The Research On External Anti-jamming Module Of Navigation Receiver

GNSS satellite navigation system has achieved rapid development in recent years, andhas been widely used in many fields of national economy. However, due to some owncharacteristics of navigation system, such as navigation signal’s fixed-band and theweakness of the received signal, navigation receivers are vulnerable to RF interference,which brings about significant losses. Based on the analysis of impact of RF interference onnavigation receivers, this paper designs an external anti-jamming module with digital RFoutput, which is compatible with existing receivers, with strong anti-jamming ability tomake sure receivers are still able to use the function of positioning and timing ininterference environment.First, the paper analyses the design requirements of each unit of the anti-jammingmodule in detail. Propose design specifications of RF receiver channel under stronginterference environment, including noise figure, dynamic range and sensitivity parametersand research the relationship between AD quantization bits and anti-jamming performance.Design each hardware circuit unit of the external anti-jamming module to meet tospecifications in strong interference environment and achieve the target of low powerconsumption, miniaturization, and low cost.Then design the baseband anti-jamming processing unit. The baseband processing unituses transform domain interference suppression algorithm based on FFT. Use overlappingwindowing technique to reduce the SNR loss caused by windowing. Analyze the principleand SNR loss of the interference suppression algorithm through simulation. Based on theanalyzing the performance of existing threshold setting algorithms, determine to use asimplified threshold setting algorithm, which is easy for engineering implementation andthe loss of interference suppression performance is in the acceptable range. Describe theimplementation process of the transform domain anti-jamming algorithm on FPGA.Last, the paper does some experiments to test the external anti-jamming module. Testparameters quantitatively, including noise coefficient, channel gain, bandwidth, IF outputpower and AGC dynamic range of RF receive channel. Results of the test show that RFreceive channel reaches requirements for strong interference environment. Connect theexternal anti-jamming module with an ordinary navigation receiver and test its performance respectively in indoor and outdoor experimental environment. Test results show that theexternal interference module may be compatible with existing receivers, and has a good processing gain of anti-interference about40dB.