Monday, May 5, 2014


Today i am going to discuss about super heterodyne receiver . It is an important topics for the students reading communication engineering .Among all of the receivers the super heterodyne receiver is the most popular and largely used receiver.To learn more about super heterodyne receiver at first we have to know the basic definition of receiver.

RECEIVER is an electronic equipment which receives radio signal and convert the information into an useable form.

The working principal of a Super heterodyne receiver can be classified into three different stages. The first section is Radio frequency  section , second section is intermediate frequency section and the third section is audio frequency section.
Block diagram of super heterodyne receiver:

RF SECTION: The first stage is a tuned RF amplifier using two variable tuned circuit. The  two tuned RF circuit form a band pass filter to pass the desired RF signal frequency and blocking the others. This stage acts to boost  the weak signal level from the antenna  above the noise level to provide some signal selectivity. The out put signal from the RF amplifier is fed to one input of the mixer circuit and the local oscillator section to the other.

IF SECTION: The mixer output is fed is fed to two cascade tuned IF amplifier which provides fixed tune and sufficient selectivity to reject adjacent channel signal.

AF SECTION: The output from the IF amplifier chain is fed to the detection circuit where the audio signal is extracted from the if carrier.  The  audio signal is passed through the low pass filter to remove the unwanted high frequency signal. The audio amplifier is one low level audio stage followed by a power amplifier and a speaker.