What is Foster-Seeley discriminator and how does it work?
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The FOSTER-SEELEY DISCRIMINATOR is also known as the PHASE-SHIFT DISCRIMINATOR. It uses a double-tuned RF transformer to convert frequency variations in the received fm signal to amplitude variations. These amplitude variations are then rectified and filtered to provide a dc output voltage.
Which of the following is a Foster-Seeley discriminator?
Foster Seeley discriminator is used in the demodulation of FM signal and it uses a double-tuned circuit with primary and secondary tuned to the same frequency.
What is the difference between the Foster-Seeley discriminator and the ratio detector?
The ratio detector has the advantage over the Foster–Seeley discriminator that it does not respond to amplitude modulation (AM) signals, thus potentially saving a limiter stage; however, the output is only 50% of the output of a discriminator for the same input signal.
What is the effect of adding the capacitor in Foster-Seeley detector?
The capacitors C1 and C2 filter any remaining RF signal which may appear across the resistors. The capacitor C4 and R3 also act as filters ensuring no RF reaches the audio section of the receiver. Like the ratio detector, the Foster-Seeley circuit operates using a phase difference between signals.
What is an FM discriminator?
FM Demodulation Detection. FM detectors are circuits that instantaneously convert the frequency changes from the carrier signal to its output voltage counterpart. They are also known as frequency demodulators or discriminators.
What is the other name for phase discriminator?
This Phase Discriminator is also known as the center-tuned discriminator or the Foster-Seeley discriminator, after its inventors.
Which one is the frequency discriminator?
A frequency discriminator is defined as a converter of frequency changes into amplitude changes. Discriminators are used in various applications, one of which is the direct demodulation of fre- quency modulated signals [1, 2]. Mixing a broad- band signal down to an intermediate frequency, can be a tedious job.
What are the types of phase discriminator?
There are two classes of phase detectors: a linear phase detector, in which the transfer function is somewhat linear between the output and the input phase error, as shown in Figure 4.41(A), and a binary phase detector (or bang-bang phase detector), in which only the sign of the phase error is extracted, as shown in …
What are the limitations of Foster Seeley detector?
Disadvantages of Foster-Seeley FM discriminator: High cost of transformer. Narrower bandwidth than the ratio detector. The circuit is sensitive to both frequency and amplitude and therefore needs a limiter before it to remove amplitude variations and hence amplitude noise.
What is electronic discriminator?
A constant fraction discriminator (CFD) is an electronic signal processing device, designed to mimic the mathematical operation of finding a maximum of a pulse by finding the zero of its slope. Some signals do not have a sharp maximum, but short rise times .
What is the function of frequency discriminator?
What is a Foster Seeley discriminator circuit?
The Foster Seeley discriminator circuit is characterised by the transformer, choke and diodes used within the circuit that forms the basis of its operation. This FM demodulator circuit was invented by Dudley E. Foster and Stuart William Seeley in 1936.
How does frequency affect the output of the Foster-Seeley discriminator?
The output of the Foster-Seeley discriminator is affected not only by the input frequency, but also to a certain extent by the input amplitude. Therefore, using limiter stages before the detector is necessary.
How does a Foster-Seeley circuit work?
Like the ratio detector, the Foster-Seeley circuit operates using a phase difference between signals. To obtain the different phased signals a connection is made to the primary side of the transformer using a capacitor, and this is taken to the centre tap of the transformer. This gives a signal that is 90° out of phase.
How does a Foster Seeley FM demodulator work?
It has an RF transformer and a pair of diodes, but there is no third winding – instead a choke is used. In many respects the Foster Seeley FM demodulator resembles the circuit of a full wave bridge rectifier – the format that uses a centre tapped transformer, but additional components are added to give it a frequency sensitive aspect.