Dual-band circularly polarized microstrip antenna and design method thereof

Abstract

The application provides a dual-frequency circularly polarized microstrip antenna and a design method thereof, and relates to the technical field of antennas.The dual-frequency circularly polarized microstrip antenna comprises an antenna plate, a feed point is arranged at the center of the antenna plate, and the feed point is used for connecting the antenna plate with a bottom plate; a first tuning network loading point is arranged on a first diagonal line of the square antenna plate, the bottom plate is provided with a first tuning network, the first tuning network loading point is connected with the first tuning network, and the first tuning network is used for adjusting a first phase of a first eigenmode on the first diagonal line to a target resonant frequency; a second tuning network loading point is arranged on a second diagonal line of the antenna plate, the bottom plate is provided with a second tuning network, the second tuning network loading point is connected with the second tuning network, and the second tuning network is used for adjusting a second phase of a second eigenmode on the second diagonal line to the target resonant frequency; and the phase difference between the first phase and the second phase is 90 degrees, so that the circularly polarized microstrip antenna can work in different frequency bands.

Description

Technical Field

[0001] This invention relates to the field of antenna technology, and in particular to a dual-frequency circularly polarized microstrip antenna and its design method. Background Technology

[0002] Antennas are the core components in wireless communication systems, converting electromagnetic waves into electrical signals. Their performance directly affects communication quality and system integration. In practical applications, microstrip antennas are a commonly used type of antenna in wireless communication systems, widely used in array antennas, phased array antennas, and radar antenna arrays, especially in applications requiring circularly polarized electromagnetic waves, such as satellite communication and navigation terminals.

[0003] Common circularly polarized microstrip antennas typically control the circular polarization direction through methods such as chamfering and slot loading to achieve left-hand or right-hand circular polarization characteristics. However, most existing circularly polarized microstrip antennas are designed based on a single resonant mode to ensure that the antenna's radiation performance and the axial ratio of the radiated electromagnetic wave within a single frequency band meet the requirements of circular polarization characteristics. However, scenarios where the transmit and receive links need to operate in different frequency bands are becoming increasingly common. If existing circularly polarized microstrip antennas are used, two independent antennas need to be configured to cover the transmit and receive frequency bands respectively. This would increase the size of the wireless communication terminal. If a single antenna is forced to be reused, problems such as axial ratio deterioration caused by frequency band offset will occur, affecting the communication reliability of the wireless communication terminal. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a dual-frequency circularly polarized microstrip antenna and its design method.

[0005] This invention provides a dual-frequency circularly polarized microstrip antenna, comprising:

[0006] An antenna board, wherein a feed point is provided in the center offset region of the antenna board, and the feed point is used to connect the antenna board to the base plate;

[0007] The antenna plate is square, and a first tuning network loading point is provided on the first diagonal of the antenna plate. A first tuning network is provided on the base plate. The first tuning network loading point is connected to the first tuning network. The first tuning network is used to adjust the first intrinsic operating mode on the first diagonal to the first phase of the target resonant frequency.

[0008] The antenna plate has a second tuning network loading point on its second diagonal, and the base plate has a second tuning network. The second tuning network loading point is connected to the second tuning network. The second tuning network is used to adjust the second intrinsic operating mode on the second diagonal to the second phase of the target resonant frequency. The phase difference between the first phase and the second phase is 90 degrees.

[0009] According to the application, a dual-frequency circularly polarized microstrip antenna is provided, and the first pair of diagonal lines or the second pair of diagonal lines are provided with antenna plate cut angles;

[0010] The antenna plate cut angle is used to generate an offset of a resonant frequency.

[0011] The first tuning network is used to adjust a first phase of a first intrinsic working mode on the first pair of diagonal lines to a target resonant frequency in cooperation with the offset.

[0012] The second tuning network is used to adjust a second phase of a second intrinsic working mode on the second pair of diagonal lines to a target resonant frequency in cooperation with the offset.

[0013] According to the application, a dual-frequency circularly polarized microstrip antenna is provided, and the first pair of diagonal lines are further provided with third tuning network loading points, the third tuning network loading points are symmetrically distributed on both sides of the center point with the first tuning network loading points, the third tuning network loading points are used to load third tuning networks, and the third tuning networks are the same as the first tuning network.

[0014] The second pair of diagonal lines are further provided with fourth tuning network loading points, the fourth tuning network loading points are symmetrically distributed on both sides of the center point with the second tuning network loading points, the fourth tuning network loading points are used to load fourth tuning networks, and the fourth tuning networks are the same as the second tuning network.

[0015] According to the application, a dual-frequency circularly polarized microstrip antenna is provided, and the tuning network includes a capacitor and an inductor, the capacitor and the inductor are connected in series, the capacitor is connected to a tuning network loading point, and the inductor is grounded.

[0016] According to the application, a dual-frequency circularly polarized microstrip antenna is provided, and the tuning network includes:

[0017] The first tuning circuit includes a first capacitor and an inductor, the first capacitor and the inductor are connected in series, the inductor is grounded, and the first capacitor is connected to a tuning network loading point.

[0018] The second tuning circuit includes a second capacitor, one end of the second capacitor is grounded, and the other end of the second capacitor is connected to the tuning network loading point.

[0019] The first tuning circuit and the second tuning circuit are connected in parallel.

[0020] According to the application, a dual-frequency circularly polarized microstrip antenna is provided, and the tuning network includes:

[0021] a first tuning circuit, the first tuning circuit comprising a capacitance and a first inductance, the capacitance and the first inductance being in series, the first inductance being grounded, the capacitance being connected to a tuning network loading point;

[0022] a second tuning circuit, the second tuning circuit comprising a second inductance, one end of the second inductance being grounded, the other end being connected to the tuning network loading point;

[0023] wherein the first tuning circuit and the second tuning circuit are in parallel.

[0024] The application also provides a design method of a dual-frequency circularly polarized microstrip antenna, the antenna board of the dual-frequency circularly polarized microstrip antenna is square, a first tuning network loading point is arranged on a first diagonal line of the antenna board, and a second tuning network loading point is arranged on a second diagonal line of the antenna board, the method comprising:

[0025] when the first tuning network loading point and the second tuning network loading point are in an open circuit state, determining a first intrinsic working mode on the first diagonal line and a second intrinsic working mode on the second diagonal line; determining a target resonant frequency of the dual-frequency circularly polarized microstrip antenna;

[0026] determining a first reference distance between the first tuning network loading point and a center point, and determining a second reference distance between the second tuning network loading point and the center point;

[0027] determining a first tuning network for shifting the first intrinsic working mode on the first diagonal line to the target resonant frequency based on the first reference distance, and determining a second tuning network for shifting the second intrinsic working mode on the second diagonal line to the target resonant frequency based on the second reference distance;

[0028] when the first tuning network meets a preset standard, obtaining a first distance between the first tuning network loading point and the center point according to the first reference distance; and when the second tuning network meets the preset standard, obtaining a second distance between the second tuning network loading point and the center point according to the second reference distance.

[0029] According to the design method of the dual-frequency circularly polarized microstrip antenna provided by the application, the first tuning network for shifting the first intrinsic working mode on the first diagonal line to the target resonant frequency based on the first reference distance, and the second tuning network for shifting the second intrinsic working mode on the second diagonal line to the target resonant frequency based on the second reference distance, comprise:

[0030] determining a circular polarization axial ratio, and obtaining a shift amount of the target resonant frequency of the dual-frequency circularly polarized microstrip antenna according to the circular polarization axial ratio;

[0031] determine a first phase of the target resonant frequency offset in a first direction based on the offset amount, and determine a second phase of the target resonant frequency offset in a second direction based on the offset amount; wherein a phase difference between the first phase and the second phase is 90 degrees.

[0032] determine a first tuning network for offsetting a first eigen-working mode on the first diagonal line to a first phase of the target resonant frequency based on a first reference distance, and determine a second tuning network for offsetting a second eigen-working mode on the second diagonal line to a second phase of the target resonant frequency based on a second reference distance.

[0033] According to the dual-frequency circularly polarized microstrip antenna design method provided by the application, the antenna plate cut angle is arranged at two corner angles of the first diagonal line or the second diagonal line.

[0034] The first tuning network for offsetting the first eigen-working mode on the first diagonal line to the target resonant frequency based on the first reference distance, and the second tuning network for offsetting the second eigen-working mode on the second diagonal line to the target resonant frequency based on the second reference distance, comprise:

[0035] determine an offset amount and an offset direction of the target resonant frequency of the dual-frequency circularly polarized microstrip antenna generated by the antenna plate cut angle;

[0036] determine a first phase of the target resonant frequency offset in a first direction based on the offset amount, and determine a second phase of the target resonant frequency offset in a second direction based on the offset amount; wherein a phase difference between the first phase and the second phase is 90 degrees.

[0037] determine a first tuning network for offsetting a first eigen-working mode on the first diagonal line to a first phase of the target resonant frequency based on a first reference distance, and determine a second tuning network for offsetting a second eigen-working mode on the second diagonal line to a second phase of the target resonant frequency based on a second reference distance.

[0038] According to the dual-frequency circularly polarized microstrip antenna design method provided by the application, the target resonant frequency includes a high-frequency frequency and a low-frequency frequency.

[0039] The first tuning network for offsetting the first eigen-working mode on the first diagonal line to the target resonant frequency based on the first reference distance, and the second tuning network for offsetting the second eigen-working mode on the second diagonal line to the target resonant frequency based on the second reference distance, comprise:

[0040] determining, based on a first reference distance, a first tuning network that shifts a first eigenmode on the first diagonal to the high frequency in the first operating frequency band and to the low frequency in the second operating frequency band;

[0041] determining, based on a second reference distance, a second tuning network that shifts a second eigenmode on the second diagonal to the high frequency in the first operating frequency band and to the low frequency in the second operating frequency band.

[0042] The dual-frequency circularly polarized microstrip antenna and the design method thereof provided by the application connect the antenna plate and the bottom plate through the feed point of the central offset area of the square antenna plate, connect the first tuning network on the first diagonal and the first tuning network on the bottom plate through the first tuning network loading point on the first diagonal, and connect the second tuning network on the second diagonal and the second tuning network on the bottom plate through the second tuning network loading point on the second diagonal, the first tuning network can adjust the first phase of the first eigenmode on the first diagonal to the target resonant frequency, and the second tuning network can adjust the second phase of the second eigenmode on the second diagonal to the target resonant frequency, so that the first tuning network connected through the first tuning network loading point on the first diagonal and the second tuning network connected through the second tuning network loading point on the second diagonal can realize the operation of the circularly polarized microstrip antenna in different frequency bands. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative effort.

[0044] Figure 1 is one of the structural schematic diagrams of the dual-frequency circularly polarized microstrip antenna provided by the application.

[0045] Figure 2 is the second structural schematic diagram of the dual-frequency circularly polarized microstrip antenna provided by the application.

[0046] Figure 3 is the third structural schematic diagram of the dual-frequency circularly polarized microstrip antenna provided by the application.

[0047] Figure 4 is the fourth structural schematic diagram of the dual-frequency circularly polarized microstrip antenna provided by the application.

[0048] Figure 5 is one of the structural schematic diagrams of the first tuning network of the dual-frequency circularly polarized microstrip antenna provided by the application.

[0049] Figure 6 Figure 5 is a structural schematic diagram of a dual-frequency circularly polarized microstrip antenna according to the present application.

[0050] Figure 7 Figure 2 is a structural schematic diagram of a first tuning network of a dual-frequency circularly polarized microstrip antenna according to the present application.

[0051] Figure 8 Figure 3 is a structural schematic diagram of a first tuning network of a dual-frequency circularly polarized microstrip antenna according to the present application.

[0052] Figure 9 Figure 1 is a Smith chart of a tuning network of a dual-frequency circularly polarized microstrip antenna according to the present application.

[0053] Figure 10 Figure 2 is a Smith chart of a tuning network of a dual-frequency circularly polarized microstrip antenna according to the present application.

[0054] Figure 11 Figure 3 is a Smith chart of a tuning network of a dual-frequency circularly polarized microstrip antenna according to the present application.

[0055] Figure 12 Figure 4 is an antenna resonance frequency schematic diagram of a dual-frequency circularly polarized microstrip antenna according to the present application.

[0056] Figure 13 Figure 5 is an axial ratio schematic diagram of a dual-frequency circularly polarized microstrip antenna according to the present application.

[0057] Figure 14 Figure 6 is a structural schematic diagram of a dual-frequency circularly polarized microstrip antenna according to the present application.

[0058] Figure 15 Figure 7 is an antenna resonance frequency schematic diagram of a dual-frequency circularly polarized microstrip antenna according to the present application.

[0059] Figure 16 Figure 8 is an axial ratio schematic diagram of a dual-frequency circularly polarized microstrip antenna according to the present application.

[0060] Figure 17 Figure 1 is a flow schematic diagram of a dual-frequency circularly polarized microstrip antenna design method according to the present application.

[0061] Reference signs:

[0062] 1: antenna plate; 2: feed point; 3: first tuning network loading point; 4: second tuning network loading point; 5: bottom plate; 6: antenna plate cut angle; 7: third tuning network loading point; 8: fourth tuning network loading point. DETAILED DESCRIPTION

[0063] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0064] The following is combined Figures 1-17 This invention describes the dual-frequency circularly polarized microstrip antenna and its design method.

[0065] Figure 1 This is a schematic diagram of the structure of the dual-frequency circularly polarized microstrip antenna provided by the present invention. Figure 1 ,like Figure 1 As shown, the dual-frequency circularly polarized microstrip antenna includes:

[0066] Antenna plate 1, with a feed point 2 provided in the center offset area of ​​the antenna plate 1, the feed point 2 being used to connect the antenna plate 1 to the base plate 5;

[0067] The antenna plate 1 is square, and a first tuning network loading point 3 is provided on the first diagonal of the antenna plate 1. A first tuning network is provided on the base plate 5. The first tuning network loading point 3 is connected to the first tuning network. The first tuning network is used to adjust the first intrinsic operating mode on the first diagonal to the first phase of the target resonant frequency.

[0068] The antenna plate 1 has a second tuning network loading point 4 on its second diagonal, and the base plate 5 has a second tuning network. The second tuning network loading point 4 is connected to the second tuning network. The second tuning network is used to adjust the second intrinsic operating mode on the second diagonal to the second phase of the target resonant frequency. The phase difference between the first phase and the second phase is 90 degrees.

[0069] Both the base plate 5 and the antenna plate 1 can be made of metal. The center deviation region refers to the area near the center point of the antenna plate 1. The specific range of the center deviation region of the feed point 2 can be determined according to the actual impedance of the antenna in the actual application scenario, and no further limitation is made in this embodiment.

[0070] Feed point 2 is used for the input and output of electromagnetic wave signals. Feed point 2 can be used to connect antenna board 1 to base plate 5 through coaxial probe or microstrip line. Base plate 5 can also be called ground plane and serves as reference ground.

[0071] Understandably, the first and second diagonals are primarily used to distinguish different diagonals, rather than to define their order or sequence.

[0072] It can be understood that the target resonant frequency of the dual-frequency circularly polarized microstrip antenna includes a high-frequency resonant frequency and a low-frequency resonant frequency. For example, the resonant frequency of the first eigenmode can be 500 MHz. The first tuning network can adjust the first eigenmode to the first phase of the high-frequency resonant frequency 700 MHz, and adjust the first eigenmode to the first phase of the low-frequency resonant frequency 300 MHz, and the like. This embodiment is not limited further.

[0073] The adjustment of the second tuning network to the second eigenmode is basically similar to the adjustment of the first tuning network to the first eigenmode, and the difference is that the second tuning network adjusts the second eigenmode to the second phase of the target resonant frequency, which is not described further in this embodiment.

[0074] Exemplarily, the first tuning network can shift the first eigenmode on the first diagonal line to the first phase of the target resonant frequency in the high-frequency direction, and the second tuning network can shift the second eigenmode on the second diagonal line to the second phase of the target resonant frequency in the low-frequency direction, so as to realize that the phase difference between the first phase and the second phase is 90 degrees, the working mode on the first diagonal line of the square antenna plate is orthogonal to the working mode on the second diagonal line, and the amplitude of the working mode on the first diagonal line is equal to the amplitude of the working mode on the second diagonal line, thereby enabling the circular polarization of the electromagnetic wave radiated by the antenna plate.

[0075] The dual-frequency circularly polarized microstrip antenna provided by the application connects the antenna plate 1 and the bottom plate 5 through the feed point 2 of the central offset area of the square antenna plate 1, connects the first tuning network on the first diagonal line and the first tuning network on the bottom plate 5 through the first tuning network loading point 3 on the first diagonal line, and connects the second tuning network on the second diagonal line and the second tuning network on the bottom plate 5 through the second tuning network loading point 4 on the second diagonal line. The first tuning network can adjust the first eigenmode on the first diagonal line to the first phase of the target resonant frequency, and the second tuning network can adjust the second eigenmode on the second diagonal line to the second phase of the target resonant frequency, so that the first tuning network connected through the first tuning network loading point 3 on the first diagonal line and the second tuning network connected through the second tuning network loading point 4 on the second diagonal line can realize the working of the circularly polarized microstrip antenna in different frequency bands.

[0076] In an embodiment, a support plate can be provided between the antenna plate 1 and the bottom plate 5, or a plurality of support members can be provided for support. In the case of providing a plurality of support members, 3 or 4 support columns can be provided, and the specific number of support columns is not limited further in this embodiment. The support column can be a separately provided support column, or a connecting metal column between the tuning network loading point and the corresponding tuning network. The specific structure of the support column is not limited further in this embodiment.

[0077] As Figure 2As shown, based on the above embodiment, an antenna plate chamfer 6 is provided at the two corners of the first diagonal or the second diagonal;

[0078] The antenna plate chamfer 6 is used to generate the offset of the resonant frequency;

[0079] The first tuning network is used to adjust the first phase of the first intrinsic operating mode on the first diagonal to the target resonant frequency in accordance with the offset.

[0080] The second tuning network is used to adjust the second phase of the second intrinsic operating mode on the second diagonal to the target resonant frequency in accordance with the offset.

[0081] by Figure 2 Taking the indicated direction as a reference, for example, the diagonal between the lower left corner and the upper right corner can be taken as the first diagonal, and the diagonal between the upper left corner and the lower right corner can be taken as the second diagonal. In this case, the power supply point 2 can be set in the area slightly below the center.

[0082] Depending on whether the electromagnetic waves radiated by the antenna are left-handed or right-handed circularly polarized, it can be specifically determined whether to set the antenna plate chamfer 6 at the corner of the first diagonal or at the corner of the second diagonal.

[0083] For example, when the antenna plate has chamfered corners 6 at the two corners of the second diagonal, the second tuning network can adjust the second intrinsic operating mode on the second diagonal to the target resonant frequency. Combined with the offset of the resonant frequency generated by the antenna plate chamfered corners 6, it shifts in the second direction to obtain the second phase of the target resonant frequency. Based on the offset of the resonant frequency generated by the antenna plate chamfered corners 6, the parameters of the first tuning network can be adjusted so that the first tuning network can adjust the first intrinsic operating mode on the first diagonal to the target resonant frequency and shift in the first direction by the same amount to obtain the first phase of the target resonant frequency. For example, if the antenna plate is square and the target resonant frequency is 300MHz, and the antenna plate chamfered corners 6 generate a 3MHz offset in the high-frequency direction, then the second tuning network can initially adjust the second intrinsic operating mode on the second diagonal to 300MHz, and finally adjust it to 303MHz with the 3MHz offset. The first tuning network can adjust the first intrinsic operating mode on the first diagonal to 297MHz.

[0084] The first tuning network can also adjust the first eigenmode on the first diagonal line to the same resonant frequency as the second tuning network adjusts the second eigenmode on the second diagonal line. For example, when the antenna board is square, the target resonant frequency is 300 MHz, and the antenna board cut angle is 6, which produces a 6 MHz offset in the direction of high frequency. The second tuning network can adjust the second eigenmode on the second diagonal line to 297 MHz, and the second tuning network can adjust the second eigenmode on the second diagonal line to 303 MHz by adjusting the offset. The first tuning network can adjust the first eigenmode on the first diagonal line to 297 MHz.

[0085] In this way, the second tuning network adjusts the second eigenmode on the second diagonal line to 303 MHz, which is higher than the target resonant frequency of 300 MHz and leads the target resonant frequency of 300 MHz in phase; the first tuning network adjusts the first eigenmode on the first diagonal line to 297 MHz, which is lower than the target resonant frequency of 300 MHz and lags behind the target resonant frequency of 300 MHz in phase, so that the phase difference between the working mode on the first diagonal line and the working mode on the second diagonal line is 90 degrees. As described above, when the antenna board is square, the working mode on the first diagonal line is orthogonal to the working mode on the second diagonal line, and the amplitude of the working mode on the first diagonal line is equal to the amplitude of the working mode on the second diagonal line. Therefore, when the phase difference between the working mode on the first diagonal line and the working mode on the second diagonal line is 90 degrees, the electromagnetic wave radiated by the microstrip antenna can be circularly polarized.

[0086] It can be understood that the offset given in the embodiment is only illustrative, and the specific offset for achieving a phase difference of 90 degrees between the working mode on the first diagonal line and the working mode on the second diagonal line can be set according to actual working conditions, and the embodiment does not make further limitations on this.

[0087] In the embodiment, based on the structure of the antenna board 1 with the antenna board cut angle 6 at the two corners of the diagonal line to form a circularly polarized antenna, the first tuning network is added to tune the first eigenmode, and the second tuning network is added to tune the second eigenmode. By combining the double tuning networks to independently control the resonant frequency and phase relationship of the two antenna modes, dual-band circularly polarized radiation is achieved on a single antenna board 1, and the compactness of the dual-band circularly polarized microstrip antenna is increased.

[0088] As shown in Figure 3 and Figure 4 Based on any of the above embodiments, the first diagonal line also has a third tuning network loading point 7, which is symmetrically distributed on both sides of the center point with the first tuning network loading point 3. The third tuning network loading point 7 is used to load a third tuning network, which is the same as the first tuning network.

[0089] The second diagonal line is also provided with a fourth tuning network loading point 8, which is symmetrically distributed on both sides of the center point with the second tuning network loading point 4, and is used to load a fourth tuning network, which is the same as the second tuning network.

[0090] The adjustment of the third tuning network to the third intrinsic working mode and the adjustment of the fourth tuning network to the fourth intrinsic working mode are basically similar to the adjustment of the first tuning network to the first intrinsic working mode, except that the fourth tuning network adjusts the fourth intrinsic working mode to the second phase of the target resonant frequency, which will not be described herein.

[0091] It can be understood that the third tuning network also adjusts the third intrinsic working mode to the first phase of the target resonant frequency.

[0092] In this embodiment, by adding a symmetrically distributed third tuning network loading point 7 on the first diagonal line and a symmetrically distributed fourth tuning network loading point 8 on the second diagonal line, and setting the third tuning network to be the same as the first tuning network and the fourth tuning network to be the same as the second tuning network, the single-point tuning network is expanded into a distributed tuning network, and the impedance to be borne by the tuning network is distributed into two tuning networks, which can reduce the risk of a single tuning network approaching a limit condition.

[0093] And the superposition effect between the distributed tuning networks can achieve a more precise equivalent parameter step, for example, when the adjustment step of a single tuning network is 0.5 pF (pico Farad), the superposition effect between two symmetric distributed tuning networks can compress the adjustment step to 0.25 pF, reducing the adjustment difficulty of each tuning network.

[0094] And the complementary characteristics of the symmetric distributed tuning networks can suppress the interference of a single tuning network on the parameter accuracy, reducing the frequency control error of the dual-frequency circularly polarized antenna.

[0095] It can be understood that the first tuning network loaded by the first tuning network loading point 3 on the first diagonal line and the third tuning network loaded by the third tuning network loading point 7 are the same, or only one tuning network loading point is retained to load the corresponding tuning network, which can simplify the design of the antenna board 1. The tuning network loading points on the first diagonal line and the setting of their tuning networks are the same, which will not be described herein.

[0096] Based on any of the above embodiments, the tuning network includes a capacitor and an inductor, the capacitor and the inductor are connected in series, the capacitor is connected to the tuning network loading point, and the inductor is grounded.

[0097] In this embodiment, the first tuning network, the second tuning network, the third tuning network and the fourth tuning network are basically the same, and the difference is that the values of the specific elements are slightly different on the basis of fine tuning. As shown in FIG. 1, in the first tuning network, the capacitor is connected with the first tuning network loading point. It can be understood that in the second tuning network, the capacitor is connected with the second tuning network loading point, and in the third tuning network, the capacitor is connected with the third tuning network loading point. Figure 5

[0098] As shown in FIG. 1, the first diagonal line is provided with the first tuning network loading point and the third tuning network loading point which are symmetrically distributed, and the second diagonal line is provided with the second tuning network loading point and the fourth tuning network loading point which are symmetrically distributed. Each tuning network loading point is loaded with the corresponding tuning network. Figure 6

[0099] It can be understood that the electromagnetic wave signal transmitted or received by the feeding point is mainly through the first working mode on the first diagonal line and the second working mode on the second diagonal line. The first tuning network loaded by the first tuning network loading point and the third tuning network loaded by the third tuning network loading point adjust the first intrinsic working mode on the first diagonal line, and the second tuning network loaded by the second tuning network loading point and the fourth tuning network loaded by the fourth tuning network loading point adjust the second intrinsic working mode on the second diagonal line.

[0100] The combined impedance of the tuning network The combined impedance of the tuning network can be represented by the following formula:

[0101]

[0102] Wherein, is the working frequency, is the element capacitor in the first tuning network, is the element inductance in the first tuning network.

[0103] In this way, when , the combined impedance of the tuning network is capacitive. By fine tuning the parameters of the elements in the tuning networks loaded by the first tuning network loading point and the third tuning network loading point, the resonant frequency of the first intrinsic working mode on the first diagonal line can be shifted from to , and the equivalent impedance of the tuning network at the resonant frequency presents capacitive . Wherein, is the shift amount, is much smaller than , , , and . ​​

[0104] Based on similar working principles, by fine-tuning the parameters of the elements in the tuning network loaded by the second tuning network loading point and the fourth tuning network loading point, the resonant frequency of the second eigenmode on the second diagonal line can be shifted from to the resonant frequency . . .

[0105] Based on similar working principles, when , i.e. , the combined impedance of the tuning network presents inductance, by fine-tuning the parameters of the elements in the tuning network loaded by the aforementioned first tuning network loading point and the third tuning network loading point, the resonant frequency of the first eigenmode on the first diagonal line can be shifted from to the resonant frequency . . Wherein, is the shift amount, is much smaller than , , and . .

[0106] By fine-tuning the parameters of the elements in the tuning network loaded by the aforementioned second tuning network loading point and the fourth tuning network loading point, the resonant frequency of the second eigenmode on the second diagonal line can be shifted from to the resonant frequency . . .

[0107] Wherein, when shifted to high frequency or shifted to low frequency, the circular polarization direction of the electromagnetic wave radiated by the antenna can be left-handed circular polarization, and the circular polarization direction of the electromagnetic wave radiated by the antenna can be right-handed circular polarization.

[0108] It can be understood that, Figure 6 in the formula, is the capacitance of the element in the second tuning network, is the inductance of the element in the second tuning network. is the capacitance of the element in the third tuning network, is the inductance of the element in the third tuning network. is the capacitance of the element in the fourth tuning network, is the inductance of the element in the fourth tuning network.

[0109] In the embodiment, the capacitor is connected in series with the inductor, the capacitor is connected with the tuning network loading point, and the inductor is grounded to the tuning network. The tuning network can present inductance in one frequency band, so that the resonant frequency of the first and second eigenmodes is shifted to high frequency. The tuning network can present capacitance in another frequency band, so that the resonant frequency of the first and second eigenmodes is shifted to low frequency. Thus, the microstrip antenna can work in two frequency bands. The tuning network loaded by the tuning network loading point on the first diagonal line can make the first eigenmode slightly shift to the first direction in the working frequency band. The tuning network loaded by the tuning network loading point on the second diagonal line can make the second eigenmode slightly shift to the second direction in the working frequency band. Thus, the circular polarization of the electromagnetic wave radiated by the microstrip antenna is realized.

[0110] In an embodiment, the element parameters of the tuning network can be adjusted so that the tuning network presents lower capacitance in one frequency band, and the eigenmode is adjusted to a high frequency lower than the original resonant frequency. The element parameters of the tuning network can be adjusted so that the tuning network presents higher capacitance in another frequency band, and the eigenmode is adjusted to a low frequency higher than the original resonant frequency. Thus, the size of the antenna can be reduced. For example, the resonant frequency of the first eigenmode can be 500 MHz. The first tuning network can adjust the first eigenmode to a first phase of a high frequency resonant frequency of 300 MHz, and adjust the first eigenmode to a first phase of a low frequency resonant frequency of 200 MHz.

[0111] The adjustment can be realized by adjusting the frequency of a single capacitor. The lower the frequency of the single capacitor, the smaller the capacitance.

[0112] Similarly, the element parameters of the tuning network can be adjusted so that the tuning network presents lower inductance in one frequency band, and the eigenmode is adjusted to a low frequency higher than the original resonant frequency. The element parameters of the tuning network can be adjusted so that the tuning network presents higher inductance in another frequency band, and the eigenmode is adjusted to a high frequency lower than the original resonant frequency. Thus, the performance of the antenna can be improved. For example, the resonant frequency of the first eigenmode can be 500 MHz. The first tuning network can also adjust the first eigenmode to a first phase of a high frequency resonant frequency of 800 MHz, and adjust the first eigenmode to a first phase of a low frequency resonant frequency of 700 MHz.

[0113] The adjustment can be realized by adjusting the frequency of a single inductor. The higher the frequency of the single inductor, the greater the inductance.

[0114] It can be understood that the high frequency and the low frequency herein both refer to the working frequency.

[0115] In addition to the above-mentioned capacitor and the inductor in series, the capacitor is connected to a tuning network loading point, and the inductor is grounded to the tuning network, and at least the following tuning network is realized to realize the above-mentioned inductive in one frequency band and the above-mentioned capacitive in another frequency band,

[0116] Based on any of the above embodiments, the tuning network comprises:

[0117] A first tuning circuit, the first tuning circuit comprising a first capacitor and an inductor, the first capacitor and the inductor being in series, the inductor being grounded, and the first capacitor being connected to a tuning network loading point;

[0118] A second tuning circuit, the second tuning circuit comprising a second capacitor, one end of the second capacitor being grounded, and the other end being connected to the tuning network loading point;

[0119] Wherein, the first tuning circuit and the second tuning circuit are connected in parallel.

[0120] In this embodiment, the first tuning network, the second tuning network, the third tuning network and the fourth tuning network are basically the same, and the difference is that the values of the specific elements are slightly different on the basis of fine tuning. As shown in Figure 7 It can be understood that in the second tuning network, the first capacitor is connected to the second tuning network loading point, and in the third tuning network, the first capacitor is connected to the third tuning network loading point.

[0121] Based on any of the above embodiments, the tuning network comprises:

[0122] A first tuning circuit, the first tuning circuit comprising a capacitor and a first inductor, the capacitor and the first inductor being in series, the first inductor being grounded, and the capacitor being connected to a tuning network loading point;

[0123] A second tuning circuit, the second tuning circuit comprising a second inductor, one end of the second inductor being grounded, and the other end being connected to the tuning network loading point;

[0124] Wherein, the first tuning circuit and the second tuning circuit are connected in parallel.

[0125] In this embodiment, the first tuning network, the second tuning network, the third tuning network and the fourth tuning network are basically the same, and the difference is that the values of the specific elements are slightly different on the basis of fine tuning. As shown in Figure 8 It can be understood that in the second tuning network, the first capacitor is connected to the second tuning network loading point, and in the third tuning network, the first capacitor is connected to the third tuning network loading point.

[0126] In an embodiment, for the convenience of analysis, a Smith chart showing the capacitive or inductive characteristics of the tuning network at different frequencies can be obtained by simulating the tuning network with software. Referring to Figure 9 The positions corresponding to different frequencies on the Smith chart shown in the figure can determine that the tuning network in which the capacitor is connected to the loading point of the tuning network and the inductor is grounded achieves the target effect. Figure 10 The positions corresponding to different frequencies on the Smith chart shown in the figure can determine that the first tuning circuit includes a first capacitor and an inductor, the first capacitor and the inductor are connected in series, the inductor is grounded, and the first capacitor is connected to the loading point of the tuning network; the second tuning circuit includes a second capacitor, one end of the second capacitor is grounded, and the other end is connected to the loading point of the tuning network; the first tuning circuit and the second tuning circuit are connected in parallel to achieve the target effect of the tuning network. Referring to Figure 11 The positions corresponding to different frequencies on the Smith chart shown in the figure can determine that the first tuning circuit includes a first capacitor and an inductor, the first capacitor and the inductor are connected in series, the inductor is grounded, and the first capacitor is connected to the loading point of the tuning network; the second tuning circuit includes a second capacitor, one end of the second capacitor is grounded, and the other end is connected to the loading point of the tuning network; the first tuning circuit and the second tuning circuit are connected in parallel to achieve the target effect of the tuning network. Wherein the frequency is the resonant frequency.

[0127] The effectiveness of the dual-band circularly polarized microstrip antenna provided in the embodiment can be evaluated by simulation.

[0128] Exemplarily, a simulation model of the dual-band circularly polarized microstrip antenna with the loading points of the tuning networks removed can be established by using three-dimensional antenna electromagnetic simulation software, and the antenna board corners at the two corners of the first diagonal line or the second diagonal line can be set to determine the eigenmodes of the single-band circularly polarized microstrip antenna on the original antenna diagonal line. Referring to Figure 12 The amplitude and Figure 13 The axial ratio shown in the figure, the resonant frequency of the single-band circularly polarized microstrip antenna on the original antenna diagonal line is 482 MHz.

[0129] Referring to Figure 14 Then, a simulation model of the circularly polarized microstrip antenna with the corresponding tuning networks loaded can be established by using three-dimensional antenna electromagnetic simulation software, wherein the capacitance in the first tuning network is 2 pF, and the inductance is 50 nH; the capacitance in the third tuning network is 2 pF, and the inductance is 50 nH; the capacitance in the second tuning network is 1.2 pF, and the inductance is 110 nH; and the capacitance in the fourth tuning network is 1.2 pF, and the inductance is 110 nH. Referring toFigure 15 amplitude and phase of the illustrated S-Parameters Figure 16 The target resonant frequency of the dual-frequency circularly polarized microstrip antenna includes two frequency bands of 394MHz and 518MHz, and the axial ratio of the dual-frequency band is less than 3dB, which meets the circularly polarized electromagnetic wave characteristic requirement. Therefore, the dual-frequency circularly polarized microstrip antenna provided in the embodiment can effectively support the simultaneous transmission of dual-frequency circularly polarized electromagnetic waves when the transmission and reception frequency bands of the wireless communication system are different.

[0130] The tuning network is connected in series with the inductor, and the capacitor is connected to the tuning network loading point.

[0131] The design method of the dual-frequency circularly polarized microstrip antenna provided by the application is described below. The design method of the dual-frequency circularly polarized microstrip antenna described below can be referred to in conjunction with the dual-frequency circularly polarized microstrip antenna described above.

[0132] Figure 17 is one of the flowcharts of the design method of the dual-frequency circularly polarized microstrip antenna provided by the application. The antenna board of the dual-frequency circularly polarized microstrip antenna is square, and the first tuning network loading point is arranged on the first diagonal line of the antenna board, and the second tuning network loading point is arranged on the second diagonal line, as shown in Figure 17 The method comprises the following steps:

[0133] Step 1701, when the first tuning network loading point and the second tuning network loading point are in an open circuit state, determine the first intrinsic working mode on the first diagonal line and the second intrinsic working mode on the second diagonal line; and determine the target resonant frequency of the dual-frequency circularly polarized microstrip antenna.

[0134] Step 1702, determine the first reference distance between the first tuning network loading point and the center point, and determine the second reference distance between the second tuning network loading point and the center point.

[0135] Step 1703, based on the first reference distance, determine the first tuning network for shifting the first intrinsic working mode on the first diagonal line to the target resonant frequency, and based on the second reference distance, determine the second tuning network for shifting the second intrinsic working mode on the second diagonal line to the target resonant frequency.

[0136] Step 1704, when the first tuning network meets the preset standard, obtain the first distance between the first tuning network loading point and the center point according to the first reference distance; and when the second tuning network meets the preset standard, obtain the second distance between the second tuning network loading point and the center point according to the second reference distance.

[0137] The open circuit state refers to that the tuning network loading point is disconnected with the corresponding tuning network, or the tuning network loading point is not loaded with the corresponding tuning network. The intrinsic working mode refers to a working mode of the antenna when radiating electromagnetic waves at a frequency determined by the physical characteristics of the antenna. The target resonance frequency refers to a resonance frequency of the antenna when radiating electromagnetic waves under the action of the loaded tuning network.

[0138] The reference distance refers to an initial position of the tuning network loading point determined based on the antenna structure. The first reference distance refers to the initial position of the first tuning network loading point, and the second reference distance refers to the initial position of the second tuning network loading point.

[0139] The distance refers to a final position of the tuning network loading point determined based on actual calculation. The first distance refers to the final position of the first tuning network loading point, and the second distance refers to the final position of the second tuning network loading point.

[0140] The tuning network meets the preset standard. The preset standard refers to that the value range of the element of the tuning network is within the set value range, so as to avoid that the value of the element of the tuning network is too extreme.

[0141] It can be understood that the set value range of the element of the tuning network can be set by itself according to actual needs, and the embodiment does not make further limitation on this.

[0142] The design method of the dual-frequency circularly polarized microstrip antenna provided by the application sets the first tuning network loading point on the first diagonal line of the antenna plate, loads the first tuning network through the first tuning network loading point, sets the second tuning network loading point on the second diagonal line of the antenna plate, loads the second tuning network through the second tuning network loading point, the first tuning network can adjust the first intrinsic working mode on the first diagonal line to the target resonance frequency, and the second tuning network can adjust the second intrinsic working mode on the second diagonal line to the target resonance frequency, so that the circularly polarized microstrip antenna can work in different frequency bands through the first tuning network connected by the first tuning network loading point on the first diagonal line and the second tuning network connected by the second tuning network loading point on the second diagonal line, while avoiding that the value of the element of the tuning network is too extreme.

[0143] Based on any one of the above embodiments, the first tuning network for shifting the first intrinsic working mode on the first diagonal line to the target resonance frequency based on the first reference distance, and the second tuning network for shifting the second intrinsic working mode on the second diagonal line to the target resonance frequency based on the second reference distance, comprise:

[0144] The circular polarization axial ratio is determined, and the shift amount of the target resonance frequency of the dual-frequency circularly polarized microstrip antenna is obtained according to the circular polarization axial ratio.

[0145] determine a first phase of the target resonant frequency offset in a first direction based on the offset amount, and determine a second phase of the target resonant frequency offset in a second direction based on the offset amount; wherein a phase difference between the first phase and the second phase is 90 degrees.

[0146] determine a first tuning network for offsetting the first eigen-working mode on the first diagonal line to a first phase of the target resonant frequency based on a first reference distance, and determine a second tuning network for offsetting the second eigen-working mode on the second diagonal line to a second phase of the target resonant frequency based on a second reference distance.

[0147] According to any one of the above embodiments, the first diagonal line or the second diagonal line is provided with an antenna panel cut corner at two corners.

[0148] The first tuning network for offsetting the first eigen-working mode on the first diagonal line to the target resonant frequency based on a first reference distance, and the second tuning network for offsetting the second eigen-working mode on the second diagonal line to the target resonant frequency based on a second reference distance, comprise:

[0149] determine an offset amount and an offset direction of the target resonant frequency of the dual-frequency circularly polarized microstrip antenna generated by the antenna panel cut corner;

[0150] determine a first phase of the target resonant frequency offset in a first direction based on the offset amount, and determine a second phase of the target resonant frequency offset in a second direction based on the offset amount; wherein a phase difference between the first phase and the second phase is 90 degrees.

[0151] determine a first tuning network for offsetting the first eigen-working mode on the first diagonal line to a first phase of the target resonant frequency based on a first reference distance, and determine a second tuning network for offsetting the second eigen-working mode on the second diagonal line to a second phase of the target resonant frequency based on a second reference distance.

[0152] According to any one of the above embodiments, the target resonant frequency includes a high-frequency frequency and a low-frequency frequency.

[0153] The first tuning network for offsetting the first eigen-working mode on the first diagonal line to the target resonant frequency based on a first reference distance, and the second tuning network for offsetting the second eigen-working mode on the second diagonal line to the target resonant frequency based on a second reference distance, comprise:

[0154] determining a first tuning network based on the first reference distance to shift the first eigenmode on the first diagonal to the high frequency in the first operating frequency band and to shift the first eigenmode on the first diagonal to the low frequency in the second operating frequency band;

[0155] determining a second tuning network based on the second reference distance to shift the second eigenmode on the second diagonal to the high frequency in the first operating frequency band and to shift the second eigenmode on the second diagonal to the low frequency in the second operating frequency band.

[0156] based on any of the above embodiments, the dual-frequency circularly polarized microstrip antenna further comprises a third tuning network loading point on the first diagonal, the third tuning network loading point being symmetrically distributed with the first tuning network loading point on both sides of the center point; and a fourth tuning network loading point on the second diagonal, the fourth tuning network loading point being symmetrically distributed with the second tuning network loading point on both sides of the center point;

[0157] before determining the first eigenmode on the first diagonal and the second eigenmode on the second diagonal, the method further comprises:

[0158] determining the third tuning network loading point and the fourth tuning network loading point to be open circuit states;

[0159] after determining the first reference distance between the first tuning network loading point and the center point and the second reference distance between the second tuning network loading point and the center point, the method further comprises:

[0160] determining a third reference distance between the third tuning network loading point and the center point and a fourth reference distance between the fourth tuning network loading point and the center point;

[0161] after determining the first tuning network based on the first reference distance to shift the first eigenmode on the first diagonal to the target resonant frequency, the method further comprises:

[0162] determining a third tuning network based on the third reference distance to shift the first eigenmode on the first diagonal to the target resonant frequency;

[0163] after determining the second tuning network based on the second reference distance to shift the second eigenmode on the second diagonal to the target resonant frequency, the method further comprises:

[0164] determining a fourth tuning network based on the fourth reference distance to shift the first eigenmode on the first diagonal to the target resonant frequency;

[0165] If the first tuning network meets the preset standard, the method further comprises the following steps of:

[0166] If the third tuning network meets the preset standard, the third distance between the third tuning network loading point and the center point is obtained according to the third reference distance.

[0167] If the second tuning network meets the preset standard, the method further comprises the following steps of:

[0168] If the fourth tuning network meets the preset standard, the fourth distance between the fourth tuning network loading point and the center point is obtained according to the fourth reference distance.

[0169] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A dual-frequency circularly polarized microstrip antenna, characterized by, The application relates to a double-frequency circularly-polarized microstrip antenna. The antenna board is provided with a feed point at a center offset area, which is used to connect the antenna board with a bottom plate; The antenna board is square, a first tuning network loading point is arranged on a first diagonal line of the antenna board, a first tuning network is arranged on the bottom plate, the first tuning network loading point is connected with the first tuning network, and the first tuning network is used for adjusting a first phase of a first intrinsic working mode on the first diagonal line to a target resonant frequency; A second tuning network loading point is arranged on a second diagonal line of the antenna board, a second tuning network is arranged on the bottom plate, the second tuning network loading point is connected with the second tuning network, and the second tuning network is used for adjusting a second phase of a second intrinsic working mode on the second diagonal line to the target resonant frequency; wherein the phase difference between the first phase and the second phase is 90 degrees; Wherein, the target resonant frequency of the double-frequency circularly-polarized microstrip antenna includes a high-frequency resonant frequency and a low-frequency resonant frequency, if the first tuning network offsets the first intrinsic working mode on the first diagonal line to the first phase of the target resonant frequency in the high-frequency direction, the second tuning network offsets the second intrinsic working mode on the second diagonal line to the second phase of the target resonant frequency in the low-frequency direction.

2. The dual-frequency circularly polarized microstrip antenna according to claim 1, wherein, Two side angles of the first diagonal line or the second diagonal line are provided with antenna board cut angles; Wherein, the antenna board cut angles are used to generate an offset amount of the resonant frequency; The first tuning network is used for adjusting the first phase of the first intrinsic working mode on the first diagonal line to the target resonant frequency in cooperation with the offset amount; The second tuning network is used for adjusting the second phase of the second intrinsic working mode on the second diagonal line to the target resonant frequency in cooperation with the offset amount.

3. The dual-frequency circularly polarized microstrip antenna according to claim 1 or 2, characterized in that, A third tuning network loading point is further arranged on the first diagonal line, the third tuning network loading point is symmetrically distributed on two sides of a center point with the first tuning network loading point, the third tuning network loading point is used for loading a third tuning network, and the third tuning network is the same as the first tuning network; A fourth tuning network loading point is further arranged on the second diagonal line, the fourth tuning network loading point is symmetrically distributed on two sides of the center point with the second tuning network loading point, the fourth tuning network loading point is used for loading a fourth tuning network, and the fourth tuning network is the same as the second tuning network.

4. The dual-frequency circularly polarized microstrip antenna according to claim 3, wherein, The tuning network includes a capacitor and an inductor, the capacitor and the inductor are connected in series, the capacitor is connected with a tuning network loading point, and the inductor is grounded; Wherein, the tuning network is the first tuning network, the second tuning network, the third tuning network or the fourth tuning network; The capacitor is connected with the tuning network loading point, that is, the capacitor is connected with the first tuning network loading point in the first tuning network, the capacitor is connected with the second tuning network loading point in the second tuning network, the capacitor is connected with the third tuning network loading point in the third tuning network or the capacitor is connected with the fourth tuning network loading point in the fourth tuning network.

5. The dual-frequency circularly polarized microstrip antenna according to claim 3, wherein, The tuning network includes: The first tuning circuit comprises a first capacitor and an inductor, the first capacitor and the inductor are connected in series, the inductor is grounded, and the first capacitor is connected to a tuning network loading point; The second tuning circuit comprises a second capacitor, one end of the second capacitor is grounded, and the other end is connected to the tuning network loading point; The first tuning circuit and the second tuning circuit are connected in parallel; the tuning network is a first tuning network, a second tuning network, a third tuning network, or a fourth tuning network; The first capacitor is connected to the tuning network loading point, which means that in the first tuning network, the first capacitor is connected to the first tuning network loading point, in the second tuning network, the first capacitor is connected to the second tuning network loading point, in the third tuning network, the first capacitor is connected to the third tuning network loading point, or in the fourth tuning network, the first capacitor is connected to the fourth tuning network loading point; The other end is connected to the tuning network loading point, which means that in the first tuning network, the other end is connected to the first tuning network loading point, in the second tuning network, the other end is connected to the second tuning network loading point, in the third tuning network, the other end is connected to the third tuning network loading point, or in the fourth tuning network, the other end is connected to the fourth tuning network loading point.

6. The dual-frequency circularly polarized microstrip antenna according to claim 3, wherein, The tuning network comprises: The first tuning circuit comprises a capacitor and a first inductor, the capacitor and the first inductor are connected in series, the first inductor is grounded, and the capacitor is connected to a tuning network loading point; The second tuning circuit comprises a second inductor, one end of the second inductor is grounded, and the other end is connected to the tuning network loading point; The first tuning circuit and the second tuning circuit are connected in parallel; the tuning network is a first tuning network, a second tuning network, a third tuning network, or a fourth tuning network; The capacitor is connected to the tuning network loading point, which means that in the first tuning network, the capacitor is connected to the first tuning network loading point, in the second tuning network, the capacitor is connected to the second tuning network loading point, in the third tuning network, the capacitor is connected to the third tuning network loading point, or in the fourth tuning network, the capacitor is connected to the fourth tuning network loading point; The other end is connected to the tuning network loading point, which means that in the first tuning network, the other end is connected to the first tuning network loading point, in the second tuning network, the other end is connected to the second tuning network loading point, in the third tuning network, the other end is connected to the third tuning network loading point, or in the fourth tuning network, the other end is connected to the fourth tuning network loading point.

7. A dual frequency circularly polarized microstrip antenna design method, characterized by, The method is applied to the dual-frequency circularly polarized microstrip antenna of any one of claims 1-6, the antenna board of the dual-frequency circularly polarized microstrip antenna is square, a first tuning network loading point is arranged on a first diagonal line of the antenna board, and a second tuning network loading point is arranged on a second diagonal line, and the method comprises: In a case that the first tuning network loading point and the second tuning network loading point are in an open circuit state, a first eigenmode on a first diagonal line and a second eigenmode on a second diagonal line are determined; and a target resonant frequency of the dual-frequency circularly polarized microstrip antenna is determined. A first reference distance between the first tuning network loading point and a center point is determined, and a second reference distance between the second tuning network loading point and the center point is determined. A first tuning network that shifts the first eigenmode on the first diagonal line to the target resonant frequency based on the first reference distance is determined, and a second tuning network that shifts the second eigenmode on the second diagonal line to the target resonant frequency based on the second reference distance is determined. In a case that the first tuning network meets a preset standard, a first distance between the first tuning network loading point and the center point is obtained according to the first reference distance; and in a case that the second tuning network meets the preset standard, a second distance between the second tuning network loading point and the center point is obtained according to the second reference distance. The target resonant frequency of the dual-frequency circularly polarized microstrip antenna includes a high-frequency resonant frequency and a low-frequency resonant frequency, and if the first tuning network shifts the first eigenmode on the first diagonal line to the first phase of the target resonant frequency in a high-frequency direction, the second tuning network shifts the second eigenmode on the second diagonal line to the second phase of the target resonant frequency in a low-frequency direction.

8. The dual-frequency circularly polarized microstrip antenna design method of claim 7, wherein, The first tuning network that shifts the first eigenmode on the first diagonal line to the target resonant frequency based on the first reference distance and the second tuning network that shifts the second eigenmode on the second diagonal line to the target resonant frequency based on the second reference distance include: A circular polarization axial ratio is determined, and a shift amount of the target resonant frequency of the dual-frequency circularly polarized microstrip antenna is obtained according to the circular polarization axial ratio; A first phase of the target resonant frequency obtained by shifting in a first direction is determined based on the shift amount, and a second phase of the target resonant frequency obtained by shifting in a second direction is determined based on the shift amount; wherein a phase difference between the first phase and the second phase is 90 degrees; The first tuning network that shifts the first eigenmode on the first diagonal line to the first phase of the first target resonant frequency based on the first reference distance and the second tuning network that shifts the second eigenmode on the second diagonal line to the second phase of the second target resonant frequency based on the second reference distance.

9. The dual-frequency circularly polarized microstrip antenna design method of claim 7, wherein, Two edges of the first diagonal line or the second diagonal line are provided with antenna plate cut angles; The first tuning network that shifts the first eigenmode on the first diagonal line to the target resonant frequency based on the first reference distance and the second tuning network that shifts the second eigenmode on the second diagonal line to the target resonant frequency based on the second reference distance include: A shift amount and a shift direction of the target resonant frequency of the dual-frequency circularly polarized microstrip antenna generated by the antenna plate cut angles are determined; determine a first phase of the target resonant frequency offset in a first direction based on the offset amount, and determine a second phase of the target resonant frequency offset in a second direction based on the offset amount; wherein a phase difference between the first phase and the second phase is 90 degrees; determine a first tuning network for offsetting a first eigen-working mode on the first diagonal line to a first phase of the target resonant frequency based on a first reference distance, and determine a second tuning network for offsetting a second eigen-working mode on the second diagonal line to a second phase of the target resonant frequency based on a second reference distance.

10. The dual-frequency circularly polarized microstrip antenna design method according to any one of claims 7-9, characterized in that, The target resonant frequency includes a high-frequency frequency and a low-frequency frequency; determine a first tuning network for offsetting a first eigen-working mode on the first diagonal line to the target resonant frequency based on a first reference distance, and determine a second tuning network for offsetting a second eigen-working mode on the second diagonal line to the target resonant frequency based on a second reference distance, comprising: determine a first tuning network for offsetting a first eigen-working mode on the first diagonal line to the high-frequency frequency in a first working frequency band, and offsetting the first eigen-working mode on the first diagonal line to the low-frequency frequency in a second working frequency band based on a first reference distance; determine a second tuning network for offsetting a second eigen-working mode on the second diagonal line to the high-frequency frequency in a first working frequency band, and offsetting the second eigen-working mode on the second diagonal line to the low-frequency frequency in a second working frequency band based on a second reference distance.

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