Timing and carrier wave joint estimation algorithm under large frequency offset satellite signal

Abstract

The invention relates to the technical field of satellite communication, in particular to a timing and carrier wave joint estimation algorithm under large-frequency-offset satellite signals, which comprises the following steps of: respectively adding two sections of unique word sequence signals UW1 and UW2 at the front end and the rear end of a target signal; under the condition that pilot signals are known, frequency offset estimation is carried out by utilizing strong correlation of known unique words. The phase angle influence of the received signal pilot frequency sequence is eliminated through conjugate multiplication of the received signal pilot frequency sequence and the pilot frequency signal, so that the frequency offset can be solved through the remaining phase angle, and the problem that large frequency offset cannot be estimated by QPSK in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the field of satellite communication technology, and in particular to a timing and carrier joint estimation algorithm under large frequency deviation satellite signals. Background Art

[0002] In the field of communications, frequency deviation refers to the frequency difference between the signal received by the receiving device and the signal sent by the transmitting device, which may occur in various wireless communication systems, such as mobile communications, satellite communications, etc. Frequency deviation is caused by many factors, including the inaccuracy of the local oscillators of the transmitting and receiving devices, the instability of the transmission medium, etc., which can lead to signal analysis errors and affect the reliability and performance of communications.

[0003] In satellite communication systems, due to the complexity of satellite communication and the characteristics of long-distance transmission, the measurement and correction of frequency offset is particularly important to ensure communication quality. Therefore, a high-precision frequency offset correction method is required to ensure accurate signal transmission.

[0004] QPSK (Quadrature Phase Shift Keying) is a commonly used digital modulation method, which transmits binary information by changing the phase of an orthogonal carrier, but it cannot be used to estimate large frequency deviations. There is no other solution to the above problem in the prior art.

[0005] Based on the above reasons, the present invention designs a timing and carrier joint estimation algorithm under large frequency deviation satellite signals, adds two unique word signals at the front and back ends of the target signal respectively, and can estimate and compensate for the large frequency deviation after receiving the signal and completing the timing. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a timing and carrier joint estimation algorithm under large frequency deviation satellite signals. Two unique word signals are added to the front and back ends of the target signal respectively. After receiving the signal and completing the timing, the large frequency deviation can be estimated and compensated.

[0007] In order to achieve the above object, the present invention provides a timing and carrier joint estimation algorithm under a large frequency deviation satellite signal, comprising the following steps: S1, using two different UW unique subsequences as pilot data UW1 and UW2 before and after the formal transmission data; S2, synchronously processing the received signal of the formally transmitted data to determine the starting position of the received signal and the pilot data; S3, select a sequence in the received sequence in the received signal The signal corresponding to the pilot data Multiply the conjugates of respectively; The formula is: , used to eliminate the phase angle influence of BPSK in the pilot signal; It is the conjugate signal of ck, which is an important step to eliminate the influence of phase angle; S4, the longer segment pilot data signal L1 is regarded as the concatenation of several shorter segment pilot signals L2, that is, L1≈n×L2, that is, the length L1 of the pilot data signal UW1 is divided into n segments of length L2, L is taken as L2, L is the length of UW2, for subsequent calculations; Then, D is taken as the distance between the second segment UW2 pilot data signal and the start of a certain segment of pilot signal after the first segment UW1 pilot data signal is divided into n segments; S5, respectively take the corresponding length signals of each segment obtained by dividing the pilot signal UW1 Perform cross-correlation calculation with the pilot signal UW2; The formula is: R= , after obtaining R, we can calculate ; in, for The conjugate signal of the signal; k and m represent the positions of the elements of the pilot data signals of the two preceding and following segments respectively; the role of k and m here is to perform operations on each element in the two preceding and following segments of the signal respectively.

[0008] S6, obtained from S5 By taking the average value, a frequency deviation estimation value Δf with high accuracy can be obtained; Among them, z(k) is obtained after the actual pilot signal position processing; L is the length of UW2; D is the distance between the second segment pilot signal and the beginning of a segment pilot signal after segmentation in the first segment; R is the intermediate value obtained by each calculation, f d is the frequency deviation calculated each time, each f d Corresponding to one D, T is the symbol duration, which is the inverse of the symbol frequency; The synchronization process is to use chirp signals for retrieval.

[0009] Compared with the prior art, the present invention has the following beneficial effects: The present invention adds two unique word sequence signals UW1 and UW2 at the front and back ends of the target signal, respectively, and uses the strong correlation of the known unique word to estimate the frequency offset when the signal is received and the timing is completed. The corresponding part of the pilot sequence of the received signal eliminates the influence of the sequence's own phase angle by conjugate multiplication with the pilot signal, so that the frequency offset can be solved by the remaining phase angle, solving the problem that QPSK in the prior art cannot estimate large frequency offsets. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic diagram of the overall steps of the present invention. DETAILED DESCRIPTION

[0011] The present invention will now be further described with reference to the accompanying drawings. See also Figure 1 The present invention provides a timing and carrier joint estimation algorithm for large frequency deviation satellite signals: The following steps are involved: S1, using two different UW unique subsequences as pilot data UW1 and UW2 before and after the formal transmission data; S2, synchronously processing the received signal of the formally transmitted data to determine the starting position of the received signal and the pilot data; S3, select a sequence in the received sequence in the received signal The signal corresponding to the pilot data Multiply the conjugates of respectively; The formula is: , used to eliminate the phase angle influence of BPSK in the pilot signal; It is the conjugate signal of ck, which is an important step to eliminate the influence of phase angle; S4, the longer segment pilot data signal L1 is regarded as the concatenation of several shorter segment pilot signals L2, that is, L1≈n×L2, that is, the length L1 of the pilot data signal UW1 is divided into n segments of length L2, L is taken as L2, L is the length of UW2, for subsequent calculations; Then, D is taken as the distance between the second segment UW2 pilot data signal and the start of a certain segment of pilot signal after the first segment UW1 pilot data signal is divided into n segments; S5, respectively take the corresponding length signals of each segment obtained by dividing the pilot signal UW1 Perform cross-correlation calculation with the pilot signal UW2; The formula is: R= , after obtaining R, we can calculate ; in, for The conjugate signal of the signal; k and m represent the positions of the elements of the pilot data signals of the two preceding and following segments respectively; the role of k and m here is to perform operations on each element in the two preceding and following segments of the signal respectively.

[0012] For example: when L=2, the length of the two signal segments is 2, and R=z*(0)z(D)+z*(0)z(D+1)+z*(1)z(D)+z*(1)z(D+1); here k and m represent the positions of the elements of the two signal segments, and the formula in this paragraph means the conjugate of each signal in the first segment multiplied by each signal in the second segment and the sum of the results.

[0013] S6, obtained from S5 By taking the average value, a frequency deviation estimation value Δf with high accuracy can be obtained; For example, 112011222xxx123, assuming that 112011222 is UW1 and 123 is UW2, then L=3, UW1 is divided into 112, 011, 222, D first takes 9+3 (UW1 length + intermediate data length) for calculation, and then takes 6+3 (UW1 length - L + intermediate data length) for calculation... until n such cross-correlation operations are performed.

[0014] Among them, z(k) is obtained after the actual pilot signal position processing; L is the length of UW2; D is the distance between the second segment pilot signal and the beginning of a segment pilot signal after segmentation in the first segment; R is the intermediate value obtained by each calculation, f d is the frequency deviation calculated each time, each f d Corresponding to one D, T is the symbol duration, which is the inverse of the symbol frequency; The synchronization process is to use chirp signals for retrieval.

[0015] The above are only preferred embodiments of the present invention, which are only used to help understand the method and core idea of ​​the present application. The protection scope of the present invention is not limited to the above embodiments. All technical solutions under the idea of ​​the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention. The present invention solves the problem in the prior art that QPSK cannot estimate large frequency deviations. Two unique word sequence signals UW1 and UW2 are added to the front and rear ends of the target signal respectively. When the signal is received and timing is completed, the strong correlation of the known unique words is used to estimate the frequency deviation when the pilot signal is known. The corresponding part of the pilot sequence of the received signal is multiplied by the conjugate of the pilot signal to eliminate the influence of the sequence's own phase angle, so that the frequency deviation can be solved by the remaining phase angle.

Claims

1. A joint timing and carrier estimation algorithm for large frequency deviation satellite signals, characterized by , including the following steps: S1, using two different UW unique subsequences as pilot data UW1 and UW2 before and after the formal transmission data; S2, performing synchronization processing on the received signal of the formal transmission data to determine the starting position of the received signal and the pilot data; S3, selecting a sequence in the received sequence in the received signal The signal corresponding to the pilot data Multiply the conjugates of respectively; The formula is: , used to eliminate the phase angle influence of BPSK in the pilot signal; Said It is the conjugate signal of ck, which is an important step to eliminate the influence of phase angle; S4, treating the longer segment pilot data signal L1 as the concatenation of several shorter segment pilot signals L2, that is, L1≈n×L2, that is, dividing the length L1 of the pilot data signal UW1 into n segments of length L2, taking L as L2, and L as the length of UW2, for subsequent calculations; Then, D is taken as the distance between the second segment UW2 pilot data signal and the start of a certain segment of pilot signal after the first segment UW1 pilot data signal is divided into n segments; S5, respectively obtain the corresponding length signals of each segment obtained by dividing the pilot signal UW1. Performing cross-correlation calculation with the pilot signal UW2; The formula is: R= , after obtaining R, we can calculate ; in, for The conjugate signal of the signal; k and m represent the positions of the two preceding and following pilot data signal elements respectively; S6, the S5 obtained By taking the average value, a frequency deviation estimation value Δf with high accuracy can be obtained; Among them, z(k) is obtained after the actual pilot signal position processing; L is the length of UW2; D is the distance between the second segment pilot signal and the beginning of a segment pilot signal after segmentation in the first segment; R is the intermediate value obtained by each calculation, f d is the frequency deviation calculated each time, each f d Corresponding to one D, T is the symbol duration, which is the inverse of the symbol frequency.

2. According to claim 1, a timing and carrier joint estimation algorithm for large frequency deviation satellite signals is characterized in that ,The synchronization processing is to use chirp signals for retrieval.

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