Compared with the superheterodyne transceivers, zero-intermediate frequency (IF) transceivers have simpler structure and lower power consumption. Moreover, communication signals can be processed digitally with a sampling rate equaling to the signal bandwidth before transmission or reception. Binary frequency shift keying (2FSK), as a type of binary single-carrier modulation with excellent anti-interference performance, can also be transmitted or received via a zero-IF structure. Therefore, broadband or frequency hopping 2FSK transceivers can be realized easily in baseband. The traditional zero-IF 2FSK signal demodulation-phase demodulation has a simple structure, but its anti-noise performance is poor due to the unused priori information. In this paper, both coherent and non-coherent demodulation schemes are proposed for zero-IF 2FSK. Mathematical derivations and numerical simulation results show the bit error rate (BER) performance of coherent demodulation of zero-IF 2FSK is 3dB better than that of bandpass 2FSK.
Most of existing methods to identify the Reed-solomon (RS) codes, commonly applied as channel codes, mainly focus on non-shortened RS codes. In this paper, a method to identify the shortened RS codes with short codeword length is proposed. Firstly, based on Gauss-Jordan elimination through pivoting (GJETP), the codeword length of shortened RS codes is identified. The shortened RS codewords are zeroized by estimating the order of finite field and the number of shortened symbols. Then, the Chinese remainder theorem(CRT) based algorithm is adopted to identify the primitive polynomial. Finally, the generator polynomial is obtained based on Galois field Fourier transform (GFFT). The simulation experiments are carried out showing that the probability of recognition of shortened RS codes is higher than 90% with bit error rate (BER) less than 5×10-3 , which demonstrates the viability of the proposed recognition approach.