Small-sized co-polarized full-duplex antenna based on mode superposition method

Abstract

The invention discloses a small co-polarized full duplex antenna based on a mode superposition method. The antenna is composed of a folded SIW resonant cavity and a square metal patch, and the size is reduced by using a folded cavity structure. When one port of the antenna is excited, a TE120-like mode generated by the folded SIW resonant cavity and a TM01 mode generated by the patch are superposed, and an electric field zero region can be generated around the non-excited port, so that low mutual coupling between the two ports is realized. The whole antenna is very simple in structure, does not need an additional decoupling structure, and has the advantages of small size, simple feed, co-polarization and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of antenna design, and in particular relates to a small co-polarization full-duplex antenna based on a mode superposition method. Background Art

[0002] With the advent of the intelligent era of the Internet of Everything, the demand for spectrum efficiency and system capacity of the new generation of mobile communication systems continues to grow, and traditional capacity improvement technologies have reached their limits. In this context, the in-band full-duplex (IBFD) system has attracted more and more attention because it has the characteristics of simultaneously sending and receiving signals, which can theoretically double the spectrum efficiency. The key to realizing an IBFD system is to suppress the self-interference between the transmitting channel and the receiving channel, a process called self-interference cancellation (SIC). It is well known that antenna design and analog and digital cancellation techniques play an important role in achieving a high level of self-interference cancellation. Therefore, the use of high-isolation antennas can reduce the design burden of other parts of the IBFD system to a certain extent, thereby improving the performance and efficiency of the overall system.

[0003] Full-duplex antennas are an important part of full-duplex systems and can generally be divided into two categories: independent radiator structures (bistatic) and shared radiator structures (monostatic). The former achieves inherent low coupling and effectively reduces self-interference by physically separating the transmit and receive channels. However, the design of bistatic antennas inevitably sacrifices the overall size of the system. In contrast, monostatic antennas are more compact because they share the same radiating aperture, but there is often strong coupling between their ports. Although the use of dual-polarization design can reduce the mutual coupling between the ports of monostatic antennas, it will also result in the generation of separate spatial channels, which does not meet the conditions of a true full-duplex antenna. In addition, full-duplex antennas used in military communication systems must also ensure that the transmitting antenna and the receiving antenna have consistent polarization characteristics and similar far-field radiation patterns, which significantly increases the design difficulty. Therefore, achieving an in-band full-duplex co-polarized antenna with a small size, low profile, and no reliance on additional decoupling structures remains a challenging and long-sought goal.

[0004] The present invention proposes a small co-polarized full-duplex antenna based on the mode superposition method. The antenna consists of a folded SIW resonant cavity and a metal patch, which is fed by a pair of coaxial probes. No additional decoupling structure is required, and decoupling is achieved by exciting the superposition of two different modes. The antenna has the advantages of small size, simple feeding and co-polarization. Although the bandwidth is relatively narrow due to the inherent limitations of the folded cavity structure, the designed antenna successfully covers the working frequency band of the direct communication of the Internet of Vehicles based on LTE-V2X technology. Summary of the invention

[0005] The purpose of the present invention is to propose a small co-polarization full-duplex antenna based on a mode superposition method in view of the problem that spectrum capacity and system efficiency need to be improved urgently under the background of rapid development of a new generation of mobile communication systems.

[0006] The technical solution to achieve the purpose of the present invention is: A small co-polarization full-duplex antenna based on a mode superposition method includes, from top to bottom, an upper metal surface, an upper dielectric substrate, a middle metal surface, a lower dielectric substrate, and a lower metal surface; A square groove is etched in the middle of the upper metal surface, and a square metal patch is placed in the square groove; The upper dielectric substrate is provided with n first metallized through holes arranged periodically, where n>1; the n first metallized through holes enclose a first square metal wall, and the projection of the square groove on the upper dielectric substrate is located in the first square metal wall; The lower dielectric substrate is provided with n second metallized through holes arranged periodically; the n second metallized through holes enclose a second square metal wall; The upper metal surface, the upper dielectric substrate, the middle metal surface, the lower dielectric substrate, the lower metal surface, the first square metal wall, and the second square metal wall together form a folded SIW resonant cavity; Two axisymmetrically arranged U-shaped gaps are etched on the middle metal surface, and the two U-shaped gaps are located inside the folded SIW resonant cavity.

[0007] Preferably, a pair of first circular holes for SMA feeding are etched on the middle metal surface; a pair of second circular holes for SMA feeding are etched on the lower metal surface; a pair of first non-metallized through holes for loading SMA are provided inside the upper dielectric substrate, and a pair of second non-metallized through holes for loading SMA are provided inside the lower dielectric substrate; the projection centers of the first circular hole, the second circular hole, the first non-metallized through hole, and the second non-metallized through hole on the lower metal surface coincide with each other.

[0008] The SMA located on the lower metal surface has an outer conductor that passes through a first circular hole, a second non-metallized through hole, and a second circular hole that penetrates the lower dielectric substrate to connect to the lower metal surface and the middle metal surface, and an inner conductor that passes through a first circular hole, a second non-metallized through hole, a second circular hole, and a first non-metallized through hole that penetrates the upper dielectric substrate to connect to the square metal patch.

[0009] Preferably, there is a gap between the square groove and the square metal patch.

[0010] Preferably, the U-shaped gap is close to the metal wall of the folded SIW resonant cavity but does not contact the metal wall.

[0011] Preferably, centers of the square metal patch, the square slot, and the folded SIW resonant cavity are located in the same straight line.

[0012] Preferably, the projections of the first metallized through hole and the second metallized through hole on the lower metal surface overlap.

[0013] Preferably, the openings of the two U-shaped gaps are both oriented toward the center of the folded SIW resonant cavity.

[0014] Preferably, on the middle metal surface, the centers of the two U-shaped gaps and the center of the first circular hole are located in the same straight line.

[0015] Preferably, the resonant frequency of the folded SIW resonant cavity is affected by adjusting the length of the short side of the U-shaped slot.

[0016] As a preferred embodiment, when one of the ports of the antenna is excited, the two U-shaped gaps are exactly located at the strongest electric field positions of the folded SIW resonant cavity, and the folded SIW resonant cavity will generate a TE-like 120 The electric field distribution of the mode is symmetrical along the center line in the upper cavity. At the same time, the square metal patch is excited to generate TM 01 mode, whose electric field in the upper cavity is oddly symmetrical along the center line; based on the electric field distribution characteristics of these two modes, when they resonate at the same frequency, the TE-like 120 Mode and patch generated TM 01 The modes are superimposed, resulting in an electric field null region around the unexcited port, achieving low mutual coupling between the two ports.

[0017] Compared with the prior art, the present invention has the following significant advantages: 1. Small size. The present invention adopts a folded SIW resonant cavity structure, which significantly reduces the size of the cavity, thereby reducing the volume of the antenna. At the same time, the transmitting and receiving ports share a single microstrip patch structure, making it more compact than a multi-radiator full-duplex antenna.

[0018] 2. The feeding structure is simple. The present invention only requires a pair of coaxial probes for feeding, avoiding complex feeding network design and reducing additional losses.

[0019] 3. No additional decoupling structure is required. The present invention adopts a mode superposition method, which can achieve high port isolation without introducing an additional decoupling structure, thereby alleviating the inconvenience of the traditional complex decoupling structure in the manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the three-dimensional structure decomposition of a small co-polarization full-duplex antenna based on the mode superposition method of the present invention.

[0021] Figure 2 It is a front view of a small co-polarization full-duplex antenna based on a mode superposition method of the present invention.

[0022] Figure 3 It is a side view of a small co-polarization full-duplex antenna based on the mode superposition method of the present invention.

[0023] Figure 4 It is a top view of a small co-polarization full-duplex antenna based on a mode superposition method of the present invention.

[0024] Figure 5 The lower dielectric substrate of the present invention includes a top view of a lower metal surface and a middle metal surface.

[0025] Figure 6 is the reflection coefficient of the present invention |S 11 |、|S 22 | and port isolation |S 21 |Curve simulation diagram.

[0026] Figure 7 It is a gain curve simulation diagram of the present invention.

[0027] Figure 8 (a) is the radiation pattern of port 1 of the present invention at 5.915 GHz.

[0028] Figure 8 (b) is the radiation pattern of port 2 of the present invention at 5.915 GHz.

[0029] Markings in the figure: 1. Upper metal surface; 1-1. Square groove; 1-2. Square metal patch; 2. Upper dielectric substrate; 2-1. First non-metallized through hole; 3. Middle metal surface; 3-1. U-shaped gap; 3-2. First circular hole; 4. Lower dielectric substrate; 4-1. Second non-metallized through hole; 5. Lower metal surface; 5-1. Second circular hole; 6. First metallized through hole; 7. Second metallized through hole. DETAILED DESCRIPTION

[0030] The implementation of the technical solution is further analyzed below in conjunction with the accompanying drawings: The small co-polarized full-duplex antenna based on the mode superposition method provided by the embodiment of the present invention is composed of a folded SIW resonant cavity and a metal patch to form a cavity-backed patch antenna, which is fed by a pair of coaxial probes without the need for an additional decoupling structure. By exciting the TE120-like mode of the folded SIW resonant cavity and the TM01 mode of the patch, the two modes of electric fields are superimposed at the unexcited port to form an electric field zero zone, thereby achieving high isolation between the transmitting and receiving ports. The proposed antenna operates in the 5.905 GHz ~ 5.925 GHz frequency band and is suitable for a variety of communication systems with narrow bandwidths such as public safety and intelligent networked vehicle systems. The designed co-linear polarized full-duplex antenna consists of a folded SIW resonant cavity and a square metal patch 1-2. The folded SIW resonant cavity is realized by etching a pair of U-shaped gaps 3-1 on the middle common metal surface of two SIW resonant cavities stacked up and down. The two U-shaped gaps 3-1 are close to the metal through-hole wall of the SIW resonant cavity and are located at a position with a strong magnetic field to achieve coupling between the upper and lower cavities. The length of the short side of the U-shaped gap 3-1 will affect the resonant frequency of the folded SIW resonant cavity. By properly controlling its length, the resonant frequency of the folded SIW resonant cavity can be further reduced to achieve the goal of miniaturization.

[0031] The antenna is fed by a pair of symmetrically placed coaxial probes. When one of the ports of the antenna is excited, the two U-shaped slots 3-1 are exactly located at the strongest positions of the electric field of the folded SIW resonant cavity, and the folded SIW resonant cavity will generate a field distribution similar to the TE120 mode, and its electric field in the upper cavity is even symmetrical along the center line. At the same time, the square metal patch 1-2 is excited to generate the TM01 mode, and its electric field in the upper cavity is odd symmetrical along the center line. Based on the electric field distribution characteristics of these two modes, when they resonate at the same frequency, the TE120-like mode generated by the folded SIW resonant cavity and the TM01 mode generated by the patch are superimposed, thereby generating an electric field zero zone around the unexcited port, achieving low mutual coupling between the two ports.

[0032] Specifically, combined Figure 1 , Figure 2 The small co-polarization full-duplex antenna based on the mode superposition method includes from top to bottom: an upper metal surface 1, an upper dielectric substrate 2, a middle metal surface 3, a lower dielectric substrate 4, and a lower metal surface 5.

[0033] A square groove 1-1 is etched in the middle of the upper metal surface 1, and a square metal patch 1-2 is placed in the square groove 1-1; there is a gap between the square groove 1-1 and the square metal patch 1-2. The upper metal surface 1 and the square metal patch 1-2 are located in the same plane.

[0034] The upper dielectric substrate 2 is provided with n first metallized through holes 6 arranged periodically, where n>1; the n first metallized through holes 6 enclose a first square metal wall, and the projection of the square groove 1-1 falling on the upper dielectric substrate 2 is located in the first square metal wall; The lower dielectric substrate 4 is provided with n second metallized through holes 7 arranged periodically; the n second metallized through holes 7 enclose a second square metal wall; The first metallized through hole 6 and the second metallized through hole 7 have the same size, and their projections on the lower metal surface 5 overlap.

[0035] The upper metal surface 1, the upper dielectric substrate 2, the middle metal surface 3, the lower dielectric substrate 4, the lower metal surface 5, the first square metal wall, and the second square metal wall together form a folded SIW resonant cavity; the centers of the square metal patch 1-2, the square groove 1-1, and the folded SIW resonant cavity are located in the same straight line.

[0036] Two U-shaped slits 3-1 are etched on the middle metal surface 3. The two U-shaped slits 3-1 are respectively located at the edges of two opposite through-hole walls of the folded SIW resonant cavity. The two U-shaped slits 3-1 are symmetrical along the center of the middle metal surface 3, and the two U-shaped slits 3-1 open to the inside of the folded SIW resonant cavity. The U-shaped slits 3-1 are close to the metal wall of the folded SIW resonant cavity, but do not contact the metal wall. The openings of the two U-shaped slits 3-1 are both toward the center of the folded SIW resonant cavity.

[0037] A pair of first circular holes 3-2 for SMA feeding are etched on the middle metal surface 3; a pair of second circular holes 5-1 for SMA feeding are etched on the lower metal surface 5; a pair of first non-metallized through holes 2-1 for loading SMA are inside the upper dielectric substrate 2, and a pair of second non-metallized through holes 4-1 for loading SMA are inside the lower dielectric substrate 4; the projection centers of the first circular hole 3-2, the second circular hole 5-1, the first non-metallized through hole 2-1, and the second non-metallized through hole 4-1 on the lower metal surface 5 coincide. The outer conductor of SMA passes through the lower dielectric substrate 4 to connect to the lower metal surface 5 and the middle metal surface 3; the inner conductor passes through the upper dielectric substrate 2 to connect to the square metal patch 1-2.

[0038] On the middle metal surface 3, the centers of the two U-shaped gaps 3-1 and the center of the first circular hole 3-2 are located in the same straight line.

[0039] The installation details and specific size requirements of the above-mentioned small co-polarization full-duplex antenna are as follows: Combination Figure 3 and Figure 4 The relative dielectric constant of the upper dielectric substrate 2 and the lower dielectric substrate 4 is 2.2, and the thickness H is 0.762 mm ( ), the side length LC is 25mm ( ). The side length La of the square groove 1-1 etched on the upper metal surface 1 is 16.7 mm ( ), the side length Lp of the square metal patch 1-2 is 15.895mm ( ), the diameter Dt of the first metallized through hole 6 in the upper dielectric substrate 2 and the second metallized through hole 7 in the lower dielectric substrate 4 are both 0.2 mm ( ), the distance S between adjacent metallized through holes on the same layer of dielectric substrate is 0.8mm ( The length of the folded substrate integrated waveguide resonant cavity Lsiw is 21.4 mm ( ).

[0040] Combination Figure 5 The long side length Ls1 of the two U-shaped gaps 3-1 etched on the middle metal surface 3 is 20.6 mm ( ), the short side length Ls2 is 1.2mm ( ), the gap width Ws is 0.3mm ( ), the distance Ds between the long side of the U-shaped gap 3-1 and the adjacent metallized through-hole wall is 0.4 mm ( The diameter D1 of the first non-metallized through hole 2-1 for loading SMA inside the upper dielectric substrate 2 is 0.15 mm ( ), the diameter D2 of the second non-metallized through hole 4-1 for loading SMA inside the lower dielectric substrate 4 is 0.345 mm ( The distance Lf between the center of the first non-metallized through hole 2-1 and the center of the second non-metallized through hole 4-1 and the metallized through hole wall closest to them is 8.7 mm ( ).in is the free-space wavelength at the center frequency of 5.915 GHz.

[0041] Combination Figure 6 , it can be seen from the given S parameter curve that the reflection coefficient of the antenna |S 11 |with|S 22 |The operating frequency band below -10dB is 5.905 GHz ~ 5.925 GHz, the bandwidth is 20 MHz, and the isolation within the operating frequency band is |S 21 | is greater than 15dB, and the maximum isolation is close to 28 dB at the center frequency of 5.915 GHz. The proposed antenna successfully covers the working frequency band of direct vehicle-to-vehicle communication based on LTE-V2X technology.

[0042] Combination Figure 7The boresight gain of antenna port 1 within the working frequency band is greater than 3.87 dBi, and the maximum gain is 3.91dBi; the boresight gain of port 2 within the working frequency band is greater than 3.9 dBi, and the maximum gain is 3.92 dBi. The gain curve within the band is relatively stable.

[0043] Combination Figure 8 , the radiation patterns of port 1 and port 2 of the antenna at the center frequency of 5.915 GHz have the same radiation characteristics, where the maximum radiation direction of the E-plane radiation pattern has an inclination of about 30°. The reason for this is that the electric field is superimposed on the right half patch where the unexcited port is located, which offsets part of the electric field, causing the energy to be concentrated on the left half patch for radiation, resulting in a tilted radiation pattern. The cross-polarization of the E-plane is less than -40 dB, and the radiation pattern of the H-plane has good symmetry.

[0044] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A small co-polarized full-duplex antenna based on the mode superposition method, including from top to bottom: An upper metal surface (1), an upper dielectric substrate (2), a middle metal surface (3), a lower dielectric substrate (4), and a lower metal surface (5); Features: A square groove (1-1) is etched in the middle of the upper metal surface (1), and a square metal patch (1-2) is placed in the square groove (1-1); The upper dielectric substrate (2) is provided with n first metallized through holes (6) arranged periodically, where n>1; the n first metallized through holes (6) enclose a first square metal wall, and a projection of the square groove (1-1) falling on the upper dielectric substrate (2) is located within the first square metal wall; The lower dielectric substrate (4) is provided with n second metallized through holes (7) arranged periodically; the n second metallized through holes (7) are surrounded by a second square metal wall; The upper metal surface (1), the upper dielectric substrate (2), the middle metal surface (3), the lower dielectric substrate (4), the lower metal surface (5), the first square metal wall and the second square metal wall together form a folded SIW resonant cavity; Two U-shaped gaps (3-1) are etched on the middle metal surface (3) and are axially symmetrically arranged. The two U-shaped gaps (3-1) are located inside the folded SIW resonant cavity.

2. The small co-polarization full-duplex antenna based on the mode superposition method according to claim 1 is characterized in that A pair of first circular holes (3-2) are etched on the middle metal surface (3); a pair of second circular holes (5-1) are etched on the lower metal surface (5); a pair of first non-metallized through holes (2-1) are inside the upper dielectric substrate (2), and a pair of second non-metallized through holes (4-1) are inside the lower dielectric substrate (4); the projection centers of the first circular hole (3-2), the second circular hole (5-1), the first non-metallized through hole (2-1), and the second non-metallized through hole (4-1) on the lower metal surface (5) overlap.

3. The small co-polarization full-duplex antenna based on the mode superposition method according to claim 2 is characterized in that There is a gap between the square groove (1-1) and the square metal patch (1-2).

4. The small co-polarization full-duplex antenna based on the mode superposition method according to claim 1 is characterized in that The U-shaped gap (3-1) is close to the metal wall of the folded SIW resonant cavity but does not contact the metal wall.

5. The small co-polarization full-duplex antenna based on the mode superposition method according to claim 1 is characterized in that The centers of the square metal patch (1-2), the square groove (1-1), and the folded SIW resonant cavity are located on the same straight line.

6. The small co-polarization full-duplex antenna based on the mode superposition method according to claim 1, characterized in that The projections of the first metallized through hole (6) and the second metallized through hole (7) on the lower metal surface (5) overlap.

7. The small co-polarization full-duplex antenna based on the mode superposition method according to claim 1 is characterized in that The openings of the two U-shaped gaps (3-1) are both oriented toward the center of the folded SIW resonant cavity.

8. The small co-polarization full-duplex antenna based on the mode superposition method according to claim 1 is characterized in that On the middle metal surface (3), the centers of the two U-shaped gaps (3-1) and the center of the first circular hole (3-2) are located on the same straight line.

9. The small co-polarization full-duplex antenna based on the mode superposition method according to claim 1, characterized in that The resonant frequency of the folded SIW resonant cavity is affected by adjusting the length of the short side of the U-shaped gap (3-1).

10. The small co-polarization full-duplex antenna based on the mode superposition method according to claim 1, characterized in that When one of the ports of the antenna is excited, the two U-shaped slots (3-1) are exactly located at the strongest electric field positions of the folded SIW resonant cavity, and the folded SIW resonant cavity will generate a TE-like 120 The electric field distribution of the mode is symmetrical along the center line in the upper cavity. At the same time, the square metal patch (1-2) is excited to generate TM 01 mode, whose electric field in the upper cavity is oddly symmetrical along the center line; based on the electric field distribution characteristics of these two modes, when they resonate at the same frequency, the TE-like 120 Mode and patch generated TM 01 The modes are superimposed, resulting in an electric field null region around the unexcited port, achieving low mutual coupling between the two ports.

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