FM Receiver

FM receiver invariably make use of superheterodyne configuration,and the basic block diagram is the same as that for an AM receiver.However,the antenna,RF amplifier and local oscillator usually operate in the VHF of 88-108 MHz and have an intermediate frequency (IF) of 10.7 MHz  with a bandpass of 2 X 75 kHz i.e.,150kHz.

In both AM and FM receivers,the purpose of stage following the IF amplifier is to extract the information from the carrier signal.Since the information was originally impressed on the carrier by modulating its frequency,the FM detector must sense frequency-not amplitude-variations.Thus,basic difference between FM and AM receiver lie in the detector (or demodulator) circuit.Also,since FM signals may occupy a wider band for given modulating signal,the RF and IF bandwidths are typically greater.Since FM is usually confined to higher frequencies,this wider bandwidth need is  more tolerable .

The audio portion of an FM receiver is identical to that for an AM receiver,except that the audio portion of an FM broadcast receiver is usually capable of amplifying without distortion a wider frequency range than an AM broadcast receiver-typically 15 kHz versus 5 kHz.

The functions of components other than limiter and de-emphasis network are the same as explained in case of superheterodyne receiver.In FM receiver limiter is provided to remove all amplitude variations,caused by noise from IF signal which might have crept into the FM signal.The de-emphasis network is provided to reduce the amplitude of high frequencies in the audio signal which was earlier increased at the transmitting station.