A compact planar Van Atta array with a loading cross structure

Abstract

The application discloses a compact planar Van Atta array loaded with cross structure, comprising 2N 2 antenna pairs, each of which is composed of two antenna units as receiving unit and transmitting unit respectively, wherein at least two antenna pairs are connected by a cross structure, each cross structure connects two antenna pairs, the cross structure is formed by cascading two branch line couplers, has the characteristic that signals are transmitted only along diagonal ports, and the connection line length of the cross structure and the antenna units is adjusted, so that the two antenna pairs connected by the cross structure have equal phase. The application connects the antenna pairs by the cross structure, so that the structure of the planar Van Atta array is more compact and is easy to integrate; the direction backtracking function can be realized by only using a single-layer structure, the antenna profile is lower, the antenna does not need to be perforated, the cost is lower, and the application can be applied to a two-dimensional array, so that the application prospect is wider.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology, and specifically relates to a compact planar Van Atta array with a loaded cross structure. Background Technology

[0002] Van Atta array is an antenna array that can achieve beamback. It consists of antenna pairs that are equidistant from the center of the antenna array. Each antenna pair is connected by a transmission line of equal length to ensure that different antennas have the same phase delay. The signal received by each antenna element is radiated by the antenna element paired with it, thus realizing the direction backtracking function.

[0003] Existing Van Atta arrays are classified into two types based on their array configuration: linear arrays and planar arrays. In a planar Van Atta array, the corresponding elements are diagonally distributed along the geometric center of the array. When the antenna array and transmission lines are placed in the same plane, wiring is typically done by wrapping wires around the antenna, which significantly increases the size of the antenna array. Furthermore, as the number of array elements increases, the number of transmission lines also increases. Continuing with the wrapping method will lead to wiring intersection problems. To prevent each transmission line from crossing, the feed network and antenna elements are usually placed in layers, thus ensuring that each antenna pair can function normally.

[0004] In 2000, Wen-Jen Tseng designed a 3×4 planar Van Atta array using slot coupling. Energy was coupled to the antenna elements through the slots between two dielectric substrates via six feed lines, thus achieving direction backtracking. In 2016, Kin Shing Bobby Yau fabricated a 16-element planar Van Atta array, using a double-layer structure to house the antenna elements and complex microstrip network, and connecting the feed network and antenna elements through metal vias. In 2022, Xiao-Fei Li proposed a planar two-dimensional Van Atta array with 64 antennas and 32 transmission lines. Due to the large number of transmission lines, they used two dielectric layers to house the feed network and placed isolation vias between the two dielectric layers to eliminate the influence of the double slots on the feed. An air layer was also added between the feed network and the antenna array to ensure phase consistency.

[0005] As can be seen from the above literature, existing planar Van Atta arrays all use non-intersecting transmission lines to connect each antenna pair, and employ a layered structure where the feed network and antenna array are placed separately. Due to the large number of transmission lines and their inability to intersect, the feed network wiring of planar Van Atta arrays is complex. Furthermore, the multi-layered structure increases the array's profile height and design costs.

[0006] Currently, most designs for Van Atta array feed networks adopt the traditional microstrip line non-crossing structure. In 2022, Youlin Du from the University of Electronic Science and Technology of China proposed a backtracking antenna array based on the Butler matrix. It realizes a one-dimensional backtracking array with crossover transmission lines by utilizing the phase allocation relationship of the Butler matrix. Although it realizes a backtracking array with crossover transmission lines, the Butler matrix wiring method it uses is still very complex. Moreover, it only studies one-dimensional backtracking arrays and does not extend it to two-dimensional arrays. Furthermore, it uses a multi-layer feeding method, which requires metal vias to connect the array and the feed network, resulting in a high antenna profile.

[0007] In general, the main problems with the aforementioned existing technologies include:

[0008] (1) In order to meet the conjugate phase requirement for backtracking, the transmission lines in the Van Atta array cannot be shared or crossed. Therefore, each antenna pair needs to be connected by an independent transmission line, resulting in a large number of transmission lines, a large array size, and high processing costs.

[0009] This invention aims to solve the problems of transmission lines not being able to cross, antenna pairs not being able to share transmission lines, and complex wiring methods in the feed network of planar Van Atta arrays.

[0010] (2) Existing planar Van Atta arrays have a large number of transmission lines, making it difficult to place the transmission lines and antennas on the same plane. Therefore, a multi-layer structure is adopted, in which the antennas and feed networks are placed in layers. The multi-layer structure not only increases the array height, but also increases the processing difficulty and processing cost. Summary of the Invention

[0011] In order to overcome the shortcomings of the prior art, the present invention aims to provide a compact planar Van Atta array with a loaded cross structure, which mainly solves the problems of the planar Van Atta array feed network being difficult to place coplanar with the antenna element, high antenna profile, and high processing cost.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0013] A compact planar Van Atta array with a loading cross structure, characterized in that it comprises 2N×2N antenna elements. 2There are 10 antenna pairs, each consisting of two antenna elements that serve as a receiving unit and a transmitting unit, respectively. At least 2 antenna pairs are connected by a cross structure, and each cross structure connects 2 antenna pairs. The cross structure is formed by cascading two branch line couplers and has the characteristic that the signal is transmitted only along the diagonal ports. The length of the connection line between the cross structure and the antenna elements is adjusted to ensure that the two antenna pairs connected to it have equal phase.

[0014] In one embodiment, N=2 k k is a natural number. The antenna elements in the array are arranged in rows and columns. The distance between adjacent antenna elements is 0.5λ0, where λ0 is the wavelength in vacuum corresponding to the operating frequency of the array. Along the center of the array, two antenna elements located in the same oblique direction and equidistant from the center of the array form an antenna pair.

[0015] In one embodiment, the 2N 2 Of the antenna pairs, there are 2 n The two antenna pairs are connected by n cross structures. n In each pair of antennas, every two antenna pairs are connected by a cross structure, and 1 ≤ n ≤ N.

[0016] In one embodiment, the 2N×2N antenna elements are arranged symmetrically along the geometric center of the dielectric substrate, with 4N antenna elements in the Nth and N+1th columns or 4N antenna elements in the Nth and N+1th rows forming the 2N×2N antenna elements. n One antenna pair.

[0017] In one embodiment, apart from the antenna pairs connected by a cross structure, the remaining antenna pairs are connected in a manner where transmission lines do not cross each other.

[0018] In one embodiment, the antenna element is rectangular and consists of a radiating patch and a microstrip feed line connected together, with a gap between the radiating patch and the microstrip feed line. The impedance matching of the antenna element is adjusted by adjusting the length and width of the gap.

[0019] In one embodiment, in each antenna pair connected by a cross structure, one antenna element is placed facing forward, and the other antenna element is placed in reverse. They are connected through the cross structure and a microstrip phase shifter, which compensates for the phase change caused by the reversal. The forward placement means that the radiating patch of the same antenna element is on the side away from the cross structure, and the microstrip feed line is on the side closer to the cross structure. The reverse placement means that the radiating patch of the same antenna element is on the side closer to the cross structure, and the microstrip feed line is on the side away from the cross structure.

[0020] In one embodiment, the length of the connection line between the cross structure and the antenna element is adjusted by increasing or decreasing the length of the microstrip feed line or microstrip phase shifter of the antenna element. In one embodiment, the two branch line couplers are cascaded, wherein the input end of the first branch line coupler serves as the P1 port of the cross structure, the isolation end serves as the P3 port of the cross structure, the through end is connected to the input end of the second branch line coupler, and the coupling end is connected to the isolation end of the second branch line coupler. The through end and coupling end of the second branch line coupler serve as the P2 port and P4 port of the cross structure, respectively. One antenna pair is connected to the P1 port and P4 port, and the other antenna pair is connected to the P2 port and P3 port, thereby realizing a cross structure connecting two antenna pairs.

[0021] In one embodiment, the main line, bypass line, and branch line are folded to a certain extent by loading an equivalent capacitance stub inside the branch line coupler or by using spatial folding, thereby achieving miniaturization.

[0022] Compared with existing technologies, this invention uses a cross structure to connect antenna pairs, making the planar Van Atta array more compact and easier to integrate; it can achieve direction backtracking function with only a single layer structure, with a lower antenna profile, no need for drilling, and lower cost; and it can be applied to two-dimensional arrays, with a wider range of application prospects. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a multi-plane Van Atta array with a cross structure according to the present invention.

[0024] Figure 2 The power supply network for a 16-element planar Van Atta array with a cross-structure is provided in this embodiment of the invention.

[0025] Figure 3 This is a schematic diagram of a 4-element planar Van Atta array model with a loaded cross structure, according to an embodiment of the present invention.

[0026] Figure 4 This paper compares the wiring method of the present invention with the wiring method of the traditional planar Van Atta array, where (a) is the wiring method of the traditional planar Van Atta array and (b) is the wiring method of the present invention.

[0027] Figure 5 This is a schematic diagram of the antenna unit model used in an embodiment of the present invention.

[0028] Figure 6 This is a schematic diagram of the cross structure model used in an embodiment of the present invention.

[0029] Figure 7The following are simulation results of the antenna element used in the embodiments of the present invention, where (a) is the reflection coefficient and (b) is the radiation pattern.

[0030] Figure 8 The above are the S-parameter simulation results of the cross structure used in the embodiments of the present invention.

[0031] Figure 9 The simulation results of the backtracking array designed in the embodiment of the present invention in the plane of Phi = 0° are shown in single-station and dual-station RCS, where (a) is the single-station RCS and (b) is the dual-station RCS.

[0032] Figure 10 The simulation results of the backtracking array designed in the embodiment of the present invention in the plane of Phi = 90° are shown in single-station and dual-station RCS, where (a) is the single-station RCS and (b) is the dual-station RCS. Detailed Implementation

[0033] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0034] As mentioned earlier, in existing planar Van Atta arrays, each antenna pair requires an independent transmission line connection, while the transmission lines in the feed network cannot be shared, leading to complex wiring. During wiring, the complex feed network is difficult to place on the same layer as the antenna array, resulting in a high array profile, significant design challenges, and high manufacturing costs.

[0035] To address the problem of numerous transmission lines and complex wiring in two-dimensional Van Atta arrays, this invention employs a cross-connection structure to link antenna pairs in a planar Van Atta array. By sharing transmission lines through this cross-connection structure, the problem of incompatible transmission lines and complex wiring in two-dimensional Van Atta array feed networks can be solved. Furthermore, the cross-connection structure and antenna array used in this invention can be placed on the same layer, thus resolving the issue of numerous antenna layers, significantly reducing the height of the Van Atta array, and decreasing manufacturing difficulty and cost.

[0036] like Figure 1 As shown, the compact planar Van Atta array with a cross-structure of the present invention includes 2N×2N antenna elements 1, with each antenna element 1 paired up to form a total of 2N. 2Each antenna pair consists of two antenna elements 1, which serve as the receiving and transmitting units, respectively. To avoid complex transmission line wiring in the feed network, this invention introduces a cross structure 3. The cross structure 3 is composed of two cascaded branch line couplers 6, with a total of 4 ports. It has the characteristic that signals are transmitted only along the diagonal ports while the other ports are basically isolated. The 4 ports of one cross structure 3 connect the 4 antenna elements 1 that make up the 2 antenna pairs. In an array, at least 2 antenna pairs are connected by one cross structure 3. At the same time, since all antenna pairs need to maintain the same phase, for the antenna pairs connected by the cross structure 3, it is necessary to adjust the length of the connection line between the cross structure 3 and each antenna element 1 to ensure that the 2 antenna pairs connected have equal phase.

[0037] Based on the above design, this invention introduces a cross structure 3 into the feed network of the planar Van Atta array, forming a novel feed network that allows the transmission lines of the planar Van Atta array to be shared. Due to the unique transmission characteristics of the cross structure 3, the conjugate phase requirement for backtracking can be guaranteed while sharing transmission lines. The feed method adopted in this invention makes the planar Van Atta array smaller and easier to integrate.

[0038] In some embodiments of the present invention, N is 2. k Where k is a natural number, representing the number of antenna elements 1 in the array as 4, 16, 64, etc., corresponding to the number of antenna pairs as 2, 8, 32, etc. The antenna elements 1 in the array are arranged in rows and columns, with a distance of 0.5λ0 between adjacent antenna elements 1, where λ0 is the wavelength in vacuum corresponding to the array's operating frequency. It is worth noting that, with current technology, a single-layer structure with coplanar placement of antenna elements and the feed network is limited to situations with a small number of array elements (the array is generally no larger than 4×4). When the number of array elements increases, limitations in transmission line width, line spacing, and array element spacing make it difficult to continue with coplanar placement. In such cases, a layered placement of the feed network and array elements may be necessary. With future advancements in materials and processing technologies, this invention may be applicable to larger arrays.

[0039] The number of antenna pairs connected by a cross structure can be selected according to the array size and space requirements, and the number should generally be a factor of 2. That is, there are 2 n The antenna pairs are connected by n cross structures 3, in which 2 n In each pair of antennas, every two antenna pairs are connected by a cross structure 3, where 1 ≤ n ≤ N.

[0040] Furthermore, in the 2N×2N antenna elements 1 arranged in rows and columns, the 4N antenna elements 1 in the Nth column and the (N+1)th column, or the 4N antenna elements 1 in the Nth row and the (N+1)th row, constitute the 2 n Two antenna pairs, and these two n Each pair of antennas is connected by a cross structure 3. Preferably, all antenna pairs consisting of these 4N antenna elements 1 are connected pairwise by a cross structure 3. For example... Figure 1 As shown, for the 2N×2N planar Van Atta array, the antenna elements 1 in the Nth and N+1th columns located at the center of the array are connected using a cross structure 3. The other corresponding antenna elements are still connected using the traditional method of non-crossing transmission lines. At the same time, the line length of the output end of the cross structure 3 needs to be adjusted to ensure that each pair of antennas has the same phase to meet the phase requirements of the Van Atta array.

[0041] Figure 2 For an example of a 16-element array, the antenna elements in the first row, second column, and fourth row, third column form one antenna pair, and the antenna elements in the first row, third column, and fourth row, second column form another antenna pair. These two antenna pairs are connected by a crossover structure 3. Similarly, the antenna elements in the second row, second column, and third row, third column form one antenna pair, and the antenna elements in the second row, third column, and third row, second column form yet another antenna pair. These two antenna pairs are connected by another crossover structure 3. The remaining antenna pairs are still connected to each other using conventional, non-crossing transmission lines.

[0042] For ease of description and verification, this invention will be further explained using k=0 as an example. In this case, N=1, as follows... Figure 3 As shown, there are 4 antenna elements 1, named sequentially in clockwise order as element one, element two, element four, and element three. There are 2 antenna pairs; element one and element four form one antenna pair, and element two and element three form another. That is, two antenna elements distributed diagonally constitute one antenna pair. The figure also shows a dielectric substrate 7, but the ground plane is not shown. The planar VanAtta array is printed on the upper surface of the dielectric substrate 7, and the lower surface is the metal ground plane. Each antenna element 1 is arranged symmetrically in rows and columns along the geometric center of the dielectric substrate 7.

[0043] The following is a detailed explanation of the working principle of this invention:

[0044] In an antenna pair, two elements act as receiving or transmitting elements to receive plane waves or transmit signals. Taking element one as an example, when element one receives an incident wave, due to the characteristic of the cross structure 3 ensuring that energy is transmitted only along the diagonal ports while other ports are isolated, the signal will only be transmitted to element four via the cross structure 3, and will not be transmitted to element two or three. After receiving the energy, element four will transmit a signal pointing in the direction of the incident wave, thus achieving direction backtracking. Conversely, the plane wave energy received by element four will only be transmitted to element one and then transmitted by element one, pointing in the direction of the incident wave, and will not be transmitted to other elements. The same applies to elements two and three. The quality of the backtracking performance is reflected by the monostatic and bistatic RCS of the antenna array. The wider the monostatic RCS angle of the array and the closer the pointing angle of the bistatic RCS is to the incident wave, the better the backtracking performance.

[0045] refer to Figure 4 (a) illustrates the wiring method of transmission lines in a conventional planar Van Atta array feed network, and (b) illustrates the wiring method of the present invention. In a conventional Van Atta array, each pair of transmit and receive antennas requires a separate transmission line for connection. To prevent transmission lines from crossing, the transmission lines need to be routed around the antennas, increasing the array size. The crossing structure used in this invention allows transmission lines to cross, and antenna pairs can share transmission lines, resulting in a more compact planar Van Atta array structure that is easier to integrate.

[0046] The following are the specific structures and simulation results of each part of the present invention:

[0047] like Figure 5 As shown, antenna element 1 is rectangular and consists of a radiating patch 4 and a microstrip feed line 5. A gap is left between the radiating patch 4 and the microstrip feed line 5. By adjusting the length and width of this gap, the impedance matching of antenna element 1 can be adjusted.

[0048] In each antenna pair connected by a cross structure 3 in this embodiment of the invention, one antenna element 1 is placed facing forward. To make the array structure more compact, the other antenna element 1 is placed in reverse and connected to a microstrip phase shifter 2 via the cross structure 3. The microstrip phase shifter 2 can compensate for the phase change caused by the reversal. Antenna elements connected by independent, non-crossing transmission lines are not subject to this restriction and can all be placed facing forward. For example, in Figure 3 In the structure shown, units one and two are placed facing forward, while units three and four are placed in reverse. Therefore, the present invention can adjust the length of the connection line between the cross structure 3 and the antenna unit 1 in two ways: either by increasing or decreasing the length of the microstrip feed line 5 of the antenna unit 1, or by increasing or decreasing the length of the microstrip phase shifter 2.

[0049] In this invention, "orthogonal placement" means that the radiating patch 4 of the same antenna element is on the side away from the cross structure 3, and the microstrip feed line 5 is on the side closer to the cross structure 3. "Reversed placement" means that the radiating patch 4 of the same antenna element is on the side closer to the cross structure 3, and the microstrip feed line 5 is on the side away from the cross structure 3. (See reference...) Figure 3 As shown.

[0050] In this embodiment, the antenna array and the feed network are placed in the same plane. The two antenna elements are placed in opposite directions, and a microstrip phase shifter 2 is used to compensate for the phase change caused by the reversal. The feed network is placed in the middle of the antenna, making the entire array structure more compact, reducing the height of the array and reducing the manufacturing cost.

[0051] like Figure 6 The diagram shows a schematic of cross structure 3. Cross structure 3 consists of two cascaded 3dB branch line couplers 6. The input of the first branch line coupler serves as port P1 of cross structure 3, the isolation terminal serves as port P3, the through terminal is connected to the input of the second branch line coupler, and the coupling terminal is connected to the isolation terminal of the second branch line coupler. The through terminal and coupling terminal of the second branch line coupler serve as ports P2 and P4 of cross structure 3, respectively. One antenna pair is connected to ports P1 and P4, and the other antenna pair is connected to ports P2 and P3, thus connecting two antenna pairs in one cross structure 3.

[0052] This crossover design ensures that signals are transmitted only along the crossover port, with other ports completely isolated. That is, when a signal is input along port P1, only port P4 has a signal output. Similarly, when a signal is input along port P3, only port P2 has an output, and vice versa. Figure 6 Z0 and These are the characteristic impedances of each branch of the branch-line coupler, where Z0 is 50 ohms.

[0053] The branch line coupler 6 can have various designs, such as rectangular or circular. It can also be miniaturized by loading equivalent capacitance stubs internally or by using spatial folding to fold the main line, bypass line, and branch line to a certain extent.

[0054] Figure 7 Simulation results for antenna element 1 are given. From (a), it can be seen that the center frequency of the antenna element is 10 GHz, the operating frequency band is 9.91-10.11 GHz, and the maximum gain is 7.46 dBi. From (b), it can be seen that the half-power beamwidth of the E plane is 84.38° and the half-power beamwidth of the H plane is 84.38°.

[0055] Figure 8The simulation structure of cross structure 3 is given. When port P1 of cross structure 3 is the input port, only S is present at the center frequency. 14 The transmission coefficient of P4 is -0.21dB, and the transmission coefficients of other ports are all below -21.92dB. This indicates that when P1 port is input, only P4 port has a signal output, and the other ports are isolated. This shows that the cross structure 3 can ensure that energy is transmitted only between corresponding antenna elements and not to other elements.

[0056] Figure 9 and Figure 10 Simulation results of the RCS of the compact planar Van Atta array with the loading cross structure of this invention are presented when the incident plane is phi = 0° (E plane) and phi = 90° (H plane). Figure 9 (a) and Figure 10 (a) shows the results for a single station. Figure 9 (b) and Figure 10 (b) shows the results from two stations. In the description of this invention, unless otherwise specified, all RCS results refer to the normalized results. Figure 9 and Figure 10 The results show that the compact planar Van Atta array with a loading cross structure designed in this invention has a backtracking range (3dB beamwidth of monostatic RCS) of more than 81° in both the E-plane and H-plane. When the incident wave is incident at different angles, the backtracking wave (bistatic RCS) of the array can point to the direction of the incident wave, and the beam pointing error does not exceed 5°, which has excellent backtracking performance.

Claims

1. A compact planar Van Atta array with a loading cross structure, comprising 2N×2N antenna elements (1) forming a 2N array. 2 A pair of antennas, each pair consisting of two antenna elements (1) serving as a receiving element and a transmitting element respectively, characterized in that, At least two antenna pairs are connected by a cross structure (3), the cross structure (3) and the antenna array are placed on the same layer, each cross structure (3) connects two antenna pairs, the cross structure (3) is formed by cascading two branch line couplers (6), and has the characteristic that the signal is transmitted only along the diagonal port. Adjust the length of the connection line between the cross structure (3) and the antenna element (1) to ensure that the two antenna pairs connected to it have equal phase. The two branch line couplers (6) are cascaded. The input end of the first branch line coupler serves as the P1 port of the cross structure (3), the isolation end serves as the P3 port of the cross structure (3), the through end is connected to the input end of the second branch line coupler, and the coupling end is connected to the isolation end of the second branch line coupler. The through end and coupling end of the second branch line coupler serve as the P2 port and P4 port of the cross structure (3) respectively. One antenna pair is connected to the P1 port and the P4 port, and the other antenna pair is connected to the P2 port and the P3 port, so that one cross structure (3) connects two antenna pairs.

2. The compact planar Van Atta array with a loading cross structure according to claim 1, characterized in that, The N=2 k k is a natural number. The antenna elements (1) in the array are arranged in rows and columns. The distance between adjacent antenna elements (1) is 0.5λ0, where λ0 is the wavelength in vacuum corresponding to the operating frequency of the array. Along the center of the array, two antenna elements (1) located in the same oblique direction and equidistant from the center of the array form an antenna pair.

3. The compact planar Van Atta array with a loading cross structure according to claim 2, characterized in that, The 2N 2 Of the antenna pairs, there are 2 n The two antenna pairs are connected by n cross structures (3), the two n In each pair of antennas, every two pairs of antennas are connected by a cross structure (3), where 1 ≤ n ≤ N.

4. The compact planar Van Atta array with a loading cross structure according to claim 3, characterized in that, The 2N×2N antenna elements (1) are arranged symmetrically along the geometric center of the dielectric substrate (7), forming the 2N×2N antenna elements (1) of the Nth column and the (N+1)th column or the 4N antenna elements (1) of the Nth row and the (N+1)th row. n One antenna pair.

5. The compact planar Van Atta array with a loading cross structure according to claim 3, characterized in that, Except for the antenna pairs connected by the cross structure (3), the other antenna pairs are connected by transmission lines that do not cross each other.

6. The compact planar Van Atta array with a loading cross structure according to claim 1, characterized in that, The antenna unit (1) is rectangular and consists of a radiating patch (4) and a microstrip feed line (5). There is a gap between the radiating patch (4) and the microstrip feed line (5). The impedance matching of the antenna unit (1) can be adjusted by adjusting the length and width of the gap.

7. The compact planar Van Atta array with a loading cross structure according to any one of claims 6, characterized in that, In each antenna pair connected by a cross structure (3), one antenna element (1) is placed facing forward, and the other antenna element (1) is placed in reverse. They are connected through the cross structure (3) and the microstrip phase shifter (2). The phase change caused by the reversal is compensated by the microstrip phase shifter (2). The forward placement means that the radiating patch (4) of the same antenna element is on the side away from the cross structure (3), and the microstrip feed line (5) is on the side close to the cross structure (3). The reverse placement means that the radiating patch (4) of the same antenna element is on the side close to the cross structure (3), and the microstrip feed line (5) is on the side away from the cross structure (3).

8. The compact planar Van Atta array with a loading cross structure according to claim 7, characterized in that, The length of the connection line between the cross structure (3) and the antenna element (1) is adjusted by increasing or decreasing the length of the microstrip feed line (5) or the microstrip phase shifter (2) of the antenna element (1).

9. The compact planar Van Atta array with a loading cross structure according to claim 1, characterized in that, The main line, bypass line and branch line are folded to a certain extent by loading an equivalent capacitance stub inside the branch line coupler (6) or by using spatial folding. This achieves miniaturization.

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