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

Abstract

The application discloses a small-size same-polarization 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 the folded cavity structure. When one of the ports of the antenna is excited, the folded SIW resonant cavity generates a TE 120 mode, and the patch generates a TM 01 mode, the TE mode and the TM mode are superposed, an electric field zero region can be generated around the unexcited port, and thus low mutual coupling between the two ports is realized. The whole antenna structure is very simple, no additional decoupling structure is needed, and the antenna has the advantages of small size, simple feeding and same polarization.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of antenna design, and particularly relates to a small-size same-polarization full-duplex antenna based on a mode superposition method. BACKGROUND

[0002] With the advent of the intelligent era of everything connected, the demand for spectrum efficiency and system capacity of the new generation of mobile communication systems is growing, and the traditional capacity improvement technology has reached the limit. In this context, the in-band full-duplex (IBFD) system has attracted more and more attention due to its simultaneous transmission and reception characteristics, which can theoretically double the spectrum efficiency. The key to implementing the IBFD system lies in suppressing the self-interference between the transmission channel and the reception channel, which is called self-interference cancellation (SIC). As we all know, antenna design and analog and digital cancellation technology play an important role in achieving a high level of self-interference cancellation. Therefore, the use of high-isolation antennas can to some extent alleviate the design burden of other parts of the IBFD system, thereby improving the performance and efficiency of the overall system.

[0003] Full-duplex antennas are an important part of full-duplex systems, which can be generally divided into two categories: independent radiator structure (bistatic) and shared radiator structure (monostatic). The former physically separates the transmission and reception channels, achieving inherently low coupling and effectively reducing self-interference. However, the design of bistatic antennas inevitably sacrifices the overall size of the system. In contrast, monostatic antennas are more compact due to sharing the same radiating aperture, but there is often strong coupling between the ports. Although the use of dual-polarized design can reduce the mutual coupling between the ports of the monostatic antenna, it will also result in separate spatial channels, which does not meet the conditions of a true full-duplex antenna. In addition, full-duplex antennas applied to military communication systems also need to ensure that the transmission antenna and the reception antenna have consistent polarization characteristics and similar far-field radiation patterns, which significantly increases the design difficulty. Therefore, it is still a challenging and long-term goal to achieve an in-band full-duplex same-polarization antenna with small size, low profile and without relying on additional decoupling structures.

[0004] The application proposes a small-size same-polarization full-duplex antenna based on a mode superposition method. The antenna is composed of a folded SIW resonant cavity and a metal patch, fed by a pair of coaxial probes, without the need for additional decoupling structures, and decoupling is achieved by exciting the superposition of two different modes. The antenna has the advantages of small size, simple feeding and same polarization. Although the bandwidth is relatively narrow due to the inherent limitations of the folded cavity structure, the designed antenna successfully covers the operating frequency band of the vehicle-to-vehicle direct communication based on the LTE-V2X technology. SUMMARY

[0005] The application aims to solve the problem of spectrum capacity and system efficiency in the context of the rapid development of the new generation of mobile communication system, and proposes a small-size co-polarized full-duplex antenna based on mode superposition method.

[0006] The technical solution for achieving the object of the application is:

[0007] The small-size co-polarized full-duplex antenna based on mode superposition method comprises, 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.

[0008] A square slot is etched in the middle position of the upper metal surface, and a square metal patch is placed in the square slot.

[0009] The upper dielectric substrate is provided with n periodic first metallized through holes, and n>1; the n first metallized through holes are enclosed to form a first square metal wall, and the projection of the square slot on the upper dielectric substrate is located in the first square metal wall.

[0010] The lower dielectric substrate is provided with n periodic second metallized through holes; the n second metallized through holes are enclosed to form a second square metal wall.

[0011] 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 jointly form a folded SIW resonant cavity.

[0012] Two U-shaped slots are etched on the middle metal surface and arranged symmetrically about an axis, and the two U-shaped slots are located inside the folded SIW resonant cavity.

[0013] As a preferred embodiment, 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 projections of the first circular holes, the second circular holes, the first non-metallized through holes, and the second non-metallized through holes on the lower metal surface coincide.

[0014] The outer conductor of the SMA on the lower metal surface penetrates the lower dielectric substrate through the first circular hole, the second non-metallized through hole, and the second circular hole to connect to the lower metal surface and the middle metal surface, and the inner conductor penetrates the upper dielectric substrate through the first circular hole, the second non-metallized through hole, the second circular hole, and the first non-metallized through hole to connect to the square metal patch.

[0015] As a preferred embodiment, a gap exists between the square slot and the square metal patch.

[0016] As preferred, the U-shaped slots are close to the metal walls of the folded SIW resonant cavity but not in contact with the metal walls.

[0017] As preferred, the center of the square metal patch, the square slot and the folded SIW resonant cavity are located on the same straight line.

[0018] As preferred, the projections of the first and second metallized via holes on the lower metal layer are coincident.

[0019] As preferred, the openings of the two U-shaped slots are both directed to the center of the folded SIW resonant cavity.

[0020] As preferred, on the middle metal layer, the centers of the two U-shaped slots and the first circular hole are located on the same straight line.

[0021] As preferred, the length of the short side of the U-shaped slot is adjusted to affect the resonant frequency of the folded SIW resonant cavity.

[0022] As preferred, when one of the ports of the antenna is excited, the two U-shaped slots are located at the positions of the strongest electric field of the folded SIW resonant cavity respectively, and the folded SIW resonant cavity produces a TE-like mode field distribution, of which the electric field in the upper half cavity is even-symmetric along the center line; at the same time, the square metal patch is excited to produce a TM mode, of which the electric field in the upper half cavity is odd-symmetric along the center line; based on the electric field distribution characteristics of the two modes, when they resonate at the same frequency, the TE-like mode produced by the folded SIW resonant cavity and the TM mode produced by the patch are superimposed, thereby producing an electric field zero zone around the unexcited port, and realizing low mutual coupling between the two ports. 120 01 120 01

[0023] Compared with the prior art, the present application has the following advantages:

[0024] 1. Small size. The present application adopts a folded SIW resonant cavity structure, which significantly reduces the size of the cavity and thus 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 multiple-radiator full-duplex antenna.

[0025] 2. Simple feed structure. The present application only needs a pair of coaxial probes for feeding, avoiding complex feed network design and reducing additional loss.

[0026] 3. No need for additional decoupling structure. The present application uses mode superposition method to achieve high port isolation without introducing additional decoupling structure, thereby reducing the inconvenience of traditional complex decoupling structure in the manufacturing process. BRIEF DESCRIPTION OF DRAWINGS

[0027] ​​​​Figure 1 is a small-size co-polarized full-duplex antenna three-dimensional structure decomposition schematic diagram based on the mode superposition method of the present application.

[0028] Figure 2 is a front view of a small-size co-polarized full-duplex antenna based on the mode superposition method of the present application.

[0029] Figure 3 is a side view of a small-size co-polarized full-duplex antenna based on the mode superposition method of the present application.

[0030] Figure 4 is a top view of a small-size co-polarized full-duplex antenna based on the mode superposition method of the present application.

[0031] Figure 5 is a top view of a lower-layer dielectric substrate comprising a lower-layer metal surface and a middle-layer metal surface of the present application.

[0032] Figure 6 is a reflection coefficient |S 11 |, |S 22 | and port isolation |S 21 | curve simulation diagram.

[0033] Figure 7 is a gain curve simulation diagram of the present application.

[0034] Figure 8 (a) is the port 1 radiation pattern of the present application at 5.915 GHz.

[0035] Figure 8 (b) is the port 2 radiation pattern of the present application at 5.915 GHz.

[0036] Legend in the figure: 1, upper-layer metal surface; 1-1, square slot; 1-2, square metal patch; 2, upper-layer dielectric substrate; 2-1, first non-metalized via; 3, middle-layer metal surface; 3-1, U-shaped gap; 3-2, first circular hole; 4, lower-layer dielectric substrate; 4-1, second non-metalized via; 5, lower-layer metal surface; 5-1, second circular hole; 6, first metalized via; 7, second metalized via. DETAILED DESCRIPTION

[0037] The implementation of the technical solutions will be further analyzed below in combination with the drawings:

[0038] The small same-polarization full-duplex antenna based on the mode superposition method provided by the embodiment of the application is composed of a folded SIW resonant cavity and a metal patch, forms a back cavity patch antenna, is fed by a pair of coaxial probes, and does not need an additional decoupling structure. By exciting the TE120 mode of the folded SIW resonant cavity and the TM01 mode of the patch, the two modes resonate at the same frequency, the electric fields of the two modes are superimposed at the non-excited port, an electric field zero region is formed, and high isolation between the transmitting and receiving ports is achieved. The proposed antenna works in the 5.905 GHz ~ 5.925 GHz frequency band and is suitable for various communication systems with narrow bandwidths such as public safety and intelligent networked vehicle systems. The same-polarization full-duplex antenna designed by the application is composed 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 slots 3-1 on the middle shared metal surface of two SIW resonant cavities stacked one above the other. The two U-shaped slots 3-1 are close to the metal through-hole wall of the SIW resonant cavity and are located at a position where the magnetic field is strong, so as to realize the coupling between the upper and lower cavities. The length of the short side of the U-shaped slot 3-1 will affect the resonant frequency of the folded SIW resonant cavity, and by properly controlling the length, the resonant frequency of the folded SIW resonant cavity can be further reduced to achieve the goal of miniaturization.

[0039] 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 located at the positions where the electric field of the folded SIW resonant cavity is the strongest, respectively. The folded SIW resonant cavity will generate a TE120 mode field distribution, and the electric field in the upper half cavity is even symmetric along the center line. At the same time, the square metal patch 1-2 is excited to generate a TM01 mode, and the electric field in the upper half cavity is odd symmetric along the center line. Based on the electric field distribution characteristics of the two modes, when they resonate at the same frequency, the TE120 mode generated by the folded SIW resonant cavity and the TM01 mode generated by the patch are superimposed, thereby generating an electric field zero region around the non-excited port, and realizing low mutual coupling between the two ports.

[0040] Specifically, in combination with Figure 1 , Figure 2 , the small same-polarization full-duplex antenna based on the mode superposition method comprises, 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.

[0041] The middle position of the upper metal surface 1 is etched with a square slot 1-1, and the square metal patch 1-2 is placed in the square slot 1-1; there is a gap between the square slot 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.

[0042] The upper layer dielectric substrate 2 is provided with n periodic first metallized vias 6, n>1; the n first metallized vias 6 enclose a first square metal wall, and the projection of the square slot 1-1 on the upper layer dielectric substrate 2 is located in the first square metal wall;

[0043] The lower layer dielectric substrate 4 is provided with n periodic second metallized vias 7; the n second metallized vias 7 enclose a second square metal wall.

[0044] The first metallized via 6 and the second metallized via 7 have the same size, and the projections on the lower layer metal surface 5 coincide.

[0045] The upper layer metal surface 1, the upper layer dielectric substrate 2, the middle layer metal surface 3, the lower layer dielectric substrate 4, the lower layer metal surface 5, the first square metal wall, and the second square metal wall together enclose a folded SIW resonant cavity; the square metal patch 1-2, the square slot 1-1, and the center of the folded SIW resonant cavity are located on the same straight line.

[0046] Two U-shaped slots 3-1 are etched on the middle layer metal surface 3, and the two U-shaped slots 3-1 are respectively located on the edges of the two opposite via walls of the folded SIW resonant cavity, the two U-shaped slots 3-1 are symmetric about the center of the middle layer metal surface 3, and the openings of the two U-shaped slots 3-1 face the inside of the folded SIW resonant cavity. The U-shaped slot 3-1 is close to the metal wall of the folded SIW resonant cavity, but does not contact the metal wall. The openings of the two U-shaped slots 3-1 both face the center of the folded SIW resonant cavity.

[0047] A pair of first circular holes 3-2 for SMA feeding are etched on the middle layer metal surface 3; a pair of second circular holes 5-1 for SMA feeding are etched on the lower layer metal surface 5; a pair of first non-metallized vias 2-1 for loading SMA are inside the upper layer dielectric substrate 2, and a pair of second non-metallized vias 4-1 for loading SMA are inside the lower layer dielectric substrate 4; the projections of the first circular hole 3-2, the second circular hole 5-1, the first non-metallized via 2-1, and the second non-metallized via 4-1 on the lower layer metal surface 5 coincide. The outer conductor of the SMA penetrates through the lower layer dielectric substrate 4 to connect to the lower layer metal surface 5 and the middle layer metal surface 3; the inner conductor penetrates through the upper layer dielectric substrate 2 to connect to the square metal patch 1-2.

[0048] On the middle layer metal surface 3, the centers of the two U-shaped slots 3-1 and the center of the first circular hole 3-2 are located on the same straight line.

[0049] The device details and specific size requirements of the above-mentioned small-size co-polarized full-duplex antenna are as follows:

[0050] In combination with Figure 3 and Figure 4The relative dielectric constant of the upper and lower dielectric substrates 2 and 4 is 2.2, and the thickness H is 0.762 mm . The side length LC of the square slot 1-1 etched on the upper metal surface 1 is 25 mm . The side length La of the square slot 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 15.895 mm , the diameter Dt of the first and second metallized vias 6 and 7 in the upper and lower dielectric substrates 2 and 4 is 0.2 mm , the distance S between adjacent metallized vias in the same dielectric substrate is 0.8 mm . The length Lsiw of the folded substrate integrated waveguide resonant cavity is 21.4 mm .

[0051] In combination Figure 5 , the long side length Ls1 of the two U-shaped slots 3-1 etched on the middle metal surface 3 is 20.6 mm , the short side length Ls2 is 1.2 mm , the slot width Ws is 0.3 mm , and the distance Ds between the long side of the U-shaped slot 3-1 and the adjacent metallized via wall is 0.4 mm . The diameter D1 of the first non-metallized via 2-1 inside the upper dielectric substrate 2 for loading SMA is 0.15 mm , and the diameter D2 of the second non-metallized via 4-1 inside the lower dielectric substrate 4 for loading SMA is 0.345 mm . The distance Lf between the center of the first and second non-metallized vias 2-1 and 4-1 and the nearest metallized via wall is 8.7 mm . Among them is the free space wavelength at the center frequency 5.915 GHz.

[0052] In combination Figure 6 , it can be seen from the given S parameter curve that the reflection coefficient |S 11 | and |S 22 | are lower than -10 dB in the operating frequency band of 5.905 GHz ~ 5.925 GHz, the bandwidth is 20 MHz, the isolation |S 21 | in the operating frequency band is greater than 15 dB, and the maximum isolation at the center frequency 5.915 GHz is close to 28 dB. The proposed antenna successfully covers the operating frequency band of the vehicle-to-everything direct communication based on LTE-V2X technology.

[0053] In combination Figure 7The boresight gain of the antenna port 1 in the working frequency band is greater than 3.87 dBi, and the maximum gain is 3.91 dBi; the boresight gain of the port 2 in the working frequency band is greater than 3.9 dBi, and the maximum gain is 3.92 dBi, and the in-band gain curve is relatively smooth.

[0054] In combination Figure 8 The directional diagrams of the port 1 and the port 2 of the antenna at the center frequency 5.915 GHz have the same radiation characteristics, wherein the maximum radiation direction of the E-plane radiation directional diagram has an inclination of about 30°. The reason for this situation is that the electric field is superimposed on the right half of the patch where the unexcited port is located, and part of the electric field is cancelled, so that the energy is concentrated in the left half of the patch radiation, and the directional diagram is inclined. The E-plane cross polarization is less than -40 dB, and the H-plane directional diagram has good symmetry.

[0055] The above is the preferred embodiment of the present application, it should be pointed out that, for those skilled in the art, without departing from the principles of the present application, can make a number of improvements and refinements, these improvements and refinements also considered to be within the scope of the present application.

Claims

1. A compact co-polarized full-duplex antenna based on pattern superposition method, comprising, in order from top to bottom: upper layer metal surface (1), upper layer dielectric substrate (2), middle layer metal surface (3), lower layer dielectric substrate (4), lower layer metal surface (5); It is characterized in that: The upper layer metal surface (1) is etched with a square groove (1-1) in the middle position, and a square metal patch (1-2) is placed in the square groove (1-1). The upper layer dielectric substrate (2) is provided with n periodic first metallized through holes (6), n>1; the n first metallized through holes (6) are enclosed to form a first square metal wall, and the projection of the square groove (1-1) on the upper layer dielectric substrate (2) is located in the first square metal wall. The lower layer dielectric substrate (4) is provided with n periodic second metallized through holes (7); n second metallized through holes (7) are enclosed to form a second square metal wall. The upper layer metal surface (1), the upper layer dielectric substrate (2), the middle layer metal surface (3), the lower layer dielectric substrate (4), the lower layer metal surface (5), the first square metal wall, and the second square metal wall together form a folded SIW resonant cavity. The middle layer metal surface (3) is etched with two axisymmetric U-shaped slots (3-1), and the two U-shaped slots (3-1) are located inside the folded SIW resonant cavity.

2. The compact co-polarized full-duplex antenna based on mode superposition method according to claim 1, characterized in that The middle layer metal surface (3) is etched with a pair of first circular holes (3-2); the lower layer metal surface (5) is etched with a pair of second circular holes (5-1); the upper layer dielectric substrate (2) has a pair of first non-metallized through holes (2-1) inside, and the lower layer dielectric substrate (4) has a pair of second non-metallized through holes (4-1) inside; the projections 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 layer metal surface (5) are coincident.

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

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

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

6. The compact co-polarized full-duplex antenna based on 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 layer metal surface (5) are coincident.

7. The compact co-polarized full-duplex antenna based on mode superposition method according to claim 1, characterized in that The openings of the two U-shaped slots (3-1) are both directed towards the center of the folded SIW resonant cavity.

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

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

10. The compact co-polarized full-duplex antenna based on 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 just located at the strongest electric field position of the folded SIW resonant cavity respectively, the folded SIW resonant cavity will generate a TE 120 like mode whose electric field in the upper half cavity is even symmetric along the center line; at the same time, the square metal patch (1-2) is excited to generate a TM 01 like mode whose electric field in the upper half cavity is odd symmetric along the center line; based on the electric field distribution characteristics of the two modes, when they resonate at the same frequency, the TE 120 like mode generated by the folded SIW resonant cavity and the TM 01 like mode generated by the patch are superimposed, thereby generating an electric field zero region around the unexcited port, realizing low mutual coupling between the two ports.

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