Numerical analysis zero point reconfigurable method for designing subarray directional diagram

Abstract

The invention provides a numerical analysis zero point reconfigurable method for designing a sub-array directional diagram, which comprises the following steps of: 1, designing a 40% relative bandwidth sub-array, and respectively extracting two orthogonal plane directional diagrams of a highest frequency band, a center frequency band and a lowest frequency band; step 2, performing numerical analysis on the sub-array radiation pattern, extracting influence parameters of the zero position and the null depth of the pattern, and adjusting corresponding parameters for designing the sub-array pattern, so that the zero position of the sub-array pattern needs to correspond to the array factor grating lobe position, and the zero position of the sub-array pattern needs to correspond to the array factor grating lobe position; the zero point of the sub-array directional diagram and the array factor grating lobe can be mutually counteracted by the null depth; and step 3, determining a structural feed network of the phase shifter capable of realizing 0-degree and 68-degree phase adjustability, wherein the structural feed network is used for realizing independent regulation and control on the phase difference of the two units in the subarray. According to the invention, + / -30-degree grating lobe-free scanning of the array with the array element center-to-center distance of 1 lambda can be realized, and good gain flatness can be maintained.

Description

Technical Field

[0001] The present application relates to the technical field of microwave antennas, and in particular to a numerical analytical zero-point reconfigurable method for designing subarray directional patterns. Background Art

[0002] Large-pitch arrays are a key approach to reducing the cost of beam-scanning arrays. By increasing the element spacing (typically greater than half a wavelength), they reduce the number of active elements in the array for the same aperture, thereby saving on transceiver components connected to the antenna array. While this design offers advantages, it also has numerous disadvantages.

[0003] Specifically, its advantages include the following: First, the reduced number of array elements makes the array thinner and lighter. Second, large-pitch arrays are simpler to manufacture than conventional antenna arrays, making them easier to process and assemble, and significantly reducing manufacturing costs. Furthermore, the reduced use of RF channels helps dissipate heat and save energy. However, its greatest drawback is the scanning grating lobe problem caused by the excessively large element spacing. Therefore, research on the effective suppression of grating lobes in large-pitch arrays is of great significance. Summary of the Invention

[0004] The present application provides a numerical analytical zero-point reconfigurable method for designing subarray radiation patterns, which can be used to solve the technical problem of reasonably suppressing grating lobes in large-spacing arrays.

[0005] The present application provides a numerical analytical zero-point reconfigurable method for designing a subarray pattern, the method comprising:

[0006] Step 1: Design a 40% relative bandwidth subarray and extract two orthogonal plane radiation patterns of the highest frequency, center frequency, and lowest frequency bands respectively;

[0007] Step 2: Perform numerical analytical analysis on the radiation pattern of the sub-array, extract the influencing parameters of the pattern zero point position and the nulling depth, and adjust the corresponding parameters to design the sub-array pattern so that the sub-array pattern zero point position corresponds to the array factor grating lobe position, and the nulling depth can make the sub-array pattern zero point and the array factor grating lobe cancel each other.

[0008] Step 3: Determine the structural feeding network of the phase shifter that can achieve 0-degree and 68-degree phase adjustment, which is used to independently control the phase difference between two units in the subarray.

[0009] Furthermore, step 1 designs a 40% relative bandwidth subarray to extract two orthogonal plane radiation patterns of the highest frequency, center frequency, and lowest frequency bands respectively; including:

[0010] A stacked broadband antenna unit is determined, including a second-order subarray composed of units 8 and 9, which is a five-layer stacked microstrip patch structure; from top to bottom, it is: parasitic patch layer, radiating patch layer, bent probe feeding layer, metal floor, and feeding network;

[0011] The dielectric board material used is F4BM-2, with a relative dielectric constant of 2.56 and a loss tangent of 0.002. The antenna unit is fed by the electrical signal input through the coaxial interface 7 connected to the metal floor, and the energy is transferred to the radiation patch layer through the bent metal probe loaded on the last three dielectric layers, and then coupled to the parasitic patch on the upper layer.

[0012] Furthermore, step 2 is to perform numerical analytical analysis on the radiation pattern of the sub-array, extract the influencing parameters of the zero point position and the nulling depth of the pattern, and adjust the corresponding parameters to design the sub-array pattern so that the zero point position of the sub-array pattern corresponds to the position of the array factor grating lobe, and the nulling depth can make the zero point of the sub-array pattern and the array factor grating lobe cancel each other, including:

[0013] The radiation pattern of the sub-array in the yoz plane is expressed as:

[0014] in is the sub-array radiation pattern, d sub is the unit spacing within the subarray, Df B is the phase difference between the units within the subarray, and M is the subarray order;

[0015] The position of the sub-array pattern zero point is derived as follows: Where i represents the i-th zero point position;

[0016] It is thus determined that the null position is related to the element spacing and phase within the sub-array. The degree of freedom of the element spacing and phase within the sub-array is numerically analyzed to adjust the null position and null depth of the sub-array pattern.

[0017] First, the subarray element spacing is adjusted to adjust the subarray pattern null position and null depth. The subarray element spacing varies between 0.46λ and 0.70λ. The null depth increases with increasing subarray element spacing, resulting in a more pronounced grating lobe suppression effect. As the element spacing increases further, the subarray pattern sidelobes gradually emerge, further weakening the grating lobe suppression effect. 0.6λ is selected as the subarray element spacing.

[0018] Then, the phase difference of the units within the subarray is adjusted to adjust the null point position and null depth of the subarray radiation pattern: when the phase difference between the two units is 0 degrees, the first null area is formed. At this time, the null area is located in the range of -90° to -47.83° and the symmetrical range of +47.83° to +90°; when the phase difference between the two units is 68 degrees, another null area is formed. At this time, the null area is located in the range of -47.83° to -30°; the null depth is -10dB.

[0019] Furthermore, step 3 determines a structural feeding network of a phase shifter capable of achieving 0-degree and 68-degree phase adjustment, for independently controlling the phase difference between two units in the subarray, including:

[0020] The switched transmission line phase shifter loaded with PIN diode provides phase difference between two units in the subarray;

[0021] The phase shifter includes a one-to-two equal-division power divider and four phase delay transmission lines; each delay line is loaded with two PIN diodes, and different phase-shifted signal outputs are controlled by adjusting the different on-off modes of the PIN diodes.

[0022] The beneficial effects of the present invention are:

[0023] This paper provides a numerically analytical zero-point reconfigurable method for designing subarray patterns. This method derives a theoretical formula for subarray pattern zero-point analysis and numerically analyzes the variables of zero-point location and null depth. The resulting subarray pattern zero-points cover 120°, with a null depth of -10dB. Based on the pattern product theorem, this method can suppress a wide range of grating lobes in wideband, widely spaced arrays.

[0024] The present invention also designs a broadband second-order sub-array, whose operating frequency band covers the X and Ku bands, with a relative bandwidth of 47.62%. At the same time, it maintains a good radiation phase center within this impedance bandwidth, and the radiation pattern is also relatively consistent;

[0025] The present invention designs a switching transmission line phase shifter, which can achieve adjustable phase difference of ±68° and 0°, with insertion loss less than 1dB and phase shift error within 1°.

[0026] The subarray designed in the present invention can replace ordinary units as the basic array element of a large-pitch array, can achieve ±30° grating-lobe-free scanning of an array with an array element center spacing of 1λ, and can maintain good gain flatness. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a structural diagram of the second-order sub-matrix of the present invention;

[0028] Figure 2is a side view of the second-order sub-array of the present invention;

[0029] Figure 3 is a front view of the second-order sub-matrix of the present invention;

[0030] Figure 4 is a simulation curve of the sub-array reflection coefficient of the present invention;

[0031] Figure 5 The radiation patterns of the antenna units in the subarray of the present invention at 8 GHz, 10 GHz, and 12 GHz;

[0032] Figure 6 1 is a graph showing the variation of the null depth of the radiation pattern of the subarray mode 1 at 12 GHz with the spacing between elements in the subarray;

[0033] Figure 7 This is a diagram showing the grating lobe suppression effect of the phased array of the present invention when scanning to a 0-degree sub-array mode and a reconfigurable pattern zero point;

[0034] Figure 8 This is a diagram showing the grating lobe suppression effect of the phased array of the present invention when scanning to a 15-degree sub-array mode with a reconfigurable pattern zero point;

[0035] Figure 9 This is a diagram showing the reconfigurable grating lobe suppression effect when the phased array scans to the 15-degree sub-array mode two-pattern zero point;

[0036] Figure 10 This is a diagram showing the reconfigurable grating lobe suppression effect when the phased array scans to the 30-degree sub-array mode's second directional pattern zero point;

[0037] Figure 11 is a front view of the feed network of the subarray of the present invention;

[0038] Figure 12 is a simulation curve of the reflection coefficient and port phase difference of the feed network of the subarray of the present invention;

[0039] Description of the accompanying drawings: 1. First dielectric substrate, 2. Second dielectric substrate, 3. Third dielectric substrate, 4. Fourth dielectric substrate, 5. Fifth dielectric substrate, 7. SSMP RF connector, 8. Unit 1 in the sub-array, 9. Unit 2 in the sub-array. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of this application clearer, the implementation methods of this application will be further described in detail below with reference to the accompanying drawings.

[0041] The following first introduces the embodiments of the present application with reference to the accompanying drawings.

[0042] Large-pitch arrays often use subarrays as their basic units, with multiple antenna elements within the subarray sharing a set of transmit and receive RF channels. This invention applies pattern null reconfiguration technology to subarray design, replacing conventional array elements with subarrays to achieve low-sidelobe, wide-angle scanning with large-pitch arrays.

[0043] First, we need to design a 40% relative bandwidth subarray to extract two orthogonal plane patterns of the highest frequency, center frequency, and lowest frequency bands. Therefore, this example studies the traveling wave broadband technology and proposes a stacked broadband unit antenna, which consists of units 8 and 9 to form a second-order subarray. The subarray structure and front view are shown in the attached figure. Figure 1 and attached Figure 3 As shown in the figure, it is a five-layer stacked microstrip patch structure. From front to back, it is: parasitic patch layer, radiating patch layer, bent probe feed layer, metal floor, and feed network.

[0044] The cross-sectional view of the subarray in this example is shown in the attached Figure 2 As shown, the dielectric material used is F4BM-2 (relative permittivity: 2.56, loss tangent: 0.002). The antenna unit is fed by an electrical signal input from a coaxial interface 7 connected to the metal ground plane. The energy is transferred to the radiating patch layer via a bent metal probe loaded on dielectric layers 3 to 5, and then coupled to the parasitic patch on the upper layer.

[0045] The working principle and characteristics of the bandwidth expansion of the sub-array in this example are briefly described as follows:

[0046] (1) The use of a multi-layer dielectric stacked structure reduces the Q value of the antenna, thereby expanding the bandwidth;

[0047] (2) A parasitic patch layer is added on top of the radiating patch layer, creating a near-resonance point and further improving the antenna bandwidth;

[0048] (3) The bent probe feed introduces additional capacitance, which offsets the parasitic inductance caused by the vertical feed port and achieves wide-band matching of the antenna port.

[0049] The reflection coefficient curve of the subarray in this example is simulated using the electromagnetic simulation software CST Studio Suite 2021. Figure 4 As shown, the antenna operates in the X and Ku bands, with |S11| less than -10dB from 8GHz to 13GHz and a relative bandwidth of 47.62%.

[0050] The far-field radiation patterns of the E-plane and H-plane of the sub-array in this example working at 8GHz, 10GHz and 12GHz are as follows: Figure 5As shown in the figure, the antenna's operating polarization mode is linear polarization in the x-direction. This shows that this subarray structure can achieve a wide impedance bandwidth while maintaining a good radiation phase center within the impedance bandwidth and a relatively consistent radiation pattern.

[0051] Then, it is necessary to perform numerical analytical analysis on the radiation pattern of the sub-array, extract the relevant influencing parameters of the pattern zero point position and the null depth, and adjust the corresponding parameters to design the sub-array pattern. The final designed sub-array pattern zero point position needs to correspond to the array factor grating lobe position and have a sufficiently large null depth so that the sub-array pattern zero point and the array factor grating lobe cancel each other out, thereby realizing grating-lobe-free scanning of large-spacing arrays.

[0052] The radiation pattern of the sub-array in this example on the yoz plane can be expressed by the formula Indicates that is the sub-array radiation pattern, d sub is the unit spacing within the subarray, Df B is the phase difference between the units within the subarray, and M is the subarray order. Based on this formula, the analytical formula for the position of the subarray pattern zero point is further derived as follows, where i represents the i-th zero point position, It can be concluded that the null position is related to the unit spacing and the phase difference of the units within the subarray. Therefore, these two degrees of freedom can be numerically analyzed to adjust the null position and null depth of the subarray pattern.

[0053] First, adjust the unit spacing within the subarray to adjust the subarray pattern zero point position and null depth. Due to the limitations of the array element spacing and the physical size of the subarray, the unit spacing within the subarray varies between 0.46λ and 0.70λ. Taking mode 1 and mode 2 as an example, in the attached Figure 6 The effect of element spacing within a subarray on grating lobe suppression is shown. The gray shaded area represents the grating lobe region, the solid line represents the subarray radiation pattern after zero-point reconfiguration within the grating lobe region for different subarray element spacings, and the dashed line represents the array's scanning factor. It can be seen that in mode 1, the trap depth increases with increasing element spacing within the subarray, resulting in increasingly significant grating lobe suppression. However, in mode 3, as the element spacing within the array increases, side lobes in the subarray pattern gradually emerge, further weakening the grating lobe suppression effect. As a compromise, a subarray element spacing of 0.6λ was selected to ensure small-angle scanning performance.

[0054] Then adjust the phase difference of the elements in the subarray to adjust the null position and null depth of the subarray pattern. When the phase difference between the two elements is 0 degrees, the first null area is formed. At this time, the null area is located in the -90° to -47.83° area and the symmetrical +47.83° to +90° area. Figure 7-8The radiation pattern of mode 1 in the broadband range is given. When the phase difference between the two units is 68 degrees, another null area is formed, and the null area is located in the range of -47.83° to -30°. Figure 9-10 The radiation pattern of mode 2 in a broadband range is given. The null depth is -10dB. According to the pattern product theorem, the wide range of grating lobes of broadband large-pitch arrays can be suppressed.

[0055] In this example, the subarray replaces the basic array elements of a large-pitch array with an element spacing of 1λ. Using MATLAB, the subarray pattern and array factor are numerically synthesized, and a preliminary array scanning pattern is calculated. It can be seen that the array can scan without grating lobes within the range of 0° to 30°, with a sidelobe level less than -8.7dB and gain flatness within 2.2dBi.

[0056] After the sub-array pattern is designed, a phase shifter feeding network with adjustable phases of 0 and 68 degrees needs to be designed to independently control the phase difference between the two units in the sub-array.

[0057] The front view of the subarray feed network in this example is shown in the attached figure. Figure 11 As shown, according to the transmission line principle, the calculation formula of the phase θ and electrical length l of the delayed transmission line can be obtained, where f is the operating frequency, e e is the dielectric equivalent permittivity. Based on the above formula, we designed a switching transmission line phase shifter loaded with PIN diodes to provide a phase difference between two units within the subarray. The phase shifter consists of a one-to-two power divider and four phase delay transmission lines. Each delay line is loaded with two PIN diodes. By adjusting the different on-off modes of the PIN diodes, different phase-shifted signal outputs are controlled. Where S represents the PIN diode, and P represents the input port and output port. The PIN diode model to be used is Macom's MA4SPS302, where C and L represent the DC blocking capacitor and AC blocking inductor in the DC bias circuit, respectively. Their package specifications are both 0603, with sizes of 10pF and 10nH, respectively. The power divider isolation resistor package specification is 0805, with a size of 100Ω.

[0058] The simulation curves of the reflection coefficient and port phase difference of the subarray feeding network of this embodiment are shown in the attached figure. Figure 12 As shown in Figure 1, the impedance bandwidth of the feed network covers the X-band in both operating modes, the insertion loss is less than 1dB, and the phase shift error is kept within 1°. The on-off status of the feed network diodes in different subarray directional patterns is shown in Table 1 below.

[0059]

[0060] Table 1

[0061] Finally, in order to demonstrate the advanced nature of the subarray pattern designed by the method of the present invention, the scanning performance of the array composed of the subarrays of this example is compared with that of a sparse array of the same aperture (an array with the same physical aperture and number of feed ports). As shown in Table 2, it can be seen that compared with the sparse array, the present array can not only achieve low sidelobe level scanning at a larger angle, but also improve the scanning gain and aperture efficiency.

[0062]

[0063] Table 2

[0064] The scanning performance of the array composed of the subarrays in this example is also compared with that of a full array of the same aperture (an array with the same physical aperture and an array element spacing of 0.5 times the wavelength). As shown in Table 3, it can be seen that compared with the full array of the same aperture, this array can achieve the same large-angle low-sidelobe scanning as the full array of the same aperture, and also improves the scanning gain and reduces the TR usage by 50%.

[0065]

[0066] Table 3

[0067] In summary, the present invention proposes a numerical analytical zero-point reconfigurable technology for designing subarray radiation patterns. The main purpose is to control the zero-point position and null depth of the subarray radiation pattern to suppress the scanning grating lobes of large-pitch arrays and achieve low-sidelobe scanning of the array. By analyzing and controlling the two influencing parameters of the subarray radiation pattern zero point, namely the unit spacing within the subarray and the unit phase difference within the subarray, the subarray radiation pattern zero point and the array factor grating lobe are offset. To verify the effectiveness of this method, a subarray with a relative bandwidth of 40% was designed. The radiation patterns of two orthogonal planes, the highest frequency, the center frequency, and the highest frequency within the band were extracted respectively. A 0-degree and 68-degree phase-adjustable phase shifter was used to provide adjustable phase differences for the units within the subarray. Finally, by comparing the scanning effects of the array composed of this subarray with those of a sparse array of the same aperture and a full array of the same aperture, it can be seen that the present invention is effective in designing the element radiation pattern of large-pitch arrays.

[0068] The above-described embodiments of the present application do not constitute a limitation on the scope of protection of the present application.

Claims

1. A numerical analytical zero-point reconfigurable method for designing subarray directional patterns, characterized in that: The method comprises: Step 1, design a 40% relative bandwidth subarray and extract two orthogonal plane radiation patterns of the highest frequency, center frequency, and lowest frequency band respectively; Step 2, numerically analyzing the radiation pattern of the sub-array radiation, extracting the influencing parameters of the zero point position and the nulling depth of the pattern, adjusting the corresponding parameters for designing the sub-array pattern, so that the zero point position of the sub-array pattern needs to correspond to the position of the array factor grating lobe, and the nulling depth can make the zero point of the sub-array pattern and the array factor grating lobe cancel each other; Step 3, determine a structural feeding network of a phase shifter capable of achieving 0 degree and 68 degree phase adjustment, which is used to achieve independent regulation of the phase difference between two units in the subarray.

2. The method according to claim 1, characterized in that Step 1, design a 40% relative bandwidth subarray, and extract two orthogonal plane radiation patterns of the highest frequency, center frequency, and lowest frequency band respectively; including: A stacked broadband antenna unit is determined, including a second-order subarray composed of unit 8 and unit 9, which is a five-layer stacked microstrip patch structure; from top to bottom: parasitic patch layer, radiation patch layer, bent probe feeding layer, metal floor, feeding network; The dielectric board material used is F4BM-2, with a relative dielectric constant of 2.56 and a loss tangent of 0.

002. The antenna unit is fed by an electrical signal input through a coaxial interface 7 connected to the metal floor, and the energy is transferred to the radiation patch layer through a bent metal probe loaded on the last three dielectric layers, and then coupled to the parasitic patch on the upper layer.

3. The method according to claim 1, characterized in that Step 2: numerically analyze the radiation pattern of the sub-array radiation, extract the influencing parameters of the zero point position and the nulling depth of the pattern, and adjust the corresponding parameters to design the sub-array pattern so that the zero point position of the sub-array pattern corresponds to the position of the array factor grating lobe, and the nulling depth can make the zero point of the sub-array pattern and the array factor grating lobe cancel each other, including: The radiation pattern of the subarray in the yoz plane is expressed as: in is the sub-array radiation pattern, d sub is the unit spacing within the subarray, Df B is the phase difference between the units within the subarray, and M is the subarray order; The position of the subarray pattern zero point is derived as follows: Where i represents the i-th zero point position; It is thus determined that the zero point position is related to the unit spacing and the unit phase within the subarray, and the degree of freedom of the unit spacing and the unit phase within the subarray is numerically analyzed to adjust the zero point position and the null depth of the subarray radiation pattern; First, the unit spacing in the subarray is adjusted to adjust the zero point position and the depth of the null trap in the subarray pattern: the unit spacing in the subarray varies between 0.46λ and 0.70λ, and the null trap depth increases with the increase of the unit spacing in the subarray, so that the grating lobe suppression effect becomes more and more significant; as the unit spacing in the array further increases, the side lobes of the subarray pattern gradually appear, so the grating lobe suppression effect is further weakened; 0.6λ is selected as the unit spacing in the subarray; Then, the phase difference of the units in the subarray is adjusted to adjust the zero point position and the null depth of the subarray radiation pattern: when the phase difference between the two units is 0 degrees, the first null area is formed, and the null area is located in the -90° to -47.83° area and the symmetrical +47.83° to +90° area; when the phase difference between the two units is 68 degrees, another null area is formed, and the null area is located in the -47.83° to -30° area; the null depth is -10dB.

4. The method according to claim 1, characterized in that: Step 3, determining a structural feeding network of a phase shifter capable of realizing 0 degree and 68 degree phase adjustment, which is used to independently adjust the phase difference between two units in the subarray, including: The switched transmission line phase shifter loaded with PIN diode provides phase difference between two units in the subarray; The phase shifter includes a one-to-two equal-division power divider and four phase delay transmission lines; two PIN diodes are loaded on each delay line, and different phase shift signal outputs are controlled by adjusting different on-off modes of the PIN diodes.

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