Design And Implementation Of The L-band RF Front-End Of Pysudolite Positioning System

Pseudolite can be used to increase the accuracy of the location application when the signal is blocked.The communication system is an important part of the Pseudolite system,and the transmitter's and receiver's RF circuit play an important role in increasing the performance of the communication system,so it's important to design the RF circuit carefully.For the sake of that the sampling technology can't support the ADC sampling the RF signal directly,the common method to design a RF circuit is to sample the IF signal,and handle the IF signal in the baseband.In this article,we use the superheterodyne receiver structure which can avoid the DC-offset problem which exists in the homodyne receiver.The receiver we realize in the article satisfies the requirement after testing.There are too many parameters in RF circuits.The different chips influence each other and finally influence the RF circuits.This article studies on the parameters in the RF circuit.On the other hand,this article studies on the microstrip line in the RF circuit to ensure the EMC is fine.Based on studying on the performance index of RF circuit and link budget theory,this article design the scheme of the L-band RF circuit in the pseudollite system.By using the ADS to simulate the scheme,we make sure that the scheme is feasible.On the basis of the simulation,we realized the PCB of the circuit.Also,this article studies on the auto gain control system used in the receiver RF circuit.Based on that,this article introduces the algorithm used in the auto gain control system.On the other hand,we finish the MCU software to control the digital-controlled chip.In the end,we build a test environment to verify the RF circuit's performance.We test the transmitter's and receiver's link gain,the passband ripple,the AGC's dynamic range and stabilization time,the phase noise of the local oscillator.After analyzing,the L-band RF circuit's performance can be used in the pseudolite.