Research And Design Of Radio Front-end Of BD Satellite Receiver Navigation

The content of this paper includes the ongoing scientific research project. Itsmajor research direction is the study and design of RF front-end of BeiDou satellitereceiver.First of all, this paper briefed the current domestic and foreign developmentstatus in satellite navigation on the background of the BeiDou satellite navigationsystem; did a thorough analysis on the relevant theories of RF front-end of satellitenavigation receiver, which helped this research to choose the appropriate topology;and also made a brief introduction of the electrical parameters of the relevant blocksin the RF front-end.Secondly, on the basis of theory and transmission line theory, this paperdescribed the design of single-frequency circular polarization, duel-band circularpolarization and passive broadband circularly polarized antenna. By means of cascadeslot or surface slot, the bandwidth of the micro-strip antenna can be significantlybroadened. The simulation result shows that this broadband circularly polarizedmicro-strip antenna has the ability of completely covering the signal wavelengths ofthe several existing satellite navigation systems.Thirdly, this paper discussed how to design a low noise amplifier to match anyfrequency point we choose in the frequency channel of the broadband antennacoverage, and how to choose low noise factor and high gain transistor. Furthermore,using the EDA aided design software to design the matching circuit and feedbackcircuit to assure the high gain characteristics, low noise property and stability of theelectrical circuit.Finally, select the center frequency of the frequency mixer according to theselected frequency point of low noise amplifier; Find the most suitable high moderatefrequency high frequency as the center frequency of the secondary down-conversionthrough theoretical analysis and numerical computation; Do whatever possible toavoid out-of-band interference, such as the mirror frequency interference and halfintermediate frequency interference; choose the appropriate mixer chip, frequencysynthesizer, crystal oscillator and band-pass filter to realize the mixing circuit.