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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.
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
In double-conversion superheterodyne receivers, a first intermediate frequency of 10.7 MHz is often used, followed by a second intermediate frequency of 470 kHz (or 700 kHz with DYNAS [15]). There are triple conversion designs used in police scanner receivers, high-end communications receivers, and many point-to-point microwave systems.
The heterodyne oscillator had to be retuned each time the receiver was tuned to a new station, but in modern superheterodyne receivers the BFO signal beats with the fixed intermediate frequency, so the beat frequency oscillator can be a fixed frequency. Armstrong later used Fessenden's heterodyne principle in his superheterodyne receiver (below).
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.
Frequency mixer symbol. In electronics, a mixer, or frequency mixer, is an electrical circuit that creates new frequencies from two signals applied to it.In its most common application, two signals are applied to a mixer, and it produces new signals at the sum and difference of the original frequencies.
A direct-conversion receiver (DCR), also known as a homodyne, synchrodyne, zero intermediate frequency or zero-IF receiver, is a radio receiver design that demodulates the incoming radio signal using synchronous detection driven by a local oscillator whose frequency is identical to, or very close to the carrier frequency of the intended signal.
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.