Key Technology Realization Of GNSS/BDS High Performance RF/IF Signal Processing

The current GNSS(Global Navigation Satellite System)system is in rapid development and is widely used in all walks of life,such as transportation,personal electronics,military,etc.However,GNSS receiving and processing system is complex and has many components which span many fields.It is extremely difficult to coordinate many functions in the study,so it limits the performance of the GNSS receiving and processing system.In order to improve the performance of GNSS navigation applications,it is necessary to break through the key technologies of GNSS RF and IF signal processing,such as antenna design,RF front-end design,and GNSS IF signal acquisition system design,digital baseband acquisition,and tracking processing.At present,the BeiDou-3 satellite system has been fully networked successfully,but most of the BeiDou satellite system receivers in China and abroad only support the signals of the BeiDou-2 system and cannot capture and track the signals of each frequency point of the BeiDou-3 system.In addition,most of the current RF acquisition devices do not have RF anti-interference function,and the suppression ability of the out-of-band signal is poor.Moreover,the indexes of the output 3rd order intercept point(OIP3)and the third-order intermodulation distortion(IMD3)of the RF channel are generally low,and the interference signal is most likely to enter the RF system through the antenna,thus affecting the acquisition,tracking and positioning of the baseband.Specific anti-jamming radio frequency is generally used in military and high power consumption,which is difficult to be applied to civil high-precision positioning.The wireless signal is complex,especially in urban application scenarios,and the interference is not a strong directional signal.It is necessary to further study and improve the miniaturized low-power RF front-end with certain anti-interference functions.The innovative work of this paper is as follows.1.The PPO/MTCLT substrate filled with 30vol%ceramic has dense microstructure and uniform filler distribution,and the dielectric loss is lower.It can be used to design microstrip antenna to achieve low loss,miniaturization and good mechanical and thermal properties.2.A new harmonic suppression method for navigation system clock is proposed.Aiming at the problem that the reference clock is prone to harmonics and lacks processing,the principle is analyzed,and the optimization circuit is designed.Under the small volume circuit layout condition,the effect of high harmonic suppression is realized,and the carrier-to-noise ratio of navigation signal positioning results is enhanced.3.The LWIP high-speed bidirectional IF signal acquisition mechanism is proposed,which realizes the high-speed IF signal acquisition and solves the problems of multi-channel parallel acquisition and configuration and multi-terminal platform compatibility.This paper systematically realizes and verifies the RF and IF processing of multisystem and multi-frequency signals and proposes and designs the following aspects in engineering implementation and verification:1.A circularly polarized doubly-fed stacked microstrip antenna based on PPO/MCTLT high-performance composite material is designed at the antenna end,which can receive GPS L1 band and BDS B1,B3 band satellite signals.2.In the RF front end,the antenna RF terminal with low noise,low power consumption,and high linearity is designed,and the RF down-conversion and mixing link suitable for multiple scenes is designed,which meets the bandwidth requirements of high-performance navigation signals and has certain anti-interference ability,and has certain anti-interference ability of RF in the complex urban environment.3.In IF signal acquisition,the ZYNQ platform is used to achieve high-speed IF data acquisition and data configuration;4.In terms of digital baseband processing,the X64 platform is used to capture and track GPS L1C/A and BDS B1C,B3I signals,and the performance of the system is verified.