Research On Noise Cancellation Correlator

In this paper, the main research is focused on the frequency conversion technologies and the correlator in the VHF hopping radio. Firstly, the principle of frequency hopping radio and software radio are introduced. Then it discusses the digital frequency conversion technologies and noise cancellation correlator based on the principle of the adaptive interference cancellation filter in the high speed frequency hopping communication systems with emphasis. In the part of digital frequency conversion technologies, this paper mainly studies the fundamental theory of NCO and digital filter, and the parameters of the digital filters satifying the system requirement are obtained through simulation. FPGA design of frequency up conversion is also implemented and the designs and the confirmations about each module on the hardware platform are accomplished. In the part of noise cancellation correlator, this paper proposes a new method which can improve the performance of correlator in the low signal-to-noise ratio (SNR) condition. In this method, it uses the improved adaptive cancellation filter to filter the I and Q signals that come form the frequency down-conversion in order to obtain the approximate signals of the noise mixed in I,Q Signals, and then subtracts the approximate noise from I and Q signals and the results are used as the input signals to correlation. The performance of the correlator will be improved. Matlab simulation shows to the performance of the method, and FPGA designs based on this method are also given.