Airspace Navigation Receiver Interference And Channel Correction Technology

The power of navigation signal is quite low, so receivers are vulnerable to all kinds of intentional or unintentional interference, which affect the navigation function. Therefore, it is very important to study the interference rejection technology of navigation receiver. Interference outside the signal bandwidth can be processed with the method of time-domain filter. While interference in the signal bandwidth should be processed in space-domain in case of signal loss when navigation signals are filtered.The basic idea of adaptive array antenna anti-jamming technology is to adjust the weighting coefficient of each array element according to the signal environment, so that the zero pattern formed aligned to the interference signal. In this case the interfere can be filtered in space-domain.There are mainly two methods of interference suppression in navigation receiver: adaptive mulling techniques based on prior information of the adaptive mulling techniques when there is interference with the direction of DOA estimation; power inversion algorithm when there is no direction information of interference. When there is a number of interference sources (more than the degrees of freedom), broadband interference or multipath interference, the approach based on spatial anti-jam methods cannot work well, while the space-time processing (STAP) technology can solve the problem. Add a group of time-domain filter in each channel, and model the space-time signal processor for adaptive beam forming.The adaptive antenna array beamforming methods is based on the ideal channel conditions, while channels in the actual system are not ideal- harmonics and channel mismatch will impact on beamforming. It can meet the requirements of adaptive beamforming after array calibration.Specific correction method is as follows: inject the test signal through a splitter before the channels, select the channel with minimum distortion as a reference channel, then adjust the filter coefficients adaptively to make the new channel response consistent with the reference channel.At last we will talk about the implementation of spatial interference suppression and channel correction. We chose the StratixII FPGA of Altera Corporation, its Embedded DSP Block is quite useful in digital signal processing. After the implementation, we tested the whole receiver system in the anechoic chamber, it came out that this reciever can effectively suppress the interference, enhance acquisition performance.