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Intermodulation - Wikipedia, the free encyclopedia Intermodulation or intermod is the result of two radio signals of different frequencies being mixed together, forming additional signals at frequencies that are not in general at harmonic frequencies (integer multiples) of either. The cause for intermodulation is the existence of non-linear characteristics of the according equipment. Intermodulation is rarely desirable in radio, as it essentially creates spurious emissions, which can create minor to severe interference to other operations on the resulting frequency (See the Rusty bolt effect for more details). en.wikipedia.org /wiki/Intermodulation   (201 words)

What is Intermodulation Interference?   (Site not responding. Last check: 2007-10-20) Intermodulation interference is the undesired combining of several signals in a nonlinear device, producing new, unwanted frequencies, which can cause interference in adjacent receivers located at repeater sites. Receiver intermodulation occurs as the results of two or more high-level off-channel signals overloading the receiver’s RF amplifier causing it to operate in it’s nonlinear region thus acting as a mixer. It may be difficult to determine where intermodulation is occurring because the new frequencies being generated are precisely the same whether they are generated in the receiver front end, transmitter PA or some other non-linearity. www.midians.com /html/intermod-explained.asp   (1264 words)

RA EMC Awareness - Mitigation - preventing intermodulation Intermodulation prevention techniques in installations are used to help prevent spurious noise frequencies from being caused by two or more frequencies being applied to a non-linear electrical bond. Intermodulation products always have a lower amplitude than the signals that gave rise to them, and in many cases are only of concern to very sensitive radio receivers operating on weak signals. Intermodulation caused by two or more frequencies being present at the same time in a non-linearity in an electrical joint (connection) or similar situation is sometimes called ‘passive intermodulation”. www.ofcom.org.uk /static/archive/ra/topics/research/RAwebPages/Radiocomms/pages/mittech/install/intermod.htm   (697 words)

Encyclopedia: Intermodulation distortion   (Site not responding. Last check: 2007-10-20) A constituent of non-linearity distortion consisting of the occurrence, in the response to co-existent sinusoidal excitations, of sinusoidal components (intermodulation products) whose frequencies are sums or differences of the excitation frequencies or of integral multiples of these frequencies. Intermodulation distortion manifests as a type of amplitude change in which sum and difference tones (harmonics of the original signal) are present in the recorded signal. 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. www.nationmaster.com /encyclopedia/Intermodulation-distortion   (311 words)

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)

Intermodulation As the intermodulation curve rises with greater slope than the fundamental curve, they cross at a point called the Third-Order Intercept Point where the intermodulation product output level is equal to the fundamental signal output level. As the X axis of the analyser display is calibrated in frequency, the various intermodulation components can be identified and their amplitudes recorded relative to the two fundamental frequencies. Intermodulation is shown on the display as an amplitude modulation waveform of the lower frequency on the higher frequency carrier. www4.tpgi.com.au /users/ldbutler/Intermodulation.htm   (3781 words)

[No title]   (Site not responding. Last check: 2007-10-20) Passive PIM control circuits may be advantageously designed to indirectly suppress intermodulation interference occurring within a desired band, such as the reception band of a communication system, by directly controlling out-of-band subject frequencies comprising one or more harmonic multiples of the transmission carrier frequencies. Intermodulation occurs whenever radio frequency signals at two or more frequencies are simultaneously present in a conductor of radio frequency energy. Intermodulation products can be a source of interference within the receive band of the system and can be a source of interference for other systems having different operational bands. www.wipo.int /cgi-pct/guest/getbykey5?KEY=03/81795.031002&ELEMENT_SET=DECL   (12383 words)

[No title]   (Site not responding. Last check: 2007-10-20) When intermodulation distortion is detected, the filter 130 is configured as a wider DC notch filter, to filter-out second order intermodulation distortion by attenuating signal components of the baseband signal in the frequency band of the intermodulation distortion. Although the intermodulation distortion may be narrower or wider than +/-60 kHz, depending upon the source of the distortion, this notch-width has been found to substantially reduce the effects of commonly occurring second-order intermodulation distortion while still retaining adequate receiver performance. The method of claim 1, wherein detecting (240) the occurrence of intermodulation distortion includes: determining (230) a plurality of signal strength measures, and determining the occurrence of intermodulation distortion based on a relationship among the plurality of signal strength measures. www.wipo.int /cgi-pct/guest/getbykey5?KEY=04/109941.041216&ELEMENT_SET=DECL   (2966 words)

[No title] Intermodulation products result in interference, when two or more signals combine in a nonlinear device and produce an undesired signal on or near the tuned frequency of the victim receiver. To minimize intermodulation, frequencies should be selected such that the frequency difference between any pair of frequencies is unlike the difference between any other pair. Intermodulation Analysis Equations The interference due to intermodulation is defined by the following equations. ntiacsd.ntia.doc.gov /msam/INTMOD/INTMOD_PROGRAM.doc   (455 words)

Collocation and Intermodulation Analysis Intermodulation Interference is produced by the mixing of transmitter frequencies at a site. As a result of system nonlinearities, these frequencies mix to produce other "intermodulation" frequencies that are potential sources of interference to the receivers at the site. Transmitter Intermodulation occurs when signals enter a transmitter and mix, and the resulting intermod frequencies are re-radiated by the transmitting antenna. www.comsearch.com /telecom/colocation_intermodulation.jsp   (419 words)

Finding, Solving and Preventing Intermodulation Problems Intermodulation products are the emissions at frequencies generated by the combination of two or more frequencies in a non-linear device, such as the output stage of a transmitter, or the input stage of a receiver. Intermodulation product -A measurable signal at a specific frequency (or occasionally multiple signals over a specific bandwidth) generated from a combination of radiated signals, which are received at a site and which can cause interference to some desired received or protected frequency. Those possible intermodulation products resulting from the combinations of second and higher order harmonics from the proposed and/or existing equipment are of lower probability because of the stringent FCC regulations regarding spurious radiation and the suppression of harmonic frequencies. www.softwright.com /faq/support/intermod_finding_solving.html   (7177 words)

BROADBAND LOOP ANTENNAS, Active Antenna Sensitivity, Intermodulation Intermodulation will appear as several stations chattering together in parts of the bands which are the sum and difference of frequencies normally in the Broadcast bands. The intermodulation performance required, depends mainly on the signal output level of the antenna (K factor) in respect to the field strength of the strongest signals. The usual measure of the intermodulation performance is the output intercept point of which the 2nd and 3rd order are referred to IP2 and IP3 respectively. www.wellbrook.uk.com /intermod.html   (999 words)

Large Multi-Channel Wireless Microphone Systems: Rent Com Inc: Audio Visual, Video, Projection, Presentation Rental AV ... Intermodulation is the result of two or more signals mixing together to produce a sum or difference signal. It is a common misconception that intermodulation is produced by the carrier frequencies mixing within the air. A specification known as intermodulation rejection is a measure of the RF input threshold before intermodulation occurs. www.rentcom.com /wpapers/senn/senn.html   (4195 words)

Comments from John Thorpe   (Site not responding. Last check: 2007-10-20) Sadly intermodulation resistance to reverse power is not a specified parameter.) The amount of IMD produced by the generator ALC is dependent on the generator to generator coupling which in turn is dependent on hybrid coupler isolation and, more importantly, DUT input impedance (power is reflected if VSWR is not unity). Odd-order intermodulation (3rd order usually being the most prominent) is normally used as an assessment of a receiver's dynamic range because there is very little that can be done external to the receiver to improve it. As well as generating the intermodulation test signal the test setup must be able to establish the level of intermodulation distortion that the receiver produces. www.aoruk.com /comments.htm   (6272 words)

Linrad support: Second order intermodulation in the RXHFA unit. This is the requirement for third order intermodulation and the "modest" requirement is due to the fact that the highest IP3 needed, +33 dBm, is not needed simultaneously with a low noise figure. Second order intermodulation is much easier to measure than third order intermodulation because the frequencies of two strong signals are well separated from the frequency of the intermodulation product. To verify the IP2 measurement on the RXHFA unit, the levels of the sum frequency and of the second order harmonic were measured with a stepped attenuator inserted between the low pass filter and the 6 dB attenuator. www.nitehawk.com /sm5bsz/linuxdsp/rxhfa/imd2_hfa.htm   (1490 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)

Intermodulation Concepts - Intermodulation between closely spaced transmitters - PROCOM The output from one transmitter antenna may be radiated into an adjacent transmitter antenna causing unwanted frequencies to appear at the output stage of the transmitter. If the presence of 2nd order intermodulation products is demonstrated, it is very likely that these products were generated outside the transmitters, for example by mixing in rectifier-type links in antennas, antenna masts, cables, connectors as a result of corrosion. One of the first steps is to determine whether the source is intermodulation in the transmitter output or in the receiver input where the interference is demonstrated. www.procom-dk.com /pco/pco_web_int.nsf/85a39e77ed6f9aa3c1256f13006b3be7/d822b1e40c95e43bc1256f02003ef9ef!OpenDocument   (848 words)

Introduction to Mixers The intermodulation products are given by IF = N*RF ± M*LO and their levels, relative to the desired output of RF ± LO, for a common mixer, are shown in table 1. The data given in a harmonic intermodulation table depends on the relative levels of the input signals, the frequencies, and the terminating impedances. The order of the intermodulation product is important because a 1-dB change in the power level of each input RF signal causes the power level of each intermodulation procut to change by an amount of dB equal to its order. members.tripod.com /michaelgellis/mixersin.html   (2755 words)

Intermodulation Concepts - Introduktion to Intermodulation - PROCOM Intermodulation is a multi-signal interference problem where two or more signals mix in a non-linear phase or ”device” to form one or more new signals, intermodulation products. The three key sources of intermodulation are described below, and various proposals to remedy the problem are described. When intermodulation products have been determined as interfering signals, it will be advisable to deal with the phenomenon in the above order of priorities. www.procom-dk.com /output/e0301-procom-intermodulation-concepts1-p!Open&p=1   (178 words)

IFR Announces New Automated Intermodulation Test Software for 2.4 GHz 2309 Signal Analyzer 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. For the first time, complex and time consuming intermodulation measurements have been simplified to allow the tests to be automated. 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)

NTIA TR-97-343, Appendix C The marine VHF radios were tested for susceptibility to 3rd and 5th order intermodulation products by using two signal generators as interfering transmitters that could possibly generate intermodulation products on channel 67 within the receiver of the radio being tested. The SINAD reduction due to intermodulation products was verified by turning each of the signal generators off and observing the SINAD meter on the test set. Once the SINAD reduction due to the intermodulation product was verified, the RF power of each signal generator, I1 and I2, at the RF input to the radio was measured in dBm with a spectrum analyzer and recorded. www.ntia.doc.gov /osmhome/reports/tr97343/tr97343c.html   (769 words)

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