"Doherty Amplifier with Envelope Tracking for High Efficiency"
- Junghwan Moon, Junghwan Son, Jungjoon Kim, Ildu Kim, Seunghoon Jee, Young Yun Woo, and Bumman Kim

A Doherty amplifier assisted by a supply modulator is presented using 2.14 GHz GaN HEMT saturated power amplifier (PA). A novel envelope shaping method is applied for high power-added efficiency (PAE) over a broad output power range.

"Advanced Design of a Double Doherty Power Amplifier with a Flat Efficiency Range"
- Yong-Sub Lee, Mun-Woo Lee, Sang-Ho Kam, and Yoon-Ha Jeong

This paper reports a new double Doherty power amplifier (DDPA) with a flat efficiency range, which consists of two-stage amplifiers.

"Design of a Broadband and Highly Efficient 45W GaN Power Amplifier via Simplified Real Frequency Technique"
- David Yu-Ting Wu, Farouk Mkadem, Slim Boumaiza

Abstract — A comprehensive approach for designing broadband and highly efficient power amplifier based on optimal impedance analysis and simplified real frequency technique SRFT) is presented.

"Novel Wide Band High-Efficiency Active Harmonic Injection Power Amplifier Concept"
- Abdullah AlMuhaisen, Peter Wright, J. Lees, P. J. Tasker, Steve C. Cripps and J. Benedikt

This paper introduces a novel approach for the realization of wide band (>octave) high-efficiency (>95%) high Power Amplifiers (PAs).

"Evaluation of a GaN HEMT Transistor for Load- and Supply-Modulation Applications Using Intrinsic Waveform Measurements"
- Hossein Mashad Nemati, Alan L. Clarke, Steve C. Cripps, Johannes Benedikt, Paul J. Tasker, Christian Fager, Jan Grahn, and Herbert Zirath

In this paper, the efficiency of a GaN HEMT transistor and its intrinsic waveforms are measured at 0.9 GHz and investigated for load- and supply-modulation applications.

May 2010

"High Power, High Conversion, Gain Frequency Doublers Using SiC MESFETs and AlGaN/GaN HEMTs"
- Kelvin Yuk, G.R. Branner and Claudia Wong

A method of determining the optimal harmonic terminations using accurate nonlinear computer models and load- and source-pull simulations is described.

"Calibration of a Digital Phased Array Polarimetric Radar"
- Caleb Fulton, William J. Chappell

This paper discusses the challenges of polarimetric phased array calibration, and demonstrates these techniques using a linear array of eight S-band dual-polarized antennas connected to an active Digital Array Radar (DAR) prototype system.

"Nonlinear Characterization Techniques for Improving the Accuracy of GaN HEMT Model Predictions in RF Power Amplifiers"
- R. Marante, J. A. García, L. Cabria, T. Aballo, P. M. Cabral, and J. C. Pedro

Two vector nonlinear characterization procedures are presented, aimed at improving available GaN HEMT models for an accurate reproduction of the device behavior operating as a current source and in switched-mode RF PAs.

"Temperature Dependent Memory Effects on a Drain Modulated GaN HEMT Power Amplifier"
- R. Marante, L. Cabria, P. Cabral, J. C. Pedro, and J. A. García

In this paper, the impact of self heating on the linearity of a drain modulated GaN HEMT power amplifier (PA) is studied.

"A Class E Power Amplifier Design for Drain Modulation under a High PAPR WiMAX Signal"
- L. Cabria, P. M. Cabral, J. C. Pedro, and J. A. García

This paper describes the design of a class E PA destined to be used as the final stage of a polar transmitter under IEEE 802.16e Mobile WiMAX signal excitation. Based on a 60 W GaN HEMT device, the load condition for optimum efficiency is set close to the maximum value of the power generating function for an OFDMA modulating signal.

"FPGA-Based Set-up for RF Power Amplifier Dynamic Supply with Real-Time Digital Adaptive Predistortion"
- Pere Gilabert; Gabriel Montoro; Eduard Bertran; Jose A. Garcia

"Methodology for Realizing High Efficiency Class-J Linear and Broadband Power Amplifier"
- Peter Wright, Jonathan Lees, Johannes Benedikt, Paul J. Tasker, and Steve C. Cripps

The design and implementation of a class-J mode RF power amplifier is described. The experimental results indicate the class-J mode’s potential in achieving high efficiency across extensive bandwidth, while maintaining predistortable levels of linearity.

"High-Gain SiC MESFETs Using Source-Connected Field Plates"
- Saptharishi Sriram, Helmut Hagleitner, Dan Namishia, Terry Alcorn, Thomas Smith, and Bill Pulz

We demonstrate for the first time improvement of radio-frequency (RF) gain of SiC MESFETs by using source-connected field plates (FPs).

"A Highly Efficient Doherty Power Amplifier Employing Optimized Carrier Cell"
- Junghwan Moon, Young Yun Woo, Bummam Kim

A novel design of the Doherty power amplifier (PA) to improve the efficiency at a back-off output power level.

"A Novel Design Method of Highly Efficient Saturated Power Amplifier based on Self-Generated Harmonic Currents"
- Jangheon Kim, Junghwan Moon, Jungjoon Kim, Slim Boumaiza, and Bumman Kim

A novel design method without requiring the special harmonic termination circuit for a highly efficient power amplifier (PA) is proposed.

"Cree Speeds Development of High-Performance GaN Doherty Amplifiers by 70%" (AWR link)

Microwave office capabilities provide first-pass design success of complex 2.1-GHz circuits using GaN HEMTs

"Hybrid EER transmitter using Highly Efficient Saturated Power Amplifier for 802.16e Mobile WiMAX application"
- Ildu Kim, Jangheon Kim, Junghwan Moon, Jungjoon Kim, and Bumman Kim

Demonstrating a highly efficient Hybrid Envelope Elimination and Restoration transmitter for IEEE 802.16e Mobile WiMAX applications using a highly efficient saturated Power Amplifier (PA). For the optimum H-EER operation, the PA has been designed to have a maximum PAE at the average Vds region by using 10 W (P3dB ) GaN High Electron Mobility Transistor.

June 2009

A systematic and consistent approach to the thermal modeling and measurement of GaN on SiC HEMT power transistors is described.

Microwave Journal: Test Bench 2009 “Mesuro Demonstrates Record Efficiencies with Cree’s 10W GaN at IMS 2009”

A 10W GaN device from Cree achieving record efficiencies in excess of 81% was also demonstrated at IMS using an active harmonic load-pull capability from Mesuro, a new measurement company with ties to Cardiff University and Tektronix.

"Advances in high power GaN HEMT transistors" (MWEE Link)
- Simon Wood, Carl Platis, Don Farrell, Brad Millon, Bill Pribble, Peter Smith, Ray Pengelly, and Jim Milligan

This article discusses various uses of Cree’s GaN HEMTs (CGH21120, CGH25120, CGH40120) in standard and novel amplifier topologies. It includes the practical use of Cree’s proprietary large signal models.

"High-Power, High-Efficiency GaN HEMT Power Amplifiers for 4G Applications" (HFE Archive)
- Simon Wood, Ray Pengelly, Don Farrell, and Carl Platis, Cree, Inc., and Jim Crescenzi, Central Coast Microwave Design

New GaN HEMT devices allow the design of high power amplifiers with the desired linearity and efficiency for 4G applications such as WiMAX, UMTS and WCDMA.

"A Saturated Power Amplifier with High Efficiency" – MTT-5 Student Design Competition Winner (2008)
- Jangheon Kim, Junghwan Moon, Bumman Kim, and Raymond S. Pengelly

This article presents the design of the winning PA with PAE of 73.2% at 3.2GHz operating frequency, which is equivalent to the weighted PAE performance of 97.9% by students from Pohang University of Science and Technology (POSTECH).

"A High Efficiency Doherty Amplifier with Digital Predistortion for WiMAX" 2008 Edition (HFE Archive)
- Ray Pengelly, Simon Wood, Jim Crescenzi

This article describes a WiMAX power amplifier, which achieves high performance using the latest device technologies and design techniques.

“Design of GaN HEMT Transistor Based Amplifiers for 5 - 6 GHz WiMAX Applications”
- Bradley J. Millon, Simon M. Wood, Raymond S. Pengelly

2.5 and 5-watt average power (15 and 30-watt peak power) GaN HEMT amplifiers for WiMAX signal protocols have been designed and fabricated for use in the 5.5 to 5.8-GHz band.

"A High-Efficiency 100-W GaN Three-Way Doherty Amplifier for Base-Station Applications"
- Marco J. Pelk, W. C. Edmund Neo, John R. Gajadharsing, Raymond S. Pengelly, Leo C. N. de Vreede

A three-way Doherty 100-W GaN base-station power amplifier at 2.14 GHz is presented.

"Highly Efficient Operation Modes in GaN Power Transistors Delivering Upwards of 81% Efficiency and 12W Output Power"
- Peter Wright, Aamir Sheikh, Chris Roff, P. J. Tasker and J. Benedikt

• Interactive Forum paper from the 2008 International Microwave Symposium (IMS)
• Presentation Supplement

This paper investigates the development of an inverse class-F design procedure for obtaining very high efficiency performance at high power levels. RF waveform engineering was used to obtain high efficiency inverse class-F waveforms at the device current-generator plane.

"Application of Non-Linear Models in a range of challenging GaN HEMT Power Amplifier Designs"

- Raymond S. Pengelly, Brad Millon, Donald Farrell, Bill Pribble, and Simon Wood

Presentation from the 2008 IEEE MTT-S International Microwave Symposium (IMS) Workshop on Challenges in Model-Based HPA Design

This presentation discusses attributes of GaN HEMTs, Cree GaN HEMT models, design examples (Broadband CW Amplifiers and Linear WiMAX Amplifier), and future model improvements.

“Characterizing the Vdd-to-AM and Vdd-to-PM Nonlinearities in a GaN HEMT Class E Power Amplifier”
- J. A. García, B. Bedia, R. Merlín, P. Cabral and J. C. Pedro

An experimental procedure is proposed for accurately characterizing the Vdd-to-AM and Vdd-to-PM nonlinearities in a Class E power amplifier (PA). Based on GaN HEMT technology,...

"A High Power, High Efficiency Amplifier using GaN HEMT"
- Bumjin Kim, D. Derickson, and C. Sun

A class B and a class F power amplifier are described using a GaN HEMT device.

"A GaN HEMT Power Amplifier with Variable Gate Bias from Envelope and Phase Signals"
- Ellie Cijvat, Kevin Tom, Mike Faulkner, and Henrik Sjöland

This paper describes the design, simulation and measurement of a GaN power amplifier suitable for envelope and phase signal combination.

"A GaN HEMT Class F Amplifier at 2 GHz With >80% PAE"
- David Schmelzer and Stephen I. Long

A Class F amplifier has been designed, fabricated, and tested using a GaN HEMT transistor and hybrid printed circuit board (PCB) packaging.

"Applied Wave Research (AWR), Macquarie University and Cree, Inc. Success Story" (AWR Link)
- Michael Boers

Michael Boers, Ph.D. Student, Wins IEEE MTT-S Power Amplifier Competition, 85% PAE Achieved with Microwave Office and Cree, Inc. GaN HEMT.

"High Efficiency, High Linearity GaN HEMT Amplifiers for WiMAX Applications" 2007 Edition (HFE Archive)
- U. H. Andre, R. S. Pengelly, A. R. Prejs and S. M. Wood, and E. J. Crescenzi

An article in High Frequency Electronics about the recent advances in the use of Cree's GaN HEMTs for WiMAX applications.

Class-E Silicon Carbide VHF Power Amplifier
- Marc Franco and Allen Katz

This paper investigates the use of silicon carbide (SiC) metal-semiconductor field effects transistors (MESFETs) in high-efficiency, class-E, RF power amplifiers in the VHF range. A maximum drain DC to RF efficiency of 87% was predicted and 86.8% achieved.

"Energy Efficient Wide Bandgap Devices"
- John W. Palmour

As wide bandgap devices begin to become commercially available, it is becoming clear that electrical efficiency improvement is one of the key drivers for their adoption.

"A GaN HEMT Class F Amplifier at 2 GHz with > 80 % PAE"
- David Schmelzer and Stephen I. Long

A Class F amplifier has been designed, fabricated, and tested using a GaN HEMT transistor and a hybrid PCB.

"High Efficiency, High Linearity GaN HEMT Amplifiers for WiMAX Applications" 2006 Edition
- S. Wood, P. Smith, W. Pribble, R. Pengelly, and J. Crescenzi

An article in High Frequency Electronics about the use of Cree's GaN HEMTs for WiMAX applications.

"High-power GaN HEMTs battle for vacuum-tube territory"
- Yifeng Wu and Primit Parikh

The vacuum tubes used in today's millimeter-wave transmitters face an increasing threat from GaN HEMTs. Cree's Yifang Wu and Primit Parikh are leading the GaN charge with designs that incorporate field plates, iron-doped buffer layers and a thin AIN interlayer to deliver a record power at 30 GHz.

"A High Efficiency Class-E Amplifier Utilizing GaN HEMT Technology"
- William L. Pribble, Jim M Milligan, and Raymond S. Pengelly

• Abstract from the 2006 IEEE Topical Workshop on PAs for Wireless Communications (RWS)
• Presentation from the 2006 IEEE Radio and Wireless Symposium in San Diego

A class-E power amplifier based on a GaN HEMT cell has been designed and tested.

"A high linearity, high efficiency WiMAX power amplifier using SiC MESFETs"
- Simon M. Wood, Raymond S. Pengelly, William L. Pribble, Dustin E. Hoekstra

• Abstract from the 2006 IEEE Topical Workshop on PAs for Wireless Communications (RWS)
• Presentation from the 2006 IEEE Radio and Wireless Symposium in San Diego

This paper describes the results of a broadband, high linearity, high efficiency power amplifier for WiMAX basestation applications in the 3.3 - 3.9 GHz band.

"Application of GaN Class E Amplifers in EER/ET Amplifier Systems"
- D. Kimball, J. Jeong, C. Hsia, P. Draxler, P. Asbeck, D. Choi, W. Pribble and R. Pengelly

Class E amplifiers offer significant advantages for high efficiency operation, although they have been largely limited to relatively low microwave frequencies and/or low output powers. GaN HFETs are well suited to Class E at high powers and high frequencies, inasmuch as their output capacitance is particularly low for a device with a given output power, and has little voltage dependence.

"Semiconductor Hardnut"
- Dr. Mike Cooke

Silicon Carbide (SiC) has been proposed for some time as a substrate for high-speed, high-temperature devices, and products are now entering the market. Dr. Mike Cooke reviews some of SiC's device opportunities and tough process challenges.

"1 GHz, 200 ºC, SiC MESFET Clapp Oscillator"
- Zachary D. Schwartz and George E. Ponchak

A SiC Clapp oscillator fabricated on an alumina substrate with chip capacitors and spiral inductors is designed for high temperature operation at 1 GHz. The oscillator operated from 30 to 200 ºC with an output power of 21.8 dBm at 1 GHz and 200 ºC. The efficiency at 200 ºC is 15 %. The frequency variation over the temperature range is less than 0.5 %.

"Two-Stage Ultrawide-Band 5-W Power Amplifier Using SiC MESFET"
- Ahmed Sayed and Georg Boeck

This paper describes a two-stage 5-W broad-band amplifier covering the frequency range from 10 MHz to 2.4 GHz. The design procedure is given in detail, and the results are being discussed and compared with simulations.

"High Temperature Performance of a SiC MESFET Based Oscillator"
- Zachary D. Schwartz and George E. Ponchak

A hybrid, UHF-Band differential oscillator based on 10 W SiC RF Power Metal Semiconductor Field Effect Transistor (MESFET) has been designed, fabricated and characterized through 475 °C. The circuit is fabricated on an alumina substrate with thin film spiral inductors, chip capacitors, chip resistors, and wire bonds for all crossovers and interconnects.

“An Ultra Wideband 5 W Power Amplifier Using SiC MESFETs”
- Ahmed Sayed, Stefan von der Mark and Georg Boeck

A 5-watt wideband power amplifier using a SiC MESFET has been designed. The frequency range covers 10 MHz to 2.4 GHz with small-signal gain of 8 dB. A broadband choke structure with a new technique was developed to obtain good isolation and low loss over the desired bandwidth. Input and output matching networks and shunt feedback topology were introduced to increase the bandwidth.

"A Comparison between Class E Power Amplifiers Employing LDMOS FETs and SiC MESFETs"
- Raymond S. Pengelly

This paper demonstrates the use of optimized analytical procedures to design lossy Class E amplifiers at 1 and 2 GHz using Si LDMOS FETs and SiC MESFETs respectively. The designs use new large-signal models for the LDMOS FETs and SiC MESFETs which provide accurate simulations in both deep sub-threshold (Class C) and fully RF driven "on" states.

April 15, 2004

"Architectural benefits of wide bandgap RF power transistors for frequency agile basestation systems"
- George Fischer

This paper focuses on how specific characteristics of wide band gap RF power transistors at device level map to benefits at architectural level with those frequency agile systems.

"Design of a High Power Doherty Amplifier Using a New Large Signal LDMOS FET Model"
- Simon M. Wood and Raymond S. Pengelly

This paper describes the use of a new large signal LDMOS FET model in the design of a high power, UMTS band 60W Doherty amplifier. This new model will be shown to be capable of providing accurate predictions of power, gain, efficiency and most importantly, linearity of the complete amplifier.

“High Power Hybrid and MMIC Amplifiers Using Wide-Bandgap Semiconductor Devices on Semi-insulating SiC Substrates”
- S. T. Sheppard, R. P. Smith, W. L. Pribble, Z. Ring, T. Smith, S. T. Allen, J. Milligan and J. W. Palmour

An overview of hybrid and monolithic high-power microwave amplifiers using SiC MESFET and GaN HEMT active devices is presented. High power densities of 5.2 W/mm and 63% power added efficiency (PAE) have been demonstrated for SiC MESFETs at 3.5 GHz. This performance has driven the development of wide-bandwidth MMIC amplifiers, which have yielded 37 W of pulsed power at 3.5 GHz.

"High Linearity, Robust, AlGaN-GaN HEMTs for LNA & Receiver ICs"
- Primit Parikh, Yifeng Wu, M. Moore, P. Chavarkar, U. Mishra, R. Neidhard, L. Kehias, T. Jenkins

AlGaN-GaN HEMTs have not only been identified as the technology of choice for next generation high-power, high frequency applications but recently have also garnered interest for low noise receiver applications.