Performance of a DSP FM demodulator in the presence of noise

The signal to noise ratio (SNR) characteristics of the demodulated signal is analyzed and confirmed by simulation. Taking into account an application to an FM broadcasting receiver, an analysis and simulation are carried out with various parameters such as input carrier to noise ratio, number of quantization digits and construction of a 90° phase shifter in a DSP (digital signal processing) demodulator. Demodulation processing is implemented by a 32-bit CPU. Simulation results show that a sufficient SNR can be obtained using an A-D converter, which is introduced in the IF stage, having only 6 and 9 quantization digits for monophonic and stereophonic signals, respectively, without appreciable increase of input signal power over what is required when an analog demodulator is used