Search

The traditional fast Fourier transform based frequency offset estimation (FFT-FOE) estimates the frequency offset by searching the spectral peak of the signal after the fourth power operation, which is suitable for multiple modulation formats. But the accuracy of FOE is limited by the number of FFT points. In this paper, we propose a high accuracy and low complexity FOE algorithm based on all phase FFT (APFFT-FOE). The accuracy of FOE can be improved effectively with lower additional computational complexity. Simulation results show that the mean square error of APFFT-FOE is reduced by more than one order of magnitude compared with the FFT-FOE. Compared with other FOE algorithms that can achieve the same accuracy, the additional computational complexity required by APFFT-FOE is reduced by more than 50$\%$. Finally, the APFFT-FOE is experimentally verified with 20 GBaud 16/64-QAM modulation signal. The experimental results show that the required OSNR for 16-QAM signal to reach 6.7$\%$ hard-decision forward-error correction is relaxed by 0.23 dB. For 64-QAM signal, the required OSNR at 20$\%$ soft-decision forward-error correction threshold is relaxed by 0.68 dB.

According to the research status and existing problems of automotive radar, an automotive radar system implementation scheme based on MFSK(multi frequency shift keying) waveform is studied in this paper. The target measurement principle of the system is analyzed in detail, the hardware structure of the system and the implementation process of the FPGA algorithm are introduced too. The algorithm combines all phase FFT and improved CA-CFAR(cell-averaging constant false alarm) algorithm to ensure the measurement accuracy of the system. The experimental results show that the system has high measurement precision, it can achieve the non fuzzy target measurement, and the system runs stably.

Self-mixing interferometry is an extreme simple and compact laser technique to develop non-contact displacement sensors. In order to enhance the precision of this type of sensor, an improved FFT algorithm, based on all phase FFT instead of conventional FFT, has been proposed to provide a phase reference for self-mixing displacement measurement system which has only single light path and lacks reference. The principle and the experimental realization of the proposed algorithm have been presented. The operation mechanism utilizes all phase FFT, which can estimate the phase from signal accurately, to achieve phase reference when the external target is held stationary and then compensate this reference to the phase when the target starts to move. Resultant displacement value reflects the actual position of the target. Reconstruction errors are on the order of nanometers in the displacements ranging from 100 nm to 1 μm. Therefore, the proposed method can find application in displacement measurement in industrial and scientific environments. [ABSTRACT FROM AUTHOR]