Varactor Tuning Applied to AM-FM Receivers

A simple, practical, analytical solution to varactor phenomena is developed. Starting with the basic equation, C = C
_o
/(l + E/ϕ)
ⁿ
, where C, the varactor capacitance is determined by E, an applied complex voltage, constituting a fixed dc voltage plus a desired and an undesired rf voltage; ϕ, the contact potential, and the exponent n, which is determined by the junction construction. The characteristics associated with var9ctors having various values of n, are analyzed. Means whereby distortion effects can be minimized are illustrated. It is shown that by using varactor tuning, practical AM-FM broadcast receivers having unique characteristics can be constructed.