Third-Order Intermodulation Distortion and Gain Compression in GaAs Fet's

A simple unilateral nonlinear circuit model of a GaAs FET is used in the analysis of the third-order intermodulation distortion and gain compression characteristics of a single-stage amplifier. Expressions are obtained for these characteristics, relating them to the input power level and to the device load admittance. The expressions are illustrated with contours on the load admittance plane of constant intermodulation distortion ratio, intercept point gain compression, AM-to-PM conversion, and output power, and as output power versus input power plots for fixed terminations. Agreement with experimentally measured distortion characteristics is good.     

Prediction of Wide-Band Power Performance of MESFET Distributed Amplifiers Using the Volterra Series Representation

The power performance of a four-section MESFET distributed amplifier is predicted over the frequency range 2-8 GHz. The nonlinear model of the MESFET used has three nonlinear elements: g/sub d/, and C/sub gs/, which are represented by power series up to the third order. The analysis employs the Volterra series representation up to the third order. Experimental verification is first made on a 0.5x400-µm medium-power MESFET device to confirm the validity of the nonlinear model used in the analysis. The agreement between predicted and measured output power at 1-dB gain compression is within +-0.5 dBm across the 2-16 GHz band. A four-section distributed amplifier was then built with four 0.5x400-µm MESFET's. The agreement between predicted and measured output power at 1-dB gain compression of this amplifier is within +-0.7 dBm across the 2-8-GHz band. The measured output power at 1-dB gain compression is (22+-1) dBm across the 2-8-GHz band.     

Intermodulation Distortion Analysis of Reflection-Type IMPATT Amplifiers Using Volterra Series Representation

Intermodulation distortion generated in a stable IMPATT amplifier is analyzed using Volterra series representation. An IMPATT amplifier model, which takes into account the interaction between the nonlinearities of the diode and its embedding circuitry, is described. The Volterra transfer functions are derived for this model. Nonlinear terms up to and including the fifth order are considered. Intermodulation distortion products are calculated for a low-level input signal consisting of two tones. The results of this analysis are extrapolated into the direction of increasing output power in order to obtain the third-order intercept point. Further, closed form expressions for the third-order intermodulation IM/sub 3/ and intercept point P/sub I/ are derived. The distortion of a specific 6-GHz IMPATT amplifier is evaluated for illustrative purposes; the predicted distortion behavior compares favorably with experimental results.     

Reduction of intermodulation distortion in microwave activebandpass filters-theory and experiments

This paper examines, both theoretically and experimentally, the dependency of the third-order intermodulation (IM) distortion and power saturation upon circuit and device parameters of an active bandpass filter using negative-resistance compensation. Nonlinear analysis is performed by means of the Volterra series formulation. We show that the IM distortion can be reduced by several orders of magnitude with suitable choice of external gate-source and feedback capacitance values. Measured performances of some 900-MHz experimental MESFET bandpass filters are presented     

Characterization of Nonlinearities in Microwave Devices and Systems

A simple model to describe a nonlinear device or system is proposed which extends the power series expansion, conventionally restricted to amplitude nonlinearities, to include phase nonlinearities as well. Four different test methods are selected for which the experimentally observed nonlinearity parameters are related to the "gain" and "phase" coefficients of the extended series. A set of simplified relationships is derived where the "1-dB gain compression point" represents gain contributions only while phase nonlinearities are included in the "intercept point," the "third-order intermodulation (IM) coefficients," and the "noise-power-ratio (npr)." For a TWT amplifier in which phase nonlinearities dominate, the third-order IM coefficient was measured. The results are compared with those calculated from single-tone and noise-loading tests using the relationships derived from the model. Agreement to /spl plusmn/ 1 dB is found over a 15-dB power range.     

A capacitance-compensation technique for improved linearity in CMOS class-AB power amplifiers

A nonlinear capacitance-compensation technique is developed to help improve the linearity of CMOS class-AB power amplifiers. The method involves placing a PMOS device alongside the NMOS device that works as the amplifying unit, such that the overall capacitance seen at the amplifier input is a constant, thus improving linearity. The technique is developed with the help of computer simulations and Volterra analysis. A prototype two-stage amplifier employing the scheme is fabricated using a 0.5-/spl mu/m CMOS process, and the measurements show that an improvement of approximately 8 dB in both two-tone intermodulation distortion (IM3) and adjacent-channel leakage power (ACP1) is obtained for a wide range of output power. The linearized amplifier exhibits an ACP1 of -35 dBc at the designed output power of 24 dBm, with a power-added efficiency of 29% and a gain of 23.9 dB, demonstrating the potential utility of the design approach for 3GPP WCDMA applications.     

6～18GHz宽带功率放大器模块

研究了ＧａＡｓ功率ＭＥＳＦＥＴ的小信号特性、大信号特性和其宽带匹配网络。选用ＴＷＴ－２型功率器件，设计研制出了单级宽带功率放大器。在６～１８ＧＨｚ的工作频率范围内，小信号增益等于５．０±１．０ｄＢ，１ｄＢ压缩输出功率等于２５．０±０．８ｄＢｍ，输入输出驻波比小于２．５。     

A 6-GHz Four-Stage GaAs MESFET Power Amplifier (Short Papers)

A 6-GHz GaAs MESFET power amplifier with 1-W output power, 26dB gain, and 8-dB noise figure is described. It is a fully integrated four-stage amplifier with an efficiency of 22 percent. The third-order intermodulation product is 31.5 dB below the carrier at an output power of 1 W.     

Highest efficiency, linear X-band performance using InP DHBTs - 48%PAE at 30 dB C/IM3

InP single heterojunction bipolar transistors have previously demonstrated 5-10 dB lower third-order intermodulation products (IM3) compared to GaAs heterojunction bipolar transistors (HBTs) under low voltage (2 V) operation. This paper reports excellent single-tone and two-tone X-band operation, including high two-tone power-added efficiency (PAE), on linear InP double heterojunction bipolar transistors (DHBTs) operated at V_ce=4 V. The InP DHBT demonstrated a 30 dB carrier to third-order intermodulation product (C/IM3) output power ratio simultaneously with 48% two-tone PAE. This is the highest known efficiency of an X-band device under linear (30 dB C/IM3) operation. This is especially significant for microwave power amplifiers for satellite communication transmitters, where lower intermodulation distortion is normally accomplished by backing off in RF drive and output power, thus sacrificing PAE performance     

Linearization of receivers using envelope signal injection

This paper presents a new linearization method for receivers employing envelope signal injection. In this technique, the third-order intermodulation distortion (IM3), at the output of a mixer in IF band, is cancelled by injecting the envelope of the RF input signal to both the low noise amplifier (LNA) and the mixer. By properly adjusting the amplitude and polarity of the injected envelope signal, up to 40-dB improvement of the IM3 and 11-dB improvement of the IM5 is obtained in a two tone test with 100-kHz separation at 1.9GHz. This method operates very well over a wide range of power up to the 1-dB compression point of the receiver. The noise performance of the receiver under this linearization technique is also investigated. The noise floor at the output of the receiver is increased by 0.8 dB only when the system is optimized for linearity.     

Analytical expressions for intermodulation distortion of a MESFET small-signal amplifier using the nonlinear Volterra series

Using the nonlinear Volterra series representation, analytical expressions for the third-order intermodulation distortion power and intercept point for a MESFET small-signal amplifier are derived when its equivalent circuit is bilateral and includes the gate-to-drain capacitance (C_gd) explicitly as a nonlinear element. Previously developed analytical expressions treated C_gd as a linear element or incorporated it as a part of gate-to-source and drain-to-source capacitances (C_gs and C_ds). These new analytical expressions are then compared with experimental data and good agreement is obtained. The analytical expressions are also used to study the variation of intermodulation distortion with input power and frequency, and the effect of the individual nonlinear elements in the MESFET’s equivalent circuit.     

Intermodulation nulling in HEMT common source amplifiers

A new model of the second- and third-order intermodulation products from HEMT and MESFET small-signal amplifiers, resulting from nonlinear drain-source current has been proposed in our previous publications. Based on this model, intermodulation nulling conditions in terms of the Taylor series coefficients, hence in terms of bias, have been investigated. This paper now examines the load dependence of the second- and third-order intermodulation products in HEMT small-signal common source amplifiers. Intermodulation nulling conditions are proposed and validated. This is useful in designing a high performance amplifier by calculation of optimum load for minimum distortion and studying distortion generation as a function of circuit topology     

采用90°分支电桥的C波段预失真线性化器

为了改善功率放大器的三阶交调失真,提出了一种基于90°分支线电桥的C波段预失真线性化器,使用肖特基二极管产生非线性信号。通过改变线性化器的偏置电压及电容,可调整线性化器的增益扩张和相位延迟特性,与功放级联后对功放的三阶交调失真有改善作用。将该线性化器应用到工作频率为7 GHz,饱和功率为20 dBm的放大器上,在输出功率回退5 dBm处对放大器的三阶交调有10 dBc的改善。     

Intermodulation Distortion Analysis of MESFET Amplifiers Using the Volterra Series Representation

Third-order intermodulation distortion generated in a MESFET amplifer is analyzed by means of the Volterra series representation. A transistor model is used which enables direct analytical determination of the nonlinear elements from small-signal measurements. The four nonlinearities considered are the gate capacitance, transconductance, drain feedback capacitance, and output conductance. Volterra transfer functions are derived for a simplified model and closed-form expressions for the third-order intermodulation ratio and intercept point are determined. The equations show the dependence of distortion on frequency, terminating impedances, and transistor parameters. Principal sources of distortion are identified and the influence of device parameters and network terminations is investigated. Experimental verification on specific MESFET amplifiers, with 2-mu m and 1-mu m gate devices, comparing predicted and measured intermodulation products for various load conditions is presented.     

一种用于射频功率放大器的新型预失真器的设计

预失真技术是功率放大器线性化的主要技术之一。分析了传统预失真器不能消除其输出端所产生双音基频分量的特点,提出一种新的预失真器,并利用它改善射频功率放大器的非线性失真。仿真结果表明,该方法可以明显改善射频功率放大器的三阶交调非线性失真。     

双音调制星间微波光子链路信号噪声失真比优化

建立了包括光源、马赫曾德尔调制器、掺铒光纤放大器和光电探测器的双音调制星间微波光子链路模型。利用贝塞尔函数展开、傅里叶变换/反变换和Graf加法定理,推导出探测器输出信号的严格通用解析解,考虑三阶交调失真的影响,得出信号噪声失真比（SNDR）的表达式。着重分析了在不同调制方式下SNDR、基波和三阶交调信号功率随射频输入功率的变化情况。数值计算结果表明:SNDR、基波和三阶交调信号功率随射频输入功率的增大先增大后减小,存在最优的射频输入信号功率使SNDR达到最大。相同射频输入功率条件下,双边带调制SNDR大于单边带调制,适合星间微波光子链路应用。     

AlGaAs/GaAs HBT linearity characteristics

Communication systems require linear power amplifiers with high efficiency and very low intermodulation distortion. AlGaAs/GaAs heterojunction bipolar transistors (HBT's) were found to have very low intermodulation distortion in power operation. Two-tone tests were carried out on both common-emitter (CE) and common-base (CB) power HBT's. At 7 GHz, the CE HBT showed -20 dBc IM₃ (third-order intermodulation ratio) and 12% power added efficiency (PAE) per tone at the 1 dB gain compression point; IM₃ dropped to -30 dBc at 1.5 dB output power backoff. The CE HBT has lower intermodulation distortion than CB HBT. Load pull data were collected to aid the understanding of the intermodulation. Parameters of the Gummel-Poon model (as used in SPICE) were derived for HBT's based on dc data and small-signal S parameters at various bias points. The accuracy and validity of the model were confirmed by comparison to experimental two-tone results. SPICE predicts that the emitter and base resistances linearize the HBT and reduce the third-order intermodulation distortion. The excellent third-order intermodulation performance of the CE HBT makes it a very attractive choice for linear power amplifiers     

A GaAs Power MESFET Operating at 3.3V Drain Voltage for Digital Hand-Held Phone

A GaAs power metal semiconductor field effect transistor (MESFET) operating at a voltage as low as 3.3V has been developed with the best performance for digital hand-held phone. The device has been fabricated on an epitaxial layer with a low-high doped structure grown by molecular beam epitaxy. The MESFET, fabricated using 0.8 μm design rule, showed a maximum drain current density of 330 mA/mm at V_gs = 0.5V and a gate-to-drain breakdown voltage of 28 V. The MESFET tested at a 3.3 V drain bias and a 900 MHz operation frequency displayed an output power of 32.5-dBm and a power added efficiency of 68%. The associate power gain at 20 dBm input power and the linear gain were 12.5dB and 16.5dB, respectively. Two tone testing measured at 900.00MHz and 900.03MHz showed that a third-order intercept point is 49.5 dBm. The power MESFET developed in this work is expected to be useful as a power amplifying device for digital hand-held phone because the high linear gain can deliver a high power added efficiency in the linear operation region of output power and the high third-order intercept point can reduce the third-order intermodulation.     

应用于WiFi6的新型高线性度功率放大器设计

针对WiFi 6的设备需求,设计了一款工作在5.15 GHz～5.85 GHz的高线性度砷化镓异质结双极型晶体管射频功率放大器。为了保证大信号和高温下功率管静态工作点的稳定性,采用了一种新型有源自适应偏置电路。对射频功率检测电路进行了设计和改进,有效降低了射频系统的功耗。针对各次谐波分量产生的影响,对输出匹配网络进行了优化。仿真结果表明：该射频功率放大器芯片小信号增益达到了32.6 dB;在中心频率5.5 GHz时1 dB压缩点功率为30.4 dBm,功率附加效率超过27.9%;输出功率为26 dBm时,三阶交调失真低于-40 dBc。实测数据表明：小信号增益大于31.4 dB;5.5 GHz时1 dB压缩点功率为29.06 dBm;输出功率为26 dBm时,三阶交调失真低于-30 dBc。当输出功率为20 dBm时,二次三次谐波抑制到-30 dBc和-45 dBc。     

Intermodulation analysis of the collector-up InGaAs/InAlAs/InP HBTusing Volterra series

The intermodulation (IM) distortion of the collector-up InGaAs/InAlAs/InP heterojunction bipolar transistor (HBT) is analyzed using Volterra-series theory. A T-equivalent circuit is used for this analysis. The contribution and interaction of four nonlinear elements: base-emitter resistance, base-emitter capacitance, base-collector capacitance, and common base-current gain are analyzed. For the particular device under investigation, it is found that the cancellation effect is not significant and the base-emitter resistance nonlinearity dominates the third-order IM