Dqpsk-based signal processing method and system

Abstract

This invention discloses a signal processing method and system based on DQPSK. The method includes the following steps: S1, based on the I-channel pseudo-random code PN at time n... I (n) and Q-way pseudo-random code PN Q Given Ir(n) and Qr(n) received at time n, obtain the correlation value PN. I (n)·I r (n), PN I (n)·Q r (n), PN Q (n)·I r (n), PN Q (n)·Q r (n); S2, based on the relevant value PN I (n)·I r (n), PN I (n)·Q r (n), PN Q (n)·I r (n), PN Q (n)·Q r (n) Obtain the correlation value corr at time n0. N Comparing corr N The magnitude of the correlation value corr at time n0 is related to the preset threshold value. N If the value is greater than the preset threshold, proceed to step S3; otherwise, return to step S1. S3: Based on the correlation value corr at time n0... N The synchronization determination logic flow is entered. If it is determined to be a synchronization moment, S4 is executed; otherwise, S1 is executed. S4: The demodulated signal dec(n0) is obtained based on the correlation value between time n0 and its next time. This invention uses a non-coherent method to synchronize and demodulate the received signal, eliminating the step of recovering the coherent carrier in traditional methods and solving the problem that coherent carriers cannot be recovered in fast frequency hopping communication.

Claims

1. A signal processing method based on DQPSK, characterized in that, The method includes the following steps: S1. Based on the I-way pseudo-random code PN at time n. I (n) and Q-way pseudo-random code PN Q Given Ir(n) and Qr(n) received at time n, obtain the relevant values. , , , ; S2, based on relevant values , , , Obtain the correlation value corr at time n0 N Comparing corr N The magnitude of the correlation value corr at time n0 is related to the preset threshold value. N If the value is greater than the preset threshold, proceed to step S3; otherwise, return to step S1. S3. Based on the correlation value corr at time n0 N Enter the synchronization determination logic flow. If it is determined to be a synchronization moment, execute S4; otherwise, return to execute S1. S4. Obtain the demodulated signal based on the correlation value between time n0 and its next time step. ; The correlation value corr at time n0 in step S3 N for: ； II, QI, IQ, and QQ are respectively , , , The accumulated value; The correlation value corr at time n0 in step S3 N for: ； in, , , , They are respectively , , , The cumulative decay factor satisfies: ； ； ； ； Frequency offset introduced by the relative frequency offset of the local oscillator. The phase offset between local oscillators; Step S3 also includes: During the listening phase, compare the correlation value corr at time n0. N If the value matches the preset threshold, then proceed to the first capture phase; In the first capture phase, the total length is X1 cycles, and the length of each cycle is N. At the end of each cycle, if the correlation value corr N If the peak value is within the specified range, the first counter is incremented by 1; otherwise, the first counter is decremented by 1. If the first counter reaches the first preset value before the end of X1 cycles, the second capture phase is entered. The second capture phase has a total length of X2 cycles, with each cycle having a length of N. At the end of each cycle, if the correlation value corr... N If the peak value is within the specified range, the second counter is incremented by 1; otherwise, the second counter remains unchanged. If the first counter reaches the second preset value before the end of X2 cycles, step S4 is executed. The demodulated signal in step S4 is: ； When frequency deviation =0, phase bias When = 0, the demodulated signal is: ； This represents the despread information symbol at time n0, and its value is either -1 or 1.

2. The signal processing method based on DQPSK according to claim 1, characterized in that, The generation methods for the I-way pseudo-random code and the Q-way pseudo-random code in step S1 are as follows: ； ； Where M is the spreading code sequence, N is the length of the spreading code sequence, and 0≤i≤N / 2-1.

3. The signal processing method based on DQPSK according to claim 2, characterized in that, In step S1, the I-channel signal Ir(n) and Q-channel signal Qr(n) received at time n are respectively: ； ； in, The I-channel modulated information at time n, The I-channel modulation waveform at time n. This represents the modulated information of the Q-path at time n+1. This is the Q-path modulation waveform at time n+1.

4. The signal processing method based on DQPSK according to claim 3, characterized in that, Relevant values ​​in step S1 , , , They are respectively: ； ； ； 。 5. The signal processing method based on DQPSK according to claim 1, characterized in that, The preset threshold value in step S3 is the average noise floor value.

6. A signal processing system based on the DQPSK signal processing method as described in any one of claims 1 to 5, characterized in that, The signal processing system includes: Related units are used to determine the I-way pseudo-random code PN at time n. I (n) and Q-way pseudo-random code PN Q Given Ir(n) and Qr(n) received at time n, obtain the relevant values. , , , ; Correlation calculation unit, used to calculate correlation values , , , Obtain the correlation value corr at time n0 N ; Synchronous decision unit, used to compare corr N The value of the preset threshold is used to obtain the n0 time point at which the synchronization process is completed. The demodulation unit is used to obtain the demodulated signal based on the correlation value between time n0 and its next time step. .

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