A full-duplex self-interference cancellation method based on antenna position adjustment

Abstract

The application discloses a full-duplex self-interference cancellation method based on antenna position adjustment and belongs to the field of wireless communication. A transmitting antenna and two receiving antennas are configured at each communication node, the transmitting antenna is fixed at the center of a slide rail, the receiving antennas are arranged on both sides of the transmitting antenna, and the two receiving antennas can move in the slide rail; the receiving antennas on both sides of the transmitting antenna are moved so that the distance between the receiving antennas and the transmitting antenna is an odd multiple of the half wavelength of the transmitting signal, the phases of the signals received by the two receiving antennas are different by (2k+1)pi, the self-interference signals are cancelled with each other after passing through a combiner, and the obtained radio frequency output signal is used as the received signal of the entire receiving antenna structure. By using the application, the self-interference signals can be cancelled and the received useful signals can be enhanced simultaneously.

Description

Technical Field

[0001] This patent relates to a method for eliminating self-interference in the radio frequency domain in full-duplex communication, specifically to a self-interference elimination receiver antenna structure based on antenna position adjustment, belonging to the field of wireless communication. Background Technology

[0002] Simultaneous full-duplex communication improves spectrum efficiency by transmitting and receiving signals simultaneously on the same frequency band. Since the receiving antenna receives self-interference signals from its own transmitting antenna, self-interference cancellation is a key issue that full-duplex communication systems need to address. Typically, the relatively close distance between the transmitting and receiving antennas results in self-interference signals having stronger received power than the useful signal. Therefore, radio frequency domain self-interference cancellation is needed to reduce the self-interference signal to a low level to ensure the proper functioning of subsequent digital domain cancellation. Traditionally, a symmetrical receiving antenna structure can be used, where different phases are added to the receiving antennas to cancel out the self-interference signals. However, this antenna structure may weaken the reception of signals from the other communication node. For example, by adding phase π and phase 0 to the signals of the two receiving links respectively, the self-interference signals can be reversed to cancel each other out. However, when the useful signal is incident perpendicularly to both receiving antennas, the phase difference π between the two receiving links will cause the useful signal to cancel out in reverse at the receiver. In this case, while the receiver cancels out the self-interference, it also significantly weakens the reception of the useful signal. Therefore, simply adjusting the added phases of the two receiving links to cancel out the self-interference signal cannot guarantee an effective improvement in the received signal-to-interference-plus-noise ratio (SNR).

[0003] In summary, existing techniques based on multi-receiver antenna phase-out cancellation of self-interference signals have not yet solved the problem of weakening the reception of useful signals while eliminating self-interference signals. Summary of the Invention

[0004] To address the potential problem of reduced useful signal reception, this invention proposes a transmitter structure based on mechanically adjusting the position of the receiving antenna. This structure can enhance the reception of useful signals while eliminating self-interference signals, thereby reducing the received power of self-interference signals and increasing the received power of useful signals.

[0005] The technical solution of the present invention is as follows:

[0006] A full-duplex self-interference cancellation method based on antenna position adjustment includes the following steps:

[0007] 1) Configure one transmitting antenna and two receiving antennas at each communication node. The transmitting antenna is fixed at the center of the slide rail, and the receiving antennas are placed on both sides of the transmitting antenna. Both receiving antennas can move in the slide rail.

[0008] 2) By moving the receiving antennas located on both sides of the transmitting antenna, the distance between the receiving antennas and the transmitting antennas is made an odd multiple of half the wavelength of the transmitted signal, i.e.

[0009]

[0010] The distances d1 and d2 between the two receiving antennas and the transmitting antenna, k is an integer, and λ is the wavelength of the transmitted single-frequency signal;

[0011] 3) The signals received on the two receiving antennas are out of phase by (2k+1)π. After passing through the combiner, the self-interference signals cancel each other out, and the resulting RF output signal is used as the received signal of the entire receiving antenna structure.

[0012] If the signal incident angle satisfies sinθ=0, that is, θ=0 or π, then the distance from receiving antenna 1 to transmitting antenna is:

[0013]

[0014] in This is the current position of receiving antenna 1, meaning that the position of antenna 1 does not need to be adjusted at this time.

[0015] The distance from receiving antenna 2 to transmitting antenna is

[0016]

[0017] in Let m be the current location of receiving antenna 2, where m is a non-negative integer and satisfies...

[0018]

[0019] If the signal incident angle satisfies sinθ≠0, i.e. θ≠0 or π, the distance from receiving antenna 1 to transmitting antenna is...

[0020]

[0021] The distance from receiving antenna 2 to transmitting antenna is

[0022]

[0023] Calculate the displacement of receiving antenna 1 as follows:

[0024]

[0025] The displacement of receiving antenna 2 is

[0026]

[0027] This invention is used to eliminate self-interference signals and enhance the reception of useful signals from the other party's communication node. Furthermore, the RF received signal can be further freed from self-interference in both the analog and digital domains to improve the received signal-to-interference-plus-noise ratio (SNR).

[0028] The advantages of the method proposed in this invention compared to existing technologies are as follows:

[0029] 1) By adjusting the positions of the two receiving antennas, both self-interference signals were eliminated and the received useful signals were enhanced.

[0030] 2) This structure only requires mechanically moving the antenna position according to the location of the other party's communication node using a displacement controller, making the structure simple.

[0031] 3) For communication nodes with a defined receiving direction, the antenna structure only needs to be adjusted once during the communication initialization phase. The receiving antenna position only needs to be adjusted again when the position of the communication node changes. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the transceiver receiving device of the present invention.

[0033] Figure 2 The figure shows the simulation results of the self-interference isolation in the embodiments of the present invention. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of the invention is not limited in any way.

[0035] Each communication node is configured with one transmitting antenna and two receiving antennas. The transmitting antenna is fixed at the center of a slide rail, and the receiving antennas are placed on either side of the transmitting antenna, with both receiving antennas movable within the slide rail. The signals from the two receiving antennas are output through a combiner. Self-interference signals are eliminated by adjusting the position of the receiving antennas on the slide rail, while simultaneously ensuring enhanced signal reception from the other communication node. The specific steps of the full-duplex self-interference cancellation method based on antenna position adjustment in this invention are as follows:

[0036] 1) The design principle for eliminating self-interference signals is as follows: Let the distances of the two receiving antennas from the transmitting antenna be d1 and d2, respectively, and the wavelength of the transmitted single-frequency signal be λ. By moving the receiving antennas located on both sides of the transmitting antenna, the distance between the receiving antennas and the transmitting antennas is made an odd multiple of half the wavelength of the transmitted signal, i.e.

[0037]

[0038] Where k is an integer. At this point, the signals received by the two receiving antennas are out of phase by (2k+1)π, and the self-interference signals cancel each other out after passing through the combiner. Based on this design criterion, the distance difference between the two receiving antennas and the central transmitting antenna can be determined. To enhance the reception of the useful signal transmitted by the other side while eliminating self-interference signals, the specific positions of the receiving antennas need to be further adjusted, as calculated below:

[0039] Let the distances from the two receiving antennas to the transmitting antenna be d1 = d0 and d2 = d0 + (2k + 1)λ / 2, respectively. The distance d0 needs to be further determined based on the receiving azimuth of the useful signal to achieve normal signal reception. Let the incident angle of the received useful signal be θ, and the path difference between the two receiving antennas be...

[0040]

[0041] To enhance the useful signal output by the combiner, the signal path difference Δd should satisfy the following condition:

[0042] Δd=lλ,

[0043] Where l is an integer. At this point, the signals received by the two receiving antennas are out of phase by 2πl. When sinθ = 0, i.e., θ = 0 or π, the signal from the other party is incident perpendicularly, the signal path difference is 0, and the signals from the two receiving antennas are superimposed in the same direction by the combiner, maximizing the received signal. Because the signal path difference is always 0 in this case, it is independent of the distance d0, and d0 can be set to any value. When sinθ ≠ 0, the distance d0 should be set to...

[0044]

[0045] Through the above steps, the distances from the two receiving antennas to the central transmitting antenna can be uniquely determined by setting specific values ​​for integers k and l.

[0046]

[0047] and

[0048]

[0049] After determining the distances d1 and d2, the two receiving antennas are moved to the designated positions calculated by the slide rail by the antenna displacement controller. This can simultaneously eliminate self-interference signals and enhance the reception of useful signals from the other party's communication node.

[0050] The invention was simulated and analyzed using Matlab software. Due to the difference in half-wavelength (an odd multiple) between the two receiving antennas and the central transmitting antenna, there is a slight difference in the received signal power, resulting in residual signals after the self-interference signals cancel each other out. Furthermore, since the design primarily considered the elimination of direct-path self-interference signals, multipath signal residues also contribute to residual self-interference signals. It should be noted that the residual self-interference signals can be further eliminated in the analog and digital domains to ensure the normal operation of the entire full-duplex system.

[0051] In the Matlab simulation analysis, operating frequencies of 2.4 GHz and 5.8 GHz were considered. The distance difference between receiving antenna 1 and receiving antenna 2 and the central transmitting antenna was set to d1-d2=λ / 2, and the incident angle of the useful signal was set to 0. At this time, the relationship between the self-interference isolation (in dB) and the distance (in meters) between receiving antenna 1 and the central transmitting antenna is as follows: Figure 2 As shown, the self-interference isolation achievable by the antenna structure of this invention increases with the distance from the receiving antenna 1 to the center antenna and the operating frequency. This reduces the gap between the self-interference signal power and the received power of the useful signal, which is beneficial for subsequent self-interference cancellation in the analog and digital domains.

[0052] It should be noted that the purpose of disclosing the embodiments is to help further understand the present invention. However, those skilled in the art will understand that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the scope of protection of the present invention is defined by the scope of the claims. Contents not described in detail in this specification are well-known to those skilled in the art.

Claims

1. A full-duplex self-interference cancellation method based on antenna position adjustment, comprising the following steps: 1) Configure one transmitting antenna and two receiving antennas at each communication node. The transmitting antenna is fixed at the center of the slide rail, and the receiving antennas are placed on both sides of the transmitting antenna. Both receiving antennas can move in the slide rail. 2) By moving the receiving antennas located on both sides of the transmitting antenna, the distance between the receiving antennas and the transmitting antennas is made an odd multiple of half the wavelength of the transmitted signal, i.e. ， The distance between the two receiving antennas and the transmitting antenna and It is an integer. Wavelength of the transmitted single-frequency signal; 3) The signals received on the two receiving antennas are combined and the self-interference signals cancel each other out. The resulting radio frequency output signal is used as the received signal of the entire receiving antenna structure. If the signal incident angle satisfies ,Right now or Then the distance from receiving antenna 1 to transmitting antenna is , in This is the current position of receiving antenna 1, meaning that the position of antenna 1 will not be adjusted at this time; The distance from receiving antenna 2 to transmitting antenna is in The current location of receiving antenna 2, parameters are non-negative integers and satisfy ， The displacement of receiving antenna 2 is ; If the signal incident angle satisfies ,Right now or The distance from receiving antenna 1 to transmitting antenna is The displacement of receiving antenna 1 is The distance from receiving antenna 2 to transmitting antenna is The displacement of receiving antenna 2 is .

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