What is discriminator in communication theory?
EC8491 COMMUNICATION THEORY FM DEMODULATORS. The following two methods demodulate FM wave. (1) Frequency discrimination method (Balanced FM Slope Detector (Balanced Frequency. Discriminator) (2) Phase discrimination method ( Foster Seeley FM Demodulator)
What are the drawbacks of slope detector?
Drawbacks of Slope Detector (i) It is inefficient. (ii) It is linear only over a limited frequency range. (iii) It is difficult to adjust as the primary and secondary winding of the transformer must be tuned to slightly different frequencies.
What is the function of a discriminator in FM receiver?
discriminator-a circuit or device in which amplitude variations are de- rived from frequency or phase varia- tions. The circuit has many uses, but is popular as a detector in FM receivers. ahead of a discriminator or ratio detector to clip AM energy and generally clean up a noisy FM signal.
What is a balanced discriminator?
Envelope Detector. • Also called balanced discriminator. • Uses two tuned circuits each set to a. fixed frequency. – f1 = 3AF + fc & f2 = 3AF – fc.
How does a slope detector work?
An FM slope detector consists of a tuned circuit where the centre frequency is tuned to a frequency slightly offset from the carrier of the signal. In this way the frequency modulated signal sits on the slope of the response curve, giving rise to the name of FM slope detector.
What is Carson’s rule in FM?
Carson’s rule gives the estimation of the bandwidth of an FM system. This rule states that the bandwidth of an FM system is double the sum of the maximum frequency deviation and the highest modulating frequency fm.
What is Armstrong method?
From Wikipedia, the free encyclopedia. In 1933, Edwin H. Armstrong patented a method for generating frequency modulation of radio signals. The Armstrong method generates a double sideband suppressed carrier signal, phase shifts this signal, and then reinserts the carrier to produce a frequency modulated signal.
How does a Foster Seeley discriminator work?
The Foster–Seeley discriminator was envisioned for automatic frequency control of receivers, but also found application in demodulating an FM signal. The Foster–Seeley discriminator uses a tuned RF transformer to convert frequency changes into amplitude changes.
Can a discriminator be used as an FM detector?
Such a discriminator, therefore, functions as an excellent FM detector provided that the resonant frequency of the discriminator tuned circuit is equal to the carrier centre frequency. The detected output is picked up from one end of the composite load while the other end is founded as shown in figure 1.
Why does the Foster Seeley FM detector need a limiter?
The circuit is sensitive to both frequency and amplitude and therefore needs a limiter before it to remove amplitude variations and hence amplitude noise. Like all circuits, the Foster Seeley FM detector has its own advantages and disadvantages.
What is the output of the limiter in a discriminator?
The output of the limiter is transformer-coupled to the discriminator. The primary and secondary of the transformer are parts of resonant circuits, tuned to the IF signal resting frequency. The output of the limiter is also capacitively coupled to the discriminator.