The output of the Foster-Seeley discriminator is affected not only by the input frequency, View (A) of figure shows a typical Foster-Seeley discriminator. FOSTER-SEELEY DISCRIMINATOR The FOSTER-SEELEY DISCRIMINATOR is also known as the PHASE-SHIFT DISCRIMINATOR. It uses a double-tuned rf. Foster–Seeley discriminator The Foster–Seeley discriminator is a common type of FM detector circuit, invented in by Dudley E. Foster and Stuart.
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Foster Seeley Discriminator: FM detector / demodulator
The capacitors C1 and C2 provide a similar filtering function. This is really a hang-over from early days of FM, and today the terms detector or probably better demodulator would probably be used.
Does not easily lend itself to being incorporated within an integrated circuit. This gives a signal that is 90 degrees out of phase. Simple to construct using discrete components.
As a result of its advantages and disadvantages the Foster Seeley detector or discriminator is not widely used these days. Proceedings of the Institute of Radio Engineersvol. When an un-modulated carrier is applied at the centre frequency, both diodes conduct, to produce equal and opposite voltages across their respective load resistors. As the carrier moves off to one side of the center frequency the balance condition is destroyed, and one diode conducts more than the other.
It has an RF transformer and a pair of diodes, but there is no third winding – instead a choke is used.
Foster Seeley Discriminator | FM Detector Demodulator | Electronics Notes
To obtain the different phased signals diiscriminator connection is made to the primary side of the transformer using a capacitor, and this is taken to the center tap of the transformer.
Simple to construct using discrete components. The capacitors C1 and C2 provide a similar filtering function.
Foster–Seeley discriminator – Wikipedia
Retrieved from ” https: These voltages cancel each one another out at the output so that no voltage is present. As a result of its advantages and disadvantages the Foster Seeley detector or discriminator is not widely used these days. Foster and Stuart William Seeley in Wound components like coils are not easy to produce to the required specification and therefore they are comparatively costly. This results in the voltage across one of the resistors being larger than the other, and foste resulting voltage at the output corresponding to the modulation on the incoming signal.
Offers good level of performance and reasonable linearity. Like the ratio detector, the Foster-Seeley circuit operates using a phase difference between signals.
Simple to construct using discrete components. The Foster Seeley circuit was widely used until the s when ICs using other techniques that were more easily integrated became widely available. The Foster Seeley discriminator circuit is characterised by the transformer, choke and diodes used within the circuit that forms the basis of its operation.
Frequency Modulation Tutorial Includes: Broadcast technology Embedded Design principles Distribution Formulae. Foster—Seeley discriminators are sensitive to both frequency and amplitude variations, unlike some detectors. Its main use was within radios constructed using discrete components. If the input equals the carrier frequency, the two halves of the tuned transformer circuit produce the same rectified voltage and the output is zero.
The circuit was envisioned for automatic frequency control of receivers, but also found application in demodulating an FM signal.
When an un-modulated carrier is applied at the centre frequency, both diodes conduct, to produce equal and opposite voltages across their respective load resistors.
The circuit topology looks very similar, having discdiminator transformer and a pair of diodes, but there is no third winding and instead a choke is used. This page was last edited on 8 Octoberat Accordingly these circuits are rarely used in modern equipment.
Offers good level of performance and reasonable linearity.