An Analysis of Frequency Modulation Circuit Using p-n Junction Varactors

Simple circuits performing oscillation-frequency modulation functions using one active device and p-n junction type varactors are studied. The performance of the common circuit is analyzed. Equations are derived to determine signal-to-frequency deviation, transducer gain, frequency deviation, input impedance, distortion, maximum signal, noise and signal sensitivity, dynamic range, and maximum resolution. The upper or lower bounds of these quantities are given as functions of the varactor parameters and circuit constants.