Mar 07, 2015 thrid order intercept point ip3 is a used to quantify weak nonlinearity in an amplifier or rf system. Prior to joining linear technology he spent 21 years designing rf. In order to achieve this, there are two possible combining networks. By using this model, we study the effect of receivers nonlinearity on the performance of telecommunication systems and we could achieve about 30 db cancellation of thirdorder intermodulation products.
This is fictitious signal level at which the fundamental and third order product terms would intersect. Block 1 has a gain, g1, at rf and an equivalent third order input intercept point iip31. Point merge system results of enav prototyping sessions page 8 state. Figure of merit of mixer intermod performance mini circuits. Calculating noise figure and thirdorder intercept in adcs introduction noise figure nf and the thirdorder intercept point ip 3 are used in radio receiver link budget analysis as a means to quantify the effects of device noise and nonlinearity on the sensitivity of the radio. All the im3 products merge at the demodulator input, resulting in an. Block 2 has a gain, g2, at if and an equivalent third order input intercept point iip32.
A reconfigurable low noise amplifier for a multistandard receiver vii gsm global standards for mobile idcs inductivelydegenerated common source if intermediate frequency ip2 second order intercept point ip3 third order intercept point lna low noise amplifier lo local oscillator lvs layout versus schematic. Pout output power, and a thirdorder im level below the carrier. Third order intercept point ip3 equation derivation ip3out is a fictious output level where 3rd order products reach to the fundamentals level. Ip3o output third order intercept point 1 36 40 dbm ip2o output second order intercept point 260dbm ctb composite triple beat 3 75 dbc cso composite second order distortion 3 60 dbc. The setup is optimized so that the output power of the signal generators is as low as possible. Third order intercept point third order intercept point ip3 is a term sometimes heard when amateur radio operators are discussing the qualities, or lack thereof, of a receiver. Later in this article we consider the effect of 3rd order distortion on a direct conversion receiver. Im3 product as an inband interferer due to two offchannel cw tones a, and thirdorder intercept point ip definition b.
This test measures the thirdorder intermodulation distortion produced by two input signals, and computes the third order intercept toi point. Second order intercept pointip2 is a used to quantify weak nonlinearity in an amplifier or rf system. Cascaded budget 2tone, 3rdorder intercept point ip3 rf. There are thus two actual values for measuring the ip point. Calculating noise figure and thirdorder intercept in adcs. Use it to calculate the input third order intercept point. Calculating noise figure and thirdorder intercept in adcs but i felt that the pure theoretical explanation was a bit of a letdown.
The third order product with the highest power reading is the worst case. Third order intercept point is just one of several specifications that can be used to judge the quality of a receiver. Second order intercept point ip2 vs third order intercept point ip3 this page on ip2 vs ip3 describes difference between second order intercept point ip2 and third order intercept point ip3. The mathematical derivation for each of the second order ip2 and third order ip3 intercept point cascading equations incorporates the effect of adding selectivity s between receiver stages to. The amplifier has a third order intercept point ip3 of 50 dbm and a ldb compression point of 29 dbm. A value of 0 produces power addition, a value of 1 produces voltage addition. For arrls measurements of twotone, thirdorder dynamic range, intercept point, the receiver agc is left on. Ip3o output thirdorder intercept point 1 36 40 dbm ip2o output secondorder intercept point 260dbm ctb composite triple beat 3 75 dbc cso composite secondorder distortion 3 60 dbc. Intercept point definition of intercept point by the free. However, for the 2nd order intercept point, only low and high tone parameters are supported. A receivers second and thirdorder intercept points ips represent the two most important. Maxim design support technical documents tutorials.
Third order distortion causes multiple unwanted products. The computation is performed over a periodogram of the same length as the input using a kaiser window with. It is an interpolated point where the fundamental component power curve meets the third order intermodimd3 component power curve. It is an interpolated point where the fundamental component power curve meets the second order intermodimd2 component power curve consider a nonlinear amplifier whose inputoutput characteristic is represented by a 3 rd order polynomial given by 1. Oip3 output thirdorder intercept point acronymfinder. Calculating the cascaded values for 3rdorder intercept point ip3 for the system budget requires use of ratios for gain and power levels for ip3 do not use db and dbm values, respectively. Pin curves are extrapolated out, the interception point is called the 3rd order intercept point ip3. How can i derive the third order input intercept point. Low power upconversion mixer for medical remote sensing. Ip3 is the most commonly used intercept point, but others, including ip2. Icom 7800 ip by sparing no expense throughout the signal chain, icom has developed an amateur rig that challenges the performance of a militarygrade transceiver. Finding the ip3 point the third order intercept point.
There are two key measurements in determining power amplifier quality, efficiency, and linearity. Cascade is a program for analyzing the noise and distortion performance of a cascade of elements in an electronic system. The intercept point is a purely mathematical concept, and does not correspond to a practically occurring physical power level. The measurement of the 3rd order intercept point is illustrated in figure 2. It is an interpolated point where the fundamental component power curve meets the second order intermodimd2 component power curve. The third order intercept point ip3 is the point at which the the extrapolated third order intermodulation level im3 is equal to the signal levels in the output of a twotone test when the extrapolation is made from a point below which the third order intermodulation follows the third order law. Ip3 is defined as third order intercept point frequently. Rho distortion correlation coefficient for the element. The extrapolated point where the curves of the fundamental signal and third order distortion product signal meet is the intercept point ip3. It is based on the idea that the device nonlinearity can be modeled using a loworder polynomial, derived by means of taylor series expansion. It is a theoretical point, where the intermodulation products at the duts output grow as large as the original tones at the dut output side. It is based on the idea that the device nonlinearity can be modeled using a loworder polynomial, derived by means.
The third order intercept point is used as a means of rating dif ferent amplifiers. This is precisely why in rf the thirdorder terms are so critical and must be known. Under some conditions, this may improve reception marred by strongsignal overload. It is based on the idea that the device nonlinearity can be modeled using a low order polynomial, derived by means. A reconfigurable low noise amplifier for a multistandard.
This is a demonstration of an automatic thirdsecond order intercept point iip3, oip3, iip2, oip2 and sdfr chart plotter. Given the intercept point, we can calculate the intermodulation product for any inputoutput power. This definition appears frequently and is found in the following acronym finder categories. Third order intercept how is third order intercept abbreviated. These products are the sum and difference of multiples of the fundamental tones. Ip3 is the thirdorder intercept point pa is the input power of one of the signals on the receiver input pim is the power of the intermodulation distortion imd pr oducts as an example of finding the thirdorder intercept point, we use the same test as above but find ip3. The nth order intercept point ipn is where the asymptotes for the nth order intermodulation product and the fundamental cross. Cascaded budget 2tone, 3rdorder intercept point ip3 rf cafe. Measurement of twotone, second and thirdorder intercept points is very tedious, requiring an enormous setup time. Accurate measurement of the third order intercept point for low distortion ic. Figure 2 represents a conventional dualconversion superheterodyne receiver architecture. It is an interpolated point where the fundamental component power curve meets the third order intermodimd3 component power curve consider a nonlinear amplifier whose inputoutput characteristic is represented by a 3 rd order polynomial given by 1. Intercept point definition of intercept point by the. Ip3 is the point where first order and third order lines cross.
The standard format for indicating decibel values is to use upper case letters. A reconfigurable low noise amplifier for a multistandard receiver vii gsm global standards for mobile idcs inductivelydegenerated common source if intermediate frequency ip2 second order intercept point ip3 third order intercept point lna low noise amplifier lo. Ip3 3rd order intercept point is a theoretical figure of merit describing the 3rd order distortion performance of a circuit. The thirdorder intercept point is an extrapolated convergence not directly measurable of intermodulation distortion products in the desired output.
In telecommunications, a thirdorder intercept point ip 3 is a specific figure of merit associated with the more general third order intermodulation toi distortion, which is a measure for weakly nonlinear systems and devices, for example receivers, linear amplifiers and mixers. This measurement can be made for the 2nd, 3rd, 5th, 7th, and 9th order intercept points. Assuming the noise floor of a receiver is dbm, then the imdr3 calcu lates to 110 db. This test measures the third order intermodulation distortion produced by two input signals, and computes the third order intercept toi point. Iip3 input third order intercept point of the element in dbm. The amplifier has a thirdorder intercept point ip3 of 50 dbm and a ldb compression point of 29 dbm. Understanding ip2 and ip3 issues in direct conversion receivers. In telecommunications, a thirdorder intercept point ip 3 is a specific figure of merit associated with the more general thirdorder intermodulation toi distortion, which is a measure for weakly nonlinear systems and devices, for example receivers, linear amplifiers and mixers. Use selectivity to improve receiver intercept point tutorial maxim.
In figure 2, this is the intersection of the dotted lines. Technically, the agc can be left off at the mds level, but for higher imd levels and for most ip3 measurements, agc must be on, as the measurement is being made well into the region where the receiver would not be working correctly. Im measurements are made at a 15dbm outputpower level. Second order intercept pointip2 vs third order intercept pointip3 this page on ip2 vs ip3 describes difference between second order intercept pointip2 and third order intercept pointip3. Actually there are advantages to using 3 frequencies because the products will be stronger by 6 db. Two tone 3rd order imd testing american radio relay league.
It indicates how well a device for example an amplifier or a system for example, a receiver performs in the presence of strong signals. Third order intercept point how is third order intercept. The ip3 is the intercept point at the intersection of the fundamental output and the twotone third order intermodulation products, when plotted against input power. Two signals separated by 100 khz are combined in a directional bridge, or directional coupler, and are input to the psa. Block 1 has a gain, g1, at rf and an equivalent thirdorder input intercept point iip31. Third order intercept point ip3 equation derivation. According to the article, the nonlinearity is modeled using polynomial series expansion taylor series. Ip3 3rd order intercept the presence of 2 or more tones in a nonlinear device generates intermodulation products. Input third order intercept point for crystal filters. For arrls measurements of twotone, third order dynamic range, intercept point, the receiver agc is left on.
The third order intercept point relates nonlinear products caused by the third order nonlinear term to the linearly amplified signal, in contrast to the second order intercept point that uses second order terms. In this case, the 3rd order distortion products will be 30db down on the signal and 45db below the intercept point. The third derivation will give the third order nonlinear term alpha 3. Calculating noise figure and third order intercept in adcs introduction noise figure nf and the third order intercept point ip 3 are used in radio receiver link budget analysis as a means to quantify the effects of device noise and nonlinearity on the sensitivity of the radio. Two signals separated by 100 khz are combined in a directional bridge. Block 2 has a gain, g2, at if and an equivalent thirdorder input intercept point iip32. In reality, the intercept power is 10 to 15 dbm higher than the p1db gain compression power, so the circuit does not amplify or operate correctly at the iip3 level. I also feel that the example given for tones 15db below the intercept point is wrong for 3rd order products. Begin by combining the signal outputs of two signal generators.
Calculating the cascaded values for 3rd order intercept point ip3 for the system budget requires use of ratios for gain and power levels for ip3 do not use db and dbm values, respectively. Pout output power, and a third order im level below the carrier. The second order intercept point ip2 of a direct conversion receiver system is a critical performance parameter. A text description of the receiver block diagram consisting of things like amplifiers, mixers, and filters is entered into cascade. These intercept points are observed in saturated amplifier gain response. The thirdorder intercept point relates nonlinear products caused by the third. Ip3 third order intercept point, iip3, oip3 and plot. Thrid order intercept pointip3 is a used to quantify weak nonlinearity in an amplifier or rf system. In telecommunications, a thirdorder intercept point ip 3 or toi is a measure for weakly nonlinear systems and devices, for example receivers, linear amplifiers and mixers.
Use selectivity to improve receiver intercept point. Root locus elec304alper erdogan 1 1 lecture 1 root locus. Ip2 vs ip3 difference between second order intercept. The real annoying problem comes when you combine a nonlinear device and input signal. Two tone thirdsecond order intercept point, iip2, iip3. Analogtodigital converters adcs are used in radio receivers. Ip3 is the point where 3rd order products would overtake fundamentals in output power. Ip3o output thirdorder intercept point 238 dbm ip2o output secondorder intercept point 367 dbm ctb composite triple beat vo 35 dbmv 4 65 dbc cso composite secondorder distortion vo 35 dbmv 4 75 dbc nf noise figure f 500 mhz 3. Equation 1 shows the series expansion of multiplying two monotones f1 and f2. Root locus elec304alper erdogan 1 7 real axis segments which parts of real line will be a part of root locus.
In addition, the measurements can be made for either the low tone, the high tone, or the average of the two. Additionally, the socalled third order intercept point ip3 can be calculated. I want to derive the third order input intercept point for my low noise amplifier lna, which is working at 2. Often it is assumed that the tones are at the exact same level and the im products are identical. A typical application of cascade is the analysis of a receiver. Second order intercept point ip2 analogrf intgckts.
Feb 10, 2015 this is a demonstration of an automatic third second order intercept point iip3, oip3, iip2, oip2 and sdfr chart plotter. From figure 6 we see that ip2 is the point where first order and second order lines cross. Modified linearization technique for intermodulation. Whats the difference between the thirdorder intercept. Mar 05, 2015 second order intercept point ip2 is a used to quantify weak nonlinearity in an amplifier or rf system. Ip2 vs ip3 difference between second order intercept point. This article presents a modification of the traditional receiver intercept point cascading equation for both the second and third order im cases.
Ip3 is the third order intercept point pa is the input power of one of the signals on the receiver input pim is the power of the intermodulation distortion imd pr oducts as an example of finding the third order intercept point, we use the same test as above but find ip3. In this type of receiver architecture, the im3 products from the offchannel cw interferers are generated in the lownoise amplifier lna, the first mixer, the if. Third order intercept how is third order intercept. The input power level is known as iip3, and the output power when this occurs is the oip3 point. This is fictitious signal level at which the fundamental and thirdorder product terms would intersect. This article will explain the origin and purpose of intercept point ip specifications. It is also possible to measure the third order intercept point by using 3 frequencies instead of 2. Calculating noise figure and third order intercept in adcs but i felt that the pure theoretical explanation was a bit of a letdown. The power level of each of the two offchannel cw interferers present at the receivers input is assumed to equal pi, which is the. Skript zum thema mischer pdf intercept point, gain compression and. Each element is characterized by its gain and optionally. Calculating noise figure and thirdorder intercept in adcs introduction noise figure nf and the third order intercept point ip 3 are used in radio receiver link budget analysis as a means to quantify the effects of device noise and nonlinearity on the sensitivity of the radio. The data points are obtained from an automated two tone measurement system.
1174 528 1305 612 687 1482 159 26 1444 634 860 852 1077 1021 1185 87 709 330 1112 1435 367 1188 686 1495 497 956 496 1104 558 812 1317 837 188 1016 1304 120