Superheterodyne receiver radio block diagram

- radio block diagram for a complete superheterodyne receiver showing the functions of the individual blocks and the complete radio receiver.

Superheterodyne radio receiver tutorial includes:

Having looked at the concepts behind the superheterodyne receiver it is helpful to look at a block diagram of a basic superhet. The superheterodyne block diagram is relatively straightforward and builds on the basic functional block used to convert the incoming frequency down to a fixed intermediate frequency stage.

While there may be some simplified versions for a superheterodyne block diagram, each receiver will be different as a result of the differing requirements for each receiver. However the basic principles are the same, and many superheterodyne block diagrams are very similar.

Basic superheterodyne block diagram and functionality

Signals enter the front end circuitry from the antenna. This contains the front end tuning for the superhet to remove the image signal and often includes an RF amplifier to amplify the signals before they enter the mixer. The level of this amplification is carefully calculated so that it does not overload the mixer when strong signals are present, but enables the signals to be amplified sufficiently to ensure a good signal to noise ratio is achieved.

The tuned and amplified signal then enters one port of the mixer. The local oscillator signal enters the other port. The local oscillator may consist of a variable frequency oscillator that can be tuned by altering the setting on a variable capacitor. Alternatively it may be a frequency synthesizer that will enable greater levels of stability and setting accuracy.

Once the signals leave the mixer they enter the IF stages. These stages contain most of the amplification in the receiver as well as the filtering that enables signals on one frequency to be separated from those on the next. Filters may consist simply of LC tuned transformers providing inter-stage coupling, or they may be much higher performance ceramic or even crystal filters, dependent upon what is required.

Once the signals have passed through the IF stages of the superheterodyne receiver, they need to be demodulated. Different demodulators are required for different types of transmission, and as a result some receivers may have a variety of demodulators that can be switched in to accommodate the different types of transmission that are to be encountered. The output from the demodulator is the recovered audio. This is passed into the audio stages where they are amplified and presented to the headphones or loudspeaker.

Block diagram of a basic superheterodyne radio receiver

Further developments for superheterodyne block diagram

The diagram above shows a very basic version of the superhet or superheterodyne receiver. Many sets these days are far more complicated. Some superhet radios have more than one frequency conversion, and other areas of additional circuitry to provide the required levels of performance. However the basic superheterodyne concept remains the same, using the idea of mixing the incoming signal with a locally generated oscillation to convert the signals to a new frequency. ..........

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