Design and FPGA Implementation of VDES Demodulation System Based on Decision Feedback Algorithm

doi:10.12382/bgxb.2022.0471

Abstract

Abstract:

VHF data exchange system (VDES) has broad application prospect as a new generation of ship communication system. Due to the high-speed motion of satellite, a large Doppler frequency shift is superimposed on the ASM uplink in VDES, and the channel parameters estimated only by training sequence in receiving end cannot meet the requirements of demodulation. Therefore, a VDES demodulation system based on decision feedback algorithm is proposed. The received data is split into small segments, which reduces the influence of frequency offset. The demodulated result of each segment is used as pilot to estimate the channel parameters in current data segment. Simulated results show that the performance of the proposed algorithm is superior to that of the coherent demodulation algorithm without feedback. On the basis of the above research, the correct demodulation of ASM uplink without pilots is implemented on the filed programmable gate array(FPGA).

Key words: signal processing, VHF data exchange system, decision feedback, filed programmable gate array

CLC Number:

TG510

SUN Dingzhu, FENG Man, DI Fang, CHEN Peng. Design and FPGA Implementation of VDES Demodulation System Based on Decision Feedback Algorithm[J]. Acta Armamentarii, 2024, 45(1): 312-318.

Figures/Tables 9

Fig.1 Schematic diagram of ASM-SAT link frame structure

Fig.2 Flow chart ofdecision feedback algorithm

Fig.3 Structure diagram offrequency estimation module

Fig.4 Performance diagram of frequency estimation algorithm

Fig.5 Simulation performance diagram of segment length

Fig.6 Performance diagram of decision feedback algorithm

Fig.7 Simulation diagram of FPGA implementation

Table 1 Actual test performance

信号功率/dBm	帧正确率/%
-80	100
-90	100
-100	100
-110	99.8
-120	77.7

Fig.8 Resource occupancy rate of FPGA implementation

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