Antenna three-terminal feeding system based on transmit-receive isolation

Abstract

The present application provides an antenna three-terminal feeding system based on transceiver isolation, which is applied to the field of radar and communication technology, including: a microstrip patch antenna, a first feeding point, a second feeding point and a third feeding point; the first feeding point, the second feeding point and the third feeding point are connected to the microstrip patch antenna; the first feeding point and the second feeding point are transmitting ports, the third feeding point is a receiving port, and the interference generated by the first feeding point and the second feeding point is offset at the third feeding point; or, the first feeding point and the second feeding point are receiving ports, the third feeding point is a transmitting port, and the interference generated by the third feeding point is offset after passing through the first feeding point and the second feeding point. By making the interference generated by the transmitting link offset each other at the receiving link end, the isolation of the antenna receiving and transmitting ports is greatly improved, interference is reduced, and the performance of the radar system is improved.

Description

Technical Field

[0001] The present application relates to the field of radar and communication technology, and in particular to a three-terminal antenna feeding system based on transmit-receive isolation. Background Art

[0002] Because the radar system's detection beacon is passive, the feedback signal is extremely weak compared to the communication equipment that actively feedbacks active signals. Therefore, the radar system usually has a larger adjustable transmission power and higher receiving sensitivity to capture weak signals. In this context, higher requirements are placed on the ability to isolate interference between high-power transmission links and high-sensitivity receiving links, which has become a bottleneck indicator affecting the comprehensive performance of the radar system.

[0003] In the field of civilian consumer radar, due to the strict restrictions on space occupancy and cost, highly integrated and miniaturized radar design has become the mainstream; further, the radar will share one antenna for the transmit and receive channels to minimize the size of the radar. Therefore, how to improve the anti-interference ability between the transmit and receive channels in a single antenna design has become a key issue in radar system design.

[0004] In the scenario where the receiving and transmitting channels share a single antenna, the key to improving their isolation is to ensure the orthogonality of the receiving and transmitting excitations; specifically, the feeding point of one channel should be set at the point where the electric field distribution is weakest when the other channel feeds the antenna. For example, for the commonly used microstrip patch antenna, the usual practice is to make the feeding points of the receiving and transmitting channels 90° orthogonal with the antenna geometric center as the coordinate origin.

[0005] However, in actual engineering, due to layout restrictions, the antenna may be placed at the edge of the radar module, or there may be metal parts around the antenna, as well as production and processing tolerances, which will destroy the orthogonality of the antenna working environment. In other words, strict isolation of the transmitting and receiving ends cannot be achieved.

[0006] Therefore, a new technical solution is needed to ensure the orthogonality of the antenna working environment. Summary of the invention

[0007] In view of this, the embodiments of this specification provide a three-terminal antenna feeding system based on transmit-receive isolation, which solves the technical problem that the antenna layout destroys the orthogonality of the antenna working environment, resulting in the inability to achieve strict isolation between the transmitting and receiving ends and the reduction of anti-interference ability.

[0008] The embodiments of this specification provide the following technical solutions:

[0009] The embodiment of this specification provides an antenna three-terminal feeding system based on transmit-receive isolation, including: a microstrip patch antenna, a first feeding point, a second feeding point and a third feeding point;

[0010] The first feeding point, the second feeding point and the third feeding point are connected to the microstrip patch antenna;

[0011] The first feeding point and the second feeding point are symmetrically arranged relative to the geometric center of the microstrip patch antenna, and the line connecting the third feeding point and the geometric center is perpendicular to the line connecting the first feeding point and the geometric center and the line connecting the second feeding point and the geometric center respectively;

[0012] The first feeding point and the second feeding point are transmitting ports, the third feeding point is a receiving port, and the interference generated by the first feeding point and the second feeding point is offset at the third feeding point;

[0013] or,

[0014] The first feeding point and the second feeding point are receiving ports, the third feeding point is a transmitting port, and the interference generated by the third feeding point is offset by the first feeding point and the second feeding point.

[0015] Preferably, a line connecting the first feeding point and the geometric center is colinear with a line connecting the second feeding point and the geometric center and has opposite directions.

[0016] Preferably, it also includes: a feeding network module, the feeding network module is arranged on the back side of the microstrip patch antenna;

[0017] A feeding network module, including: an isolation power divider and a differential network;

[0018] An initial port is set at the first end of the isolation power divider, and the second end of the isolation power divider is connected to the first end of the differential network. A resistor is set at the connection between the second end of the isolation power divider and the first end of the differential network, and the resistor bridges the first starting point and the second starting point of the first end of the differential network; the second end of the differential network includes a first feeding point and a second feeding point.

[0019] Preferably, the midpoint of the line connecting the first feeding point and the second feeding point is the geometric center of the antenna.

[0020] Preferably, the impedance of the resistor is equal to the impedance of the transmission line of the isolation power divider and the differential network.

[0021] Preferably, the first feeding point, the first starting point, the resistor, the second starting point and the second feeding point form a first path;

[0022] The first feeding point, the first starting point, the initial port, the second starting point and the second feeding point form a second path;

[0023] The difference in length between the first path and the second path is half the wavelength of the electromagnetic wave signal.

[0024] Preferably, the difference between the path from the first starting point to the first feeding point and the path from the second starting point to the second feeding point is half the wavelength of the electromagnetic wave signal.

[0025] Preferably, the impedance of the antenna is determined according to the distances between the first feeding point, the second feeding point and the third feeding point and the geometric center;

[0026] The impedance of the antenna is matched to the impedance of the transmission line of the isolation power divider and the differential network.

[0027] Preferably, the phase difference between the electromagnetic wave signal at the first feeding point and the signal at the second feeding point is an odd multiple of 180°.

[0028] Preferably, the amplitude of the electromagnetic wave signal at the first feeding point is equal to the amplitude of the electromagnetic wave signal at the second feeding point.

[0029] Compared with the prior art, the beneficial effects that can be achieved by at least one of the above-mentioned technical solutions adopted in the embodiments of this specification include at least: feeding through the three ports of the antenna, where two ports are used as transmitting ports and the other port is used as a receiving port, or, where two ports are used as receiving ports and one port is used as a transmitting port, so that the interference generated by the two transmitting links can offset each other in the receiving link, or the interference generated by the two receiving links can offset each other in the transmitting link, thereby greatly improving the isolation between the antenna receiving port and the transmitting port, reducing interference, and improving the performance of the radar system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 It is a structural schematic diagram of a three-terminal antenna feeding system in this application;

[0032] Figure 2 This is a schematic diagram of the distribution of radiation signals from a first feeding point in the present application;

[0033] Figure 3 is a schematic diagram of the distribution of radiation signals of a second feeding point in the present application;

[0034] Figure 4 This is a schematic diagram of the interference signal distribution of a third feeding point in the present application;

[0035] Figure 5 It is a structural schematic diagram of a feeding network module in this application;

[0036] Figure 6 It is a working schematic diagram of a feeding network module in this application;

[0037] Figure 7 It is a synthetic schematic diagram of a radiation signal of a feeding network in the present application;

[0038] Figure 8 It is a synthetic schematic diagram of an interference signal of a feeding network in the present application;

[0039] Fig. 9 This is a schematic diagram of isolation comparison in this application;

[0040] Fig.10 It is a schematic diagram of the layout of a radar module in this application. DETAILED DESCRIPTION

[0041] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0042] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0043] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspect described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0044] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The drawings only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0045] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the examples can be practiced without these specific details.

[0046] In the field of civilian consumer radar, due to the strict restrictions on space occupancy and cost, highly integrated and miniaturized radar design has become the mainstream; further, the radar will share one antenna for the transmit and receive channels to minimize the size of the radar. Therefore, how to improve the anti-interference ability between the transmit and receive channels in a single antenna design has become a key issue in radar system design.

[0047] In the scenario where the receiving and transmitting channels share a single antenna, the key to improving their isolation is to ensure the orthogonality of the receiving and transmitting excitations; specifically, the feeding point of one channel should be set at the point where the electric field distribution is weakest when the other channel feeds the antenna. For example, for the commonly used microstrip patch antenna, the usual practice is to make the feeding points of the receiving and transmitting channels 90° orthogonal with the antenna geometric center as the coordinate origin.

[0048] In view of this, the inventors conducted in-depth research and improvement exploration on various websites, web page structures and their page information, as well as various extraction schemes, and found that: in actual engineering, due to layout restrictions, the antenna may be arranged at the edge of the radar module, or there may be metal parts around the antenna, as well as production and processing tolerances, which will destroy the orthogonality of the antenna working environment, that is, strict isolation of the transmitting and receiving ends cannot be achieved.

[0049] Based on this, an embodiment of this specification proposes a processing solution: through the antenna three-port feeding solution, the interference generated by the two transmitting links can cancel each other out at the receiving link end, or the interference generated by the two receiving links can cancel each other out at the transmitting link end.

[0050] The technical solutions provided by various embodiments of the present application are described below in conjunction with the accompanying drawings.

[0051] like Figure 1As shown, an embodiment of the present specification provides an antenna three-terminal feeding system based on transmit-receive isolation, including: a microstrip patch antenna, a first feeding point A1, a second feeding point A2 and a third feeding point B, wherein the first feeding point A1, the second feeding point A2 and the third feeding point B are connected to the microstrip patch antenna, and the microstrip patch antenna is arranged on the front side of the ground plane.

[0052] Specifically, the first feeding point A1 and the second feeding point A2 are symmetrically arranged relative to the geometric center O of the microstrip patch antenna, and the line connecting the third feeding point B and the geometric center O is respectively perpendicular to the line connecting the first feeding point A1 and the geometric center O and the line connecting the second feeding point A2 and the geometric center O. The line connecting the first feeding point A1 and the geometric center O is collinear with the line connecting the second feeding point A2 and the geometric center O, and the directions are opposite.

[0053] In the embodiments of this specification, coordinate point O is the geometric center of the antenna, A1 and A2 are a pair of feeding points, which can be used as a transmitter or a receiver at the same time; B is the third feeding point, which acts as an opposite receiver or transmitter according to the situation of A1 and A2. Note that the lines A1-O and A2-O are on the same straight line and in opposite directions; and the line BO is orthogonal to both A1-0 and A2-O.

[0054] In the embodiments of this specification, the antenna is a microstrip patch antenna, and the shape of the microstrip patch antenna is required to be completely symmetrical. For example, it can be a regular octagon, a square, a circle, etc.

[0055] The distribution of the radiation signal of the microstrip patch antenna is described below.

[0056] like Figure 2 As shown, when the first feeding point A1 is used as the excitation source, the electromagnetic field distribution generated around the microstrip patch antenna is as follows: Figure 2 As shown by the arrows in Figure 3 As shown, when the second feeding point A2 is used as the excitation source, the generated electromagnetic field distribution is as follows: Figure 3 As shown by the arrows in Figure 2 and Figure 3 It can be seen that the electromagnetic fields generated by the first feeding point A1 and the second feeding point A2 have the same distribution and amplitude, but opposite directions, that is, the phases of the electromagnetic waves differ by 180°.

[0057] Next, the distribution of interference signals is shown.

[0058] like Figure 4 As shown in the figure, the electrical paths of the interference signals are A1-B and A2-B. After being received by the third feeding point B, the two signals are transmitted along the normal direction of the antenna, along the paper surface, and toward the feeding network module behind the reference surface. That is, the interference signals of A1 and A2 are Figure 4 The scheme in is superimposed.

[0059] Further, the feeding network module on the back of the reference plane is described, and the feeding network module is arranged on the back of the microstrip patch antenna; Figure 5 As shown, the feeding network module includes: an isolation power divider and a differential network; an initial port, i.e., port A, is set at the first end of the isolation power divider, the second end of the isolation power divider is connected to the first end of the differential network, a resistor is set at the connection between the second end of the isolation power divider and the first end of the differential network, and the resistor bridges the first starting point A1' and the second starting point A2' of the first end of the differential network; the second end of the differential network includes a first feeding point A1 and a second feeding point A2.

[0060] Among them, port B is the port where the third feeding point B is located, and port A and port B are Figure 5 It can act as a transmitting port or a receiving port respectively; the signal of port A is divided into two paths, A1 and A2, through the isolation power divider and the differential network. A1 is the port where the first feeding point A1 is located, and A2 is the port where the second feeding point A2 is located. There is a resistor at the connection point between the isolation power divider and the differential network, and the resistor bridges the first starting point A1' and the second starting point A2' of the differential network. The midpoint of the line connecting the first feeding point A1 and the second feeding point A2 is the geometric center of the antenna.

[0061] Furthermore, in the embodiments of the present specification, the impedance of the resistor is equal to the impedance of the transmission line of the isolation power divider and the differential network. The first path is composed of the first feeding point A1, the first starting point A1', the resistor, the second starting point A2' and the second feeding point A2; the second path is composed of the first feeding point A1, the first starting point A1', the initial port A, the second starting point A2' and the second feeding point A2; the length difference between the first path and the second path is half of the wavelength of the electromagnetic wave signal. The difference between the path from the first starting point A1' to the first feeding point A1 and the path from the second starting point A2' to the second feeding point A2 in the differential network is half of the wavelength of the electromagnetic wave signal.

[0062] Specifically, there are two paths from A1' to A2', namely, through the bridge resistor and through a circle from A1' to port A and then to A2'; the length difference between these two paths must be half the wavelength of the electromagnetic wave signal; in the differential network, the length difference between the two paths A1' to A1 and A2' to A2 must also be half the wavelength of the electromagnetic wave signal.

[0063] In the embodiments of this specification, the impedance of the antenna is determined according to the distance between the first feeding point A1, the second feeding point A2 and the third feeding point B and the geometric center O; the impedance of the antenna matches the impedance of the transmission line of the isolation power divider and the differential network. The distance between the three feeding points A1, A2 and B and the origin O determines the antenna impedance. The farther away from the antenna, the greater the impedance; the distance between A1, A2 and O must be equal, the distance between B and O can be adjusted by itself, and the transmission line impedance should match the antenna impedance. The isolation power divider does not have to be in the shape of a ring. As long as its length satisfies the relationship with the wavelength, it can be other shapes such as a square.

[0064] Further, the phase difference between the electromagnetic wave signal at the first feeding point A1 and the signal at the second feeding point A2 is an odd multiple of 180°. The amplitude of the electromagnetic wave signal at the first feeding point A1 and the signal at the second feeding point A2 is equal.

[0065] In the embodiment of this specification, the phase difference between the electromagnetic wave signal at the first feeding point A1 and the signal at the second feeding point A2 is an odd multiple of 180°, and there is no limitation on the specific multiple.

[0066] Among them, the first feeding point and the second feeding point are transmitting ports, the third feeding point is a receiving port, and the interference generated by the first feeding point and the second feeding point is offset at the third feeding point; or, the first feeding point and the second feeding point are receiving ports, the third feeding point is a transmitting port, and the interference generated by the third feeding point is offset after passing through the first feeding point and the second feeding point.

[0067] like Figure 6 As shown in the figure, taking port A as the transmitting port, the electromagnetic wave signal is divided into two signals of equal size through the isolation power divider, forming a signal with an amplitude of ɑ0 and a phase of θ0 at A1' and A2'; the two signals pass through the differential network to form a signal with an amplitude of ɑ and a phase of θ at A1; and a signal with an amplitude of ɑ and a phase of θ+180° at A2. Since the signals of A1 and A2 are 180° opposite at this time, combined with Figure 2 and Figure 3 From the radiation characteristics, we can see that the radiation electric field distribution diagram of A1 and A2 is as follows: Figure 7 As shown, it is a strong superposition relationship; that is, the existence of the differential feeding network does not affect the antenna radiation performance.

[0068] Next, let's look at the synthesis of interference signals; Figure 8 As shown, since the signals of A1 and A2 are 180° opposite to each other, Figure 4 From the circuit characteristics, we can see that the interference signals of A1 and A2 cancel each other out at point B, so the interference signal received by B from port A is greatly reduced.

[0069] In the above example, port A is used as the transmitting port and port B is used as the receiving port; however, the principle is similar in reverse, that is, port B normally transmits electromagnetic waves; ports A1 and A2 receive electromagnetic waves with phases 180° opposite to each other. After passing through the differential network, the phases of the two signals become consistent and are superimposed at port A; and the interference signal emitted by B is received by A1 and A2 with equal amplitude and phase, and cancels each other out after passing through the differential network. The interference signal finally received by port A is greatly reduced.

[0070] The scheme of the present application includes a microstrip patch antenna, three feeding points connected to the microstrip patch antenna, a feeding network module located on the back of the microstrip patch antenna, and a ground plane located between the antenna layer and the feeding network layer. The shape of the microstrip patch antenna must be equilaterally symmetrical, such as a square, a regular polygon, or a circle; the three feeding points connected to the antenna, two of which are split from the same port (transmit or receive) through the feeding network, and the other is directly connected to the remaining port (receive or transmit); the two feeding points split from the same port must maintain mirror symmetry with the antenna geometric center as a reference, and remain vertically orthogonal to the third feeding point; the feeding network module consists of an isolation power divider and a differential network; the isolation power divider is an equal power divider, and the amplitudes of the two signals after the split are equal, that is, the amplitudes of the first feeding point and the second feeding point are equal; the two signals are bridged by a resistor at the end of the isolation power divider; at the same time, the circumference of the entire isolation power divider should match Match half the wavelength of the electromagnetic wave at the working frequency; similarly, the path length difference between the two paths of the differential network should match half the wavelength of the electromagnetic wave at the working frequency; the transmission line impedance value of the feeding network module should match the impedance value of the antenna, and the impedance value of the antenna is related to the distance from the feeding point to the geometric center, generally set between 70Ω-90Ω; similarly, the resistance impedance needs to be consistent with the transmission line impedance; the shape of the ground plane should be mirror-symmetrical relative to the first feeding point and the second feeding point; specifically, connect the first feeding point and the second feeding point, then the geometric center of the antenna will be located at the midpoint of the line segment; make a cutting line perpendicular to the connecting line and through the geometric center to cut the ground plane into two halves, then the two halves of the ground plane should be mirror-symmetrical relative to the cutting line.

[0071] like Fig. 9 As shown, the horizontal axis is frequency (Frequency, Freq), the unit is GHZ, the vertical axis is the isolation between the transmitting and receiving ports, the unit is decibel (dB), the dotted line represents the isolation curve of the dual-port feeding, and the solid line represents the isolation curve of the solution of the present application. By comparing the isolation of the solution of the present application with that of the general dual-port feeding, it can be seen that near the radar operating frequency of 5.86G, the isolation has a benefit of 25dB+, that is, the interference signal is reduced to about 0.3% of that of the dual-port feeding.

[0072] In addition, because the application only requires the addition of a symmetrical port and a matching feeding network module on the basis of a general dual port, and there are no new requirements for the antenna form, occupied area, PCB stacking, etc., it can be used flexibly in practical applications.

[0073] like Fig.10 The layout of the present application in the actual radar module is shown. The antenna is the same as the above, and the octagonal shape is used. The differential network and the isolation power divider are adjusted according to the actual module layout, routing and shape, but the corresponding relationship with the wavelength remains unchanged; the three feeding points A1, A2, and B connect the antenna and the feeding network module in the form of PCB through holes. In addition, the A port is the transmitting port and the receiving port, and an amplifier is added between the B port and the B feeding point to amplify the receiving signal or the transmitting signal.

[0074] It can be seen that coupled feeding can be used in this application, that is, the transmission line is not directly connected to the antenna, but the electromagnetic wave transmission between the antenna and the feeding network is realized through a certain coupling area. Analogously to the capacitance effect, in theory, three-port feeding can also be used to improve the isolation between the receiving and transmitting ends.

[0075] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the product embodiment described later, since it corresponds to the method, the description is relatively simple, and the relevant parts can be referred to the partial description of the system embodiment.

[0076] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. An antenna three-terminal feeding system based on transmit-receive isolation, characterized in that: include: a microstrip patch antenna, a first feeding point, a second feeding point, and a third feeding point; The first feeding point, the second feeding point and the third feeding point are connected to the microstrip patch antenna; The first feeding point and the second feeding point are symmetrically arranged with respect to the geometric center of the microstrip patch antenna, and the line connecting the third feeding point and the geometric center is perpendicular to the line connecting the first feeding point and the geometric center and the line connecting the second feeding point and the geometric center respectively; The first feeding point and the second feeding point are transmitting ports, the third feeding point is a receiving port, and the interference generated by the first feeding point and the second feeding point is offset at the third feeding point; Alternatively, the first feeding point and the second feeding point are receiving ports, the third feeding point is a transmitting port, and the interference generated by the third feeding point is offset by the first feeding point and the second feeding point; It also includes: a feeding network module, wherein the feeding network module is arranged on the back side of the microstrip patch antenna; The feed network module comprises: an isolation power divider and a differential network; An initial port is set at the first end of the isolation power divider, and a second end of the isolation power divider is connected to the first end of the differential network. A resistor is set at the connection between the second end of the isolation power divider and the first end of the differential network, and the resistor bridges the first starting point and the second starting point of the first end of the differential network; the second end of the differential network includes the first feeding point and the second feeding point; The first feeding point, the second feeding point, the first starting point, the resistor and the second starting point form a first path; The first feeding point, the first starting point, the initial port, the second starting point and the second feeding point constitute a second path; The length difference between the first path and the second path is half of the wavelength of the electromagnetic wave signal.

2. The antenna three-terminal feeding system based on transmit-receive isolation according to claim 1 is characterized in that: A line connecting the first feeding point and the geometric center and a line connecting the second feeding point and the geometric center are colinear and in opposite directions.

3. The antenna three-terminal feeding system based on transmit-receive isolation according to claim 1, characterized in that: The midpoint of the line connecting the first feeding point and the second feeding point is the geometric center of the antenna.

4. The antenna three-terminal feeding system based on transmit-receive isolation according to claim 1, characterized in that: The impedance of the resistor is equal to the impedance of the isolation power divider and the transmission line of the differential network.

5. The antenna three-terminal feeding system based on transmit-receive isolation according to claim 1, characterized in that: A difference between a path from the first starting point to the first feeding point and a path from the second starting point to the second feeding point is half a wavelength of the electromagnetic wave signal.

6. The antenna three-terminal feeding system based on transmit-receive isolation according to claim 5, characterized in that: determining the impedance of the antenna according to the distances between the first feeding point, the second feeding point, and the third feeding point and the geometric center; The impedance of the antenna is matched with the impedance of the isolation power divider and the transmission line of the differential network.

7. The antenna three-terminal feeding system based on transmit-receive isolation according to claim 6, characterized in that: A phase difference between the electromagnetic wave signal at the first feeding point and the electromagnetic wave signal at the second feeding point is an odd multiple of 180°.

8. The antenna three-terminal feeding system based on transmit-receive isolation according to claim 7, characterized in that: The amplitude of the electromagnetic wave signal at the first feeding point is equal to the amplitude of the electromagnetic wave signal at the second feeding point.

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