With the help of a block diagram, explain the operation of FM super heterodyne receivers.
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Solution
The block diagram of FM super heterodyne is given below
The signal received by antenna is amplified using RF amplifier.
The amplified signal is then applied to Mixer, in which the second signal comes from a local oscillator. The mixer now has two input frequencies, combining both generates an IF signal of 10.7 MHz . This signal is again amplified using an IF amplifier.
The output of IF amplifier is allowed to flow in the Limiter circuit. The limiter circuit gives a constant amplitude signal by removing the noise from the signal it received.
The output of the Limiter is then applied to the FM discriminator which recovers the modulating signal.
This signal is still not the original modulating signal, therefore, before applying it to the Audio amplifier it is de- emphasized. De- emphasis attenuates the higher frequencies to bring them back to their original amplitudes.
The output of this De-emphasis is the audio signal which is applied to the audio stages and then to the speaker.
