A method and device for fast acquisition of low signal-to-noise ratio large frequency offset signals

Abstract

The application discloses a kind of low signal-to-noise ratio large frequency offset signal's fast acquisition method and device, it is related to signal detection field in communication system.The present application includes digital signal preprocessing, multi-bit difference, full correlation operation, multiple correlation value addition, threshold decision and the like steps, can realize the fast acquisition of digital signal under the condition of low signal-to-noise ratio large frequency offset, while giving consideration to the saving condition of resource, solve the problem that receiver is difficult to capture under the condition of low signal-to-noise ratio large frequency offset.The present application is applicable to any rate burst or continuous signal in communication, especially has good adaptability to large frequency offset low speed signal, with the advantages of fast acquisition, less resource occupation, especially suitable for signal acquisition of communication system.

Description

Technical Field

[0001] This invention relates to a method and apparatus for rapid acquisition of low signal-to-noise ratio (SNR) signals with large frequency offset, belonging to the field of signal detection in communication systems, and can be used for rapid acquisition of low SNR signals with large frequency offset. Background Technology

[0002] With the development of low-Earth orbit satellites and weapon platforms, the extremely high flight speeds of satellites and weapon platforms bring high-dynamic Doppler application scenarios to communication systems, while also placing high demands on communication quality, communication performance, and acquisition time.

[0003] Currently, traditional acquisition methods struggle to simultaneously address the requirements of high frequency offset and low signal-to-noise ratio. To achieve this, some methods require significant hardware resources, increasing costs; others necessitate auxiliary information from navigation signals, reducing the flexibility of the communication system. Therefore, there is an urgent need for an acquisition method that comprehensively considers high dynamic range, large frequency offset, low signal-to-noise ratio, and resource efficiency. Summary of the Invention

[0004] In view of this, the present invention provides a method and apparatus for rapid acquisition of low signal-to-noise ratio (SNR) signals with large frequency offset, solving the problem of high-dynamic signal acquisition for low-Earth orbit satellites and weapon platforms. The present invention can achieve rapid acquisition of digital signals under low SNR and large frequency offset conditions, while also saving resources, thus solving the problem of receiver difficulty in acquisition under these conditions.

[0005] The objective of this invention is achieved as follows:

[0006] A method for fast acquisition of low signal-to-noise ratio and large frequency offset signals includes the following steps:

[0007] (1) Receive the AD sampling signal sent from the outside, with a sampling multiple of more than or equal to 2 times, that is, the number of sampling points of one symbol is more than or equal to 2 times;

[0008] (2) After preprocessing, the AD sampling signal is multiplied by k to obtain the sampling signal;

[0009] (3) Split the k times sampled signal into k parallel signals;

[0010] (4) Take one of the parallel signals and perform multi-bit differential operation; that is, each symbol performs differential operation with its first, second, third...mth adjacent signal to obtain m differential signals; then, output these m signals and record them as rx-diff1, rx-diff2...rx-diffm;

[0011] (5) Perform multi-bit differential operation on the local known codewords to obtain m differential signals, and store them according to the codeword length, denoted as code-diff1, code-diff2...code-diffm;

[0012] (6) Perform full correlation operation on rx-diff1 and code-diff1. Similarly, perform full correlation operation on the signals and codewords after the other differential paths, and output m correlation values ​​peak1, peak2...peakm;

[0013] (7) Add the m relevant values ​​together to get Peak_1;

[0014] (8) Following the steps (4) to (7), the other k-1 paths are also processed in the same way to obtain peak_2 to peak_k;

[0015] (9) Add peak_1 to peak_k to get peak_out, and output it;

[0016] (10) Compare peak_out with the threshold value. If it is greater than the threshold, the capture is considered successful. If it is less than the threshold, continue to perform sliding capture.

[0017] Furthermore, the preprocessing in step (2) includes down-conversion, low-pass filtering, sampling rate conversion, and partial or complete decimation.

[0018] If the AD sampling signal is a baseband signal, down-conversion is not required; if the sampling signal is an intermediate frequency signal, it needs to be down-converted to a baseband signal.

[0019] If the sampling multiple is an integer multiple of the symbol rate, no sampling rate transformation is needed. If the sampling multiple is a fractional multiple of the symbol rate, interpolation is required to convert the sampling multiple to an integer multiple of the symbol rate.

[0020] Furthermore, the sampling rate transformation employs interpolation to convert the original sampling rate to the target sampling rate, including:

[0021] Calculate the ratio of the original sampling rate to the target sampling rate to obtain the sampling step after the sampling rate transformation;

[0022] Create an accumulator, using the sampling step as the accumulator's step size;

[0023] The accumulator value is used as the phase to generate the low-pass filter coefficients;

[0024] The overflow carry of the accumulator is used as the starting position for reading the sampled signal before the sampling rate conversion, and several consecutive data points are read out; the number of consecutive data points is equal to the number of filter coefficients.

[0025] By convolving these continuous data points and coefficients, the signal after sampling rate transformation is obtained.

[0026] A fast acquisition device for low signal-to-noise ratio and large frequency offset signals includes an AD sampling module a, a preprocessing module b, and an acquisition module c;

[0027] Preprocessing module b includes a down-conversion module, a low-pass filter module, a sampling rate conversion module, and a decimation module. Preprocessing module b receives the sampling data from AD sampling module a, and performs down-conversion, low-pass filtering, sampling rate conversion, and decimation according to the parameters of sampling center frequency, original sampling rate, target sampling rate, and symbol rate, and then sends it to the acquisition module c.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. This invention is applicable to burst or continuous signals of any rate in communication.

[0030] 2. The present invention has the advantages of rapid capture and low resource consumption.

[0031] 3. This invention is a high-dynamic acquisition method that can adapt to the characteristics of high-speed motion of low-orbit satellites. Attached Figure Description

[0032] Figure 1 This is a flowchart of the method of the present invention.

[0033] Figure 2 This is a schematic diagram of the connection relationship of the device of the present invention. Detailed Implementation

[0034] The present invention will now be described in further detail.

[0035] like Figure 1 As shown, a fast acquisition method for low signal-to-noise ratio, large frequency offset signals includes the following steps:

[0036] (1) Receive the sampling signal sent by the AD device or other devices, and the sampling multiple is required to be greater than or equal to 2 times, that is, the number of sampling points of one symbol is greater than or equal to 2 times;

[0037] (2) After the AD sampling signal is preprocessed, a double sampling signal is obtained; the preprocessing includes: down-conversion, low-pass filtering, sampling rate conversion, and decimation;

[0038] (3) Split the double-sampled signal into two parallel signals;

[0039] (4) Take one of the signals and perform m-bit differential operation.

[0040] Taking m=2 as an example, this means performing a 2-bit differential operation. Each symbol is differentially divided with its first and second adjacent signals to obtain two differential signals. These two signals are then output and denoted as rx-diff1 and rx-diff2.

[0041] (5) Perform multi-bit differential operation on the local known codewords to obtain two differential signals, and store them according to the codeword length, denoted as code-diff1 and code-diff2 respectively;

[0042] (6) Perform a full correlation operation on rx-diff1 and code-diff1 to obtain the correlation value peak1. Similarly, perform a full correlation operation on the other differential signal and codeword to obtain the correlation value peak2.

[0043] (7) Add the two related values ​​together to get peak_a.

[0044] (8) Similarly, following steps 4 to 7, the other signal is processed in the same way to obtain peak_b.

[0045] (9) Add peak_a and peak_b together to get peak_out, and output it.

[0046] (10) Compare peak_out with the threshold value. If it is greater than the threshold, the capture is considered successful. If it is less than the threshold, continue to perform sliding capture.

[0047] Furthermore, the preprocessing steps in step (2), including down-conversion, low-pass filtering, sampling rate conversion, and decimation, can be flexibly adjusted according to the AD sampling signal conditions. Some processing steps can be selected or skipped. Specifically:

[0048] If the AD sampling signal is a baseband signal, downconversion is not required; if the sampling signal is an intermediate frequency signal, it needs to be downconverted to a baseband signal.

[0049] If the sampling multiple is an integer multiple of the symbol rate, no sampling rate transformation is needed. If the multiple is a fractional multiple of the symbol rate, interpolation is required to convert the sampling multiple to an integer multiple of the symbol rate.

[0050] Furthermore, the sampling rate transformation in step (2) is implemented using interpolation to transform the original sampling rate to the target sampling rate. This includes:

[0051] Calculate the ratio of the original sampling rate to the target sampling rate to obtain the sampling step after the sampling rate transformation;

[0052] Create an accumulator, using the sampling step as the accumulator's step size;

[0053] The accumulator value is used as the phase to generate the low-pass filter coefficients;

[0054] The overflow carry of the accumulator is used as the starting position for reading the sampled signal before the sampling rate conversion, and several consecutive data points are read out; the number of consecutive data points is equal to the number of filter coefficients.

[0055] By convolving these continuous data points and coefficients, the signal after sampling rate transformation is obtained.

[0056] like Figure 2 As shown, a fast acquisition device for low signal-to-noise ratio and high frequency offset signals includes an AD sampling module a, a preprocessing module b, and an acquisition module c.

[0057] The preprocessing module b includes a down-conversion module, a low-pass filter module, a sampling rate conversion module, and a decimation module. The preprocessing module b receives the sampling data from the AD sampling module a, and performs down-conversion, low-pass filtering, sampling rate conversion, and decimation according to parameters such as the sampling center frequency, the original sampling rate, the target sampling rate, and the symbol rate. Then, it sends the data to the acquisition module c.

[0058] In summary, this invention includes steps such as digital signal preprocessing, multi-bit differential processing, full correlation operation, summation of multiple correlation values, and threshold decision. It enables rapid acquisition of digital signals under conditions of low signal-to-noise ratio and large frequency offset, while also conserving resources, thus solving the problem of difficult acquisition by receivers under such conditions. This invention is applicable to burst or continuous signals of arbitrary rates in communication, and is particularly adaptable to low-speed signals with large frequency offsets. It has the advantages of rapid acquisition and low resource consumption, making it especially suitable for signal acquisition in communication systems.

[0059] The above description is merely one specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art based on the technical solution and inventive concept of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for fast acquisition of low signal-to-noise ratio, high frequency offset signals, characterized in that, Includes the following steps: (1) Receive the AD sampling signal sent from the outside, with a sampling multiple of more than or equal to 2 times, that is, the number of sampling points of one symbol is more than or equal to 2 times; (2) After preprocessing, the AD sampling signal is multiplied by k to obtain the sampling signal; (3) Split the k times sampled signal into k parallel signals; (4) Take one of the parallel signals and perform multi-bit differential operation; that is, each symbol performs differential operation with its first, second, third...mth adjacent signal to obtain m differential signals; then, output these m signals and record them as rx-diff1, rx-diff2...rx-diffm; (5) Perform multi-bit differential operation on the local known codewords to obtain m differential signals, and store them according to the codeword length, denoted as code-diff1, code-diff2...code-diffm; (6) Perform full correlation operation on rx-diff1 and code-diff1. Similarly, perform full correlation operation on the signals and codewords after differentiating the other paths, and output m correlation values ​​peak1, peak2...peakm; (7) Sum the m relevant values ​​to get Peak_1; (8) Following the steps (4) to (7), the other k-1 paths are also processed in the same way to obtain peak_2 to peak_k; (9) Add peak_1 to peak_k to get peak_out, and output it; (10) Compare peak_out with the threshold value. If it is greater than the threshold, the capture is considered successful. If it is less than the threshold, continue to perform sliding capture.

2. The method for fast acquisition of low signal-to-noise ratio and large frequency offset signals according to claim 1, characterized in that, The preprocessing in step (2) includes down-conversion, low-pass filtering, sampling rate conversion, and partial or complete decimation. If the AD sampling signal is a baseband signal, down-conversion is not required; if the sampling signal is an intermediate frequency signal, it needs to be down-converted to a baseband signal. If the sampling multiple is an integer multiple of the symbol rate, no sampling rate transformation is needed. If the sampling multiple is a fractional multiple of the symbol rate, interpolation is required to convert the sampling multiple to an integer multiple of the symbol rate.

3. The method for fast acquisition of low signal-to-noise ratio and large frequency offset signals according to claim 2, characterized in that, The sampling rate transformation uses interpolation to convert the original sampling rate to the target sampling rate, including: Calculate the ratio of the original sampling rate to the target sampling rate to obtain the sampling step after the sampling rate transformation; Create an accumulator, using the sampling step as the accumulator's step size; The accumulator value is used as the phase to generate the low-pass filter coefficients; The overflow carry of the accumulator is used as the starting position for reading the sampled signal before the sampling rate conversion, and several consecutive data points are read out; the number of consecutive data points is equal to the number of filter coefficients. By convolving these continuous data points and coefficients, the signal after sampling rate transformation is obtained.

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