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.