power distribution means for distributing and outputting a signal having power and phase; First distributing means for distributing electric power and controlling a phase of the signal received from the input electric power distributing means so as to satisfy a predetermined rectangular beam pattern power supply requirement; Second distributing means for distributing and outputting a signal received from the first distributing means into a signal having the same power and phase; And radiating means for radiating a signal received from the second distribution means to the free space.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, whereby those skilled in the art may easily implement the technical idea of the present invention. There will be. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The planar array antenna having the spherical beam pattern may be applied to a multi-sector base station antenna system as shown in FIGS. 1A and 2A below.

1A is an exemplary diagram illustrating an embodiment of a planar array antenna having a spherical sector beam pattern to which the present invention is applied.

The present invention is applicable to a planar array antenna having a spherical sector beam pattern arranged in one column — six sectors as shown in FIG. 1A.

FIG. 1B is an exemplary diagram showing beam coverage in the azimuth direction of the planar array antenna shown in FIG. 1A.

Figure 2a is an exemplary view showing another embodiment of a planar array antenna having a rectangular sector beam pattern to which the present invention is applied.

More specifically, FIG. 2A illustrates a planar array antenna structure having a spherical sector beam pattern arranged in two columns — six sectors as an embodiment to which the present invention is applied when spatial multiplexing of antenna beams is required.

2B is an exemplary diagram showing beam coverage of a planar array antenna embodiment having a spherical sector beam pattern to which the present invention is applied.

More specifically, FIG. 2B illustrates beam coverage of a planar array antenna having a spherical sector beam pattern arranged in one column_six sectors and two columns_12 sectors as an embodiment to which the present invention is applied.

The antenna structure may be implemented as a single-row array structure of multiple beam antennas or a two-row array structure of single beam antennas.

On the other hand, the planar array antenna may control the power (or current) amplitude and phase of the antenna aperture to form a desired spherical beam pattern.

That is, the power (or current) amplitude and phase combination of the antenna aperture is determined by the required spherical beam width, which may result in several amplitude and phase combinations depending on the limiting performance of the desired pattern.

In the present description has a 90 ^o rectangular beam pattern in the azimuth direction, as an embodiment of the present invention, the elevation angle direction in a description is made of the planar array antenna design having a fixed form beam patterns of 10 ^o.

The spacing of the array antenna elements for obtaining the required beam pattern such 0.55λ _o the azimuth direction, is 0.65λ _o the elevation direction.

In the planar array antenna according to the preferred embodiment of the present invention, the aperture power (or current) distribution used to form the 90 ^o spherical beam pattern in the azimuth direction uses a method of controlling amplitude and phase, and symmetrically. A total of 16 array elements, 8 each, were used.

According to a preferred embodiment of the present invention, data representing the required amplitude and phase distribution of the 16 antenna array elements arranged in the azimuth direction are shown in Table 1 below, and the graph is shown in FIG. 3.

The mobile communication base station antenna for the IMT2000 is considered as an application field for the planar array antenna with the 90 ^o spherical beam pattern. Design specifications of such an antenna are shown in Table 2 below.

4 is a configuration diagram of an embodiment of a planar array antenna having a spherical beam pattern according to the present invention.

As shown in FIG. 4, the planar array antenna having a spherical beam pattern according to the present invention having a symmetrically divided into four parts is composed of a feed network and 128 radiating elements.

The feed network consists of 4 input power divider (IPD) 40, 4 heat divider (RD # 1 ~ RD # 4) (30), 32 (= 8x4) row divider (CD # 1 ~ CD # 8) (20) It includes, the radiating element 10 is a microstrip radiating element (RA # 1 ~ RA # 4) is applied.

The input power divider 40 has a Wilkinson power divider structure, and outputs four signals having four identical powers and phases to four heat dividers 30 by using an antenna input signal AI received from the outside. It provides high isolation between each output terminal.

In addition, the heat distributor 30 uses the 180 ^o ring hybrid coupler as a basic element to satisfy the power supply (amplitude and phase) requirements of the input power divider 40 as shown in [Table 1] and FIG. 3. The power is distributed and the phase is controlled so as to be output to eight row dividers 20 connected by coaxial cables. At this time, the heat splitter 30 has excellent isolation characteristics between terminals, and the unused isolation terminals among the four terminals of the 180 ^o ring hybrid coupler element are matched to 50 Hz, and the short circuit is a 0.25 wavelength transmission line. Is implemented.

In addition, the row divider 20 uses a Wilkinson power divider as a basic structure, and supplies the same amplitude and phase to the four radiating elements connected by coaxial pins using the signal received from the corresponding column divider 30, and between each radiating element. High isolation properties.

The functional mutual relationship of each component is summarized as follows.

The input power divider 40 divides and outputs the signal AI input to the antenna into four signals having the same power and phase, and outputs the four signals divided by four heat splitters (RD # 1 to RD) by the same coaxial cable. # 4) (30).

Each heat distributor 30 outputs eight signals satisfying the feeding (amplitude and phase) requirements as shown in [Table 1] or FIG. 3 using a 180 ^o ring hybrid coupler as a base element.

The eight output signals are input to the corresponding row dividers (CD # 1 to CD # 8) 20 via coaxial cables. At this time, the length of the coaxial cable can be adjusted to satisfy the required amplitude and phase conditions. A detailed description of the row divider will be provided later with reference to FIG. 9.

Each row divider 20 provides the same output power and phase distributed to each of the four radiating elements connected through the coaxial feeder FP1 using the signal received from the corresponding column divider.

5 is a front view and a cross-sectional view showing an embodiment structure of a radiating element having a coaxial feed according to the present invention.

As shown in FIG. 5, the radiating elements (RA # i, i = 1 to 4) 10 according to the present invention having a coaxial feeding structure are microstrip structures, respectively, having a length L = 67mm and a width W = 34 mm, Coaxial feeding has a position lexe = 53.5 mm and a height h = 8 mm. Between h heights are filled with air.

6A shows a PCB layout as a detailed structural diagram of one embodiment of a row divider in accordance with the present invention.

A row divider (CD # i, i = 1, 4) 20 having a structure as shown in FIG. 6A using a 1: 1 Wilkinson power divider as a base element receives the same power and receives the same power. And output signals having a phase characteristic (Output 1 to Output 4). That is, one input has four identical outputs.

The input and output VSWR of the Wilkinson power divider used as the base element used in the feed circuit is less than 1.2 in the 1.92 to 2.17GHz operating band, and the insertion loss is less than 3.3dB in bandwidth. As the isolation resistor R, a 100kΩ chip resistor is used.

In addition, four radiating elements 10 are connected to one row divider 30 by coaxial pins FP1, and each of the four radiating elements 10 listed in the vertical (or elevation) direction in FIG. 4 has the same amplitude and Phase is provided.

6B is an outline view of the radiating element and the row divider according to the structure of FIGS. 5 and 6A.

7A shows a PCB layout as a detailed structural diagram of an embodiment of a heat distributor according to the present invention.

As described above, four heat distributors RD # i, i = 1, 8) 30 are required for the entire array antenna, and each heat distributor 30 has left and right symmetrical structures.

The PCB diagram (layout) of each heat distributor 30 is the same as that of FIG. 7A, using a 180 ^o ring hybrid coupler as a base element.

180 ^o-ring structure of the hybrid coupler is excellent in isolation characteristic between the input and output VSWR, and a terminal in a relatively wide band as compared to the 90 ^o branch-line hybrid structure.

Figure 7b is an illustration of an embodiment of a 180 ^o ring hybrid coupler device according to the present invention, Figure 7c is an external view of a heat distributor manufactured according to Figures 7a and 7b.

Seven 180 ^o ring hybrid coupler elements as shown in FIG. 7B are used for each heat distributor. The design parameters of each ring hybrid coupler are shown in Table 3 below.

The heat distributor 30 outputs eight required amplitude and phase values at one input to form a 90 ^o spherical beam pattern.

In addition, the eight outputs of one column divider 30 are connected via a coaxial cable with each input of the row divider 20.

It is 2.0 or less within the bandwidth as an electrical characteristic of the heat distributor 30 manufactured according to the preferred embodiment of the present invention, the isolation characteristic between the output terminals is 20dB or more.

The matching load used in the 180 ^o ring hybrid coupler according to the present invention was experimentally adjusted with a λ / 4 open microstrip line and a 50 kW chip resistor was used as the termination resistor.

Electrical short-circuits in the ultra-high frequency band can be realized with λ / 4 open microstrip lines.

8A is a detailed structural diagram of an embodiment of an input power divider according to the present invention, showing a PCB layout.

As shown in FIG. 8A, the input power divider (IPD) 40 has a structure similar to the row divider 20.

The input power divider 40 outputs the same power and phase characteristics, and the appearance of the input power divider manufactured according to the structure of FIG. 8A is the same as that of FIG. 8B.

The input power divider 40 uses a 1: 1 Wilkinson power divider as a base element, and four heat dividers 10 are connected to one input power divider 40 through a coaxial cable.

Hereinafter, a process of obtaining a relative power ratio and phase difference in each radiating element required by the planar power feeding array antenna will be described with reference to FIG. 9.

9 is an exemplary view showing an experimental correction device for correcting the relative power ratio and phase difference of the planar array antenna according to the present invention.

Relative required power ratios and phase differences between the input power divider IPD and the four heat dividers RD # i, i = 1 and 8 may be implemented through the experimental correction apparatus as shown in FIG.

Three of the four outputs of the input power divider (IPD) are fitted with 50-kV termination elements (T1 # i, i = 1, 3) and the remaining output terminals remain connected to the corresponding heat divider (RD # 1).

In addition, seven of the eight output terminals of the RD # 1 heat splitter are output terminals # 2 (CD # 2), the remaining one output terminal terminated by a 50-kΩ termination element (T2 # i, i = 1, 7). Only connecting terminals are used for the experiment.

Therefore, the relative required power ratio and phase difference are experimentally measured and corrected between the antenna input terminal (AI) and the output terminal of RD # 1 heat splitter # 2.

In the same way, the same is done for all output terminals of the RD # 1 heat splitter and for the remaining heat splitters.

Experimental calibration results of each heat splitter measured and calibrated according to the above process are shown in Table 4 below.

For reference, the requirements are based on the values of the heat splitter RD # 4, and the relative required amplitude ratio and phase error of each heat splitter show 1.3 dB rms amplitude error and 8.1o rms phase error, respectively. If we consider only the 5, 6, 7, and 8 array elements that are sensitive to the spherical beam pattern characteristics, they show 0.6 dB rms amplitude error and 6.1o rms phase error, respectively. These results indicate that 1, 2, 3, and 4 array elements are less sensitive to spherical beam pattern characteristics, and that it is difficult to accurately implement a relatively large amplitude ratio (-20 to -26 dB) on a feeder circuit. do. The relative required amplitude ratios and phase differences in Table 1 or FIG. 3 required by the entire array element are corrected using coaxial cables based on Table 4.

Figure 10a is an exemplary view showing a LOST o'clock front of the plane array antenna having a 90 ^o rectangular beam pattern according to the invention, Figure 10b is a one embodiment the back of the plane array antenna having a 90 ^o rectangular beam pattern according to the invention It is an exemplary figure to show.

10A and 10B show front and rear portions of a planar array antenna having a 90 ^o spherical beam pattern, respectively, fabricated as one preferred embodiment of the present invention.

Hereinafter, the radiation pattern characteristics of the planar array antenna having the spherical beam pattern according to the present invention will be described by comparing measured radiation pattern characteristics and simulation patterns with reference to FIGS. 11A to 11C and 12A to 12C.

The simulation results were obtained by multiplying the array pattern by the beam pattern of a microstrip patch radiating element actually designed using a commercial simulator, HFSS.

Measurement and simulation performance comparison graphs for the characteristics of Co_Pol and Cross_Pol radiation patterns in the azimuth direction. FIG. 11A shows f = 1.920 GHz, FIG. 11B shows f = 2.045 GHz, and FIG. 11C shows f = 2.170. The result obtained using GHz is shown.

Here, "Simulated Co_Pol" described in the figure is a simulated polarization radiation pattern, "Simulated Cross_Pol" is a simulated cross polarization radiation pattern, "Measured Co_Pol" is a measured polarization radiation pattern, and "Measured Cross_Pol" is simulation Cross-polarized radiation pattern.

The simulation and measurement results shown in FIGS. 11A-11C are slightly different in the side lobe portion, but the main beam portion of the beam pattern is almost identical, resulting in a satisfactory spherical beam having very low side lobe characteristics. It can be seen that.

In general, side lobe characteristics are greatly affected by the antenna's own performance and its reflection in the measurement room. Therefore, the beam pattern was measured by rotating the antenna 180 ^o to confirm the effect of the room environment. The beam pattern was symmetrical to the left and right, indicating that the room environment had little effect on the beam pattern. Could. Therefore, in the side lobe portion of the simulation and measurement results, the level difference is assumed to be due to the amplitude and phase error of the cable and the mutual coupling effect between the radiating elements. The measured side lobe level was above 22 dBc in band and the cross polarization level was above 30 dBc in the forward direction.

In addition, as a graph comparing the measurement and simulation performance of the characteristics of the polarization radiation pattern in the elevation angle, FIG. 12A shows results obtained at f = 1.920 GHz, FIG. 12B shows f = 2.045 GHz, and FIG. 12C shows f = 2.170 GHz, respectively. .

As shown in Figs. 12A to 12C, it can be seen that a normal shaped beam is formed in the elevation angle, and the measurement and simulation comparison results are very satisfactory. And the measured side lobe level was 12.8 dBc or more in band.

Antenna gain of the planar array antenna manufactured according to the preferred embodiment of the present invention was measured using a standard horn antenna (15.1 ~ 15.7dBi, 1.92 ~ 2.17GHz), the measurement results are shown in Table 5 below.

The ideal directivity of an antenna with a spherical beam pattern of 90 degrees in the azimuth direction and a general beam pattern of 10 degrees in the elevation direction is about 16 dBi.

The simulation results and the measurement results in [Table 5] showed very similar results, showing a 14.0 dBi value at the center frequency of 2.045 GHz.

Antenna efficiency is presumed to be due to errors (phase and amplitude) of the cabling cable, circuit loss, the effect of mutual coupling between radiating elements, and irregularities. Compared with the spherical beam pattern antenna having the same aperture, it can be seen that the antenna having the spherical beam has a relatively very low directivity.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings. For example, the radiating element may be applied by substituting the direct feeding micro strip stack radiating element instead of the coaxial feed micro strip single radiating element described above as an embodiment.

As described above, the present invention has the effect of reducing beam interference with adjacent cells and forming a spherical beam having uniform gain characteristics and low side lobe characteristics within a desired beam directing range. The effect is simple to implement.

On the other hand, the present invention can be useful in the design of the base station microcell by reducing the beam interference with the surrounding area, and in the near field wireless network communication, ITS (Intelligent Transport System) communication, including the application field of the base station antenna for mobile / satellite communication / broadcasting In addition, there is an additional effect that can be directly utilized in a low profile planar array antenna system in which communication is performed only within a limited service area.

Claims (8)

Input power distribution means for distributing and outputting a signal received from the outside into a signal having the same power and phase; First distributing means for distributing power and controlling a phase of the signal received from the input power distributing means to satisfy a rectangular beam pattern feeding requirement; Second distributing means for distributing and outputting a signal received from the first distributing means into a signal having the same power and phase; And Radiating means for radiating a signal received from the second distribution means to a free space Array antenna having a spherical beam pattern comprising a. The method of claim 1, The input power distribution means divides and outputs one input signal into four signals, and the first distribution means divides and outputs one input signal into eight signals and the second distribution means outputs one input signal. Outputting by dividing into four signals Array antenna having a spherical beam pattern, characterized in that. The method of claim 1, The radiating means and the second distribution means are connected by coaxial pins, the second distribution means and the first distribution means are connected by a coaxial cable, and the first distribution means is coaxial with the same length as the input power distribution means. Connected by cable Array antenna having a spherical beam pattern, characterized in that. The method according to any one of claims 1 to 3, The radiating means An array antenna having a spherical beam pattern, characterized by radiating linear vertical polarization using a coaxial feed microstrip radiating element. The method according to any one of claims 1 to 3, The radiating means An array antenna having a spherical beam pattern characterized by radiating linear vertical polarization using a direct feed microstrip stack element. The method according to any one of claims 1 to 3, The first distribution means and the second distribution means An array antenna having a spherical beam pattern, characterized by using a Wilkinson power divider structure. The method according to any one of claims 1 to 3, The second distribution means An array antenna having a spherical beam pattern, characterized by using a 180 ^o ring hybrid coupler structure. The method of claim 7, wherein The second distribution means An array antenna having a spherical beam pattern, characterized by using a λ / 4 microstrip transmission line as a short circuit.

Images