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.     

Theory and Analysis of GaAs MESFET Mixers (Short Papers)

A generalized analysis of the GaAs MESFET mixer is presented. Its advantage is that many of the simplifying assumptions in previous approaches have been substantially eliminated. Using this approach, the nonlinearities of any number of elements in the FET equivalent circuit may be included, any number of Iocal oscillator (LO) harmonics and mixing products may he considered, unusual mixers such as subharmonic mixers, upconverters, and mixers with high IF frequencies can be analyzed. The theory has been verified experimentally. Two mixers are described: one exhibits 11.5-dB conversion gain with + 9-dBm LO power, 5.6-dB minimum noise figure and + 15-dBm third-order intermodulation intercept, and another which exhibits 500-MHz bandwidth, 6-dB minimum gain, 5.5-dB maximum noise figure, and + 12-dBm third-order intercept at + 6-dBm LO power.     

Cuber predistortion linearizer for relay equipment in 800 MHz band land mobile telephone system

New relay equipment for a tunnel relay system used in an 800 MHz band land mobile telephone network has been developed. Significant improvements in size and power consumption have been achieved using a predistortion (PD) circuit to compensate for third-order intermodulation (IM) distortion generated in the power amplifier. This predistortion circuit features a simple configuration and easy adjustment, as well as high distortion reduction performance. The circuit configuration is derived from an analysis based on a complex power series representation of input-output nonlinearities for microwave transistor amplifiers. This analysis shows that two kinds of nonlinearities, AM-AM and AM-PM conversions, are uniquely related through the third-order distortion phase, In addition, an automatically controlled predistortion system is introduced to establish an adjustment and maintenance-free compensator. Using the developed predistortion circuit, a stable distortion reduction of more than 20 dB per 25 MHz bandwidth has been attained.     

Optimization of Third-Order Intermodulation Product and Output Power from an X-Band MESFET Amplifier Using Volterra Series Analysis

A third-order analysis for accurately predicting large-signal power and intermodulation distortion performance for GaAs MESFET amplifiers is presented. The analysis is carried out for both single- and two-tone input signals using the Volterra series representation and is based only on small-signal measurements. Simple expressions for the nonlinear power gain frequency response, the output power, the gain compression factor, and the third-order intermodulation (IM/sub 3/) power are presented. The major sources of gain compression and intermodulation distortion are identified. Based on the developed nonlinear analysis in conjunction with the device nonlinear model, a systematic procedure for designing a MESFET amplifier under large-signal conditions for optimum output power and IM/sub 3/ performance is proposed. The method utilizes out of band computed matching compensation through a nonlinear model of the amplifier. The accuracy of the device large-signal and IM/sub 3/ distortion characterization and the practicability of the proposed method are illustrated through comparison between measured and predicted results.     

A Single Supply, High Linearity 2-W PA MMIC for WLAN Applications Using Quasi-Enhancement Mode PHEMTs

A fully matched, 2-W high linearity amplifier monolithic microwave integrated circuit, by using quasi-enhancement mode technology of AlGaAs/InGaAs/ GaAs pseudomorphic high electron mobility transistors, is demonstrated for wireless local area network applications. At Vgs= 0 V, V_ds= 5 V, this power amplifier has achieved 14-dB small-signal gain, 33-dBm output power at 1-dB gain compression point, and 34.5-dBm saturated output power with 35% power added efficiency at 5.8 GHz. Moreover, high-linearity with 45.2-dBm third-order intercept point is also achieved     

Linearization of CMOS Broadband Power Amplifiers Through Combined Multigated Transistors and Capacitance Compensation

We present the development of a device-level linearization technique and its applications in broadband power amplifiers (PAs). The proposed topology firstly combines derivative transconductance superposition method and gate capacitance compensation technique, and creates a "sweet region" for suppressing third-order intermodulation (IM3) without the penalty of large power consumption. The effectiveness of the proposed technique has been demonstrated through a fully integrated distributed amplifier. The experimental results in 0.18-mum RF CMOS technology show that IM3 is improved by 11 dB. The achievable power-added efficiency is up to 25%, which is the highest among the broadband CMOS PAs reported thus far. The amplifier achieves a measured 3-dB bandwidth of 3.7-8.8 GHz, and a gain of 8.24 dB. The amplifier only consumes 154-mW dc power, and the measured saturation power (P_sat) is 19 dBm.     

Design and Performance of Microwave Amplifiers with GaAs Schottky-Gate Field-Effect Transistors

The design and performance of an X-band amplifier with GaAs Schottky-gate field-effect transistors are described. The amplifier achieves 20 /spl plusmn/ 1.3-dB gain with a 5.5-dB typical noise figure (6.9 dB maximum) over the frequency range of 8.0-12.0 GHz. The VSWR at the input and output ports does not exceed 2.5:1. The minimum output power for 1-dB gain compression is +13 dBm, and the intercept point for third-order intermodulation products is +26 dBm. The design of practical wide-band coupling networks is discussed. These networks minimize the overall amplifier noise figure and maintain a constant gain in the band.     

A variable gain amplifier with 50-dB control range for 900-MHz applications

A variable gain amplifier for 900-MHz applications has been designed and fabricated in a BiCMOS process with f/sub T/ = 24 GHz. The amplifier has linear-in-dB gain control with a 50-dB control range. The maximum gain is 28 dB and the third-order output intercept point (OIP3) is 13.7 dBm. The gain is achieved in one gain stage with a cascoded output. The amplifier bias network and the gain-control circuitry are temperature compensated for temperature-independent gain at any gain setting. The bias network also uses a feedback loop to cancel out undesired low frequencies present at the radio-frequency input. The maximum output power is +10 dBm and the output 1-dB compression point is +8.7 dBm. Active chip area is 0.1 mm/sup 2/. The amplifier is packaged in a SOT-363 and consumes 30 mA from a 2.8-V supply.     

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.     

A fully integrated differential CMOS LNA for 3-5-GHz ultrawideband wireless receivers

A fully integrated differential low-power low-noise amplifier (LNA) for ultrawideband (UWB) systems operating in the 3-5-GHz frequency range is presented. A two-section LC ladder input network is exploited to achieve excellent input match in a wideband fashion and to optimize the noise performance. Prototypes fabricated in a digital 0.13-/spl mu/m complementary metal oxide semiconductor technology show the following performance: 9.5-dB peak power gain, 3.5-dB minimum noise figure, -6-dBm input-referred 1-dB compression point, and -0.8-dBm input-referred third-order intercept point, while drawing 11mA from a 1.5-V supply. The realized LNA is compared with previously reported LNAs tailored for the same frequency range.     

Design and characterization of a microwave feed-forward amplifier with improved wide-band distortion cancellation

A new approach to the design of a wide-band feed-forward amplifier (FFAMP) is presented in this paper. Phase equalizers are employed in an FFAMP to match the nonlinear delay/phase characteristics of the main and error amplifiers, improving phase balances within the cancellation loops and providing improvement in signal cancellations over a wide bandwidth. The proposed 1.7-1.9-GHz FFAMP was fabricated and characterized. The conventional FFAMP obtains an average of 15-dB third-order intermodulation (IM3) distortion cancellation over the whole bandwidth. With the phase equalizers, the proposed FFAMP achieves a further 6-dB reduction on IM3 level.     

An Ultra-Wideband High-Linearity CMOS Mixer With New Wideband Active Baluns

A 2-11-GHz high linearity CMOS down-conversion mixer with wideband active baluns using 0.18-mum CMOS technology is demonstrated in this paper. The mixer employs a folded cascode Gilbert cell topology and on-chip broadband active baluns. The folded cascode approach is adopted to increase the output swing, and the linearity is enhanced by a harmonic distortion canceling technique derived from the harmonic balance analysis. The proposed configuration shows the highest IIP₃ and IP_{1 dB}, and exhibits more compact size than most published studies. A broadband active balun is used to generate wideband differential signals, together with the derivation of a closed-form expression for the phase imbalance. This single-ended wideband mixer has the conversion gain of 6.9plusmn1.5 dB, input 1-dB compression point (IP_{1 dB}) of - 3.5 dBm, single-sideband noise figure of 15.5 dB, and third-order input intercept point (IIP₃) of 6.5 dBm under the power consumption of 25.7 mW from a 1.8-V power supply. The chip area is 0.85 x 0.57 mm².     

Noise model of InP-InGaAs SHBTs for RF circuit design

A scalable small-signal and noise model of InP-InGaAs single heterojunction bipolar transistors was developed. Effects which become important at higher frequencies such as the correlation between base and collector current noise and frequency-dependent base current noise are taken into account. We will show that these effects are significant at frequencies higher than 40 GHz and can no longer be neglected. Our model also includes the effects of the different emission coefficients of the base and collector currents. Using this improved model, a direct-coupled, lumped broad-band amplifier was designed. We completely characterized the fabricated circuit with respect to small-signal, noise, and linearity behavior. A -3-dB bandwidth of 50 GHz with a dc gain of 9.8 dB and a gain-peaking of only 1.2 dB were achieved. All these values agree very well with the simulation results. The noise figure is 7.5 dB over a large frequency range. In the frequency range from 2 to 50 GHz, the third-order intercept point IP₃ and 1-dB compression point at the output have values from 17 to 10 dBm and 3 to 0 dBm, respectively     

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.     

Generalized analysis of subcarrier multiplexing in dispersive fiber-optic links using Mach-Zehnder external modulator

A new exact analytical model is presented to analyze the dispersive transmission in subcarrier multiplexing (SCM) fiber-optic links using dual-drive Mach-Zehnder external modulator (DD-MZM). The model is very general and can be applied to almost all operating conditions of DD-MZM, such as bias point, drive level, phase shift, and modulation index difference between DD-MZM drives. The model results in simple, new, and closed-form expressions for output power spectrum, permitting an accurate and fast analysis of such links. Two special cases, double sideband (DSB) and single-sideband (SSB) modulation, are studied in detail. Some important system parameters, such as 1-dB compression point, the input third-order intercept point (IIP3), and the system capacity, are derived for the first time. Measured results for system capacity and intermodulation products of different orders match very well with the calculated results.     

A 1-V transformer-feedback low-noise amplifier for 5-GHz wireless LAN in 0.18-/spl mu/m CMOS

A low-noise amplifier (LNA) uses low-loss monolithic transformer feedback to neutralize the gate-drain overlap capacitance of a field-effect transistor (FET). A differential implementation in 0.18-/spl mu/m CMOS technology, designed for 5-GHz wireless local-area networks (LANs), achieves a measured power gain of 14.2 dB, noise figure (NF, 50 /spl Omega/) of 0.9 dB, and third-order input intercept point (IIP3) of +0.9 dBm at 5.75 GHz, while consuming 16 mW from a 1-V supply. The feedback design is benchmarked to a 5.75-GHz cascode LNA fabricated in the same technology that realizes 14.1-dB gain, 1.8-dB NF, and IIP3 of +4.2 dBm, while dissipating 21.6 mW at 1.8 V.     

A fully matched high linearity 2-W PHEMT MMIC power amplifier for 3.5 GHz applications

A 2-W monolithic microwave integrated circuit power amplifier, operating between 3.3 and 3.8GHz by implementing AlGaAs/InGaAs/GaAs pseudomorphic high electronic mobility transistor for the applications of wideband code division multiple access, wireless local loop, and multichannel multipoint distribution service, is demonstrated. This two-stage amplifier is designed to fully match 50/spl Omega/ input and output impedances. With a dual-bias configuration, the amplifier possesses the characteristics of 30.4dB small-signal gain and 34dBm 1-dB gain compression power with 37.1% power added efficiency. Moreover, with a single carrier output power level of 24dBm, high linearity with a 43.5-dBm third-order intercept point operating at 3.5GHz is also achieved.     

A large-signal HSPICE model for the heterojunction bipolartransistor

The development of an accurate nonlinear HSPICE model for a 3-×10-μm² heterojunction bipolar transistor (HBT) is described. The model allows the simulation of nonlinear measurements such as gain at the 1-dB compression point (P_{1 dB}) and third-order intercept point. Experimental data characterizing an HBT at 12.5 GHz are presented, demonstrating the validity of the model for MMIC chip designs     

Analytical performance evaluation of the OFDM systems in the presence of jointly fifth order nonlinearity and phase noise

This paper presents an exact theoretical analysis of the performance degradation in an orthogonal frequency division multiplexing (OFDM) system when the signal including phase noise is passed through a nonlinear circuit such as high power amplifier (HPA). This circuit is modeled as a fifth order memory-less nonlinear polynomial model (5th order MLNPM). The nonlinear model is derived from important electrical parameters such as gain, 1-dB compression and 3rd order intercept point. Theoretical analysis shows that the detected data symbol at the receiver consists of attenuated version of the original transmitted data symbol, common phase error (CPE), inter-sub-carrier interference (ICI), third and fifth order intermodulation (IM) components. The analytical expressions for intermodulation noise term are derived using combinatorial methods. By use of the derived expressions, a closed-form output signal to noise ratio (SNR), degradation factor (DF) and probability of error can be evaluated theoretically. For verifying the accuracy of our analysis, comparisons between the theoretical and simulated results with electrical parameter of an actual and applicable HPA are presented. The comparisons show that bit error rate (BER) of analytical results is closely match with simulation results for OFDM system using M-QAM modulation.     

A temperature-dependent nonlinear analysis of GaN/AlGaN HEMTs usingVolterra series

Gain and intermodulation distortion of an AlGaN/GaN device operating at RF have been analyzed using a general Volterra series representation. The circuit model to represent the GaN FET is obtained from a physics-based analysis. Theoretical current-voltage characteristics are in excellent agreement with the experimental data. For a 1 μm×500 μm Al_0.15Ga_0.85N/GaN FET, the calculated output power, power-added efficiency, and gain are 25 dBm, 13%, and 10.1 dB, respectively, at 15-dBm input power, and are in excellent agreement with experimental data. The output referred third-order intercept point (OIP₃) is 39.9 dBm at 350 K and 33 dBm at 650 K. These are in agreement with the simulated results from Cadence, which are 39.34 and 35.7 dBm, respectively. At 3 GHz, third-order intermodulation distortion IM₃ for 10-dBm output power is -72 dB at 300 K and -56 dB at 600 K. At 300 K, IM₃ is -66 dB at 5 GHz and -51 dB at 10 GHz. For the same frequencies, IM ₃ increases to -49.3 and -40 dB, respectively, at 600 K