Research And Realization Of Signal Synchronization Technology In FH/DS Navigation Receiver

Direct sequence spread spectrum system is applied in advanced radio navigation systems typically. Direct sequence spread spectrum system is vulnerable to enemy interference, for its disadvantage of serious distance effect and poor anti aimed-jamming ability. As the development of information warfare technology, direct sequence spread spectrum navigation system faces a serious threat. Frequency Hopping Spread Spectrum/Direct Sequence (FH/DS) hybrid spread spectrum system has excellent anti-interference ability. For improve resistance capabilities of radio navigation systems to jamming and interception, FH/DS hybrid spread spectrum technology applied in radio navigation system has an urgent need and great value. In this paper, Research and FPGA realization of signal synchronization technology in FH/DS navigation receiver is focused.Based on introduce of basic spread-spectrum theory, the each principles, mathematical models, advantages and disadvantages of direct sequence spread spectrum, frequency hopping spread spectrum systems, and FH/DS hybrid spread spectrum system are analyses. Compared to a single mode spread spectrum system, the performance advantage of FH/DS hybrid spread spectrum system in disturbance and intercepted is demonstrated; for the short-wave marine navigation applications, the type of matched filter waiting-displacement synchronization method is selected, a innovative FH/DS navigation signal structure of DS chip and FH chip solid related is designed, FH/DS acquisition method based on programmable matched filter (PDMF) is design in detail, and the detection probability, mean acquisition time and the of Doppler's effect of the acquisition method are theoretical derived and simulated, the specific parameters of the acquisition method are determined, the DS/FH code 2-D tracking method with combination of double coherent value is designed, and the carrier tracking method can predictable Doppler shift jump is designed too; the same time, a wide interval frequency hopping patterns based on the RS codes and DS code based on m sequences are designed and simulated, the FH/DS navigation signal is specific designed and simulated, the frequency of each frequency spot for ensure the signal transmission performance and continuity of the carrier phase are determined, the navigation transmitter and receiver DDS carrier synthesizer is designed, for the problem of large-scale matched filter's excessive resource occupation, a improved directly folding PDMF optimize structure can significantly reduce the resource consumption is designed too.Based on the theoretical analysis, FPGA implementation and test of acquisition method is carried out in this paper, the FPGA implementation of FH/DS navigation signal acquisition circuit, FH/DS navigation signal generator and channel simulator are completed, each module are designed in detail, the realization and test results of each module are given, then a FH/DS acquisition method test system is set up, the system performance of acquisition circuit is testing in Stratix EP1S80B956C6 FPGA development board. Test results show that the fast acquisition of long PN code FH/DS navigation signal in low SNR environment is achieved by this acquisition circuit.