Highly Stable, One Step Conversion, Superheterodyne FM Receiver

Overview

This system is a high-performance, discrete component Frequency Modulation (FM) radio receiver utilizing a superheterodyne architecture. It intercepts ambient RF signals through an antenna, down-converts them to an Intermediate Frequency (IF) using a high-precision digital local oscillator, and processes them through an integrated narrow-band FM subsystem to deliver clear demodulated audio output.

Key features

• Discrete RF front end: HF transistors plus LC networks for tuned RF amplification and mixing, with explicit control of gain, match, and noise figure.
• Si5351 programmable clock generator as the local oscillator — precise, low-jitter LO drive into the mixer for stable tuning.
• MC3361 low-power narrow-band FM IF IC for IF gain, limiting, quadrature FM demodulation, and squelch.
• Discrete LC IF filter for sharp bandpass selectivity and rejection of images / adjacent channels.
• Integrated audio output stage to drive listening hardware from the discriminator output.

PCB layout

The Si5351 is physically isolated from the sensitive RF front end, with short, direct clock routing to reduce radiated EMI and LO leakage into the antenna path. LC filter parts are oriented orthogonally to reduce mutual inductance. The bottom layer is a continuous ground plane to limit parasitics, stray capacitance, and crosstalk across high-frequency stages.