L3 Narda-MITEQ manufactures two distinctly different types of Frequency Discriminators. Both types are utilized to convert an input frequency to a bipolar DC voltage corresponding to frequencies above and below crossover (center frequency).
Typical applications of Frequency Discriminators include automatic frequency control (AFC) systems and high-fidelity FM demodulation systems.
The narrow bandwidth type uses an input limiting amplifier to drive two staggered tuned L-C circuits. Opposing rectification of the circuits create the discriminator ‘S’ curve. A video amplifier is utilized to provide adequate output slope (specified in mV/MHz). The ability to precisely align the skirts of the tuned circuits, which represents the linear bandwidth, is the major advantage of this type of design.
The wide bandwidth type of Frequency Discriminators employ delay line techniques to achieve the desired frequency detection. A limiting amplifier drives an in-phase power divider, where one port is delayed an appropriate amount and applied to a double-balanced mixer being used as a phase detector. A wide bandwidth video amplifier takes advantage of this design’s extremely wide demodulation bandwidth. The ability to process narrow input pulse widths with minimal distortion is the fundamental advantage of this type of frequency discriminator. You can visit the L3 Narda MITEQ frequency disciminator section here.