Fully digital FM receiver

This project presents the design of a broadcast FM receiver implemented using software defined radio. The analogue components are minimized, so an FM filter and an automatic gain control are only used before digitalizing. The rest of the receiver is implemented on an FPGA device. Pass-band sub-sampling is utilized to sample the FM spectrum (88-108MHz). The receiver is composed by a digital down-converter based on Hilbert transform and a FM detector based on a digital phase-lock loop.

FM receiver features:

  • FM Band: 88 – 108 MHz
  • Channel bandwidth: 200 kHz
  • Standard deviation: 75 kHz
  • This receiver only demodulates the sum of the right and left channel audio signals (L+R)
Block diagram of the FM receiver
Receiver signal
Signal after passband sampling
Signal after mixer
Filtered channel
Prototype