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Topic: Intermodulation distortion

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	Astrolab - Engineering - Intermodulation Distortion in Passive Components
		Intermodulation distortion in passive microwave components is caused by internal nonlinearities.
		Intermodulation distortion is most pronounced in systems where the high power transmission and low power receiver signals are carried simultaneously in the same transmission line, such as in the cable between the duplexer and the antenna in GSM base stations and in certain space applications.
		Intermodulation distortion in connectors is usually caused by thin-surface oxide layers at the connector junctions or by insufficient contact pressure when the current-carrying contact zones become separated.
	www.astrolab.com /13.asp (436 words)

	Total harmonic distortion - Wikipedia, the free encyclopedia
		The total harmonic distortion, or THD, of a signal is a measurement of the harmonic distortion present, that is, any departure of the output signal waveform from that which should result from the input signal waveforms being operated on by the system's specified or ideal transfer function.
		This is a measurement of the extent of that distortion.
		The THD is usually expressed in percent as distortion factor or in dB as distortion attenuation.
	en.wikipedia.org /wiki/Total_harmonic_distortion (279 words)

	Intermodulation distortion - Wikipedia, the free encyclopedia
		Intermodulation distortion: Nonlinear distortion characterized by the appearance, in the output of a device, of frequencies that are linear combinations of the fundamental frequencies and all harmonics present in the input signals.
		Note: Harmonic components themselves are not usually considered to characterize intermodulation distortion.
		When the harmonics are included as part of the distortion, a statement to that effect should be made.
	en.wikipedia.org /wiki/Intermodulation_distortion (96 words)

	AudioVideo101.com - Audio/Video Dictionary
		Needless to say, this form of distortion results in a multitude of additional frequency signals beyond the original two produced, and each of these frequencies may be heard distorting the original signal.
		Intermodulation distortion begins with additional frequencies being produced by the sum and difference (addition and subtraction) of two original frequencies.
		Intermodulation distortion would create two additional signals at 10 kHz (the sum or addition of 2 and 8 kHz) and 6 kHz (the difference between the numbers or subtraction of 2 from 8 kHz).
	www.audiovideo101.com /dictionary/im-distortion.asp (437 words)

	AllRefer.com - distortion (Electrical Engineering) - Encyclopedia
		distortion, in electronics, undesired change in an electric signal waveform as it passes from the input to the output of some system or device.
		Frequency distortion occurs when the amplitudes of the different frequency components of an input signal are changed by a factor that is not the same for all frequencies.
		Intermodulation distortion, also known as cross modulation, results from the mixing of signals in a non-linear system; the output will contain the sums and differences of the input signals' harmonics.
	reference.allrefer.com /encyclopedia/D/distorti.html (278 words)

	Audio Amplifiers
		Another type of distortion is intermodulation distortion, which occurs when different frequencies in the signal mix to produce sum and difference frequencies which didn't exist in the signal.
		This intermodulation distortion is particularly troublesome in the reproduction of music because it generates frequencies which were not present in the original music and are thus very noticeable.
		Harmonic distortion may also be serious, but at least the musical sound probably already had these harmonics present as part of the harmonic content of the sound, so it can be tolerated to a greater degree than intermodulation distortion.
	hyperphysics.phy-astr.gsu.edu /hbase/audio/amp.html (354 words)

	MTN110 Extending Limits of Intermodulation Distortion Measurements (Site not responding. Last check: 2007-11-04)
		The net result is distortion levels, that are difficult to measure in a single amplifier, may be fatal in a cascade.
		Crest factor is the ratio of peak to average ratio of the noise or distortion.
		For composite distortions, calibration is done by inserting a carrier on the measurement channel, 100% amplitude modulated by a 1 KHz square wave, and recording the magnitude of the 1 KHz at the audio analyzer.
	www.matrixtest.com /Literat/MTN110.htm (2853 words)

	Intermodulation distortion reduction circuit utilizing variable attenuation - Patent 6026285
		The IM distortion reduction circuit of claim 1, wherein said variable attenuator includes a variable impedance path to ground for the RF input receiver line, and wherein the impedance of said variable impedance path to ground varies in response to the RF input signal power levels.
		The IM distortion reduction circuit of claim 3, wherein said variable impedance element varies in impedance according to a control voltage generated by said attenuator controller, and wherein said impedance varies in a non-linearly changing manner throughout the range of RF input signal power levels.
		While the problems of IM distortion are not isolated to one particular type of radio communication system the wideband spread spectrum cellular communication system is one type of radio communication system which is sensitive to the problems of IM distortion.
	www.freepatentsonline.com /6026285.html (6387 words)

	Selective intermodulation distortion measurement - Patent 4028622
		Those distortion products in the frequency band of the notch, typically both second and third order distortion products, are selected from the signal output of the channel by a passband filter designed to pass signals at selected frequencies in the band of the notch.
		Low intensity intermodulation distortion products, which contribute to the overall distortion of the channel, are generally the contribution of segments or portions of the channel, for example, active components such as repeaters.
		A particular order of intermodulation distortion appearing in the quiet band is selected and its level indicated to obtain a measure of the nonlinearity in the operation of the transmission apparatus.
	www.freepatentsonline.com /4028622.html (5909 words)

	Passive intermodulation distortion in base station antennas
		Passive intermodulation (PIM) distortion generated in a GSM base station antenna appears as interference at the base station receiver, which can degrade the performance of the receiver.
		Intermodulation products are generated when two or more high power transmitting signals enter a nonlinear component.
		During this research, typical causes of passive intermodulation distortion in antennas have been identified, the physical phenomena behind these non-linearities have been investigated, and measurement methods of passive intermodulation have been developed.
	www.hut.fi /Units/Radio/research/rf_applications_in_mobile_communication/pim/passive_intermodulation.htm (382 words)

	TVTechnology - Digital TV
		Distortion comes in two basic classes: Linear distortion, which is not an oxymoron; and nonlinear distortion, which includes all other distortions except noise.
		Because intermodulation distortion produces such havoc in audio, simply measuring the harmonic distortion is not sufficient; we should also measure intermodulation distortion.
		Intermodulation is a much more important consideration and it determines whether we will have interference or not, which is the real subject of this column.
	www.tvtechnology.com /features/digital_tv/f_digital_tv.shtml (2405 words)

	Intermodulation distortion measurements
		Intermodulation distortion occurs when two or more frequencies become mixed across a nonlinear device.
		The presence of intermodulation distortion is determined by a two-tone test method.
		Intermodulation distortion cannot be entirely suppressed, but it can be minimized by shielding components and circuitry, parasitic suppression circuitry, and antenna spacing.
	www.tpub.com /neets/book21/89b.htm (407 words)

	B2 Spice v5 IM Distortion Meter
		The percent intermodulation distortion is defined as the percentage of amplitude modulation represented by the 2nd and 3rd sidebands, i.e.
		With this test, the percent intermodulation distortion is defined as the amplitude of the frequency component at Fh-Fl as a percentage of the source amplitude.
		The single frequency distortion test and the intermodulation distortion test are often performed on amplifier circuits because with this class of circuit you want to minimize the distortion of the signal during the amplification process.
	www.beigebag.com /imdisto_meter.htm (228 words)

	[music-dsp] emulating Distortion Vs. Overdrive (Site not responding. Last check: 2007-11-04)
		I just want to build a really beautiful distortion and overdrive effects instrument that people can use as an effects unit or as an add on for their other creations.
		Distortion: (Hard Clipping) Usually marketed as "distortion", where the signal level is restricted within a range.
		For just two notes played, intermodulation distortion produces an additional note with a frequency of the difference between the original two notes.
	shoko.calarts.edu /pipermail/music-dsp/2002-August/017175.html (1017 words)

	CED February 2001: A General Algorithm ... (Site not responding. Last check: 2007-11-04)
		Intermodulation distortion analysis is more difficult in broadband systems because all intermodulation products can interfere with many channels simultaneously.
		The frequency location of intermodulation distortion interferers in a broadband system with third-order non-linearity is investigated by applying N arbitrary channel frequency tones.
		The definition of the third-order intermodulation given in equation 9 is the same as for tones used to describe intermodulation distortion in narrowband analysis.
	www.cedmagazine.com /ced/2001/0201/webx/x02.htm (1654 words)

	Designing Audio Power Amplifiers.
		Seven of the most common one and two transistor input stages are compared by calculating their levels of intermodulation distortion under identical stage output current levels.
		To test our low distortion designs an alternative to buying expensive distortion measuring instruments is to use the bridge-nulling method in which the input and output are directly compared.
		Common-mode distortion is examined, a test method described, and the performance of typical input stage transistors tested and compared.
	www.angelfire.com /ab3/mjramp/designing.html (309 words)

	Stereophile: Red Shift: Doppler distortion in loudspeakers
		First, the common origin of these distortions is obscured by the fact that they go by different names and are quantified differently.
		Well, that reflects the second reason: Doppler effects in loudspeakers came and went as an issue between the 1960s and early 1980s, the consensus at the end of that period being that FIM distortion in typical hi-fi speakers is inaudible and therefore irrelevant.
		First, the amount of Doppler distortion generated by a loudspeaker is dependent on the amplitude of the signal's low-frequency content, because this is the principal determinant of diaphragm velocity.
	www.stereophile.com /reference/1104red (984 words)

	Intermodulation distortion (Site not responding. Last check: 2007-11-04)
		Intermodulation distortion: Nonlineardistortion characterized by the appearance, in the output of a device, offrequencies that are linear combinations of the fundamental frequencies andall harmonics present in the input signals.
		Note: Harmonic components themselves are not usually considered tocharacterize intermodulation distortion.
		When the harmonics areincluded as part of the distortion, a statement to that effect should be made.
	www.therfcc.org /intermodulation-distortion-20118.html (82 words)

	Daqarta for DOS - Inharmonic (Intermodulation) Distortion (Site not responding. Last check: 2007-11-04)
		In a two-tone intermodulation test, the 2nd order term B will cause intermodulation components to appear as an f2 - f1 difference tone.
		Intermodulation distortion is typically a problem when you are generating two tones from the same speaker or other source at high sound levels.
		It is particularly important to reduce intermodulation in loudspeaker and audio amplifier designs, since inharmonic distortion is subjectively much more objectionable to the ear than harmonic distortion.
	www.daqarta.com /0diidist.htm (520 words)

	"Close-3rd Order" Intermodulation distortion measurement
		The concept of harmonic distortion is easy to understand -- you apply a clean sine wave, with very low content at its harmonic frequencies, and then analyze the output from the device you are testing for increased relative levels at those harmonic frequencies.
		As the harmonic distortion is calculated as a ratio involving both, the accuracy or even the intelligibility of the resulting curve will be badly degraded.
		Measurement of "close" third-order intermodulation is not subject to the same frequency range constraints of harmonic distortion.
	www.libinst.com /close3rd.htm (1045 words)

	Method and apparatus providing improved intermodulation distortion protection - US Patent 6125272 (Site not responding. Last check: 2007-11-04)
		Second order intermodulation distortion (IM2) occurs when two interfacing signals mix with each other through a second order nonlinearity to produce an intermodulation product at the sum and difference frequencies of the two interferers.
		To minimize the effects of second order intermodulation within critical circuit blocks in the signal path, it is known in the art to use differential circuits.
		As previously stated, the basic problem of second order intermodulation distortion within an integrated, fully differential mixer arises from mismatches or imbalances between like devices within the circuit (hereinafter referred to as a parametric mismatch).
	www.patentstorm.us /patents/6125272.html (3461 words)

	Audio Characterization Report for the DS1802 Dual Digital Audio Potentiometer - Maxim/Dallas
		Intermodulation distortion data is provided for the SMPTE and the CCIF intermodulation measurement standards.
		The percentage intermodulation distortion is defined as the percentage of amplitude modulation, represented by the second and third order pair of sidebands, of the high-frequency signal.
		CCIF intermodulation distortion testing consists of using two equal-amplitude, high-frequency signals spaced closely in frequency.
	www.maxim-ic.com /appnotes.cfm/appnote_number/2119 (1754 words)

	Daqarta for DOS - Low-Level Distortion Measurement Techniques
		Typical modern amplifiers may have distortion levels (harmonic or intermodulation) that are below the noise floor of your ADC board.
		Even with waveform averaging to reduce the noise in the measurement, you may find that distortion from the board itself is larger than anything from the amplifier.
		The solution is to use intermodulation measurements instead of harmonic distortion measurements, since harmonic distortion of the individual sources does not compromise the results.
	www.daqarta.com /0deedist.htm (1376 words)

	IFR Announces New Automated Intermodulation Test Software for 2.4 GHz 2309 Signal Analyzer
		The 2309 signal analyzer is ideal for RF designers and production ATE engineers who must measure intermodulation distortion of wireless systems and components such as receivers, amplifiers, frequency converters and mixers.
		The 2309 intermodulation software uses FFT analysis to perform fast and accurate measurements of intermodulation with dynamic range beyond the capability of conventional swept spectrum analyzers and does so at speeds formerly unachievable by conventional methods.
		Although spectrum analyzers can be used to make intermodulation measurements, their performance, speed and accuracy are often unacceptable because of the errors in the level-measuring systems used in spectrum analyzers and their inherent noise.
	www.aeroflex.com /aboutus/pressroom/newsrelease/ifr2002/pr251.htm (870 words)

	Distortion - Intermodulation Distortion (Site not responding. Last check: 2007-11-04)
		The worst sounding type of distortion, besides clipping, is probably the crossover distortion.
		This type of distortion cannot be measured with a distortion meter and is not quantified in numbers.
		Crossover distortion is created in push-pull amplifier stages, regardless of whether these are based on transistors or vacuum tubes.
	www.lennartlabs.com /theory/distortion/distortion5.htm (170 words)

	Stereophile: Lamm Industries L2 Reference preamplifier
		Levels of intermodulation distortion were also extremely low.
		But from the balanced outputs at 10V, the intermodulation spectrum was one of the cleanest I have ever seen (fig.7).
		Figs.8 and 9 show the level of distortion and noise plotted against output voltage from the unbalanced and balanced outputs, respectively.
	www.stereophile.com /amplificationreviews/354/index7.html (548 words)

	[No title]
		Intermodulation distortion, which produces non-musically related frequencies at multiples of the sum and differences of two frequencies, is considered to sound harsh to the ear.
		Unfortunately, all known harmonic distortion methods also produce intermodulation distortion when fed two or more different frequencies simultaneously, but the exact method of producing distortion may result in lower or higher amounts of harsh sounding intermodulation; there is no exact way to predict the harshness.
		In general, the "softer" the clipping or distortion (that is, the fewer and softer the "corners"), the less intermodulation, but this is only a generality.
	www.geofex.com /effxfaq/distn101.htm (3250 words)

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