Ceramic Discriminator Application Notes

What is Discriminator?

The discriminator functions to convert the change of the frequency into audio frequency, an unique system of detection only used for FM broadcasting. The detection of FM wave is made through the circuit in which the relation between the frequency and the output voltage is linear. FM wave detection methods as known as ratio detection, Foster-Seeley detection, quadrature detection, differential peak detection, etc.

FM Wave Detection Methods

  • Ratio Detection:
    Ratio detection is the most popular method in use at present. The impedance characteristic of a ceramic resonator is designed into the circuit, then a coil as a detector is unnecessary. The fact is that adjustment is eliminated.

  • Quadrature Detection:
    This detection method was originally developed as a sound detector for TV sets, but recently it has become popular in the consumer market (FM tuners, car radios, etc.). The Quadrature Detection Method utilizes the phase characteristic.

    An FM signal is supplied directly to one side of the multiplier's input with an IC to the other side of the multiplier’s input an FM-IF signal, which is passed through the phase shifting circuit mainly composed of a tank circuit tuned to FM-IF, is applied. By taking advantage of the phase characteristic of the ceramic resonator as a discriminator, we can eliminate adjustment of the FM-IF circuit.

  • Differential Peak Detection:
    This detection method was developed by RCA as a sound detector for TV sets. The method has following features.

    1. Can output large level.
    2. Can function with only 1 synchronous coil.

    Non-linearities of synchronous characteristics are compensated each other by applying rectified intermediate frequency voltage. Thus, linearity can be obtained.

Advantage of Direct Electronics' Piezoelectric Ceramics

Direct Electronics had been able to develop specialized piezo materials which when combined with an advance design have resulted in a complete line of practical, inexpensive piezo devices for entertainment and communications applications.

Direct reliably deliver high-quality components according to the each customer special needs with respect to performance, costs, and technology modifications.

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