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The behavior of a power amplifier (PA) is substantially affected by the output mismatch and mutual coupling in modern compact transmitters. To date, different works in the literature address the problem of coupling and mismatch separately, which are limited in terms of performance with a higher level of mismatch and mutual coupling. This paper identifies the reflection at the PA–antenna interface to be an effective parameter to unify the problem of mismatch and mutual coupling. Thus, a reflection-aware PA modeling and linearization method is proposed to compensate the adverse effect of mismatch and/or mutual coupling. The performance of the proposed method is investigated with a class AB and a Doherty PA under wide range of output mismatch and/or mutual coupling conditions with a 20-MHz WCDMA signal. The proposed method shows robust performance with an average adjacent channel power ratio better than 45 dBc. Such robust linearization performance under diverse output mismatch and mutual coupling conditions is highly desirable for modern and future communication systems that are subject to undergo rapid fluctuations under antenna matching and cross-coupling conditions. [ABSTRACT FROM AUTHOR]

This paper derives a novel continuum of Doherty power amplifier (PA) solutions with enhanced load modulation over an extended RF bandwidth. It is analytically shown that Doherty PAs with efficiency peaks at maximum power and at an arbitrary back-off level can be achieved with numerous configurations of output power combiner. Generalized governing equations for carrier and peaking transistor current ratios, voltage profiles, and biasing conditions are derived in order to assess the performance of any Doherty amplifier configuration. The generalization demonstrates the impact of the selection of the output combiner on PA performance and highlights the tradeoffs between the different solutions. A wideband Doherty PA was designed based on the proposed methodology and implemented using packaged gallium nitride transistors. Over the frequency band of 0.55–1.10 GHz, the Doherty PA exhibited drain efficiency in excess of 40% and 56% at 6-dB output power back-off (OPBO) and peak power, respectively. The Doherty PA was successfully linearized when driven with modulated stimulus and achieved average drain efficiency above 40% at 7.1-dB OPBO. [ABSTRACT FROM PUBLISHER]

A new biasing scheme is proposed for transistors used in power-amplifier applications. In the proposed biasing scheme, a constant current source is used as the power supply for the transistor’s output terminal. A whole new family of amplifier classes can be defined using this biasing scheme. Analytical equations are obtained and verified for current and voltage waveforms of a current-biased transistor for both resistive and tuned load impedances. Using the proposed current biasing scheme, the transistor presents completely different behaviors compared with the conventional voltage biasing scheme. These properties can be utilized for new design concepts and can provide new possibilities in the future designs and applications. Some of the differences between current-biased and voltage-biased amplifiers are discussed. One of the different behaviors shown by the current-biased transistor amplifiers is the reversed load modulation. Using this property of the current-biased amplifiers, a reversed modulation dual branch (RMDB) amplifier structure is proposed for ultra-wideband high efficiency at power back-off. Due to the reversed load modulation of current-biased transistors, a multibranch amplifier can be implemented to obtain high efficiency at power back-off without the need for an impedance inverter at the output of the current-biased amplifier. By using the proposed amplifier structure, a wideband RMDB amplifier was fabricated and tested exhibiting higher than 37% efficiency for long-term evolution (LTE) signals in 0.8–2.2-GHz bandwidth, which is equivalent to 93% fractional bandwidth. [ABSTRACT FROM PUBLISHER]

A co-design methodology for antenna miniaturisation with an integrated radio frequency (RF) amplifier is proposed for power-efficient and compact RF front-ends. This approach relaxes the standalone antenna matching requirement which is of interest in miniaturised antenna design. The detailed design and measurement procedure is presented and the concept is demonstrated with two examples for both narrowband and wideband scenarios considering transmitting and receiving front-ends. The amplifiers and the antennas are co-designed so that optimum performance is achieved in terms of gain, noise figure and efficiency. The antenna has the size of 0.033λ0² at 2.45 GHz. It is miniaturised from its natural resonance frequency of 3.5-2.45 GHz which provides 51% of size reduction. The minimum bandwidth of the integrated antenna is found to be 37 and 150 MHz, respectively, for the narrowband and wideband designs. The active integrated antenna (AIA) efficiency is more than 47% when operating in the band of 2.45-2.6 GHz. The gain and noise figure of the AIA systems are optimised along with the antenna performance and found to be >10 dB and <2 dB, respectively. Measurement results are presented which are in well agreement with the design procedure and simulations. [ABSTRACT FROM AUTHOR]

In this paper, a new Doherty amplifier architecture along with an analytical based design methodology is proposed. The proposed architecture uses novel three-port network as the output matching/combining network (OMCN). The three-port OMCN performs the power combining for any arbitrary output power ratios from the two transistors of the Doherty amplifier. It also performs the impedance matching from any arbitrary complex load impedance to the optimum impedances for both transistors at peak output power. Commonly in Doherty amplifiers, an optimum performance at peak power and a sub-optimum performance at power back-off are often obtained. Using the proposed output network, optimum performance can be reached at power back-off, as well as at peak power. Another three-port network is proposed for input matching/dividing network (IMDN) at the input of the proposed Doherty amplifier. The three-port IMDN is designed to perform the power division with any arbitrary division ratio, adjust the arbitrary phase difference between the input signals to the two transistors, and provide the impedance matching from any arbitrary complex source impedance to the optimal source impedances for the two transistors. To verify the provided theory, two prototype amplifiers are designed and tested. A 12-W amplifier is designed for a 50-\Omega source and load impedances at 1 GHz. Another 12-W amplifier is designed at 1 GHz for complex source and load impedances. Both amplifiers have efficiency of higher than 50% at 7-dB output power range. [ABSTRACT FROM PUBLISHER]

This paper introduces a new architecture of frequency-agile Doherty power amplifier (PA)-based RF front-end. This architecture incorporates a baseband equalizer that is implemented using finite-impulse-response (FIR) digital filters to improve the performance of Doherty PAs when driven with large bandwidth and multiband wireless radios. Depending on the center frequency and bandwidth of the input signal, the FIR filters of the proposed equalizer are synthesized to compensate for the nonideal frequency behavior of the RF building blocks of the Doherty PA. It is shown that the proposed architecture enables the Doherty PA to operate with significantly improved power efficiency and linearity performance beyond its nominal frequency of design, which is suitable for multistandard applications. As a matter of fact, when driven with a 140-MHz bandwidth long-term evolution (LTE) signal centered around 2.30 GHz, the average efficiency of a 2.14-GHz Doherty PA prototype with the proposed digital baseband equalizer is enhanced from 33.5% to 44.7%. Moreover, its linearity performance in terms of adjacent channel leakage ratio (ACLR) is improved from -21 to -\26 dB. In addition, when operated in concurrent dual-band mode with two 20-MHz bandwidth LTE signals centered at 1.96 and 2.34 GHz, the proposed Doherty PA enabled a reduction in dc power consumption by nearly 15%. Furthermore, it is demonstrated that the integration of the proposed baseband equalizer does not compromise the linearizability of the Doherty PA. To the best of the authors’ knowledge, this is the first demonstration of the use of digital equalization for performance enhancement of RF Doherty PAs. [ABSTRACT FROM PUBLISHER]

This paper reports a novel digital predistortion (DPD) scheme for concurrent tri-band power amplifiers (PAs). The proposed tri-band DPD is based on a pruned Volterra model that takes into account the impact of the phase distortion observed in multi-band PAs as well as the compound amplitude distortion. By taking into account the phase variation effects across a wide frequency band, the proposed 3-D phase-aligned Volterra DPD can effectively compensate for the crosstalk effects between the fundamental frequencies, their harmonics, and intermodulation products due to the nonlinearity the tri-band PA exhibited. The performance of the proposed DPD is validated using a broadband Class-AB PA driven concurrently by three independent carrier-aggregated long-term evolution signals at separation frequencies around 100 MHz. The measurement results validate the accurate performance of the proposed 3-D phase-aligned pruned Volterra DPD in suppressing the in-band and cross-band intermodulation effects, and shows improvement over a basic 3-D tri-band DPD model that neglects phase variation effects across frequency. [ABSTRACT FROM AUTHOR]

The behavior of power amplifiers (PAs) driven by concurrent dual-band signals is analyzed theoretically in this paper. According to the analysis, the impedance matching at intermodulation (IM) frequency is very important for PAs working in concurrent mode. Based on the concept of IM impedance tuning, a family of new operation modes can be introduced, including concurrent Class-A, Class-AB, Class-B, and Class-C. The theoretical performance of these modes are derived and the overdrive effects of them are also discussed. A possible structure is proposed to implement the proposed IM impedance tuning, and a concurrent Class-AB dual-band example PA operating at 1.9–2.6-GHz long-term evolution (LTE) bands is demonstrated. Experimental results show good consistence with the theoretical analysis, and the concurrent Class-AB PA prototype exhibits higher than 36.1% power-added efficiency in concurrent mode when driven by 10- and 15-MHz LTE signals in two bands concurrently. To our best knowledge, this is the state-of-the-art efficiency performance of concurrent dual-band PAs, even higher than previously reported dual-band Doherty PAs. Additionally the proposed PA, which is fabricated using a 10-W GaN HEMT, can output more than 34.3-dBm power with a peak-to-average ratio of 7 dB in concurrent mode, showing a remarkable power utilization factor for concurrent dual-band PAs. [ABSTRACT FROM AUTHOR]

This paper proposes a new method for extending the bandwidth of Doherty power amplifiers (PAs) in the digital domain. The bandwidth enhancement is achieved through a frequency-selective pre-compensation mechanism that is derived to prevent the efficiency degradation that naturally occurs as the frequency of operation deviates from the center frequency. A methodical analysis of the frequency response of the conventional Doherty PA and that of the proposed Doherty PA is carried out to point out the limitations of the former and demonstrate the capability of the latter in recovering the bandwidth. Over the frequency range spanning from 1.96 to 2.46 GHz, the measured drain efficiency at 6–7-dB output power back-off is higher than 40% for the proposed Doherty PA. Such efficiency performance is achievable only from 2.04 to 2.22 GHz using the conventional Doherty PA. Hence, the bandwidth is enhanced from 180 to 500 MHz, which corresponds to an increase by a factor of 2.8 (i.e., almost triple). By applying the proposed methodology, a Doherty PA that is originally designed at the center frequency of 2.14 GHz for downlink wideband code division multiple access became operative at 1.98-GHz uplink wideband code division multiple access (UL-WCDMA), 2.22-GHz long-term evolution (LTE), and 2.34-GHz worldwide interoperability for microwave access (WiMAX) bands. The average drain efficiencies for UL-WCDMA, LTE, and WiMAX applications, were 40.1%, 44.2%, and 41.4%, respectively, using the proposed Doherty PA, and 37%, 37.3%, and 35.2%, respectively, using the conventional Doherty PA. [ABSTRACT FROM PUBLISHER]

An architecture and design procedure for transformer-less load-modulated power amplifiers (PAs) having high efficiency at power back-off is presented. This architecture utilizes a comparable load modulation concept as in the Doherty PA; however, contrary to the Doherty PA, it neither requires an output impedance transformer, nor offset lines, which are the main limiting factors in designing wideband Doherty amplifiers. In this architecture, the proper load modulation at the transistor drain levels is directly dependant on the design of the main and peaking amplifiers' matching networks. It is shown that the design of the output impedance of the peaking amplifier as a frequency-varying susceptance rather than as a quasi-open circuit impedance (as in Doherty amplifiers) helps in achieving better wideband performance. Based on the analytical results, a step-by-step procedure is proposed for designing wideband load-modulated PAs having high efficiency over a wide power back-off region. Based on the proposed architecture and its design procedure, a 10-W PA is designed and prototyped in the 1.96–2.46-GHz band exhibiting a power-added efficiency of more than 40% at a 6-dB power back-off. In comparison with a symmetrical Doherty amplifier design using the same device, the proposed architecture exhibits a 250% enhancement in its fractional bandwidth. [ABSTRACT FROM PUBLISHER]

A large-signal model for GaN HEMT transistor suitable for designing radio frequency power amplifiers (PAs) is presented along with its parameters extraction procedure. This model is relatively easy to construct and implement in CAD software since it requires only DC and S-parameter measurements. The modeling procedure was applied to a 4-W packaged GaN-on-Si HEMT, and the developed model is validated by comparing its small- and large-signal simulation to measured data. The model has been employed for designing a switching-mode inverse class-F PA. Very good agreement between the amplifier simulation and measurement shows the validity of the model. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011. [ABSTRACT FROM AUTHOR]

This paper presents a study of performance evaluation metrics for behavioral models of power amplifiers and transmitters. A novel normalized absolute mean spectrum error criterion is proposed as a performance evaluation metric along with a method for accurate benchmarking of behavioral models and their ability to predict the in-band response, static nonlinearity, and memory effects of the device under test. The proposed metric and method are validated with a study of different memory polynomial based models, focusing on the model accuracy, complexity, and identification robustness. This experimental validation highlights the robustness of the proposed metric and its ability to accurately quantify the performance of several behavioral models in predicting the static nonlinearity and memory effects of the device under test for several test conditions. In addition, the results of the comparative study between the memory polynomial models are used to propose a hybrid memory polynomial model. The superiority of the proposed model is assessed by comparing its performance to that of the studied memory polynomial models. [ABSTRACT FROM AUTHOR]

In this paper, a study of the power alignment issue in digital predistorters is presented. The proper alignment is achieved by adjusting the normalization gain used to synthesize the predistortion function. The dependencies of the linearity and power efficiency of the linearized amplifier upon the gain normalization factor are investigated, and it is shown that the efficiency of the linearized amplifier is almost unaffected by variation of the nor- malization gain. Conversely, the linearity performance of the linearized power amplifier is found to bedependent on the gain normalization factor, as a consequence of the average power variation through the predistorter. Indeed, the proper power alignment of the predistorter following an adequate choice of the normalization gain shows a significant improvement in the measured adjacent channel power ratio at the linearized amplifier output. [ABSTRACT FROM AUTHOR]

This paper analyzes the power losses in distributed multiharmonic matching networks and proposes a methodology to minimize these losses, which are critical in designing harmonic controlled or switching mode power amplifiers (PAs). The effect of the harmonic output matching topology on PA performance is studied. An analytical evaluation is developed to show the effect of the harmonic network topology on the conduction losses in the fundamental matching network. This analysis is validated through the comparison of two different matching network topologies in the design of an inverse class F PA with a carrier frequency of around 1 GHz. A 0.2-dB improvement in the losses is achieved, allowing for an improvement of the output power and gain and for an increase in the power-added efficiency by 4%, reaching 81%. [ABSTRACT FROM AUTHOR]

A novel approach for power amplifier (PA) characterization suitable for single iteration digital predistorter synthesis is proposed. This approach consists of synergetic crest factor reduction and baseband digital predistortion to avoid the average power variation at the input of the PA between the characterization and linearization steps. This is achieved by bypassing the crest factor reduction block during the characterization step and by applying it concurrently with digital predistortion in the linearization step. First, the PA's behavior sensitivity to the average input power is evaluated. The limitations of conventional approaches for the PA characterization, in the context of single iteration digital predistortion, are then demonstrated. The performance of the proposed technique is validated experimentally on a 3OO!W peak PA. The measured improvement of the adjacent channel power ratio at the output of the linearized amplifier is 16 dBc for the conventional approach and 29 dBc for the proposed approach. [ABSTRACT FROM AUTHOR]

This paper reports a novel voltage and current wave-form measurement system suitable for large-signal transistor and power amplifier characterization and optimization. This technique is original in its use of a double six-port (SP) refiectometer as a homodyne vector network analyzer, which is calibrated in magnitude and phase by means of a reference multiharmonic signal generator, to measure the waveforms at the output terminal of the device. An active branch load-pull setup is used to control the source impedance at the fundamental frequency, and the load impedance at the fundamental, second, and third harmonic frequencies. The capability of the proposed SP refiectometer-based configuration is demonstrated experimentally, by measuring the voltage and current waveforms of a GaAs metal-semiconductor field-effect transistor that is biased in class AB and tuned for maximum efficiency. To assess the level of accuracy of the proposed method, the same waveforms were also measured using a microwave-transition-analyzer-based system. A comparison of the results shows that the proposed SP reflectometer setup obtains results accurate enough for power amplifier characterization with lower equipment cost. [ABSTRACT FROM AUTHOR]

A design-oriented analysis of microwave transmission-line class-E and class-F amplifiers is presented in this paper. Multiharmonic transmission-line load networks are analyzed and compared in terms of harmonic suppression and their effects on output power and efficiency. Based on this study, a design of highly efficient monolithic-microwave integrated-circuit amplifiers has been carried out. To allow circuit optimization and to simplify the design process, analytic expressions were derived for the most practical multiharmonic transmission-line networks. Fabricated amplifiers achieve state-of-the-art efficiency of 56.2% and 59.0% for class-E and class-F operation at K-band for power levels of 19.1 and 20.0 dBm, respectively. Moreover, without the need for supplementary filtering sections, harmonic suppression for operation well into compression is better than -25 and -30 dBc for the transmission-line class-F and class-E amplifiers, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive study of the robustness of the digital predistortion function synthesis is presented. This study covers two aspects: the processing of the power amplifier (PA) input and output measured data intended for the extraction of the corresponding predistortion function, and the optimal setting of the predistorter's small-signal gain to adaptively track the average power variation between the input and output of the predistorter. First, the accuracy of the polynomial curve fitting and the lookup table's scheme in mimicking the measured AM/AM and AM/PM characteristics of the PA is investigated. To address the high dispersion of coefficients of the polynomial function, which limits the order that can be implemented and the fitting capabilities, a pre-processing technique is proposed. Second, the fitted PA curves are used to investigate the effects of the small-signal gain of the predistortion function on the linearization performance. An automated average power tracking technique is introduced in order to maintain a unit average gain of the predistorter. The measured spectra at the output of the amplifier show an additional 12-dBc improvement in the output spectrum regrowth. [ABSTRACT FROM AUTHOR]

This paper proposes a new amplifier architecture based on the outphasing technique intended for the efficiency enhancement of linear amplification with nonlinear components (LINC) transmitters. The proposed mode-multiplexing linear amplification with nonlinear components (MM-LINC) scheme operates according to the LINC concept for input signal magnitude drive levels below a certain threshold and as a balanced amplifier beyond this threshold. The setting of this threshold level influences the performance of the amplifier in terms of average power-added efficiency and linearity. A 2-W up-link transmitter prototype for worldwide interoperability for microwave access (WiMAX) applications was designed using this new architecture and optimized for a WiMAX signal with an 11.3-dB peak-to-average power ratio. The experimental results revealed a significant increase in power-added efficiency, from 6% for a LINC transmitter to 21% for the MM-LINC amplifier, while maintaining an error vector magnitude value under 8%, which is compliant with the standard requirement. [ABSTRACT FROM AUTHOR]

An active load-pull-based large-signal modeling approach, suitable for designing and optimizing load modulated amplifiers such as Doherty or linear amplification using nonlinear components based amplifiers, is proposed. A Doherty amplifier was designed by optimizing the dynamic loads seen by the amplifier's transistor using a large-signal load-pull-based behavior model built into computer-aided-design software. Simulation and measurement results showed good agreement, while results obtained using an empirical model of this transistor demonstrated discrepancies. The load-pull-based model was then used to study performance degradation of the Doherty amplifier when load impedance was moved out from the perfect 50 Ω. It has been shown that the load mismatch can greatly affect the linearity and efficiency performance of the amplifier unless its phase is controlled and kept within a specific range. A load mismatch system level compensator scheme, capable of restituting the linearity loss and maintaining the power-added efficiency close to its maximum range, is proposed. [ABSTRACT FROM AUTHOR]

This paper proposes a digital signal-processing-based approach suitable for the performance optimization of third-generation (3G) amplifiers in terms of spectrum and power. A peak-to-average power ratio (PAPR) reduction method, which is coding and modulation independent, based on peak clipping and digital filtering techniques, is proposed. Moreover, the multi-branch memory polynomial pre-distorter identified with an optimized recursive least square technique was efficiently implemented in a digital signal processor. The cascade of the proposed PAPR reduction technique with the memory pre-distorter results in a substantial enhancement of the power amplifier (PA) output linear power and efficiency, while still meeting the 3G partnership project standard requirements. An experimental validation carried out on a 90-W laterally diffused metal-oxide-semiconductor PA, which was fed with a wide-band code-division multiple-access signal, led to a 4-dB rise in output mean linear power accompanied with 60% increase in its power-added efficiency. [ABSTRACT FROM AUTHOR]

In this paper, an augmented lookup-table-based Hammerstein predistorter is proposed for the first time in order to further improve the pre-correction capability of the traditional Hammerstein predistorter in the context of broad-band high-power wireless transmitters. The predistorter scheme consists of two separate modules, and its parameters are determined in two steps, which are: 1) static predistorter identification and then 2) dynamic part identification. The performance assessment of the newly proposed predistorter is carried out on a wireless transmitter prototype, which includes an L-band push-pull GaAs field-effect transistor 45-dBm peak-envelope power amplifier. Moreover, one- and three-carrier Third-Generation Partnership Projects frequency-division duplex wide-band code-division multiple-access signals are used as test signals to verify the robustness of this novel predistorter under different bandwidth signals. The linearized transmitter prototype output spectrum demonstrates noticeable superiority of the proposed augmented predistorter in suppressing the spectrum regrowth caused by the memory effects in comparison to the traditional Hammerstein predistorter. [ABSTRACT FROM AUTHOR]

In this paper, a robust modeling technique for memoryless wide-band radio frequency transmitters using a dynamic exponential weighted moving average algorithm is developed and tested. To improve the relatively limited accuracy of the conventional Wiener model in predicting the response of dynamic nonlinear transmitters, a new augmented Wiener model is proposed along with its parameter-identification procedure. The accuracy of the augmented Wiener model is compared with that of the conventional Wiener model by using an L-band 60-W peak-envelope-power GaAs field-effect-transistor push-pull amplifier-based transmitter, which is driven by a two-carrier wide-band code-division multiple-access signal. [ABSTRACT FROM AUTHOR]

In this paper, an active load-pull-based large-signal modeling approach suitable for designing and optimizing Doherty amplifiers is proposed. The optimization of the drive dependant dynamic loads seen by both carrier and peaking amplifier's transistors was carried out using a large-signal load-pull-based behavior model built into CAD software. The latter was also used to optimize the biasing conditions of the peaking and carrier amplifier transistors. The simulation versus measurement results demonstrated the strong ability of the constructed model to predict the nonlinear behavior of 16 watts peak-envelope power designed Doherty amplifier in terms of power added efficiency, AM/AM, and AM/PM distortions. In addition, a complex digital predistortion technique was used to significantly enhance the linearity of the Doherty amplifier and to preserve an ACPR level better than 50 dBc under a WCDMA signal while attaining a power added efficiency of about 44% at the same time. [ABSTRACT FROM AUTHOR]

This paper studies the influences of two new adaptation methods and the class of main amplifier operation on the achievable power efficiency of the feedforward amplifier under typical design constraints. These two influences are weak for a two-tone driving signal, but they interact powerfully for a real-life high-stress signal, leading to optimal designs involving Class AB or even Class B main amplifiers, depending on the required output linearity. Assuming a code-division multiple-access signal, typical MESFETs, and an output linearity commonly used in mobile systems design, the new adaptation methods allowed relative efficiency improvements of 21% and 36% using main amplifiers biased near Class B and at Class B, respectively. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel real-valued time-delay neural network (RVTDNN) suitable for dynamic modeling of the baseband nonlinear behaviors of third-generation (3G) base-station power amplifiers (PA). Parameters (weights and biases) of the proposed model are identified using the back-propagation algorithm, which is applied to the input and output waveforms of the PA recorded under real operation conditions. Time- and frequency-domain simulation of a 90-W LDMOS PA output using this novel neural-network model exhibit a good agreement between the RVTDNN behavioral model's predicted results and measured ones along with a good generality. Moreover, dynamic AM/AM and AM/PM characteristics obtained using the proposed model demonstrated that the RVTDNN can track and account for the memory effects of the PAs well. These characteristics also point out that the small-signal response of the LDMOS PA is more affected by the memory effects than the PAs large-signal response when it is driven by 3G signals. This RVTDNN model requires a significantly reduced complexity and shorter processing time in the analysis and training procedures, when driven with complex modulated and highly varying envelope signals such as 3G signals, than previously published neural-network-based PA models. [ABSTRACT FROM AUTHOR]

Memory effects, which influence the performance of RF power amplifiers (PAs) and predistortion-based linearizers, become more significant and critical in designing these circuits as the modulation signal bandwidth and operation power increase. This paper reports on an attempt to investigate, model, and quantify the contributions of the electrical nonlinearity effects and the thermal memory effects to a PA's distortion generation, as well as how to compensate for these effects in designing baseband predistortion schemes. The first part of this paper reports on the development of an accurate dynamic expression of the instantaneous junction temperature as a function of the instantaneous dissipated power. This expression has been used in the construction of an electrothermal model for the PA. Parameters for the new proposed behavior model were determined from the PA measurements obtained under different excitation conditions (e.g., small-signal and pulsed RF tests). This study led us to conclude that the effects of the transistor self-heating phenomenon are more important under narrow-band signal (e.g., enhanced data for global evolution of global system for mobile communications) than for signals with wide modulation bandwidth (CDMA2000, Universal Mobile Telecommunications System). In the second part of this paper, the newly developed model has also been used to design a temperature-compensated predistortion function to compensate for these effects. The linearized PA output spectrum and error vector magnitude show a significant performance improvement in the temperature-compensated predistortion function over a memoryless predistortion. The results of these measurements that have been conducted on a 90-W peak lateral double-diffused metal-oxide-semiconductor PA are in agreement with those obtained from simulations using the developed PA and the predistorter models implemented in an ADS environment. Index Terms—Behavior model; distortion; electrothermal; measurements; memory effects; RF power amplifier (PA). [ABSTRACT FROM AUTHOR]

An alternative method for large signal characterization of microwave/millimeter-wave power transistors suitable for high power amplifier design is presented. Constant output power contours, constant added-power efficiency contours, and constant power dissipation contours over the full Smith chart are obtained for a NEC 71083 MESFET. [ABSTRACT FROM AUTHOR]