In this paper we present the study and obtained results of a MMIC High Power Amplifier operating in X-band. The device is designed using 250nm GaN HEMT on SiC process. The targeted specifications include pulsed operation from 8 to 10.5GHz. In pulsed mode and 28V of drain voltage, an output power more than 40W with (37-40)% PAE has been achieved throughout the bandwidth, while remarkable 52.4W output power with associated 37% PAE has been recorded at 8.75GHz for a 32V of drain voltage. The HPA stability has been studied by considering the influence of external decoupling components and dedicated testing environment

Diego Arroyo, Laura

Drissi, M'Hamed

Fourn, Erwan

Haentjens, Benoît

Herrera Guardado, Amparo

Mjema, Charles Alphonce

English

UCrea

Over 40W, X-Band GaN on SiC MMIC AmplifierCharles A. Mjema#, Benoı̂t Haentjens#, Erwan Fourn*, M’Hamed Drissi*,Laura Diego Arroyo#, Amparo Herrera Guarardo^#VECTRAWAVE, 4 rue Ampère, 22300 Lannion, France*Univ Rennes, INSA Rennes, IETR, UMR CNRS 6164, F-35000 Rennes, France^UNICAN, University of Cantabria, 39005 Santander, Cantabria, Spain{charles.mjema, benoit.haentjens, laura.diego}@vectrawave.com, {erwan.fourn, mhamed.drissi}@insa-rennes.frAbstract — In this paper we present the study and obtainedresults of a MMIC High Power Amplifier operating in X-band.The device is designed using 250nm GaN HEMT on SiC process.The targeted specifications include pulsed operation from 8 to10.5GHz. In pulsed mode and 28V of drain voltage, an outputpower more than 40W with (37-40)% PAE has been achievedthroughout the bandwidth, while remarkable 52.4W outputpower with associated 37% PAE has been recorded at 8.75GHzfor a 32V of drain voltage. The HPA stability has been studiedby considering the influence of external decoupling componentsand dedicated testing environment.Keywords — MMIC, Gallium Nitride (GaN), High PowerAmplifiers (HPA), X-band, Radar.I. INTRODUCTIONWide-band High Power Amplifiers (HPA) are keycomponents in modern RADAR transceivers and point topoint communication systems. Their design requires a trade-offamong targeted frequency bandwidth, output power and poweradded efficiency (PAE). In addition, good reliability and hightemperature operation must be considered during the designanalysis. Gallium Nitride on Silicon Carbide process canoffer a junction temperature higher than 200◦C with morethan one million hours of median time to failure which isfar better compared to Gallium Arsenide [1]. Its ability todeliver high power density in a small area allows low payloadtransceiver structures and high level of module integration [2].For that type of high output power devices, it becomes morechallenging to design an efficient heat sink while preservingRF performance. This is why thermal management has to betaken into account from die layout design in order to improveheat dissipation in a more compact cooling system. In othercases, particular brazing materials can help to improve heatdissipation from the die backside to the heat sink [3].In recent years, numerous works on GaN amplifiersat X-band have been reported, which show a promisingimprovement to obtain the desirable performances in terms ofoutput power and PAE [4]–[10]. However, in a wide microwavefrequency band is still a challenge to achieve simultaneouslyhigh level of output power and PAE at a low input drive. Thiswork reports measured performance and design methodologyof an X-band MMIC amplifier fabricated by using commercialavailable GaN on SiC technology. In order to reduce amplifierdevelopment time, combiners and dividers of each stage weredesigned separately, then after being integrated into the globalarchitecture they were re-tuned by observing the evolutionof output power for each stage. S-probes were inserted ineach stage to control the matching condition between optimumsource and load impedance obtained from load-pull analysiswith their respective input and output transistor’s impedance.The complete design is based on a compact three-stagesamplifier topology.II. HPA DESIGNA. Transistor selectionOur goal was to design an HPA that can deliver accross thebandwidth (8-10.5GHz), an output power more than 46.1dBm(40W), with more than 35% of associated PAE, at an inputpower less than 25dBm. Transistor baredie samples of differentsize from our foundry were characterized and load pullsimulation was also done using the foundry PDK. From abovementioned analysis, a unit power cell of 170μm gate widthwas selected for the output stage. It gives a maximum outputpower of 38.3dBm (6.5W) and peak PAE of 55% at 10GHzfor an optimum load and source impedance of (14+j21)Ω and(2+4j)Ω respectively as shown in Fig.1a.Fig. 1b shows fundamental load impedance for outputpower (red) and PAE (blue), from 8 to 11 GHz simulatedfrom drain and gate plane of the selected output cell for aninput power of 27dBm and source impedance of (2+4j)Ω. Loadpull study has been conducted for second harmonic and thirdharmonic frequency range in order to gives us a scope onhow we can minimize those harmonics by using appropriatematching elements [11], [12].In Fig. 2 we show analysis which has been done ona unit cell of output stage at 10GHz for fixed optimumsource impedance of (2+4j)Ω. Blue curves from graphs (a)to (c) represent small and large signal performance whenthe transistor is matched to the load impedance that givesmaximun power (14+j21)Ω, while red curves represent smalland large signal performance when transistor is matched toits output impedance (7-j28)Ω. We can conclude that theimpedance to obtain maximum power is not close to the outputimpedance of the transistor. Hence, this increases the difficultyto achieve simultaneously high output power, high PAE andlarge bandwidth with good output return loss.978-2-87487-060-6 © 2020 EuMA 11–12 January 2021, Utrecht, The NetherlandsProceedings of the 15th European Microwave Integrated Circuits Conference265Authorized licensed use limited to: BIBLIOTECA DE LA UNIVERSIDAD DE CANTABRIA. Downloaded on February 15,2021 at 15:54:52 UTC from IEEE Xplore.  Restrictions apply. (a)(b)Fig. 1. Simulated unit output power cell. (a): Load-pull contours at 10GHz,Pout (red dot), PAE (blue bold). (b): Load impedance at fundamentalfrequencies [8-11GHz], Pout (red), PAE (blue) and load impedance foroptimized output combiner (pink) (Pin=27dBm, VDS=28V, Idq=30mA).(a) Pout vs. Pin (b) PAE vs. Pin(c) S(2,2) vs. freqFig. 2. Impedance matching conditions for a unit cell at 10GHz using 2different loads at constant optimum source impedance (2+j4)Ω. (blue squarecurves: performance at optimum impedance for maximum power, red dotcurves: performance at output impedance for best output return loss, VDS=28V,Idq =30mA).B. HPA architecture selectionIn order to meet our design goals mentioned at thebeginning of section II, a three stages amplifier topologyhas been adopted in order to give high linear gain above30dB which will helps to use low output power externaldrivers. Eight transistors with total gate width of 1.36mmeach are used for the output stage in order to deliver thedesired output power. Each stage was biased in class ABwith drain voltage of 28V and total quiescent current of200mA. The ratio between the third and second stages isaround 3:1. Fig. 3 shows the proposed amplifier synoptic.Our MMIC is comprised of two identical structures, north andsouth, combined together. Each structure includes three stagesamplifier chain with independent decoupling circuits.Fig. 3. Proposed amplifier synoptic.On the die, after decoupling location, we have decided tolink gate and drain accesses of stages 1 and 2 together. Suchconfiguration helps users to minimize the number of externaldecoupling components.RC circuits in series at each gate were used to minimize theoccurrence of low frequency oscillations which linked to lowfrequency high gain value of FET transistor. The odd-modeoscillation has to be suppressed by inter-drain resistors whosevalues were chosen after STAN analysis [13]. In order topreserve enough gain at second and third stages, RC circuitswere optimized to ensure a trade-off between K factor andthe maximum available gain. Their values are set to be highcompared to those located at the input driver.C. Matching Network StrategyFrom the selected optimum load impedance, aneight-to-one port combiner is designed. Reactive matchingelements required to transform the selected impedance to 50ohm were directly incorporated to this combiner. Using seriesof T-mode LC elements in distributed and lumped form, it hasbeen possible to match the impedance and reach the targetedbandwidth ratio of 27%. The insertion loss of designed outputcombiner was less than 0.7dB throughout the bandwidth. Thesame technique was used for inter stages combination anddivision as well as input divider.When all combiners/dividers and active devices areintegrated together, S-probes were used to read the impedance266Authorized licensed use limited to: BIBLIOTECA DE LA UNIVERSIDAD DE CANTABRIA. Downloaded on February 15,2021 at 15:54:52 UTC from IEEE Xplore.  Restrictions apply. presented by those matching network against the input/outputimpedance of transistor. The current probes help to trace theevolution of output power from input stage to the last stage. Bydoing so, it has been possible to re-optimize the structure andto achieve good trade off between output power and returnlosses despite the difference observed between transistor’soptimum load impedance and output one see (Fig. 2). In Fig.1b, we show the optimized load impedance of a designedoutput combiner (pink curve), which is between the load formaximum power (red) and maximum PAE (blue) but closerto the first in order to achieve the targeted output power. Thewidth of drain lines for output stage is directly linked to thepeak biasing current reached during high power operations.D. Stability AnalysisTo ensure the stability performance for this amplifier, bothexternal and internal stability analysis were carried out byusing existing trust tools such as the Rollet factor (K) andSTAN study. Using K-factor tool, only external small-signalstability analysis is performed and simulation results show thatthe amplifier is unconditionally stable. For internal stabilityof each active device, a current source has been appliedat the drain and gate location of each stage in order tointroduce perturbing signal and see its response. Linear andnonlinear pole-zero identification methods were performed toensure amplifier stability during small-signal and large-signaloperations. The variation of gate voltage toward internaloscillation has been also analyzed. Poles and zeros show tobe on negative side to all analyzed nodes, which implies thatour amplifier was stable toward the odd-mode oscillations [14].III. RESULTSFabricated amplifier was brazed on a copper carrier andappropriate biasing networks were included on both sides ofthe MMIC. The carrier was mounted to the dedicated heatsink with radiator which helps to improve heat dissipation. Fig.4 presents under probes measurement setup for the proposedamplifier.Small-signal measurement was done at 28V of drainvoltage with a quiescent current of 200mA. We observe a goodagreement between the measured and simulated results. in thefull operating bandwidth an input and output matching levelsare lower than -10dB and -8dB respectively as shown in Fig.5.Large signal measurements were taken for pulse width of10μs and duty cycle of 10%. Fig. 6 illustrates the resultswhen the device was biased at 28V and 200mA of quiescentcurrent. More than 46.1dBm (40W) of output power with aPAE of (37-40)% from 8GHz to 10.5GHz frequency rangehave been measured at 24dBm of input power, which is ingood correlation with our targeted application. More precisely,for that range of input power, a GaAs amplifier device can beused as an external input driver for this type of GaN/SiC HPA,offering a higher linearity regime to the system chain.The MMIC was then tested under same pulsed conditionwith drain voltage of 32V. At this voltage the MMIC deliversan output power of 47.2dBm (52.4W) with a maximum PAEof 37% at 8.75GHz for 24dBm of input power as shown inFig. 7.Fig. 4. Fabricated MMIC on Test fixture.Fig. 5. Under-probes measured (solid line) and simulated (dotted line)linear gain, input and output return losses versus frequency for the proposedamplifier, (VDS=28V, Idq=200mA).Fig. 6. Measured (solid line) and simulated (solid dotted line) Pout, Gain andPAE versus frequency for the proposed amplifier, (Pulse width= 10μs, Dutycycle= 10%, Pin=24dBm, VDS=28V, Idq=200mA).267Authorized licensed use limited to: BIBLIOTECA DE LA UNIVERSIDAD DE CANTABRIA. Downloaded on February 15,2021 at 15:54:52 UTC from IEEE Xplore.  Restrictions apply. Table 1. Comparison with other state-of-the-art 250nm AlGaN/GaN X-band HPARef Freq(GHz)Pulse/Duty(μs/%)Pout(W)PAE(%)Power Gain(dB)VDS(V)This work 8-10.5 10/10 40-45 37-40 >22 28This work 8-10.5 10/10 42-52 33-37 >22 32[4] 8.8-10.8 100/10 30-40 38-44 18 28[5] 8.5-10.5 10/1 50-58 30 13-15 35[6] 9-11 20/10 35-45 40-52 16.3 25[7] 7.8-8.8 CW 22.5 50 19.53 28[8] 8.8-10.4 50/15 14 38-44 18 26[9] 8-12 100/10 56-74 40-45 21.5-22.7 28[10] 9 20/1 58 38 14.6 32Fig. 7. Measured Pout and PAE versus frequency for the proposed amplifier,(Pulse width= 10μs, Duty cycle= 10%, Pin=24dBm, VDS=32V, Idq=220mA).IV. CONCLUSIONIn this paper, we have presented the design methodologyand the results obtained for a High Power Amplifier MMICoperating from 8 to 10.5GHz. Different analysis and strategieshave been presented in order to ensure better performances andbest trade-off in terms of output power, PAE and bandwidth.Under pulsed measurements the device demonstrates an outputpower higher than 46.1dBm (40W) with more than 37% ofassociated PAE. The performances of this MMIC put its selfin a good position compared to other state-of-the arts workspreviously reported (Table 1).REFERENCES[1] L. B. Walker et al., “Handbook of RF and Microwave Power Amplifiers,”Cambridge University Press, pp. 305, 424, 530, 2012.[2] M. van Heijningen, G.C. Visser, J. Würfl, and F.E. van Vliet, “S-BandAlGaN/GaN Power Amplifier MMIC with over 20 Watt Output Power,”2008 Proceedings of the 3rd European Microwave Integrated CircuitsConference, Oct. 2008.[3] Raymond S. Pengelly, Simon M. Wood, James W. Milligan, ScottT.Sheppard and William L. Pribble, “A Review of GaN on SiC HighElectron-Mobility Power Transistors and MMICs,” IEEE Transactionson Microwave Theory and Techniques, vol. 60, no. 6, Jun. 2012.[4] Dong-Hwan Shin, In-Bok Yom, and Dong-Wook Kim, “X-band GaNMMIC power amplifier for the SSPA of a SAR system,” IEEEInternational Symposium on Radio-Frequency Integration Technology(RFIT), pp. 93–95, 2017.[5] C. Costrini, A. Cetronio, P. Romanini, G. Breglio, A. Irace, and M.Riccio, “50W X-band GaN MMIC HPA: Effective Power Capabilityand Transient Thermal Analysis,” Proceedings of the 5th EuropeanMicrowave Integrated Circuits Conference, pp. 408–411, 2010.[6] S. Piotrowicz, Z. Ouarch, E. Chartier, R. Aubry, G. Callet, D. Floruit,J.C.Jacquet, O. Jardel, E. Morvan , T. Reveyran , N. sarazin, andS.L. Delage, “43W, 52% PAE X-Band AlGaN/GaN HEMTs MMICAmplifiers,” IEEE MTT-S International Microwave Symposium, pp.505–508, 2010.[7] A.M. Couturier, N. Poitrenaud, V. Serru, R. Dionisio J.J. Fontecave, andM. Camiade, ”50% High Efficiency X-Band GaN MMIC Amplifier forSpace Applications,” 48th European Microwave Week Conference, pp.352–355, Sep. 2018.[8] Davide Resca, Antonio Raffo, Sergio Di Falco, Francesco Scappaviva,Valeria Vadalà, and Giorgio Vannini, ”X-Band GaN Power Amplifierfor Future Generation SAR Systems,” IEEE Microwave and WirelessComponents Letters, vol. 24, no. 4, pp. 266–268, Apr. 2014.[9] Hong-Qi Tao, Wei Hong, Fellow, IEEE, Bin Zhang, and Xu-Ming Yu,“A Compact 60W X-Band GaN HEMT Power Amplifier MMIC,” IEEEMicrowave and Wireless Components Letters, vol. 27, no. 1, January2017.[10] S. Piotrowicz et al., “State of the art 58W, 38% PAE X-bandAlGaN/GaN HEMTs microstrip MMIC amplifiers,” 2008 IEEECompound Semiconductor Integrated Circuits Symposium, Oct. 2008,pp. 1–4.[11] Jangheon Kim, Junghwan Moon, Jungjoon Kim, Slim Boumaiza,and Bumman Kim, ”A Novel Design Method of Highly EfficientSaturated Power Amplifier based on Self-Generated Harmonic Currents,”European Microwave Conference (EuMC), pp. 1082–1085, 2009.[12] Ji Lan, Jianyi Zhou, Zhiqiang Yu,and Binqi Yang, ”A broadband highefficiency Class-F power amplifier design using GaAs HEMT,” IEEEInternational Wireless Symposium (IWS), pp. 1–4, 2015.[13] Natanael Ayllon, Juan-Mari Collantes, Aitziber Anakabe, IboneLizarraga, Geoffroy Soubercaze-Pun, and Stephane Forestier,“Systematic Approach to the Stabilization of Multitransistor Circuits,”IEEE transactions on microwave theory and techniques, pp. 2073–2082,Aug. 2011.[14] A. Anakabe, S. Mons, T. Gasseling, P. Casas, R. Quere, 1.M. Collantesand A. Malet, ”Efficient nonlinear stability analysis of microwavecircuits using commercially available tools,” European Microwave WeekConference, pp. 1017–1020, 2002.268Authorized licensed use limited to: BIBLIOTECA DE LA UNIVERSIDAD DE CANTABRIA. Downloaded on February 15,2021 at 15:54:52 UTC from IEEE Xplore.  Restrictions apply. 

Over 40W, X-Band GaN on SiC MMIC amplifier

International audienceIn this paper we present the study and obtained results of a MMIC High Power Amplifier operating in X-band. The device is designed using 250nm GaN HEMT on SiC process. The targeted specifications include pulsed operation from 8 to 10.5GHz. In pulsed mode and 28V of drain voltage, an output power more than 40W with (37-40)% PAE has been achieved throughout the bandwidth, while remarkable 52.4W output power with associated 37% PAE has been recorded at 8.75GHz for a 32V of drain voltage. The HPA stability has been studied by considering the influence of external decoupling components and dedicated testing environment. © 2021 EuMA

Over 40W, X-Band GaN on SiC MMIC amplifier

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