The one notable exception to heterodyne ( downconversion ) radar systems is ultra-wideband radar.

These systems are referred to as " heterodyne systems " or " color-under systems ".

Other videotape formats with heterodyne color systems include Video-8 and Hi8.

In the 1990s, LPB, Inc., possibly the largest manufacturer of these transmission systems, designed and supplied several extensive campus-based systems that included fiber-optic links between linear amplifiers to prevent heterodyne interference.

The original heterodyne detector was pioneered by Canadian inventor Reginald Fessenden in 1905, but it was not pursued far because local oscillators available at the time ( the oscillating arc ) were unstable in their frequency output.

Thus, sensitive detection of specific optical frequencies necessitates optical heterodyne detection, in which two different ( close-by ) wavelengths of light illuminate the detector so that the oscillating electrical output corresponds to the difference between their frequencies.

However, almost any nonlinear electronic component will also multiply signals applied to it, producing heterodyne frequencies in its output, so these are most often used as mixers.

The only drawback to using a nonlinear component rather than a multiplier is that, in addition to the sum and difference frequencies, it produces other unwanted frequency components called harmonics which must be filtered from the output to leave the desired heterodyne frequency.

These unwanted frequencies, along with the unwanted heterodyne frequency, must be filtered out of the mixer output to leave the desired heterodyne.

Ring modulators frequency mix or heterodyne two waveforms, and output the sum and difference of the frequencies present in each waveform.

This and other sophisticated FD detectors also include a heterodyne detector and provide a jack output so that independent outputs can be recorded for later analysis.

With dual output FD detectors, headphones can be used to monitor both outputs simultaneously, or the loudspeaker used with the heterodyne function and the FD output recorded and analysed later.

There will also be flicker noise caused by electrons transit through amplification devices, which is reduced using heterodyne amplification.

Synthetic array heterodyne detection was developed to reduce speckle noise in coherent optical imaging and coherent DIAL LIDAR.

The word heterodyne is derived from the Greek roots hetero-" different ", and-dyne " power ".

Fessenden coined the word heterodyne from the Greek roots hetero-" different ", and dyn-" power " ( cf.

To demonstrate mathematically how a nonlinear component can multiply signals and generate heterodyne frequencies, the nonlinear function F can be expanded in a power series ( MacLaurin series ):

In this circuit, the incoming radio frequency signal from the antenna is mixed with a signal from a LO and converted by the heterodyne technique to a lower fixed frequency signal called the intermediate frequency ( IF ).

The heterodyne system in these cases is used to convert quadrature phase-encoded and amplitude modulated sine waves from the broadcast frequencies to frequencies recordable in less than 1 MHz bandwidth.

In this circuit, the incoming radio frequency signal from the antenna is mixed with a signal from a LO and converted by the heterodyne technique to a lower fixed frequency signal called the intermediate frequency ( IF ).

At the receiver, the received signal is mixed with a heterodyne signal from a BFO ( beat frequency oscillator ) to change the radio frequency impulses to sound.

But quenching with overtones acts further as a heterodyne receiver mixing additional unneeded signals from those bands into the working frequency.

While the wavelength was always announced as " 266 metres " The station experimented with various frequencies between 1133 and 1137. 5 kHz and tended to suffer nighttime heterodyne interference from stations in Zagreb and elsewhere.

It was equipped with heterodyne receivers covering frequencies between 210 and 880 GHz, corresponding to wavelengths between 0. 35 and 1. 4mm, for observations of lines from the interstellar medium.

It covered a greater portion of the high frequency ( HF ) and medium wave spectrum than did the SW-4, by using a large set of selectable heterodyne oscillator crystals for selecting the tuning range, each covering a 500 kHz wide segment.

In heterodyne receivers, an image frequency is an undesired input frequency equal to the station frequency plus twice the intermediate frequency.

* The heterodyne technique is used for ( 1 ) shifting an input signal into a new frequency range as well as ( 2 ) amplifying a weak input signal ( assuming use of an active mixer ).

This creates a heterodyne or " beat " signal at the difference between the two frequencies.

To monitor a frequency of 1500 kHz for example, he could set up an oscillator at, for example, 1560 kHz, which would produce a heterodyne difference frequency of 60 kHz, a frequency that could then be more conveniently amplified by the triodes of the day.

However, if f < small >< sub > LO </ sub ></ small > is set to f < small >< sub > d </ sub ></ small > + f < small >< sub > IF </ sub ></ small >, then an incoming radio signal at f < small >< sub > LO </ sub ></ small > + f < small >< sub > IF </ sub ></ small > will also produce a heterodyne at f < small >< sub > IF </ sub ></ small >; this is called the image frequency and must be rejected by the tuned circuits in the RF stage.

They do this by mixing the television signal frequency, f < sub > CH </ sub > with a local oscillator at a much higher frequency f < sub > LO </ sub >, creating a heterodyne at the sum f < sub > CH </ sub >+ f < sub > LO </ sub >, which is added to the cable.

At the consumer's home, the cable set top box has a downconverter that mixes the incoming signal at frequency f < sub > CH </ sub >+ f < sub > LO </ sub > with the same local oscillator frequency f < sub > LO </ sub > creating the difference heterodyne, converting the television channel back to its original frequency: ( f < sub > CH </ sub >+ f < sub > LO </ sub >) − f < sub > LO </ sub > = f < sub > CH </ sub >.

Armstrong's solution was to set up an oscillator tube that would create a frequency near the incoming signal, and mix it with the incoming signal in a ' mixer ' tube, creating a ' heterodyne ' or signal at the lower difference frequency, where it could be amplified easily.

Betamax records relatively low resolution composite video using a heterodyne color recording system and only two recording heads, while Betacam uses four heads to record in component format, at a much higher linear tape speed ( 10, 15 cm / s compared with Betamax ' 1, 87 cm / s ), resulting in much higher video and audio quality.

Just as two different musical notes played together create a beat note at the difference in frequency between them, so these two radio signals are mixed to create a " beat " signal ( called a heterodyne ) and an electrical circuit then measures this frequency using a digital counter and displays the number on a digital display as the object's speed.

In real time mode, with or without an associated heterodyne or FD detector, the slowed down calls can be heard as a drawn-out bat call at audible frequencies.

In heterodyne detection, the high frequency components and usually the constant components are filtered out, leaving the intermediate ( beat ) frequency at.

The instrument operated between 1994 and 2005 at the South Pole with four heterodyne receivers and three acousto-optical spectrometers.

The disadvantages of a heterodyne bat detector are that it can only convert a narrow band of frequencies, typically 5 kHz, and has to be continually retuned, and can easily miss species out of its current tuned range.

The autodyne receiver, which has one stage function as both a local oscillator and a heterodyne mixer, had several inventors around 1912 to 1913.

The theremin, an electronic musical instrument, uses the heterodyne principle to produce a variable audio frequency in response to the movement of the musician's hands in the vicinity of some so called antennas, which act as capacitor plates.

As his work progressed, Fessenden also evolved the heterodyne principle, which combined two signals to produce a third audible tone.

However, heterodyne reception was not fully practical for a decade after it was invented, since it required a means for producing a stable local signal, which awaited the development of the oscillating vacuum-tube.

Then the signal is either sampled or processed by the four-quadrant multiplier which produces the complex envelope components ( I, Q ) through multiplying it by the heterodyne frequency.

Regenerative Detectors work well for narrow-band signals, especially for CW and SSB which need a heterodyne oscillator or BFO.

The reference beam is also sent to the photodetector where optical heterodyne detection produces an electrical signal proportional to the Doppler shift, by which the particle velocity component perpendicular to the plane of the beams can be determined.

; HIFI ( Heterodyne Instrument for the Far Infrared ): A heterodyne detector which is able to electronically separate radiation of different wavelengths, giving a spectral resolution as high as R = 10 < sup > 7 </ sup >.

The JCMT is also equipped with three heterodyne receivers, which allow submillimetre spectral line observations to be made.

As a result of the plan most medium wave ( and later longwave ) stations outside North and South America operate on exact multiples of 9 kHz which helps reduce heterodyne interference.

HgCdTe can be used as a heterodyne detector, in which the interference between a local source and returned laser light is detected.