Low-frequency discriminator of improved linearity

The paper presents the design and performance of a new frequency discriminator for widely deviated low-frequency subcarriers as used in multichannel communication links. A simple theory is developed to evolve a design procedure and to determine the conditions for wideband linearity in the frequency/voltage characteristics of the circuit, and this theory is confirmed experimentally. The use of inductors is avoided in the circuit to eliminate practical problems associated with the use of necessarily large inductors at low subcarrier frequencies, the alignment procedure is simple and straight-forward and the centre frequency of the discriminator can be altered by a single noninteracting control.