A New Method for Demodulation of FSK Signal with Severe Impulse Interference

In this paper, a new method for demodulation of FSK signal with severe impulse interference is presented. This method is suitable for incoherent demodulation of FSK signal. At first, a unique part of amplitude limiting is used to reduce the influence of strong impulse interference; then, sometimes, strong impulse interference changes FSK sin wave upside down or reversely in half a cycle. As a result, after quantified by compactor into 0 or 1, and after edges detect, edge pulses will reduce, the result of demodulation may be wrong. The tradition method of incoherent demodulation can't handle this case well, but this interpolation method can handle this problem easily, which can find where the signal is interfered badly and correct the FSK signal. This method is tested by MATLAB and FPGA. It can achieve 99.999% bit accuracy rate when signal to noise ratio is 10dB and severe impulse interference is around once in a while in real environment, and this method is actually used for practical engineering application.