A new method of an IF I/Q demodulator for narrowband signals

I/Q demodulators have been widely used for demodulating quadrature modulated signals such as the QPSK signal and GMSK signal. Conventional analog/digital I/Q demodulators have some serious disadvantages. In this paper we present two new digital I/Q demodulators for narrowband signals, in which digital filters will not be used. The simulation results are also presented. Due to the higher sample rate and resolution the influence of the quantization noise can be ignored. The new I/Q demodulators maintain the advantages of the earlier digital I/Q demodulator such as zero DC offset and matched channel frequency responses, but their structures are much more simple.