Second order intercept point ip2 analogrf intgckts. It is an interpolated point where the fundamental component power curve meets the third order intermodimd3 component power curve. Then, the input third order intercept point ip3 is defined as. Third order intercept how is third order intercept abbreviated. This is precisely why in rf the thirdorder terms are so critical and must be known. Ip3 3rd order intercept point is a theoretical figure of merit describing the 3rd order distortion performance of a circuit. Use it to calculate the input third order intercept point. The amplifier has a thirdorder intercept point ip3 of 50 dbm and a ldb compression point of 29 dbm. 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. These products are the sum and difference of multiples of the fundamental tones.
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 intercept point is a purely mathematical concept, and does not correspond to a practically occurring physical power level. This article will explain the origin and purpose of intercept point ip specifications. 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. Ip3 is the point where first order and third order lines cross. Oip3 output thirdorder intercept point acronymfinder. Pout output power, and a third order im level below the carrier. 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. All the im3 products merge at the demodulator input, resulting in an. Iip3 input third order intercept point of the element in dbm. Low power upconversion mixer for medical remote sensing. 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.
Analogtodigital converters adcs are used in radio receivers. Under some conditions, this may improve reception marred by strongsignal overload. Calculating noise figure and third order intercept in adcs but i felt that the pure theoretical explanation was a bit of a letdown. Ip3 third order intercept point, iip3, oip3 and plot. Given the intercept point, we can calculate the intermodulation product for any inputoutput power. Im measurements are made at a 15dbm outputpower level. 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. Cascaded budget 2tone, 3rdorder intercept point ip3 rf cafe. 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. Ip2 vs ip3 difference between second order intercept.
Thrid order intercept pointip3 is a used to quantify weak nonlinearity in an amplifier or rf system. This definition appears frequently and is found in the following acronym finder categories. Skript zum thema mischer pdf intercept point, gain compression and. Third order intercept how is third order intercept. The third order intercept point is used as a means of rating dif ferent amplifiers. A reconfigurable low noise amplifier for a multistandard. The measurement of the 3rd order intercept point is illustrated in figure 2. This article presents a modification of the traditional receiver intercept point cascading equation for both the second and third order im cases.
The thirdorder intercept point relates nonlinear products caused by the third. Assuming the noise floor of a receiver is dbm, then the imdr3 calcu lates to 110 db. Ip2 vs ip3 difference between second order intercept point. A value of 0 produces power addition, a value of 1 produces voltage addition. A typical application of cascade is the analysis of a receiver. The second order intercept point ip2 of a direct conversion receiver system is a critical performance parameter. Mar 05, 2015 second order intercept point ip2 is a used to quantify weak nonlinearity in an amplifier or rf system.
Whats the difference between the thirdorder intercept. It is an interpolated point where the fundamental component power curve meets the second order intermodimd2 component power curve. The input power level is known as iip3, and the output power when this occurs is the oip3 point. Root locus elec304alper erdogan 1 1 lecture 1 root locus. Intercept point definition of intercept point by the free.
Block 2 has a gain, g2, at if and an equivalent thirdorder input intercept point iip32. The third derivation will give the third order nonlinear term alpha 3. 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. Finding the ip3 point the third order intercept point. Block 1 has a gain, g1, at rf and an equivalent thirdorder input intercept point iip31. Point merge system results of enav prototyping sessions page 8 state. A text description of the receiver block diagram consisting of things like amplifiers, mixers, and filters is entered into cascade. Accurate measurement of the third order intercept point for low distortion ic. These intercept points are observed in saturated amplifier gain response. Use selectivity to improve receiver intercept point tutorial maxim. 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. Ip3 is the most commonly used intercept point, but others, including ip2.
Ip3 3rd order intercept the presence of 2 or more tones in a nonlinear device generates intermodulation products. Actually there are advantages to using 3 frequencies because the products will be stronger by 6 db. The data points are obtained from an automated two tone measurement system. It is based on the idea that the device nonlinearity can be modeled using a low order polynomial, derived by means. Figure 2 represents a conventional dualconversion superheterodyne receiver architecture.
Third order intercept point ip3 equation derivation. 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. Each element is characterized by its gain and optionally. Cascaded budget 2tone, 3rdorder intercept point ip3 rf. There are two key measurements in determining power amplifier quality, efficiency, and linearity. The extrapolated point where the curves of the fundamental signal and third order distortion product signal meet is the intercept point ip3. In this case, the 3rd order distortion products will be 30db down on the signal and 45db below the intercept point. Feb 10, 2015 this is a demonstration of an automatic third second order intercept point iip3, oip3, iip2, oip2 and sdfr chart plotter. It indicates how well a device for example an amplifier or a system for example, a receiver performs in the presence of strong signals. Two tone thirdsecond order intercept point, iip2, iip3. Modified linearization technique for intermodulation. The power level of each of the two offchannel cw interferers present at the receivers input is assumed to equal pi, which is the. 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. Ip3 is defined as third order intercept point frequently.
Often it is assumed that the tones are at the exact same level and the im products are identical. Two signals separated by 100 khz are combined in a directional bridge. I also feel that the example given for tones 15db below the intercept point is wrong for 3rd order products. Use selectivity to improve receiver intercept point. 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. A receivers second and thirdorder intercept points ips represent the two most important. In order to achieve this, there are two possible combining networks. How can i derive the third order input intercept point. 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. Pin curves are extrapolated out, the interception point is called the 3rd order intercept point ip3. The nth order intercept point ipn is where the asymptotes for the nth order intermodulation product and the fundamental cross. 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.
Second order intercept pointip2 is a used to quantify weak nonlinearity in an amplifier or rf system. I want to derive the third order input intercept point for my low noise amplifier lna, which is working at 2. However, for the 2nd order intercept point, only low and high tone parameters are supported. Third order intercept point ip3 equation derivation ip3out is a fictious output level where 3rd order products reach to the fundamentals level. It is based on the idea that the device nonlinearity can be modeled using a loworder polynomial, derived by means. Im3 product as an inband interferer due to two offchannel cw tones a, and thirdorder intercept point ip definition b. 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. From figure 6 we see that ip2 is the point where first order and second order lines cross.
Pout output power, and a thirdorder im level below the carrier. 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. It is also possible to measure the third order intercept point by using 3 frequencies instead of 2. Calculating noise figure and thirdorder intercept in adcs but i felt that the pure theoretical explanation was a bit of a letdown. This is a demonstration of an automatic thirdsecond order intercept point iip3, oip3, iip2, oip2 and sdfr chart plotter. Input third order intercept point for crystal filters. Later in this article we consider the effect of 3rd order distortion on a direct conversion receiver. 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. For arrls measurements of twotone, thirdorder dynamic range, intercept point, the receiver agc is left on. Cascade is a program for analyzing the noise and distortion performance of a cascade of elements in an electronic system. Third order distortion causes multiple unwanted products. 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. The third order product with the highest power reading is the worst case. There are thus two actual values for measuring the ip point.
Prior to joining linear technology he spent 21 years designing rf. Measurement of twotone, second and thirdorder intercept points is very tedious, requiring an enormous setup time. Third order intercept point is just one of several specifications that can be used to judge the quality of a receiver. Maxim design support technical documents tutorials. Begin by combining the signal outputs of two signal generators. 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. Block 2 has a gain, g2, at if and an equivalent third order input intercept point iip32. Intercept point definition of intercept point by the. In figure 2, this is the intersection of the dotted lines. Understanding ip2 and ip3 issues in direct conversion receivers.
Block 1 has a gain, g1, at rf and an equivalent third order input intercept point iip31. The computation is performed over a periodogram of the same length as the input using a kaiser window with. Two tone 3rd order imd testing american radio relay league. The thirdorder intercept point is an extrapolated convergence not directly measurable of intermodulation distortion products in the desired output. The standard format for indicating decibel values is to use upper case letters. 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. Third order intercept point how is third order intercept. Two signals separated by 100 khz are combined in a directional bridge, or directional coupler, and are input to the psa.
The real annoying problem comes when you combine a nonlinear device and input signal. 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. 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. It is based on the idea that the device nonlinearity can be modeled using a loworder polynomial, derived by means of taylor series expansion. This measurement can be made for the 2nd, 3rd, 5th, 7th, and 9th order intercept points. Figure of merit of mixer intermod performance mini circuits. 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. Additionally, the socalled third order intercept point ip3 can be calculated. 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. 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. The setup is optimized so that the output power of the signal generators is as low as possible. 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. 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.
This is fictitious signal level at which the fundamental and thirdorder product terms would intersect. This is fictitious signal level at which the fundamental and third order product terms would intersect. Mar 07, 2015 thrid order intercept point ip3 is a used to quantify weak nonlinearity in an amplifier or rf system. In addition, the measurements can be made for either the low tone, the high tone, or the average of the two. 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.
940 233 1295 1604 29 494 988 188 14 1189 127 1544 1418 640 495 1406 1094 890 1592 1224 898 1175 256 1070 378 1413 114 946 838 804 1578 486 528 1060 797 653 995 1387 681 1194 761 958 286 268 1266 956 137 178 1196 44 811