Design Of GNSS Intermediate Frequency Signal Collector And Signal Processing Platform

The development level of global navigation satellite system(GNSS)has increasingly become an important reference to measure national strength,and is a hot field for countries to compete for development.The Beidou Navigation Satellite System(BDS)is a global navigation system constructed by China with independent intellectual property rights.It greatly promotes the development of related social fields and produces great economic benefits,becoming an important engine of national economic development.However,GNSS signals will be affected by a variety of human and natural interference in the process of transmission,thus affecting the normal operation of GNSS receiver.As an important part of GNSS receiver,IF signal collector and signal processing platform of GNSS will be further studied to improve the anti-interference capability of the receiver.Carrying out this research has very important engineering application value.In this paper,the hardware design and implementation of GNSS IF signal collector are firstly carried out to convert the received RF signal into IF signal,which provides data for the subsequent acquisition,tracking,PVT solution and interference detection research.The GNSS IF signal collector uses the software radio platform of AD9361+ZYNQ to design the circuit of the ZYNQ baseband processing board,and connects to the RF front end of AD9361 through the FMC interface to form the GNSS IF signal collector.The collected IF data is saved to the computer file through the gigabit network port.GNSS signal processing algorithm reads the collected IF data,carries out data capture,tracking and PVT calculation processing,and designs signal processing platform based on MATLAB App Designer to analyze and display the signal processing results,which is used to test the function and index of IF signal collector.GNSS signal processing captures and tracks signals through time-domain parallel acquisition algorithm and frequency-locked loop assisted phase-locked loop tracking algorithm.After capturing and tracking signals,bit synchronization and frame synchronization are processed,so as to obtain signal transmission time and navigation message and realize receiver positioning.At the same time,the simulation analysis of GNSS interference detection algorithm based on energy detection is also carried out,which can detect interference without prior information.Experimental tests show that the GNSS IF signal collector can realize the acquisition of1 GHz ～ 2GHz GNSS all-band IF signal,and the GNSS signal processing platform can realize the capture,tracking and positioning of IF signal,and the positioning error of the three directions in the ENU coordinate system is kept within ±5m.After simulation analysis,the GNSS interference detection algorithm based on energy detection can carry out reliable detection under the condition that the dry noise ratio reaches-4d B.