Intermodulation product an overview sciencedirect topics. It can be a tremendous job to calculate the intermodulation products from several frequencies, below is a calculator that calculates the intermodulation product from two and three frequencies. Strong signals external to the transmitter combine with the signal being generated. The graphic above depicts the most common case of intermodulation. Jun 30, 2016 intermodulation with wireless microphones 3 key points. These intermodulation products can cause the transmitter to output spurious signals.
Synchronous measurement of even and odd order intermodulation. The deviation of the intermodulation product is equal to the sum of each individuals signal deviation, multiplied by the coefficient for that signal. Enter your tours equipment list and recalculation for the next event is completed within minutes. The fifth order product is also closer to the fundamentals than corresponding even order products.
For example, in our original example above, thirdorder intermodulation products imps occur where in many radio and audio applications, oddorder imps are of most interest, as they fall within the vicinity of the original frequency components, and may therefore interfere with the desired. The coefficients of the thirdorder imd term in equation 7 can be used as a starting point in the analysis. Oddorder intermodulation products fall inband, with sidebands close to the carrier. Intermod assist intermodulation calculator and frequency coordination software is a unique tool it will change the way you approach the problem of intermodulation interference and the challenges of frequency coordination and channel assignment. Understanding intermodulation distortion measurements.
In that case, you get intermodulation distortion, not harmonic distortion, and these rules about odd and even harmonics no longer apply. Intermodulation distortion occurs at frequencies that are the sum andor difference of integer multiples of the fundamental frequencies. Note that one third order product 2f 1 f 2 is only 1 khz lower in frequency than f 1 and another 2f 2 f 1 is only 1 khz above f 2. Rf intermodulation calculator,formula for rf intermodulation. Even and odd order intermodulation nonlinearity from superconductive. In 4 the relative strength of second and third order intermodulation distortion imd was shown to vary. The intermodulation products are sum and difference as well as other integer and non integer multiple of these frequencies. Fundamentally, it describes the ratio in db between the power of fundamental tones. It does this by testing for odd andor even order products caused by the mixing of multiple. It can be seen from this figure and the equations that all the even order terms produce outputs at. It is becoming routine for multiple wireless licensees to. Why you should use frequency coordination software every time. Hauppauge, ny intermodulation interference is typically calculated based on two signals present in the rf or if bandwidth.
The fix may not be easy either because the nonlinear location of the mix could be some distance away from the repeater and or the 154. A nonlinear third order distorting amplifier produces four types of tones. It includes features you wont find in any other product including those that cost many times more. Buy midian electronics intermod intermodulation product. The most critical intermodulation distortion product is the third order intermodulation toi product. Therefore, two tone figure 12 the spectra of the intermodulation side signals experiment result in figure suggests that tone at 7 khz with the gain knob fixed to 95 and even order distortion factor significantly enhances the gain amplifier power supply voltage of 6. Intermodulation im or intermodulation distortion imd is the amplitude modulation of signals. Reviewing the basics of intermodulation distortion. The coefficients of the linear, second order imd, and third order imd terms become. The analysis only considers inband modulation products. Pdf even and odd order intermodulation nonlinearity from.
Nov 24, 2017 intermodulation is a phenomenon of combining undesired frequency components within an active system or from an external source. The toi products are usually within or close to the useband, i. When the bandwidth is less than an octave, even order intermodulation products, such as second and fourthorder intermodulation. Rf cascade workbook 2018 help worksheet contents rf cafe. The order of a given intermodulation product is the sum of the absolute values of the coefficients. Intermodulation study software intermodulation calculator. Repeat adding attenuation until intermodulation products disappear into the noise. A software program by professional wireless, along with a database of most wireless equipment and their frequency bands. Procedure for measuring intermodulation performance. The thirdorder intermodulation product was chosen in the past to evaluate the intermodulation performance of passive rf components.
When the bandwidth is less than an octave, evenorder intermodulation products, such as second and fourthorder intermodulation. Here is what prfintermod reports for the same intermod study. Nov 07, 2018 additional orders of im products are generated beyond the 5 th order, but the power levels of such products are typically low enough so as not to cause imd, even if they do fall inband, so they too are usually ignored. For system bandwidths less than an octave, evenorder intermodulation products are out of band. Even if an intermodulation product falls outside the receiver passband, the deviation especially of the higher order products may swing across the receiver passband, causing interference. Intermodulation is also referred to as intermodulation distortion, im, imd, intermod and intermod distortion.
Like thirdorder distortion in amplifiers, mixer spurs can end up close to or on top. While other order distortion products are present, the amplitude and. A general algorithm to calculate third order intermodulation. See nonlinear mixers such as mixer diodes and even singletransistor.
Intermodulation product secondorder interferers in dual. Two or more tones applied to an amplifier and produce additional intermodulation products. However, if the distortion is symmetrical, the evenorder sidebands wont exist, and they will be spaced at. Intermodulation interference calculations in the landmobile. It can be seen from this figure and the equations that all the even order terms produce outputs at harmonics of the input signal and that the sum and difference products are well removed in frequency far from the input signal. For instance, the second harmonics mixed with the base frequencies produce what we call thirdorder intermodulation products 2f1 f2 and 2f2 f1. Intermodulation im or intermodulation distortion imd is the amplitude modulation of signals containing two or more different frequencies, caused by nonlinearities or time variance in a system. Symmetrical distortion means that there are only oddorder harmonics even order. Combination of two or more signals will create another signal which may fall into another frequency band of the system and cause interference to the system. One fifth order product 3f12f2 is 2 khz below f1 and another 3f22f1 is 2 khz above f2. Inband 3rd order im products in a twocarrier system. A nonlinear thirdorder distorting amplifier produces four types of tones. A method has been developed that uses three input tones to measure both even and odd order intermodulation distortions imds inside the pass band of resonant devices.
Rf venue vantage spectrum monitoring software for mac osx showing dtv. Calculate intermodulation products from 2 and 3 frequencies. Technical feature topics in communication system design. The duts output will contain signals at the frequencies. The intermodulation between frequency components will form additional components at frequencies that are not just at harmonic frequencies integer multiples of either, like harmonic distortion, but. Intermodulation distortion is an important metric of linearity for a wide range of rf and microwave components. Especially the 3rd order intermodulation has to be considered as it results in the highest im. Sep 01, 2000 the thirdorder intermodulation product was chosen in the past to evaluate the intermodulation performance of passive rf components. These odd order intermodulation products are of interest in the first mixer state of a superheterodyne receiver. Performance testing of software defined radios by andrew. Rf blockset formerly simrf provides a simulink model library and simulation engine for designing rf communications and radar systems rf blockset lets you simulate nonlinear rf amplifiers and model memory effects to estimate gain, noise, even order, and oddorder intermodulation distortion. The odd order products, however, produce signals near the input frequencies f 1 2f 2 et f 2 2f 1. To understand imd, consider a twoport network, such as an amplifier. Finding, solving and preventing intermodulation problems.
In pcn, gsm and pcs systems with certain carrier frequencies, it is possible that the third order intermodulation product falls into the receive band and disturbs or even completely blocks discrete channels. Basically, 3im is produced by the mixing of the 2nd harmonic or overtone of one tx signal with the fundamental 1st. This is the ratio of the carrier power to the spurious 5th order intermodulation power in db. The terminology, third order intermodulation product is traditionally used to define the important intermodulation products in narrowband analysis. In sum, the intermodulation products generated from even order terms cancel out in a differential signal. However, it must be pointed out that the intermodulation products closer to the fundamental frequencies are generated by oddorder terms. Intermodulation interference calculations in the land. This is the power of the spurious 5th order intermodulation signal in dbm units, measured with the spectrum analyzer. Third order intermodulation products of the two signals, f. Thirdorder intermodulation interference is caused when two signals are present in the same nonlinear.
For example, in our original example above, thirdorder intermodulation. The interference due to intermodulation is defined by the following equations. It is generated when two signals are applied to a nonlinear device. A little inspection and thought shows that the majority of these are repeats or phantoms.
Enter your tours equipment list and recalculation for the next event is. It is becoming routine for multiple wireless licensees to share communications sites, and cellular towers, even antennas. The radio is tested by injecting two tones, either 2khz or 20khz apart, some labs use 5khz spacing and measuring the intermodulation product on the receiver frequency. One third order product 2f1f2 is 1 khz lower in frequency than f1 and another 2f2f1 i is 1 khz above f2.
One popular intermod calculator reports seven third order hits. Jan 26, 2018 intermodulation products third order from matlab and fft are too low. Jan 01, 2002 technical feature topics in communication system design. Intermodulation study may also be a useful tool when investigating and seeking resolution to rf intermodulation interference problems at an existing colocation site. Rf calculator conversion from and to various rf units intermodulation calculate intermodulation for 2 and 3 frequencys up to the 9th order. The terminology, thirdorder intermodulation product is traditionally used to define the important intermodulation products in narrowband analysis. For instance, applying a fullwave rectifier even symmetry to the following signals. Oddorder, rather than evenorder, intermodulation distortion products are of concern in linear power amplifiers because they are relatively close in frequency to the desired. Types of intermodulation the simplest kind of intermodulation is the mixing of two frequencies.
The true ones will be attenuated by the value of the attenuator, the secondorder ones by twice in db and thirdorder ones by three times. The third order intermodulation product was chosen in the past to evaluate the intermodulation performance of passive rf components. Intermodulation product secondorder interferers in dualband. Rf frequency selectivity parameters at frequency deviations f 1 and f 2 from. Intermodulation calculator intermod study software. The amplified waveform doesnt have even order harmonics, only odd and i am also confused. Intermodulation with wireless microphones 3 key points. Oddorder, rather than even order, intermodulation distortion products are of concern in linear power amplifiers because they are relatively close in frequency to the desired. Intermodulation is caused by nonlinear behaviour of the signal processing physical equipment or even algorithms being used.
Midians intermod calculator predicts the possible occurrence of intermodulation products that may cause receiver interference at the radio repeater site. Improve twotone, thirdorder intermodulation testing. Therefore, the odd order intermodulation products cannot be removed by filtering, only by improvement in linearity. Amplitude of 3rd imd tones 3k3e1 2e 2 2 converting to db provides. Both even and odd orders of nonlinearity can arise, but from different physical origins. Imd3maxn psigmaxn oip3minn psigmaxn dbm also includes gain variation due to vswr mismatch if use vswr is set to y. Because it is 2x one frequency 2nd order minus 1x the other frequency 1st order the test is known as a 3 rd order intermodulation test 3 order imd. Imd3 min dbm cumulative calculated minimum 3rdorder intermodulation distortion product power imd3min. Aes elibrary harmonics and intermodulation distortion. Esp audio pages intermodulation distortion things you didnt know. Sep 11, 2007 in order to further simplify the analysis, it is customary though not necessary to make the amplitude of the input sinusoids equivalent, that is a 1 a 2 a. The theoretical outcome of these nonlinearities can be calculated by generating a volterra series of the characteristic, or more approximately by a taylor series.
Rouphael, in rf and digital signal processing for softwaredefined. Radio mobile rf propagation simulation software on. It does this by testing for odd andor even order products caused by the mixing of multiple transmitters at a given site in a nonlinear device. Interaction of intermodulation products between dut and. Intermodulation products third order from matlab and fft. This software calculates the frequencies based on avoiding intermodulation products. In pcn, gsm and pcs systems with certain carrier frequencies, it is possible that the thirdorder intermodulation product falls into the receive band and disturbs or even completely blocks discrete channels. Some people have worked around this by horn loading the driver for low frequencies, but bass. Intermodulation with wireless microphones dbb audio.
Imd measurement with e5072a ena series network analyzer. This terminology, though technically incorrect, is used to define the same products in broadband intermodulation analysis and will be clarified later. Cumulative calculated maximum 3rdorder intermodulation distortion product power imd3max. How does intermodulation distortion occur, what are the. Midians intermodcalculator predicts the possible occurrence of intermodulation products that may cause receiver interference at the radio repeater site. Looking carefully at the table, we see that only the odd order intermodulation products are close to the two fundamental frequencies f1 and f2. Intermodulation im is a source of interference from the interaction between two or more signals at different frequencies when they are combined in a nonlinear system. Identify which signals were true and which were second and thirdorder intermodulation artifacts.