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This paper presents an in-depth investigation of both isolated and non-isolated outphasing power amplifiers, with and without supply modulation. X-band GaN MMIC power amplifiers with 70% power-added efficiency and 2.7 W output power at 10.1 GHz are configured in hybrid outphasing circuits with several combiners that include bi-directional couplers, enabling calibrated measurements of internal load modulation. It is experimentally demonstrated that the load modulation critically depends on the power balance of the two internal MMIC PAs. Despite the additional loss in the combiner, peak total efficiencies greater than 47% are achieved by full outphasing PAs with more than 3.7 W of output power. A comparison between several outphasing configurations quantifies the improvement in efficiency for both isolated and non-isolated outphasing PAs with supply modulation.

International audience; This paper reports on the design of a new power cell dedicated to Ku-band power amplifier (PA) applications. This cell called "integrated cascode" has been designed in order to propose a strong decrease in terms of circuit size for PA. The technology used relies on 0.25-μm GaAs pseudomorphic high electron mobility transistors (PHEMT) of United Monolithic Semiconductors (UMS) foundry. A distributed approach is proposed in order to model this power cell. The challenge consists of obtaining, with a better shape factor (ratio between the vertical and horizontal sizes of the transistor), the same performances than a single transistor with the same gate width. In order to design a 2W amplifier, we have used two 12 × 100 μm transistors. Cascode vertical size is 413 μm whereas a transistor with the same gate width exhibits a vertical size of 790 μm. Therefore, the shape factor is nearly one as compared to a shape factor of 4 for a classical parallel architecture. This new device allows us to decrease the Monolithic microwave integrated circuit amplifier area of 40% compared to amplifier based on single transistors.

This paper presents design, analysis and experimental results on synchronous and self- synchronous microwave transistor rectifiers implemented with GaN HEMTs at frequencies from 2 to 10GHz. The rectifier/power amplifier duality is explained and measurements confirming this mode of operation are presented. Finally, rectifier applications in wireless power transfer and high- frequency integrated dc-dc converters are discussed, including a GaN MMIC dc-dc converter switching at 4.6GHz.

This paper presents a theoretical analysis of harmonically terminated high-efficiency power rectifiers and experimental validation on a class-C single Schottky-diode rectifier and a class- F-1 GaN transistor rectifier. The theory is based on a Fourier analysis of current and voltage waveforms, which arise across the rectifying element when different harmonic terminations are presented at its terminals. An analogy to harmonically terminated power amplifier (PA) theory is discussed. From the analysis, one can obtain an optimal value for the dc load given the RF circuit design. An upper limit on rectifier efficiency is derived for each case as a function of the device on-resistance. Measured results from fundamental frequency source-pull measurement of a Schottky diode rectifier with short-circuit terminations at the second and third harmonics are presented. A maximal device rectification efficiency of 72.8% at 2.45 GHz matches the theoretical prediction. A 2.14-GHz GaN HEMT rectifier is designed based on a class-F-1 PA. The gate of the transistor is terminated in an optimal impedance for self-synchronous rectification. Measurements of conversion efficiency and output dc voltage for varying gate RF impedance, dc load, and gate bias are shown with varying input RF power at the drain. The rectifier demonstrates an efficiency of 85% for a 10-W input RF power at the transistor drain with a dc voltage of 30 V across a 98-Ω resistor.

International audience; The design of high speed integrated circuits heavily relies on circuit simulation and requires compact transistor models. This paper presents a non-linear electro-thermal model of SiGe heterojunction-bipolar transistor (HBT). The non-linear model presented in this paper uses a hybrid π topology and it is extracted using IV and S-parameter measurements. The thermal sub-circuit is extracted using low-frequency S-parameter measurements. The model extraction procedure is described in detail. It is applied here to the modeling of npn SiGe HBTs. The proposed non-linear electro-thermal model is expected to be used for the design of high-speed electronic functions such as broadband analog digital converters in which both electrical and thermal aspects are engaged. The main focus and contribution of this paper stands in the fact that the proposed non-linear model covers wideband-frequency range (up to 65 GHz).

International audience; The electrical modeling of power packages is a major issue for designers of high-efficiency hybrid power amplifiers. This paper reports the synthesis and the modeling of a packaged Gallium nitride (GaN) High electron mobility transistor (HEMT) associating a nonlinear model of the GaN HEMT die with an equivalent circuit model of the package. The extraction procedure is based on multi-bias S-parameter measurements of both packaged and unpackaged (on-wafer) configurations. Two different designs of 20 W packaged GaN HEMTs illustrate the modeling approach that is validated by time-domain load-pull measurements in S-band. The advantage of the electrical modeling dedicated to packaged GaN HEMTs is to enable a die-package co-design for power matching. Internal matching elements such as Metal oxide semiconductor (MOS) capacitors, Monolithic microwave integrated circuits (MMICs), and bond wires can be separately modeled to ensure an efficient optimization of the package for high power Radio frequency (RF) applications.

International audience; This paper describes a novel fully calibrated four channel broadband time-domain measurement system for the characterization of nonlinear microwave devices with memory. The hardware architecture of the proposed time-domain measurement system is based on a wideband sub-sampling principle. The sampling heads work at a high strobe signal repetition frequency that can be tuned between 357-536 MHz. We achieve a 40-GHz RF frequency bandwidth and a 160-MHz IF bandwidth. This instrument enables the measurement of carrier and envelope waveforms at both ports of nonlinear microwave devices driven by broadband modulated multicarriers. The test-bench is applied to the cross modulation characterization of a 15-W GaN HEMT CREE S-band power amplifier with memory due to different biasing circuit configurations. The amplifier under test is driven by the sum of a large-signal modulated carrier (double-sideband amplitude modulation at 3.6 GHz) and a small single-tone signal at a 110-MHz offset frequency. Our significant contribution comes from the capability of the measurement system to record the time-domain waveforms of several nonadjacent modulated signals on a similar time equivalent scale for different cases of memory effects of the power amplifier under test.

The present paper presents the transistor modeling work achieved in the GaN European project KorriGaN (“Key Organisation for Research in Integrated Circuits in GaN technology”). The KorriGaN project (2005–09) has released 29 GaN circuits such as high-power amplifiers (HPAs), low-noise amplifiers (LNAs), and switches. Modeling is one of the main key to reach successful designs. Therefore, nonlinear models of European GaN HEMT models have been developed. This work deals with characterization tools such as pulsed IV, pulsed [S] parameters, load-pull measurements, and measurement-based methods to perform GaN HEMT compact models parameters extraction. The present paper will describe the transistor modeling activities in KorriGaN for HPA designs (nonlinear models including trapping and/or self-heating effects) and LNA designs (nonlinear models and noise parameters).

International audience; This paper presents a calibrated measurement technique that enables phase and magnitude measurements of wideband multisines. This study is based on the use of a large-signal network analyzer (LSNA) performing harmonic sub-sampling and a fine frequency grid (20 MHz) comb generator calibrated using a high-frequency 50-GHz equivalent-time sampling scope. This comb generator is used as a harmonic phase reference generator for the calibration of the LSNA. The research reported here is applied to L-band multisine measurements, but it can be extended to higher microwave frequencies. The motivation of this study is to measure the multipactor phenomena effect in output RF multiplexers of satellite payloads.

A large-signal electrothermal model for AlGaN/GaN HEMTs including gate and drain related trapping effects is proposed here. This nonlinear model is well formulated to preserve convergence capabilities and simulation times. Extensive measurements have demonstrated the impact of trapping effects on the shapes of I(V) characteristics, as well as load cycles. It is shown that accurate modeling of gate-and drain-lag effects dramatically improves the large-signal simulation results. This is particularly true when the output loads deviate from the optimum matching conditions corresponding to real-world simulations. This new model and its modeling approach are presented here. Large-signal simulation results are then reported and compared to load-pull and large-signal network analyzer measurements for several load impedances at high voltage standing wave ratio and at two frequencies.

This paper presents a general measurement based design method for outphasing amplifiers. Both isolated and non-isolated combiners are designed based on individual PA load-pull measurements, in order to load modulate two 0.15μm GaN MMIC power amplifiers at 10.1GHz. Load modulation measurements are performed at ports internal to the PA, with the inclusion of couplers in the combiner and a four-port LSNA, to gain insight into the dynamics of load modulation during outphasing operation. Both outphasing systems exhibit a peak PAE greater than 41.5% at a peak output power greater than 35.7 dBm.

This paper presents a performance evaluation of GaN X-Band power amplifiers operating as self-synchronous rectifiers. Two single-stage MMIC power amplifiers are characterized under continuous wave conditions at 10.1GHz. One PA is designed with a single 10 × 100μm HEMT in a 0.15μm GaN process, while the other contains two 10 × 100μm power-combined devices. The MMICs exhibit 67% and 56% power added efficiency at V DD = 20V in deep class-AB bias, respectively. In rectifier mode, biased in class-C, the same MMICs show a RF-to-DC efficiency of 64%. The output powers of the two MMIC PAs are around 3.2W. In rectifier mode, the gate DC bias and the load-pull determined RF gate impedance are set for optimal efficiency. The DC load does not affect the efficiency substantially, and can be chosen for a desired voltage or current. The paper demonstrates that high-power efficient GaN rectifiers can be achieved by designing high-efficiency PAs at least up to X-band.

The efficiency of a wireless powering system is maximized when the power transmitter power-added efficiency (PAE), power receiver conversion efficiency (η C ) and wireless coupling efficiency (η W ) are maximized. This paper focuses on a general approach to the design of an efficient transmitter and receiver of a high-power wireless powering system, which is valid for any type of wireless power coupling. Experimental results for high-efficiency power transmitters and receivers at various frequencies and with various power levels are discussed.

International audience; In the present paper, we present a dynamic gate biasing technique applied to a 10 W, S-band GaN amplifier. The proposed methodology addresses class-B operation of power amplifiers that offers the potential for high efficiency but requires a careful attention to maintain good linearity performances at large output power back-off. This work proposes a solution to improve the linearity of class-B amplifiers driven by radio frequency-modulated signals having large peak to average power ratios. An important aspect of this work concerns the characterization of the dynamic behavior of GaN devices for gate bias trajectory optimization. For that purpose, the experimental study reported here is based on the use of a time-domain envelope setup. A specific gate bias circuit has been designed and connected to a 10 W - 2.5 GHz GaN amplifier demo board from CREE. Compared to conventional class-B operation with a fixed gate bias, a 10-dB improvement in terms of third-order intermodulation is reached. When applied to the amplification of 16-QAM signals the proposed technique demonstrates significant ACPR reduction of order of 6 dB along with error vector magnitude (EVM) improvements of five points over 8 dB output power back-off with a minor impact on power-added efficiency performances.

International audience; This paper examines the distinctive feature of studying the direct interaction between high power amplifiers located at the vicinity of the radiating elements without the use of isolators. In that case, the coupling effect between antennas, which leads to output impedance mismatching and degradation of the radiation pattern, will be described. Alongside, two methods have been developed to address this major drawback with some experimental results to validate the theoretical approach. An active antenna prototype including power amplifiers has been manufactured to validate a first approach of active antenna joint simulation, taking into account all the mentioned effects.

International audience; This paper presents a design method of internally-matched packaged GaN high electron mobility transistors (HEMTs) for achieving not only high-efficiency and high-power performances but also a wide bandwidth and insensitivity to harmonic terminations in the S-band. The package and its internal matching networks are synthesized to confine the second harmonic impedances seen by the GaN die to high-efficiency regions whatever the harmonic impedances presented outside the package. This paper reports the design of a packaged GaN HEMT achieving 78% of power-added-efficiency (PAE) and 25 W of output power at 2.5 GHz. A packaged GaN power bar is also reported with the addition of fundamental matching networks inside the package. In 50V environment, the packaged GaN power bar provided more than 56% of PAE from 2.5 to 3.1 GHz and was desensitized to harmonic load variations with less than two points of PAE variation when a load-pull is performed at second harmonic frequencies outside the package.

Static X-parameter (XP) models for RF power amplifiers (PAs), derived from both simulations and nonlinear vector network analyzer (NVNA) measurements, are investigated for the prediction of PA performance under dynamic signal conditions such as in envelope tracking (ET). The instantaneous AM-AM, AM-PM and PAE predictions of XP models extracted from simulation are compared under ET dynamic signal conditions to two types of circuit models using envelope simulation. An XP PA model is extracted for a peak 8W GaN class-F-1 ET PA from NVNA measurements with automated bias control. By applying a constant gain shaping table derived from the XP model to the drain supply voltage, the average PAE is improved from 40% to 57% for 3.84 MHz WCDMA signals at 2.14 GHz compared to fixed drain bias operation.

International audience; We propose here a non-linear GaN HEMT model for CAD including a trapping effects description consistent with both small-signal and large-signal operating modes. It takes into account the dynamics of the traps and then allows to accurately model the modulated large signal characteristics that are encountered in telecommunication and radar signals. This model is elaborated through low-frequency S-parameter measurements complementary to more classical pulsed-IV characterizations. A 8x75um AlInN/GaN HEMT model was designed and particularly validated in large-signal pulsed RF operation. It is also shown that thermal and trapping effects have opposite effects on the output conductance, thus opening the way for separate characterizations of the two effects

International audience; This paper focuses on the time domain envelope measurements based analysis of power amplifiers in order to improve both linearity and efficiency of microwave transmitters. First of all, a versatile time domain envelope test bench is presented. Then, two applications related to those RF PA measurements are reported. The first application concerns linearity characterization that can be specified in term of Noise Power Ratio (NPR) and Error Vector Magnitude (EVM). Those figures of merit are essential to compute the final bit error rate in a system level simulation tool. A relationship between NPR and EVM is presented and validated by measurements. As a result it can be advantageously used to simplify simulation and measurement procedures for the linearity characterisation of devices and subsystems. The second application is regarding enhancement of the trade-off between linearity and energy efficiency. In order to have a good efficiency, a 10 W class-B GaN Power amplifier is considered. The work presented here, proposes a solution for linearity specifications at large output power back-off thanks to a dynamic gate bias control related to low instantaneous envelope power level. Meanwhile, a dynamic drain bias control handles good efficiency at a constant gain for high instantaneous envelope power level. The measurement-based gate and drain bias trajectory extraction will be fully detailed and take into account GaN dispersive effects such as thermal and trapping effects.

International audience; This paper presents an ultracompact antenna design suited for digital video broadcasting-handheld (DVB-H) reception devices. The DVB-H frequency band is ranging from 4 70 to 862 MHz and divided in 49 channels of 8 MHz. Designed to be integrated in a tablet, it is not only heavily miniaturized (λ0 /49 × λ0/71 ×λ0/160 at 470 MHz), but also able to cover each channel thanks to the use of a magneto-dielectric material. The advantage of using such a material is studied and described in this paper. Moreover, the operating frequency is continuously tuned over the whole DVB-H band by the integration of a varactor diode. This varactor diode has been characterized and modeled to properly cosimulate its behavior within the antenna. Limitations in terms of accepted power by the diode are emphasizing. Finally, the antenna design, including both magneto-dielectric material and varactor diode is integrated in the DVB-H receiver device. Measurement performances are presented and discussed.

International audience; This paper reports on the design of a new power cell dedicated to Ku-band power amplifier (PA) applications. This cell called '"integrated cascode"' has been designed in order to propose a strong decrease in term of circuit size for Power Amplifier (PA). The technology used relies on 0.25-µm GaAs Pseudomorphic High Electron Mobility Transistors (PHEMT) of United Monolithic Semiconductors (UMS) foundry. A distributed approach is proposed in order to model this power cell. The challenge consists to obtain, with a better shape factor (ratio between the vertical and horizontal sizes of the transistor), the same performances than a single transistor with the same gate development. In order to design a 2W amplifier, we have used two 12×100 µm transistors. Cascode vertical size is 413 µm whereas a transistor with the same gate development exhibits a vertical size of 790 µm. Therefore the shape factor is nearly one as compared to a shape factor of 4 for a classical parallel architecture. This new device allows to decrease the MMIC amplifier area of 40 % compared with amplifier based on single transistors.

International audience; This paper reports a package synthesis method in order to ensure good performances in PAE, output power and bandwidth. The internal matching circuits of the optimized package enable to reach the best impedance pre-matching at fundamental frequencies and also to confine the harmonic impedances seen by the internal GaN power bar into safe-efficiency regions whatever the external impedances presented to the package at second harmonic frequencies. In a 50Ω environment, the packaged GaN HEMT delivers 55 W output power associated with 60% PAE and 13.3 dB power gain at 2.7 GHz. By optimizing source and load impedances at the fundamental frequencies, the packaged GaN HEMT demonstrates more than 58% PAE from 2.6 GHz to 3.0 GHz.

International audience; This paper presents a mixed simulation approach for an active antenna operating at 8.2 GHz. This approach is composed of three main parts which they will be detailed and described with some experimental validation as well. The first part of this approach is an electromagnetic (EM) macromodel for antennas array. The second part is a bilateral behavioral model for power amplifiers (PA). Finally, a mixed simulation approach was elaborated and implemented into a circuit simulator using both developed models. Theoretical and experimental results show the reliability of EM, PA models and the mixed simulation approach as well. The originality of this work is the elimination of isolator between PA and antennas while maintaining a correct radiation pattern despite high antenna impedance mismatches.

This paper describes a new method that enables time domain pulsed RF measurements with any sub-sampling system. The method consists of replacing the FFT with a rectangular windowed short-time Fourier transform (STFT). The algorithm automatically extracts Fourier co-efficients within the pulses and the system does not need any trigger signal or clocking circuit. This minimal software modification enhances the standard Large Signal Network Analyzer (LSNA), enabling pulsed measurements without any hardware modifications. Our algorithm has been tested with a wideband amplifier at 1.5 GHz.

This paper proposes a high sampling rate, 4-channel Track and Hold Amplifier based time-domain measurement setup. It achieves an equivalent high sampling rate using Coherent Time Interleaved Sampling (CTIS) technique to accurately characterize high Power amplifiers driven by repetitive pulsed RF large signal. The acquired samples are the combination of non-sequential sub-sampling technique and the measurement system based on the use of Track and Hold amplifiers to avoid Intermediate Frequency (IF) aliasing and IF filtering. This principle is applied to the large signal pulsed characterization of S-band 50 W GaN amplifier. Fully calibrated acquired time-domain waveforms and power characteristics under varying load conditions are presented. To the authors knowledge the transients at the beginning and end of pulses are measured and exhibited for the first time.

International audience; This paper describes a mixed simulation approach of electromagnetic (EM) macromodel and nonlinear circuit bilateral model to correct the output signal for a power amplifier (PA) and obtain an optimal radiation pattern for an active antenna array transmit (TX) chain. Various experimental results show the reliability of EM, nonlinear PA models and mixed simulation approach as well. The originality of this work is the elimination of isolators between PAs and antennas while maintaining a matched PA and a correct radiation pattern in regards to the antenna's high impedance mismatch.

AlInN/GaN HEMTs have shown outstanding power performances for high frequency applications, due in particular to their high current densities and their thinner barrier layers than in AlGaN/GaN HEMTs that minimize short channel effects. In this paper, we present the first published power results of two K-band hybrid amplifier demonstrators at 20GHz and 26.5GHz using 0.25µm gate length devices. At these frequencies, respectively, cw RF output power of 4.5 Watts with 20% PAE and 1.65 W with 15.5 % of PAE were obtained. These state-of-the-art results confirm the potential of AlInN/GaN technology for high frequency applications.

International audience; In this paper Low Frequency (LF) parasitic effects are assessed through three kinds of measurements. It is shown that LF S-parameters measurements allow to extract the thermal impedance of Heterojunction Bipolar Transistors (HBTs) and to put dispersive effects of AlGaN/GaN High Electron Mobility Transistors (HEMTs) into evidence. Large signal (RF pulsed and two tone intermodulation) confirm the impact of those parasitic effects on performances of Power Amplifiers.

International audience; We propose in this paper a 4-channel time-domain test bench for the characterization and linearity enhancement of microwave power amplifiers (PAs). The proposed time-domain measurement system utilizes four track and hold amplifiers (THAs) for direct subsampling of radiofrequency (RF) signals. The use of wideband THAs to replace samplers or mixers enables reducing analog IF circuit complexity. It permits direct digitization of RF signals like CW, two-tone and pulsed modulated signals, bringing more flexibility in the receiver's performance by enhancing the dynamic range and bandwidth. This test bench is capable of completely extracting the phase, amplitude, and transfer characteristics of non-linear devices excited with CW or modulated RF signals. In this work, two-tone transfer characteristics of a 50 W GaN HEMT Nitronex PA were extracted and processed for applying digital pre-distortion linearization to enhance linearity performance. Time-domain envelope and carrier waveforms (voltage and current) along with third-order inter-modulation distortion (IMD) products with and without digital pre-distortion scheme are also presented.

This paper presents an internally-matched packaged GaN HEMT for achieving not only high-efficiency and high-power performances but also wide bandwidth and insensitivity to harmonic terminations in S-band. The internal matching circuits of the optimized package enable to reach a wider bandwidth and to confine the harmonic impedances seen by the internal GaN powerbar into high-efficiency regions whatever the external impedances presented to the package. In a 50Ω environment, the packaged GaN HEMT delivers 45 W output power with more than 55% PAE from 2.9 to 3.7 GHz (24% relative bandwidth). By optimizing source and load impedances at the 1st-harmonic, the packaged GaN HEMT demonstrates 50 W output power with more than 60% PAE over 21% bandwidth.

The design of agile active antennas requires an efficient modeling methodology in order to quantify the impact of other components on the array radiation pattern, and especially the influence of power amplifiers (PA). Therefore, the performance prediction of PA on TX chains is of prime importance. This article describes two different approaches for active antenna applications. The first one concentrates on PA macro-modeling, which takes into account a large output load impedance mismatch with a voltage standing wave ratio up to 4:1. A PA behavioral model based on nonlinear scattering functions was developed and extracted from CW measurements. The model validity was checked by comparison with the measured data. The second one describes a novel technique for synthesizing a given radiation pattern, whereas taking into account the mutual coupling and calculated matching impedances (ZL ≠ 50 Ω) of each antenna in the array according to frequency and pointing angle.

We propose in this paper a time-domain test bench for the pulsed characterization of a high Power GaN Amplifier. Our findings are based on a Track and Hold Amplifier for the down-conversion of RF spectra using the sub harmonic sampling principle. The use of wideband THA to replace samplers or mixers enables reducing component density in an analog domain. It permits direct digitization of entire pulsed RF spectrum, bringing more flexibility in the receiver's performance by enhancing the dynamics and bandwidth. This test bench is capable of completely extracting the phase, amplitude and pulse profile of the RF signal. Power characteristics, phase and amplitude information for multiple bursts of pulses of a 50 W GaN HEMT Nitronex (NPTB00050B) power amplifier have been measured using the proposed calibrated measurement system. The low frequency memory effects (thermal and trapping) of high power GaN amplifier were also measured.

International audience; Today's increase of functions, improvement of performance, and cost reductions required on an active electronically scanned array (AESA), associated to the limited amount of available areas and volumes to implement the equipment, drive an approach leading to directly connect power amplifiers (PAs) to the antennas array without placing an isolator/circulator between them. In this letter, an electromagnetic/radio frequency (EM/RF) circuit mixed simulation technique will be theoretically introduced and experimentally demonstrated on transmission (Tx) chains to deal with the proposed challenge.

International audience; This paper reports on the design of new power cells based on GaAs PHEMT transistors with 0.25μm gate length in MMIC technology. The design starts from a fishbone power cell initially designed by United Monolithic Semiconductors (UMS). This one allows us to validate the elementary transistor model. This model is used for other power cells design as cascode cell.

International audience; This paper proposes a packaged transistor modeling using lumped elements. This model allows studying the input impedance dispersion when a range of variation is applied to various package components. This dispersion is also highlighted when a load impedance variation is applied to the package transistor. It is demonstrated that this dispersion can be corrected using a specific input pre-matching and by having a very good information about input return loss contours. Moreover, this specific packaged transistor presents input impedance close to 50Ω over [3.0-3.8]GHz.

International audience; A study of the electrical performances of AlInN/GaN High Electron Mobility Transistors (HEMTs) on SiC substrates is presented in this paper. Four different wafers with different technological and epitaxial processes were characterized. Thanks to intensive characterizations as pulsed-IV, [S]-parameters, and load-pull measurements from S to Ku bands, it is demonstrated here that AlInN/GaN HEMTs show excellent power performances and constitute a particularly interesting alternative to AlGaN/GaN HEMTs, especially for high-frequency applications beyond the X band. The measured transistors with 250 nm gate lengths from different wafers delivered in continuous wave (cw): 10.8 W/mm with 60% associated power added efficiency (PAE) at 3,5 GHz, 6.6 W/mm with 39% associated PAE at 10.24 GHz, and 4.2 W/mm with 43% associated PAE at 18 GHz.

International audience; In this paper a two-stage 2-GHz GaN HEMT amplifier with 15-W output power, 28-dB power gain, and 70% power-added efficiency (PAE) is presented. The power stage is designed to operate under class F conditions. The driver stage operates under class F-1 conditions and feeds the power stage with both fundamental and second harmonic components. The inter stage matching is designed to target a quasi-half sine voltage shape at the intrinsic gate port of the power stage. The goal is to reduce aperture angle of the power stage and get PAE improvements over a wide frequency bandwidth. In addition to the amplifier design description, this paper reports original time-domain waveform measurements at internal nodes of the designed two-stage power amplifier using calibrated high-impedance probes and large signal network analyzer. Furthermore, waveform measurements recorded at different frequencies show that aperture angle remains reduced over large frequency bandwidth. In this study, a PAE greater than 60% is reached over 20% frequency bandwidth.

This paper presents the results obtained on X-Band GaN MMICs developed in the frame of the Korrigan project launched by the European Defense Agency. GaN has already demonstrated excellent output power levels, nevertheless demonstration of excellent PAE associated to very high power in MMIC technology is still challenging. In this work, we present State-of-the-Art results on AlGaN/GaN MMIC amplifiers. An output power of 43W with 52% of PAE was achieved at 10.5 GHz showing that high power associated with high PAE can be obtained at X-band using MMIC GaN technology.

International audience; this paper presents a time domain envelope measurement system that enables the study and the optimization of high efficiency and linear power amplifiers by applying both envelope tracking and digital base band predisrtorsion techinques. A main focus of this paper is the description of the set up architecture along with its capability to achieve in depth investigations on the dynamic behavior of envelope tracking amplifiers (ET PAs). to reach optimal efficiency and linearity performances ET PAs need to be accurately characterized under dynamic operating conditions in order to perform a well suited control of RF input envelope and bias voltage tracking signals. The proposed set up is applied here to a 10 W GaN Power amplifier from Cree at 3.6 GHz.

International audience; The design of reconfigurable active antennas requires an efficient system simulation in order to analyze the impact of other components on the array pattern, especially the Power Amplifiers (PA) effect. Therefore, the performance prediction of PA on Tx-Rx chains is important. This paper presents a behavioral model of a PA, which is able to take into account the load impedance mismatch with a VSWR (Voltage Standing Wave Ratio) up to 3. The proposed behavioral model, based on non-linear scattering functions, is extracted from simple CW measurements, and then implemented in Agilent Advanced Design System (ADS). Our behavioral model is validated by comparison with measurement results in the case of loading impedance mismatch (VSWR ≤ 3). Another model was validated (expansion of Taylor series to the second order), taking into account large VSWR (VSWR =3.5).

International audience; This presented study focuses on the impact of gate-source voltage waveforms on power added efficiency performances of GaN HEMTs for the design of class F and class F-1 amplifiers. It is shown that second-harmonic signal injection at the gate port of transistors can lead to efficiency improvements in the case of class F operation and efficiency deteriorations in the case of class F-1 operation. This work is applied to a 15 W GaN HEMT die from Cree at a fundamental frequency Fo equal to 2 GHz. Calibrated on-wafer time domain measurements are reported.

We present here a new set of equations for modeling the I–V characteristics of Field Effects Transistors (FETs), particularly optimized for AlGaN/GaN HEMTs. These equations describe the whole characteristics from negative to positive breakdown loci, and reproduce the current saturation at high level. Using this model enables to decrease the modeling process duration when a same transistor topology is used for several applications in a T/R module. It can even be used for switches design, which is the most demanding application in terms of I–V swing. Moreover, particular care was taken to accurately model the first third orders of the current derivatives, which is important for multione applications. We also focused on an accurate definition of the nonlinear elements such as capacitances for power applications. There are 18 parameters for the main current source (and six for both diodes Igs and Igd). This can be compared to Tajima's equations-based model (13 parameters) or to the Angelov model (14 parameters), which only fit the I–V characteristics for positive values of Vds. We will detail here the model formulation, and show some measurements/modeling comparisons on both I–V, [S]-parameters and temporal load-pull obtained for a 8 × 75 μm GaN HEMT, with 0.25 μm gate length.

International audience; Activities have been carried out to determine the best electrical operating conditions of GaN HEMT that enable maximum power added efficiency at L-Band for Switch Mode Power Amplifiers (class F, inverse class F and class E). Satellite Radio navigation applications (Galileo) are targeted. Maximization of power added efficiency is of prime importance to save DC power consumption, reduce self heating effects and improve reliability of power amplifiers. At 50V drain bias, a maximum power added efficiency (PAE) of 72% and 40.3 dBm output power (Pout) are obtained using class-F operating conditions at 2dB gain compression while a 75% PAE and 41.0 dBm Pout are obtained using class E at 3dB gain compression.

International audience; The first part of this paper deals with curled shunt capacitive MEMS switched varactors with good power handling capabilities. These devices have been able to achieve 1 billion cycles under 5 W in hot switching conditions. These cantilevers have been used as switched capacitors periodically loaded along a Coplanar Wave Guide (CPW) line to form a Distributed MEMS Transmission Line (DMTL) phase shifter. In the second part, the integration of these beams in 90° and 180° DMTL sections operating at 15 GHz is shown. For these respective configurations, phase shifts of 89.3° and 178° have been observed and validate this conception. With reasonable loss of 60°/dB, these devices are among the first MEMS based phase shifter in literature able to operate at such power level in hot s witching conditions.

International audience; This paper presents a novel pulsed I/V measurement methodology applied to HBTs characterization using very narrow 40 ns pulse widths. The measurement procedure consists in applying pulsed collector emitter voltages while driving the transistor base with constant DC currents. The proposed measurement technique is applied here to the characterization and electro-thermal modeling of InGaAs/InP DHBTs from Alcatel Thales III-V Lab. By monitoring pulse widths from 400 ns down to 40 ns, non isothermal, quasi isothermal and isothermal behaviors of transistors are observed respectively. Measurements and simulations are then done to study electro-thermal effects in bipolar current mirrors.

International audience; This paper presents a calibrated 4 channel broadband time-domain measurement system for the characterization of nonlinear microwave devices. The hardware architecture of the proposed measurement system is described with particular emphasis on the samplers and intermediate frequency (IF) circuit configuration. The sampling heads are working at a high strobe signal repetition frequency that can be tuned between 357 MHz and 536 MHz. 40 GHz RF frequency bandwidth is achieved. The calibration procedure of this system is also described. This instrument is then used for cross-modulation characterization of a 15W GaN HEMT CREE power amplifier at S Band. Cross-modulation measurements between a double side band amplitude modulation and a single tone signal at a 60 MHz offset frequency are performed to illustrate the capabilities of the proposed system. Time-domain waveforms are measured and variations of amplitude and phase modulation indices versus input power are recorded.

International audience; This paper deals with non-linear modeling of power GaN HEMT and design of power balanced cascode cell for wideband distributed power amplifiers. The active device is a 8times50 mum AlGaN/GaN HEMT grown on SiC substrate. The cascode die is flip-chipped onto an AlN substrate via electrical and mechanical bumps. This GaN-based cascode cell is dedicated to act as the unit power device within a broad-band capacitively-coupled 4-18 GHz distributed amplifier.

This paper presents the results obtained on X-Band GaN MMICs developed in the frame of the Kerrigan project launched by the European Defense Agency. A new step was achieved, 58 W of output power with 38% PAE in X-Band were obtained using an 18 mm 2 2-stages amplifier. To our knowledge, these results present a new state-of-the-art of X-Band MMIC power amplifiers.

This paper presents a behavioral modeling approach for solid state power amplifiers (SSPAs) used in Radar applications. This model takes into account strong output loading impedance mismatch, with a VSWR (voltage standing wave ratio) equal to two. The proposed behavioral model, based on non-linear Scattering functions, is extracted from simple CW measurements or Harmonic Balance (HB) simulations. This model has been implemented in a general purpose system simulation environment, Scilab/Scicos, thanks to a toolbox dedicated to solving implicit problems. In this paper, the proposed behavioral model is extracted from HB simulation results of an S-band 20 Watt power amplifier. Our macromodeling methodology is validated by comparisons of circuit and behavioral model simulations under pulse signal excitation in the case of loading impedance mismatch. This work has the financial support of the DGA (French defence and security agency).