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A 5-tube superheterodyne receiver manufactured by Toshiba circa 1955 Superheterodyne transistor radio circuit circa 1975. A superheterodyne receiver, often shortened to superhet, is a type of radio receiver that uses frequency mixing to convert a received signal to a fixed intermediate frequency (IF) which can be more conveniently processed than the original carrier frequency.
The name superheterodyne was a contraction of supersonic heterodyne, to distinguish it from receivers in which the heterodyne frequency was low enough to be directly audible, and which were used for receiving continuous wave (CW) Morse code transmissions (not speech or music).
An important and widely used application of the heterodyne technique is in the superheterodyne receiver (superhet). In the typical superhet, the incoming radio frequency signal from the antenna is mixed (heterodyned) with a signal from a local oscillator (LO) to produce a lower fixed frequency signal called the intermediate frequency (IF
A schematic of a superhet AM receiver. Note that the radio includes an AGC loop in order to maintain the RF and IF stages in their linear region, and to produce an audio output not dependent on the signal power received. Here we show block diagrams for typical superheterodyne receivers for AM and FM broadcast respectively.
Image response (or more correctly, image response rejection ratio, or IMRR) is a measure of performance of a radio receiver that operates on the superheterodyne principle. [1] In such a radio receiver, a local oscillator (LO) is used to heterodyne or "beat" against the incoming radio frequency (RF), generating sum and difference frequencies.
Block diagram of a superheterodyne receiver. The RF front end consists of the components on the left colored red. In a radio receiver circuit, the RF front end, short for radio frequency front end, is a generic term for all the circuitry between a receiver's antenna input up to and including the mixer stage. [1]
Local oscillators are used in the superheterodyne receiver, the most common type of radio receiver circuit. They are also used in many other communications circuits such as modems, cable television set top boxes, frequency division multiplexing systems used in telephone trunklines, microwave relay systems, telemetry systems, atomic clocks, radio telescopes, and military electronic ...
A superheterodyne receiver only needs to track the RF and LO stages; the onerous selectivity requirements are confined to the IF amplifier which is fixed-tuned. During the 1920s, an advantage of the TRF receiver over the regenerative receiver was that, when properly adjusted, it did not radiate interference.