A new digital method of demodulation for MSK

In this paper we present a new scheme of demodulation for minimum shift keying (MSK) in the context of low-frequency and narrow-band. According to the characteristic of MSK signal, a digital demodulation approach based on discrete Fourier transform (DFT) is described. To expand the frequency difference of the two carriers at the receiver, received signal multiplies with itself. So we can get its second harmonic by a band pass filter. Then we use the samples of second harmonic signal in each symbol to do DFT operation. Easily, we can find the amplitudes of the second harmonic frequencies for 1 code and 0 code. After that, the hard-decision is set up by the comparing result of amplitudes. The performance of this system in AWGN (additive white Gaussian noise) channel is analyzed. Compared with classic demodulation, the new receiver architecture is not very sensitive to frequency shift. The whole system which has a simple structure is stable and has good hardware realization.