QPSK carrier recovery large frequency offset compensation system and method
A carrier recovery and compensation method technology, which is applied in high-speed digital demodulators and aerospace measurement and control communication fields, can solve the problems of small bandwidth of digital phase-locked loops, inability to distinguish input signal and noise, etc., to overcome the influence and eliminate bipolarity The influence of symbols and the effect of accurate frequency offset estimation results
Active Publication Date: 2018-03-09
ZHEJIANG UNIV
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To capture the carrier frequency, the most commonly used method is to use the phase-locked loop technology, but the bandwidth of the digital phase-locked loop is small, which is not conducive to capturing the carrier with a large frequency deviation
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[0018] Such as figure 1 As shown, a QPSK carrier recovery large frequency offset compensation system includes a first multiplier 1, a numerically controlled oscillator NCO2, a second multiplier 3, a first low-pass filter 4, a second low-pass filter 5, a first Square operator 6, second square operator 7, first subtractor 8, third multiplier 9, double gainer 10, third square operator 11, fourth square operator 12, fourth multiplier 13, A second subtractor 14, an adder 15, an FFT module 16, an accumulation and averaging module 17;
[0019] The first multiplier 1, the first low-pass filter 4, the first square operator 6, the first subtractor 8, the fourth multiplier 13, the adder 15, the FFT module 16, the accumulative mean module 17, the digitally controlled oscillator NCO2 is connected in sequence; the second multiplier 3, the second low-pass filter 5, the third multiplier 9, the double gainer 10, the fourth square operator 12, the second subtractor 14, and the adder 15 are con...
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The invention discloses a QPSK carrier recovery large frequency offset compensation system and method. The method mainly includes the following steps: separately multiplying two paths of signals thatare I and Q signals in a QPSK signal by a recovery carrier output by a numerically controlled oscillator (NCO), and then filtering out high-frequency components by using a low-pass filter respectively; calculating two paths of signals that are cosine and sinusoidal signals containing frequency offset information by performing a certain operation on I and Q filtering results, and then combining thetwo paths of signals into a complex signal, searching for a peak value by using a fast Fourier transform (FFT) to perform frequency offset estimation, accumulating multiple frequency offset estimation values and calculating a mean value to obtain a frequency offset value, and finally compensating the frequency offset value to a frequency control amount of the NCO to further eliminate a large frequency offset caused by the Doppler frequency shift. The invention provides an algorithm for extracting the cosine and sinusoidal signals only related to frequency offset information, which can eliminate the influence of bipolar code elements in the signals, overcome the influence of the bipolar code elements on FFT frequency offset estimation, and make the frequency offset estimation result more accurate.
Description
technical field [0001] The invention relates to the field of aerospace measurement and control communication, in particular to the field of high-speed digital demodulators, in particular to a QPSK carrier recovery large frequency offset compensation system and method. Background technique [0002] QPSK modulation is widely used in digital satellite communication systems because of its better anti-interference performance and spectrum utilization, and is easier to implement. The QPSK modulated signal adopts coherent demodulation technology, which has strict requirements on the synchronization of the carrier signal. Carrier recovery is a key component of the demodulator. In the aerospace measurement and control communication system, the Doppler frequency deviation caused by the relative motion between the ground receiver and the spacecraft has a great impact on the carrier recovery, which will cause the demodulation of the receiver to be unable to complete. The size of Dopple...
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IPC IPC(8): H04L27/00H04L27/227H04L27/26
CPCB63B35/44B63B2035/4453B63C11/36G01C7/00G01C13/00H02S20/00H04L27/0014H04L27/2275H04L27/265H04L27/2695H04L2027/0026H02S10/20Y02E10/50Y02E70/30
Inventor 赵昌昌张顾洪金仲和
Owner ZHEJIANG UNIV