A single-channel signal detection design method suitable for multi-feed antenna

Abstract

The application discloses a single-channel signal detection design method suitable for a multi-feed antenna, and relates to the field of satellite communication.The method comprises the following steps: S1, a modulator is used to perform orthogonal modulation on multiple-channel signals generated by the multi-feed source, and a combiner is used to form a combined signal; S2, the combined signal is converted into an L-band combined signal by a low-noise down converter (LNB); S3, the L-band combined signal is converted into a zero intermediate frequency baseband digital signal by a tracking receiver; S4, a baseband processing unit is used to complete frequency coarse estimation on the baseband digital signal by using a multi-path parallel frequency search method, so that signal detection is realized; and S5, the baseband processing unit is used to perform frequency coarse correction, FFT frequency offset estimation, phase-locked tracking and power estimation on the signal, so that signal tracking of the multi-feed antenna is completed.The application adopts a code domain synthesis scheme, has low requirements on the antenna feed part of the multi-feed source, can reduce the system cost by using a single-channel receiver, and can improve the reliability of the system.In addition, the multi-path parallel frequency search method is simple in calculation and high in detection precision, and is suitable for signal detection and tracking of a multi-feed antenna system which is cost-sensitive, low in complexity and high in precision.

Description

Technical Field

[0001] This invention relates to the field of satellite communications, and in particular to a single-channel signal detection design method suitable for multi-feed antennas. Background Technology

[0002] Satellite communication has always been one of the most important communication methods in the field of communications. Satellite communication ground station equipment integrates antenna technology, communication technology, automatic control technology, signal processing technology, structural design technology, and other technologies. Satellite communication ground station equipment can provide secure and reliable voice, fax, image, video, data communication, and IP services, and can be widely used in battlefield military communications, mobile command, emergency communication support, live broadcasting of competitions, and listening to radio and television programs.

[0003] In the field of satellite communications, real-time and accurate control of narrow-beam antennas to point at communication targets is crucial. Currently, automatic tracking technologies mainly include step tracking, conical scan tracking, monopulse tracking, and multi-feed tracking. Step tracking is relatively slow, conical scan tracking has poor accuracy, while monopulse tracking offers higher accuracy and computational speed compared to step and conical scan tracking, making it widely used in satellite communications, ground stations, and radar stations. However, monopulse tracking is expensive. Multi-feed tracking, due to its lower cost, is more widely studied and can be applied to cost-sensitive scenarios. The key to multi-feed tracking is how to receive and detect signals.

[0004] To reduce costs, when a multi-feed antenna tracking receiver uses a single-channel signal reception, it is necessary to combine multiple signals. However, the observed signals output from different feed sources have the same frequency but uncertain relative phase relationships, so they cannot be directly combined. Each signal needs to be modulated to achieve separability in the time, frequency, or code domains. When using time-domain combining, multiple signals are processed at the front end through a time-division multiplexing channel. Due to the high switching frequency and potential large channel power variations, gain control in the back-end processing needs to be fast and precise, making implementation difficult and resulting in low detection accuracy. When using frequency-domain combining, multiple signals are modulated at different frequencies and processed through frequency division multiplexing. Because multiple different frequencies are used for modulation, varying degrees of intermodulation interference may exist between frequencies, causing problems for back-end signal processing. Currently, there is no code-domain combining method to solve the modulation and signal separation of multiple signals. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems by designing a single-channel signal detection method suitable for multi-feed antennas. It includes the following steps:

[0006] S1. Use an O / Π modulator to perform quadrature modulation on the multi-channel signals generated by the multiple feed sources respectively, and form a combined signal through a combiner;

[0007] S2, the combined signal is converted to an L-band combined signal by a low-noise downconverter (LNB);

[0008] The S3 and L band combined signals enter the tracking receiver and are converted into a zero-IF baseband digital signal;

[0009] S4. The baseband processing unit uses a multi-channel parallel frequency search method to perform coarse frequency estimation of the baseband digital signal and realize signal detection.

[0010] S5, the baseband processing unit performs coarse frequency offset correction, FFT frequency offset estimation, phase-locked tracking and power estimation on the signal to complete signal tracking of the multi-feed antenna.

[0011] The 0 / Π modulator in S1 modulates the K-channel signals by generating a 0 / Π phase shift through the control of the modulation switch. The modulated signal is a square wave signal with the following form: The modulation switch control frequency is This is achieved by generating quadrature switching signals from the tracking receiver.

[0012] In S1, the quadrature modulation uses M-order orthogonal vectors. M can be selected based on system performance; the larger M is, the higher the frequency offset estimation accuracy. The number of orthogonal vectors is K, equal to the number of antenna feeds and channels. Based on the characteristics of the O / Π modulator, K M-order orthogonal vectors V are selected to control the O / Π modulator to achieve quadrature modulation. Assuming the signal symbol rate is R, then... The modulated signal chip rate is .

[0013] The L-band combined signal in S3 enters the tracking receiver, and after filtering, I / Q quadrature demodulation and A / D sampling, it is converted into a zero-IF baseband digital signal and input to the baseband processing unit.

[0014] The specific process of the multi-path parallel frequency search method in S4 is as follows:

[0015] S41. Perform multi-channel preset frequency offset correction on the baseband digital signal. The preset frequency offset range is [-DF, +DF], and the interval between preset frequency offsets is... The number of preset frequency offsets f , If the value is rounded to zero, then the preset frequency offset is... If the baseband digital signal is The signal after the preset frequency offset is ;

[0016] S42. Perform K-channel orthogonal despreading on each channel of the preset frequency offset corrected signal. The K M-order orthogonal vectors V obtained from the despreading should be consistent with the orthogonal vectors used in the quadrature modulation in S1, resulting in the despread signal. ;

[0017] S43. The accumulated energy calculated by averaging the spread spectrum symbols of the despread signal is used as the decision statistic. Assuming the number of accumulated symbols is N, calculate the energy of each averaged symbol and accumulate it over N points. The symbol period of a spread spectrum symbol is represented by the symbol period, where The decision statistic of the despread signal. ;

[0018] S44. The preset frequency offset value that has the highest frequency of occurrence of the decision statistic in K channels is the coarse frequency estimate. Specifically, first, the maximum value of the decision statistic is selected for each channel. The maximum value of the k-th channel is... At this time, the preset frequency offset is Then The value that appears most frequently is selected as the coarse frequency estimate. , There are K. The value that appears most frequently.

[0019] Selected from S41 The preset frequency offset interval is based on the fact that the frequency offset is greater than 100%. As the frequency shifts, the orthogonality of the signal gradually weakens, therefore the preset frequency offset is recommended to be at least less than 100%. The preset frequency offset interval is recommended to be at least less than . The larger the value of , the smaller the preset frequency offset interval, the more resources are consumed, and the higher the accuracy of the final estimated frequency.

[0020] The beneficial effects of this invention are as follows: the single-channel signal detection design method of the multi-feed antenna adopts a code domain synthesis scheme, which has lower requirements for the antenna feed part of the multi-feed antenna. Using a single receiving channel can reduce system cost and improve system reliability. In addition, the multi-parallel frequency search method is simple to calculate and has high detection accuracy, making it suitable for signal detection and tracking of cost-sensitive, low-complexity, and high-precision multi-feed antenna systems. Attached Figure Description

[0021] Figure 1 This is a typical block diagram of a single-channel signal detection and tracking system architecture with a multi-feed antenna.

[0022] Figure 2 This invention relates to a flowchart of a single-channel signal detection design method for a multi-feed antenna.

[0023] Figure 3 This is a schematic block diagram of a 0 / Π modulator.

[0024] Figure 4 Block diagram for tracking receiver design.

[0025] Figure 5 This is a flowchart of a multi-path parallel frequency search detection method.

[0026] Figure 6 This is a design block diagram for the baseband processing unit.

[0027] Figure 7 Simulation graphs showing the signal detection success rate under different signal-to-noise ratios;

[0028] Figure 7 In the diagram: Curve A is the simulation curve of the success rate of signal detection frequency estimation for 50 single beacon symbols; Curve B is the simulation curve of the success rate of signal detection frequency estimation for 100 single beacon symbols plus ±200KHz interference beacons; Curve C is the simulation curve of the success rate of signal detection frequency estimation for 50 single beacon symbols plus ±200KHz interference beacons. Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0030] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0031] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0032] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0033] This invention proposes a single-channel signal detection design method suitable for multi-feed antennas, and its typical system architecture block diagram is shown below. Figure 1 As shown, the K feed sources, consisting of one main feed source and K-1 sub-feed sources, generate K channel signals. These signals are orthogonally modulated under the control of the quadrature switching signal generated by the tracking receiver. The signals are then combined into a single-channel combined signal by a combiner and input to the tracking receiver for signal detection and subsequent processing.

[0034] This invention is based on a single-channel signal detection design method suitable for multi-feed antennas, such as... Figure 2 As shown, it includes the following steps:

[0035] S1. Use an O / Π modulator to perform quadrature modulation on the multi-channel signals generated by the multiple feed sources respectively, and form a combined signal through a combiner;

[0036] S2, the combined signal is converted to an L-band combined signal by a low-noise downconverter (LNB);

[0037] The S3 and L band combined signals enter the tracking receiver and are converted into a zero-IF baseband digital signal;

[0038] S4. The baseband processing unit uses a multi-channel parallel frequency search method to perform coarse frequency estimation of the baseband digital signal and realize signal detection.

[0039] S5, the baseband processing unit performs coarse frequency offset correction, FFT frequency offset estimation, phase-locked tracking and power estimation on the signal to complete signal tracking of the multi-feed antenna.

[0040] Specifically, the 0 / Π modulator in S1 modulates the K-channel signals by generating a 0 / Π phase shift through the control of the modulation switch. The modulated signal is a square wave signal with the following form: The modulation switch control frequency is This is achieved by generating quadrature switching signals from the tracking receiver. A block diagram of the 0 / Π modulator is shown below. Figure 3 As shown.

[0041] Specifically, the orthogonal modulation in S1 uses M-order orthogonal vectors. M can be selected based on system performance; the larger M is, the better the signal after symbol averaging can approximate a complex Gaussian random variable, resulting in higher frequency offset estimation accuracy. The number of orthogonal vectors is K, equal to the number of antenna feeds and channels. Based on the characteristics of the O / Π modulator, K M-order orthogonal vectors V are selected to control the O / Π modulator to achieve orthogonal modulation. Assuming the signal symbol rate is R, then... The modulated signal chip rate is We can choose orthogonal Walsh codes as orthogonal vectors.

[0042] Specifically, the channel signal in S1 is ,in, Let the amplitude of the signal in the k-th channel be denoted as . For carrier frequency, Let be the phase of the k-th channel. Then, the combining signal is: .

[0043] Specifically, the L-band combined signal in S3 enters the tracking receiver, where it undergoes filtering, I / Q quadrature demodulation, and A / D sampling, converting it into a zero-IF baseband digital signal which is then input to the baseband processing unit. The tracking receiver design block diagram is shown below. Figure 4 As shown.

[0044] Specifically, the process of the multi-path parallel frequency search method in S4 is as follows: Figure 5 As shown:

[0045] S41. Perform multi-channel preset frequency offset correction on the baseband digital signal. The preset frequency offset range is [-DF, +DF], and the interval between preset frequency offsets is... The number of preset frequency offsets f , If the value is rounded to zero, then the preset frequency offset is... If the baseband digital signal is The signal after the preset frequency offset is ;

[0046] S42. Perform K-channel orthogonal despreading on each channel of the preset frequency offset corrected signal. The K M-order orthogonal vectors V obtained from the despreading should be consistent with the orthogonal vectors used in the quadrature modulation in S1, resulting in the despread signal. ;

[0047] S43. The accumulated energy calculated by averaging the spread spectrum symbols of the despread signal is used as the decision statistic. Assuming the number of accumulated symbols is N, calculate the energy of each averaged symbol and accumulate it over N points. The symbol period of a spread spectrum symbol is represented by the symbol period, where The decision statistic of the despread signal. ;

[0048] S44. The preset frequency offset value that has the highest frequency of occurrence of the decision statistic in K channels is the coarse frequency estimate. Specifically, first, the maximum value of the decision statistic is selected for each channel. The maximum value of the k-th channel is... At this time, the preset frequency offset is Then The value that appears most frequently is selected as the coarse frequency estimate. , There are K. The value that appears most frequently.

[0049] Specifically, S41 selects The preset frequency offset interval is based on the fact that the frequency offset is greater than 100%. As the frequency shifts, the orthogonality of the signal gradually weakens, therefore the preset frequency offset is recommended to be at least less than 100%. The preset frequency offset interval is recommended to be at least less than . The larger the value of , the smaller the preset frequency offset interval, the more resources are consumed, and the higher the accuracy of the final estimated frequency.

[0050] Specifically, the design block diagram of the baseband processing unit is as follows: Figure 6 As shown, the baseband digital I / Q signal enters the baseband processing unit. First, it undergoes preset frequency offset correction for F channels. Then, each corrected signal is orthogonally despread with K orthogonal vectors, resulting in F despread signals across K channels. The decision statistic for each despread signal is calculated, and the preset frequency offset value that has the highest frequency among the K channels is the coarse frequency estimate. Then, the signal is coarsely corrected for frequency, FFT frequency offset estimated, phase-locked tracking and power estimated, thus completing the signal tracking of the multi-feed antenna.

[0051] This example uses the design method of this invention to simulate the success rate of signal detection frequency estimation. The simulation results are as follows: Figure 7 As shown. The number of channels K is 5, the orthogonal vector V uses 5-channel M=128-order Walsh code, and the symbol rate of the signal is R=5Ksps. The value is set to 2, and the preset frequency offset interval is... .

[0052] Assuming the simulation frequency offset is a random number between [-100kHz, +100kHz], and the simulation phase offset is \left [ {-\pi ,+\pi} \right ] Random numbers between intervals, frequency controlled by modulation switch The filter cutoff frequency is 320kHz, and 10,000 simulations were performed using Matlab tools at different signal-to-noise ratios.

[0053] Assuming the beacon frequency is f0, 50 symbol points are selected for simulation. Curve A is the simulation curve of the frequency estimation success rate of 50 single beacon symbols. Assuming there is interfering beacon near the beacon with a frequency of f0±200KHz, curve B is the simulation curve of the signal detection frequency estimation success rate of 100 single beacon symbols plus interfering beacon. Curve C is the simulation curve of the signal detection frequency estimation success rate of 50 single beacon symbols plus interfering beacon.

[0054] Depend on Figure 7It can be seen that when using 50 symbol points, with a single beacon frequency and a signal-to-noise ratio (SNR) greater than 6dB, the frequency estimation success rate can reach over 99%. When there are equal-amplitude interference beacons at ±200kHz of the beacon, with 100 symbol points, the frequency estimation success rate is over 95% with an SNR greater than 10dB, and over 98% with an SNR greater than 15dB. With 50 symbol points, the frequency estimation success rate is over 90% with an SNR greater than 10dB, and over 96% with an SNR greater than 15dB.

[0055] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A single-channel signal detection design method suitable for multi-feed antennas, characterized in that, include: S1. Use an O / Π modulator to perform quadrature modulation on the multi-channel signals generated by the multiple feed sources respectively, and form a combined signal through a combiner; S2, the combined signal is converted to an L-band combined signal by a low-noise downconverter (LNB); The S3 and L band combined signals enter the tracking receiver and are converted into a zero-IF baseband digital signal; S4, the baseband processing unit uses a multi-channel parallel frequency search method to perform coarse frequency estimation of the baseband digital signal, thereby achieving signal detection; the specific steps of the multi-channel parallel frequency search method in S4 are as follows: S41. Perform multi-channel preset frequency offset correction on the baseband digital signal. The preset frequency offset range is [-DF, +DF], and the interval between preset frequency offsets is... The number of preset frequency offsets f , If the value is rounded to zero, then the preset frequency offset is... If the baseband digital signal is The signal after the preset frequency offset is ; S42. Perform K-channel orthogonal despreading on each preset frequency offset corrected signal. The K M-order orthogonal vectors V obtained from the despreading should be consistent with the orthogonal vectors used in the quadrature modulation in S1, to obtain the despread signal. ; S43. The accumulated energy calculated by averaging the spread spectrum symbols of the despread signal is used as the decision statistic. Assuming the number of accumulated symbols is N, calculate the energy of each averaged symbol and perform N-point accumulation. The symbol period of a spread spectrum symbol is represented by the symbol period, where The decision statistic of the despread signal. ; S44. The preset frequency offset value that has the highest frequency of occurrence of the decision statistic in K channels is the coarse frequency estimate. First, select the maximum value of the decision statistic for each channel. The maximum value of the k-th channel is... At this time, the preset frequency offset is Then The value that appears most frequently is selected as the coarse frequency estimate. , There are K. The value that appears most frequently; S5, the baseband processing unit performs coarse frequency correction, FFT frequency offset estimation, phase-locked tracking, and power estimation on the signal to complete signal tracking for the multi-feed antenna.

2. The single-channel signal detection design method suitable for multi-feed antennas according to claim 1, characterized in that, In S1, the 0 / Π modulator modulates the K-channel signals by generating a 0 / Π phase shift through the control of the modulation switch. The modulated signal is a square wave signal with the following form: The modulation switch control frequency is This is achieved by generating quadrature switching signals from the tracking receiver.

3. The single-channel signal detection design method suitable for multi-feed antennas according to claim 1, characterized in that, In S1, orthogonal modulation uses M-order orthogonal vectors. M can be selected based on system performance; the larger M is, the higher the frequency offset estimation accuracy. The number of orthogonal vectors is K, equal to the number of antenna feeds and channels. Based on the characteristics of the O / Π modulator, K M-order orthogonal vectors V are selected to control the O / Π modulator to achieve orthogonal modulation. Assuming the signal symbol rate is R, then... The modulated signal chip rate is .

4. The single-channel signal detection design method suitable for multi-feed antennas according to claim 1, characterized in that, The L-band combined signal in S3 enters the tracking receiver, and after filtering, I / Q quadrature demodulation and A / D sampling, it is converted into a zero-IF baseband digital signal and input to the baseband processing unit.

5. The single-channel signal detection design method suitable for multi-feed antennas according to claim 1, characterized in that, Select in S41 The preset frequency offset interval is based on the fact that the frequency offset is greater than 100%. As the frequency shifts, the orthogonality of the signal gradually weakens, therefore the preset frequency offset must be at least less than 1 / 3. Then the preset frequency offset interval is at least less than , The larger the value of , the smaller the preset frequency offset interval, the more resources are consumed, and the higher the accuracy of the final estimated frequency.

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