Dual-Receiver Unit Joint Anti-Jamming Method Based on Propagation Delay Difference

Abstract

The present invention discloses a joint anti-interference method based on propagation delay difference for dual receiving units. The method includes: (1) Receiving unit 1 and receiving unit 2 simultaneously receive the useful signal and the interference signal; (2) Down-converting the signals of path A and path B to a frequency band suitable for sampling; (3) Sampling the down-converted signals of path A and path B; (4) Comparing the delays between the sampled signals of path A and path B, and estimating the delay adjustment value N1 of path A and the delay adjustment value N2 of path B; (5) Delaying the sampled signal of path A by N1*T seconds and delaying the sampled signal of path B by N2*T seconds; (6) Jointly processing the delayed sampled signal of path A and the delayed sampled signal of path B to obtain a mixed signal of the useful signal in the delayed sampled signal of path 3B; (7) Processing the mixed signal in step (6) to obtain the useful signal; (8) Demodulating the useful signal in step (7). The present invention obtains the useful signal based on the delay between the signals received by two receiving units.

Description

Technical Field

[0001] The present invention relates to an anti-interference method for a communication system, in particular to a joint anti-interference method for dual receiving units with radio signal time delay differences caused by different propagation distances, belonging to the field of communication technology. Background Art

[0002] Radio is an electromagnetic wave propagating in free space. Radio communication is a communication method that uses radio electromagnetic waves to transmit information in space. Radio communication does not require the erection of communication lines, has a long communication distance, good mobility, and can be established quickly, and has extensive applications in both military and civilian communication fields. However, wireless communication is easily affected by natural factors and interference signals, and the communication quality is unstable. Anti-interference has always been a research hotspot in the field of wireless communication. Especially when the power of the interference signal is much greater than the power of the useful signal itself, how to cancel the interference signal and achieve the correct reception of the useful signal has always been the focus and difficulty of the research on wireless communication anti-interference technology.

[0003] Currently, when the power of the interference signal is much greater than the power of the useful signal, a common method to maintain smooth communication is to deploy an antenna array at the receiving end, and use the sidelobe characteristics of the antenna elements and the correlation between the elements to suppress the interference signal. In this method, assume that the useful signal is S(t) and the interference signal is K(t); the main lobe of element A1 points to S(t), and it is the direct radiation element of S(t); the main lobe of element A2 points to K(t), and it is the direct radiation element of K(t); the signal received by element A1 is A1(t) = S(t) + ξK(t) + n(t), and the signal received by element A2 is A2(t) = ζS(t) + K(t) + n(t), where ξ and ζ are sidelobe attenuation factors, ξ, ζ << 1. Since the distance between the elements is small, the time delay of the transmitted signal arriving at different elements can be ignored. Using the above formula, it can be deduced that ξA2(t) = ξζS(t) + ξK(t) + n(t), and A1(t) - ξA2(t) = S(t) - ξζS(t) + n(t). Since ξζS(t) can be regarded as an infinitesimal quantity, the transmitted signal S(t) can be obtained by weighted difference of the two elements. The antenna array with N elements can solve the transmitted signal under the condition of at most N - 1 interference sources.

[0004] However, the above scheme is only applicable to the scenario where the interference signal source, the useful signal source and the receiving antenna array are not on the same straight line. When the interference signal source, the useful signal source and the antenna array are on the same straight line, the direct radiation elements of the interference signal source and the useful signal source are the same element, and the receiving system cannot use the sidelobe characteristics of the antenna elements to cancel the influence of the interference signal, and this method fails.

[0005] For the scenario where the interfering signal source and the useful signal source are located in approximately the same direction relative to the receiving antenna, the sidelobe characteristics of the antenna elements cannot be used to cancel the influence of the interfering signal, and the power of the interfering signal K(t) is much greater than that of the useful signal S(t), the present invention proposes a joint anti-interference method for two receiving units based on the difference in propagation delay. Propagation delay refers to the time it takes for an electromagnetic wave to propagate a certain distance in a channel. Propagation delay is equal to the channel length divided by the propagation rate. The propagation rate of an electromagnetic wave in free space is the speed of light, i.e., 3*10 8 km / s. This method uses two receiving units located at different spatial positions. Due to the difference in the distances between the signal sources and the interference sources, the difference in the signal propagation delays is used to eliminate the influence of the interfering signal and obtain the useful signal. Summary of the Invention

[0006] To overcome the above defects, the object of the present invention is to propose a joint anti-interference method for two receiving units based on the difference in propagation delay. This method uses two receiving units located at different spatial positions and the difference in the propagation delays of the received signals to eliminate the influence of the interfering signal whose power is much greater than that of the useful signal and obtain the useful signal.

[0007] To achieve the above object, the joint anti-interference method for two receiving units based on the difference in propagation delay proposed by the present invention includes the following steps:

[0008] (1) The antennas of receiving unit 1 and receiving unit 2 simultaneously receive the useful signal and the interfering signal from free space. Let the signal received by receiving unit 1 be the A-channel signal, and the signal received by receiving unit 2 be the B-channel signal;

[0009] (2) Down-convert the A-channel signal and the B-channel signal in step (1) to a frequency band suitable for sampling;

[0010] (3) Using the same clock, sample the down-converted A-channel and B-channel signals in step (2) with a sampling interval of T seconds;

[0011] (4) Compare the delays between the A-channel and B-channel sampled signals, and estimate the A-channel delay adjustment value N1 and the B-channel delay adjustment value N2;

[0012] (5) Delay the A-channel sampled signal by N1*T seconds and delay the B-channel sampled signal by N2*T seconds;

[0013] (6) Jointly process the A-channel sampled signal and the B-channel sampled signal delayed in step (5) to eliminate the interfering signal and obtain a mixed signal of the useful signal in the A-channel sampled signal delayed by N1*T seconds and the useful signal in the B-channel sampled signal delayed by N2*T seconds;

[0014] (7) Process the mixed signal in step (6) to obtain the useful signal;

[0015] (8) Demodulate the useful signal in step (7) to obtain data.

[0016] In the above method, the receiving unit 1 and the receiving unit 2 are located at different spatial positions.

[0017] In the above method, the positions of the useful signal source and the interference signal source do not overlap.

[0018] In the above method, the signals received by the receiving unit 1 and the receiving unit 2 in step 1 are mixed signals of the useful signal and the interference signal.

[0019] In the above method, the power of the interference signal received by the receiving unit 1 and the receiving unit 2 is much greater than the power of the useful signal.

[0020] In the above method, the A-channel sampling signal in step 4 is the signal after down-conversion and sampling of the mixed signal received by the receiving unit 1 in step 1

[0021] In the above method, the B-channel sampling signal in step 4 is the signal after down-conversion and sampling of the mixed signal received by the receiving unit 2 in step 1

[0022] In the above method, based on the delay between the A-channel sampling signal and the B-channel sampling signal in step 4, the difference in the propagation delay of the interference signal received by the A-channel and the interference signal received by the B-channel can be approximately estimated.

[0023] In the above method, the values of N1 and N2 in step 4 are the number of sampling points.

[0024] In the above method, the difference in the propagation delay of the interference signal in the A-channel signal and the B-channel signal after the delay in step 5 is approximately 0.

[0025] In the above method, the mixed signal in step 5 contains two useful signals with different propagation delays.

[0026] In the above method, the installation positions of the antennas of the receiving unit 1 and the receiving unit 2 should ensure that the interference signal can be cancelled and the useful signal will not be cancelled.

[0027] The dual-receiving-unit joint anti-interference method based on the difference in propagation delay proposed by the present invention has the following advantages:

[0028] 1. The present invention is particularly applicable to the strong interference situation where the power of the interference signal is much greater than the power of the useful signal.

[0029] 2. The present invention utilizes the difference in the propagation delay of the useful signal and the interference signal received by the antennas of two receiving units located at different spatial positions to cancel the interference signal and obtain the useful signal.

[0030] 3. The present invention can use a directional antenna or a non - directional antenna.

[0031] 4. The receiving end of the present invention does not need to know the specific positions of the signal source and the interference source. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 . Flowchart of the joint anti - interference method for two receiving units based on propagation delay difference DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will be further described below with reference to the drawings.

[0034] The flow of the joint anti - interference method for two receiving units based on propagation delay difference of the present invention is as Figure 1 shown. Figure 1 In the figure, two receiving units are deployed at the receiving end to receive the signals sent by the useful signal source and the interference signal source. The power of the interference signal radiated by the interference signal source is much greater than the power of the useful signal radiated by the useful signal source. P is the position of the useful signal source, Q is the position of the interference signal source, G is the position of the antenna of receiving unit 1, and H is the position of the antenna of receiving unit 2. The distance between G and H should ensure that the interference signal can be cancelled, but the useful signal will not be cancelled.

[0035] Figure 1 The two receiving units in the figure are composed of their respective antennas, down - converters, sampling modules, and delay modules. The performance indicators of the antennas and down - converters of the two receiving units are exactly the same. The sampling modules use the same clock, and the sampling interval is T seconds. After the signals received by antenna 1 and antenna 2 are down - converted and sampled, on the one hand, they respectively enter their own delay modules, and on the other hand, they enter the delay estimation module simultaneously. The delay estimation module real - time estimates the delay between the signals received by the two antennas, and gives the interference signal delay adjustment value N1 of receiving unit 1 and the interference signal delay adjustment value N2 of receiving unit 2. Delay module 1 delays the sampled signal of antenna 1 by N1*T seconds, and delay module 2 delays the sampled signal of antenna 2 by N2*T seconds. The delayed mixed signals enter the interference cancellation module for processing to eliminate the interference signal and obtain the mixed signal composed of useful signals with different propagation delays. The useful signal extraction module separates the mixed signal of the useful signals with different propagation delays received by the two receiving units to obtain the useful signal and perform demodulation.

[0036] Assume that the performance indicators of the antennas and down - converters of receiving unit 1 and receiving unit 2 are exactly the same, and ignore the difference in signal amplitude attenuation caused by different propagation distances. Then, for the useful signals and interference signals received by receiving unit 1 and receiving unit 2, there is only a difference in propagation delay. Let the analog mixed signal received by receiving unit 1 be A1(t), and the analog mixed signal received by receiving unit 2 be A2(t). Then:

[0037] A1(t) = S(t) + K(t - Δt1) + n1(t) (1)

[0038] A2(t) = S(t - Δt2) + K(t - Δt3) + n2(t) (2)

[0039] In Equation (1), S(t) is the useful signal received by receiving unit 1, K(t - Δt1) is the interference signal received by receiving unit 1, and n1(t) is the noise of receiving unit 1. In Equation (2), S(t - Δt2) is the useful signal received by receiving unit 2, K(t - Δt3) is the interference signal received by receiving unit 2, and n2(t) is the noise of receiving unit 2. In Equation (1), Δt1 is the difference in propagation delays between path QG and path PG, Δt2 is the difference in propagation delays between path PH and path PG, and Δt3 is the difference in propagation delays between path QH and path PG. For clarity of expression, the noises n1(t) and n2(t) are omitted in the subsequent formula derivations.

[0040] After receiving unit 1 and receiving unit 2 sample the received analog mixed signals, the obtained digital signals are expressed as follows:

[0041] A1(k) = S(k) + K(k - Δk1) (3)

[0042] A2(k) = S(k - Δk2) + K(k - Δk3) (4)

[0043] Perform a correlation process on A1(k) and A2(k) to obtain the delay between A1(k) and A2(k). Since the power of the interference signal is much greater than the power of the useful signal, therefore, the difference in propagation delays Δk of the interference signals received by receiving unit 1 and receiving unit 2 can be approximately estimated from the delay between A1(k) and A2(k), that is

[0044] Δk = Δk3 - Δk1 (5)

[0045] Delay A1(k) by Δk and subtract it from A2(k), the noise signal in A1(k) can be cancelled, leaving only the mixed signal composed of useful signals with different delays, and the formula is as follows:

[0046]

[0047] Process the mixed signal composed of S(k - Δk) and S(k - Δk2) in Equation (6), and the useful signal S(k) can be obtained. Demodulate S(k), and the data sent by the signal source can be obtained.

Claims

1. A joint anti-jamming method for dual receiving units based on propagation delay difference, characterized in that For the scenario where the interfering signal source and the useful signal source are located in approximately the same direction relative to the receiving antenna, the sidelobe characteristics of the antenna elements cannot be used to cancel the influence of the interfering signal, and the power of the interfering signal K(t) is much greater than that of the useful signal S(t). The method described is implemented using receiving unit 1 and receiving unit 2. Among them, the antennas and down-converters of receiving unit 1 and receiving unit 2 have exactly the same performance indicators; receiving unit 1 and receiving unit 2 are located at different spatial positions; the signals received by receiving unit 1 and receiving unit 2 are mixed signals of the useful signal and the interfering signal; the power of the interfering signal received by receiving unit 1 and receiving unit 2 is much greater than the power of the useful signal; the installation positions of the antennas of receiving unit 1 and receiving unit 2 should ensure that the interfering signal can be cancelled and the useful signal will not be cancelled; the positions of the useful signal source and the interfering signal source do not overlap. The method described includes the following steps: (1) The antennas of receiving unit 1 and receiving unit 2 simultaneously receive the useful signal and the interfering signal from free space. Let the signal received by receiving unit 1 be the A-channel signal, and the signal received by receiving unit 2 be the B-channel signal. Among them, Let the analog mixed signal received by receiving unit 1 be A1(t), and the analog mixed signal received by receiving unit 2 be A2(t). Then: A1(t) = S(t) + K(t - Δt1) + n1(t) (1) A2(t) = S(t - Δt2) + K(t - Δt3) + n2(t) (2) In formula (1), S(t) is the useful signal received by receiving unit 1, K(t - Δt1) is the interfering signal received by receiving unit 1, n1(t) is the noise of receiving unit 1. In formula (2), S(t - Δt2) is the useful signal received by receiving unit 2, K(t - Δt3) is the interfering signal received by receiving unit 2, n2(t) is the noise of receiving unit 2; in formula (1), Δt1 is the difference in propagation delay between path QG and path PG, Δt2 is the difference in propagation delay between path PH and path PG, Δt3 is the difference in propagation delay between path QH and path PG; for clarity of expression, the noises n1(t) and n2(t) are omitted in the subsequent formula derivation. Among them, P is the position where the useful signal source is located, Q is the position where the interfering signal source is located, G is the position where the antenna of receiving unit 1 is located, and H is the position where the antenna of receiving unit 2 is located; the distance between G and H should ensure that the interfering signal can be cancelled, but the useful signal will not be cancelled. (2) Down-convert the A-channel signal and the B-channel signal in step (1) to a frequency band suitable for sampling. (3) Use the same clock to sample the down-converted A-channel and B-channel signals in step (2) with a sampling interval of T seconds; the obtained digital signals are expressed as follows: A1(k) = S(k) + K(k - Δk1) (3) A2(k) = S(k - Δk2) + K(k - Δk3) (4) (4) Compare the delays between the sampled signals of path A and path B, and estimate the delay adjustment value N1 of path A and the delay adjustment value N2 of path B; perform correlation processing on A1(k) and A2(k) to obtain the delay between A1(k) and A2(k). Since the power of the interference signal is much greater than that of the useful signal, therefore, the difference Δk in the propagation delays of the interference signals received by receiving unit 1 and receiving unit 2 can be approximately estimated from the delay between A1(k) and A2(k), that is Δk = Δk3 - Δk1 (5) Among them, the sampled signal of path A is the signal after down-conversion and sampling of the mixed signal received by receiving unit 1 in step (1); The sampled signal of path B is the signal after down-conversion and sampling of the mixed signal received by receiving unit 2 in step (1); Based on the delay between the sampled signals of path A and path B, approximately estimate the difference in the propagation delays of the interference signals received by path A and path B; the values of N1 and N2 are the number of sampling points; (5) Delay the sampled signal of path A by N1*T seconds, and delay the sampled signal of path B by N2*T seconds; the difference in the propagation delays of the interference signals in the delayed sampled signal of path A and the delayed sampled signal of path B is approximately 0; (6) Perform joint processing on the sampled signal of path A and the sampled signal of path B delayed in step (5) to eliminate the interference signal, and obtain the mixed signal of the useful signal in the sampled signal of path A in step (3) delayed by N1*T seconds and the useful signal in the sampled signal of path B in step (3) delayed by N2*T seconds; the mixed signal contains two useful signals with different propagation delays; (7) Process the mixed signal in step (6) to obtain the useful signal; (8) Demodulate the useful signal in step (7) to obtain the data.

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