Jump to Superheterodyne receiver - The direct-conversion (heterodyne) detector was invented to make continuous wave radio-frequency signals audible. The "heterodyne" or "beat" receiver has a local oscillator that produces a radio signal adjusted to be close in frequency to the incoming signal being received.‎Superheterodyne receiver · ‎Heterodyne (disambiguation). The Heterodyne Receiver. The original radio receiver design was the heterodyne receiver. The desired radio signal was selected by tuning a narrow-band amplifier! For example, say at the output of the antenna we find the following signal spectrum. A Heterodyne Receiver. Details about the overall block diagram for the superheterodyne radio receiver: major circuit blocks, functions, overall operation.


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Applications[ edit ] Heterodyning, also called frequency conversion, is used very widely in communications engineering to generate new frequencies and move information heterodyne receiver one heterodyne receiver channel heterodyne receiver another.

Besides its use in the superheterodyne circuit found in almost all radio and television receivers, it is used in radio transmittersmodemssatellite communications and set-top boxes, radarradio telescopestelemetry systems, cell phones, cable television converter boxes and headendsmicrowave relaysmetal detectorsatomic clocksand military electronic countermeasures jamming systems.

Up and down converters[ edit ] In large scale telecommunication networks such as telephone network trunks, microwave relay networks, cable television systems, and communication satellite links, large bandwidth capacity links are shared by many individual communication channels by using heterodyning to move the frequency of the individual signals up to different frequencies, which share the channel.

This is called frequency division multiplexing FDM.

Superheterodyne Receiver | Block Diagram | Electronics Notes

For example, a coaxial cable used by a cable television system can carry television channels at the same time because each one is given a different frequency, so they don't interfere with one another. At the cable source or headendelectronic upconverters convert each incoming television channel heterodyne receiver a new, higher frequency.

Each channel is moved to a different higher frequency. The original lower basic frequency of the signal is called the basebandwhile the higher channel it is moved to is called the passband.

Analog videotape recording[ edit ] Many analog videotape systems rely on a downconverted color subcarrier to record color information in their limited bandwidth. These systems are referred to as "heterodyne systems" or "color-under systems".

Other videotape formats with heterodyne color systems include Video-8 and Hi8. On playback, the recorded color information is heterodyne receiver back to the standard subcarrier frequencies for display on televisions and for interchange with other standard video equipment.

Superheterodyne receiver history This form of receiver is based around the heterodyne receiver of mixing signals in a non-linear fashion.

This idea was heterodyne receiver noticed when beats were detected between two signals. R A Fessenden was the first person to notice this and he patented the idea in However the idea lay dormant for some years as most receivers consisted of detectors and tuned circuits.

The diode thermionic valve or vacuum tube was invented by Ambrose Fleming inand then a third grid was heterodyne receiver by Lee de Forest. Although early valves or tubes were in use, they were very unstable and it was difficult to gain much useful performance from them.

A young engineer named Edwin Heterodyne receiver started to utilise the power of the vacuum tube or thermionic valve, inventing the regenerative receiver around This provided a considerable increase in useful gain over what was previously attained.

Heterodyne receiver

It was the onset of the Great War heterodyne receiver that gave fresh impetus to radio receiver design. There was a requirement for sensitive radio receivers for a variety of tasks.

The first major step was taken heterodyne receiver a Frenchman named Lucien Levy. At the time the performance of valves was very poor at frequencies above kHz or so, and he devised a system for reducing heterodyne receiver frequency of the incoming signal using the system of beats - the signal could then be tuned and amplified more effectively at a lower frequency.

Here significant levels of amplification are applied and the signals are filtered.


This filtering selects signals on one channel against those on the next. It is much larger than that employed in the front end. The advantage of the IF filter as opposed to RF filtering is that the filter can be designed for a fixed frequency.

This allows for much better tuning. Variable filters are never able to provide the same level of selectivity that can be provided by fixed frequency ones. Once filtered the next block in the superheterodyne receiver is the demodulator.

This could be for amplitude modulation, single sideband, frequency modulation, or indeed any form of modulation. To avoid tooling costs associated with these components, most manufacturers then tended to design their receivers around a fixed range of heterodyne receiver offered, which resulted in a worldwide de facto standardization of heterodyne receiver frequencies.