The Baseband Signal Processing Based On Local Ground-based Navigation System Receiver

Electronic technology is developing rapidly nowadays and modern defense technology’s requirements for navigation and positioning is becoming increasingly strict. Existing navigation technology has been unable to fully meet the claims of high accuracy, high immunity, confidentiality and other needs in wartime. In such a situation, this paper presents the concept of local land-based navigation system based on satellite navigation technology and pseudo-satellite navigation technology. The system set base stations on the ground as signal sources to transmit navigation signals to the receiver placed in high dynamic shell. In this system the signal frequency, spreading codes are adjustable so it is confidential, the transmission distance is short so the signal is strong, greatly increases the difficulty of interference and improves the system’s anti-jamming capability. So the local land-based navigation system has a wide range of military applications foreground, the baseband signal processing module in the receiver as a core section of it is of great significance.The main content of this research is to design a receiver’s baseband signal processing module based on local land-based navigation system. The paper first analyzes the principles and advantages of local land-based navigation system and receiver, leads to the theoretical basis of designing a baseband signal processor. Then the paper analyzes how the Doppler shift affects signal reception, followed by parametric analysis and structural design for a four-channel correlator, plans out the correlator’s overall structure and composition of the module structure, quantified the design parameters of each module. Based on FPGA "top-down" approach to design, the paper uses Verilog HDL language to write codes of modules, adopting Xilinx’s ISE development software to realize correlator circuit, according to the simulation waveform of the circuit by simulation software Modelsim to improve the design, while the right program is converted to a binary bit stream file downloaded to Spartan3A-DSP chip series XC3S3400A model. Finally the paper uses the online logic analyzer Chipscope Pro to test and debug4-channel correlator and composition module circuit on FPGA, verifing the circuit waveforms under the curve of the module to improve and recommissioning verification,debugging the correct correlator circuits.