A Distinctive Parallel R–C Matching Technique for Nonlinearity Reduction in GaN MMIC PA for FMCW Radar Applications

A 50 W dual‐band high‐efficiency gallium nitride (GaN) high electron mobility transistor (HEMT) power amplifier with a three‐stage L‐type DC bias circuit capable of individually adjusting second‐harmonic impedances is proposed for 1.8 and 2.6 GHz frequencies. The output network of this power amplifier is composed of an output matching network comprising five‐stage transmission lines and a three‐stage L‐type DC bias circuit with three L‐type circuits and one transmission line. The one‐stage L‐type circuit comprises a series transmission line and a quarter‐wavelength open‐ended shunt stub. For the high‐efficiency performance of the power amplifier, the output matching network is matched to the optimum impedances of the fundamental frequencies, and the DC bias circuit optimizes the impedances individually at the second‐harmonic frequencies without affecting the matched fundamental frequency impedances in the output matching network. Measured results show that the proposed dual‐band GaN HEMT power amplifier achieved gains of 15.6 and 13.8 dB as well as maximum power‐added efficiencies of 70.5% and 66.3% with 47 dBm output power at 1.8 and 2.6 GHz, respectively.

This paper presents design, development and characterization of GaN based high power amplifier Monolithic Microwave Integrated Circuits (MMICs) at C-band and Ka-band. The MMICs are designed using GaN MMIC processes from UMS foundry. The C-band MMIC is designed using space evaluated $0.25\mu\mathrm{m}$ Gallium Nitride (GaN) High Electron Mobility Transistors (HEMT) process and the Kaband MMIC is designed using $0.15\mu$ m GaN HEMT process which is under space evaluation. On-wafer measurements of both the MIMICs were carried out. The C-band MIMIC exhibits output power, Power Added Efficiency (PAE) and Gain better than $ 43\mathrm{dBm},$43% and 25dB respectively. At Ka-band output power, PAE and Gain better than $ 38\mathrm{dBm},$ 30% and 18dB are achieved respectively. The MMICs are tested in test modules exhibiting similar performances. The paper also discusses about observed drain current runaway phenomena in GaN amplifiers due to gate leakage current. Importance of gate series resistor value selection is discussed to avoid this runaway and to prevent eventual burn-out of the chip transistor.

This review article investigates the current status and advances in Ku-band gallium nitride (GaN) high-electron mobility transistor (HEMT) high-power amplifiers (HPAs), which are critical for satellite communications, unmanned aerial vehicle (UAV) systems, and military radar applications. The demand for high-frequency, high-power amplifiers is growing, driven by the global expansion of high-speed data communication and enhanced national security requirements. First, we compare the main GaN HEMT process technologies employed in Ku-band HPA development, categorizing the HPAs into monolithic microwave integrated circuits (MMICs) and internally matched power amplifier modules (IM-PAMs) and examining their respective characteristics. Then, by reviewing the literature, we explore design topologies, major issues like oscillation prevention and bias circuits, and heat sink technologies for thermal management. Our findings indicate that silicon carbide (SiC) substrates with gate lengths of 0.25 μm and 0.15 μm are predominantly used, with ongoing developments enabling MMICs and IM-PAMs to achieve up to 100 W output power and 30% power-added efficiency. Notably, the performance of MMIC power amplifiers is advancing more rapidly than that of IM-PAMs, highlighting MMICs as a promising direction for achieving higher efficiency and integration in future Ku-band applications. This paper can provide insights into the overall key technologies for Ku-band GaN HPA design and future development directions.

Gallium Nitride (GaN) high electron mobility transistor (HEMT) is one of the promising candidates to replace existing switches in high-frequency high power converter applications. Reliability of GaN HEMT is an important issue for its commercial deployment. Online prognosis of this transistor ensures robust reliability for mission critical applications. Online prognosis requires identification of fault precursors which shows sensitivity to degradation. Although gate threshold voltage and gate leakage current are identified as fault precursors, Extraction methods of these parameters are offline. In this paper, on-state resistance (R DS, ON ) is investigated as an online fault precursor for GaN HEMT. Temperature variation during its operation results in irreversible damage to GaN HEMT. Adaptive thermal network based temperature estimation method using Extended Kalman Filter (EKF) is also proposed. A sequential Monte-Carlo simulation based data driven remaining useful life (RUL) estimation method is also proposed which can be applicable for schedule maintenance before breakdown. Experimental validation of these proposed methods have been presented.

: A key component of microwave telecommunication systems is the power amplifier (PA). The design parameters of a communication system, such as link performance, power budget, and thermal design are typically driven by the power amplifier's linearity, output power, and efficiency. These design parameters of PA are the key to ensuring an efficient system because the PA is the most power-consuming circuit in the communication system. In an effort to have students involved in this research area, the International Microwave Symposium (IMS) sponsored by IEEE Microwave Theory and Technique Society (MTT-S) has introduced a High Efficiency Power Amplifier Design Competition. In this report, we present a 2.8-GHz, 5-W, highly efficient PA based on a wide bandgap gallium nitride (GaN) high electron mobility transistor (HEMT) device (CGH 40010f from CREE). The PA design was presented at the 2010 IMS Student Design Competition and achieved the competition goal of output power greater than 5 W with a measured power added efficiency (PAE) of 61% at 2.8 GHz.

Wide bandgap gallium nitride (GaN) high electron mobility transistor (HEMT) has been extensively studied [1]. The material properties of GaN compared to competing materials are presented in Table I. The superior material properties high breakdown voltage, which allows large drain voltages to be used, leading to high output impedance per watt of RF power, and lower loss matching circuits. High current density of 2-D electron gas (2-DEG) leads to large sheet charge [2] and transistor area can be reduced resulting in high watts per millimeter of gate periphery. High saturated velocity leads to high saturation current densities and watts per unit gate periphery. These result GaN based HEMT are suitable for high-power and high-frequency monolithic microwave integrated circuit (MMIC) applications [3-5]. Due to these excellent material characteristics, the output power and efficiency of GaN power amplifier between L-band and Ka-band was not only more superior to the conventional LDMOSFETs and GaAs power amplifier, but also the die area can be reduced. The GaN HEMT can be operated at 42 V of V DS and even higher, while also demostrated the similar f T and f max with GaAs pHEMT. The high powers from GaN HEMT transistors at a wide frequency range have been reported form a single die up to several hundred watts [6-7]. However, these high power densities also present extreme power dissipation on the layouts and the semiconductor substrates. Nevertheless, the SiC substrates with a high thermal conductivity (> 330 W/mK) allows high power densities to be efficiently dissipated for practical drain efficiencies, preventing the extreme channel that would result due to self-heating with other substrate technologies.

In this work, a novel gallium nitride/aluminium gallium nitride (GaN/AlGaN) high electron mobility transistor (HEMT) structures, such as TiN as Schottky contact, HEMT with TiN as Schottky contact, and AlInGaN barrier layer are propounded and have analyzed its DC, RF performance parameters in comparison with SiO2‐based metal‐oxide‐semiconductor high electron mobility transistor (MOSHEMT) utilizing Synopsys Sentaurus technology computer‐aided design (TCAD) simulator. HEMT with TiN as Schottky contact and AlInGaN barrier layer is showing peak transconductance (Gm) of 135 mS mm−1, which is higher than HEMT with TiN as Schottky contact, that is, 117 mS mm−1. The device with TiN Schottky gate contact for the HEMT exhibits high cutoff frequency (fT = 20 GHz) and maximum oscillation frequency (fmax = 94.6 GHz) when compared with SiO2‐based MOSHEMT (fT = 12.8 GHz, fmax = 27.5 GHz). Introducing the AlInGaN barrier layer for the TiN Schottky contact‐based HEMT further increased the cutoff frequency (fT = 59.6 GHz) and maximum oscillation frequency (fmax = 324 GHz), indicating high frequency operation range for communication applications.

The design and simulation of a Ka-band power amplifier Monolithic microwave integrated circuits (MMIC) utilizing 0.15μm gallium nitride (GaN) high electron mobility transistor (HEMT) technology is presented. The power amplifier MMIC is three-stage design utilizing a total gate width of 1.6mm in the output stage. The staging ratio of the whole MMIC corresponds to 1:1.5:5 to achieve higher power added efficiency and output power. Output matching network is carefully designed to achieve broadband. The simulation demonstrates for the design 34-35.6dBm of output power with 22%-26% power added efficiency (PAE) between 26-32GHz. The dimensions of the design are 4×1.7mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

The Doherty power amplifier (PA) is widely recognized as one of the most promising power amplification techniques in wireless transmitters for both mobile terminals and base stations. In this paper, the efficiency enhancement that is achieved by the Doherty technique is briefly presented. Then, the impact of the finite OFF-state impedance of the peaking branch on the efficiency response of the Doherty PA is theoretically analyzed. For the practical validation, this problem is studied for laterally diffused metal oxide semiconductor (LDMOS) field effect transistors (FETs) as well as gallium nitride (GaN) high electron mobility transistors (HEMTs). It is demonstrated that GaN HEMTs processes superior material properties that make them very suitable for the design of high efficiency Doherty PAs. Lastly, an overview of recent implementations of GaN monolithic microwave integrated circuit (MMIC) Doherty PAs is presented.

This paper reports a new fully-integrated 2-stage S-band GaN (Gallium Nitride) HEMT (High Electron Mobility Transistors) MMIC (Monolithic Microwave Integrated Circuit) power amplifier (PA) QPA2935 in an overmold QFN (Quad Flat No-Lead) package. The MMIC PA uses Qorvo&#x2019;s high performance 40 V, 0.25 um, GaN-on-SiC process technology. Dimensions of the complete PA module are 4 mm &#x00D7; 4 mm &#x00D7; 0.8 mm. This PA delivers a typical 34.3 dBm (2.7 W) power, 54.8 % Power added efficiency (PAE) with 19.3 dB power gain under CW condition. It operates from 2.7 to 3.5 GHz.

A C-band high-power and high power added efficiency (PAE) high power amplifier (HPA) monolithic microwave integrated circuit (MMIC) fabricated by using 0.25 μm gallium nitride (GaN) high electron mobility transistor (HEMT) technology has been developed for phased array antennas. The MMIC operates in pulse conditions of 100 μs pulse width and 10% of duty cycle over the frequency from 5.2 to 6.8 GHz. The MMIC exhibits an output power of 45.7 dBm to 46.4 dBm and a power added efficiency (PAE) of 51.5% to 56.5% under a drain voltage of 30 V. The MMIC size is as small as 12.54 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , generating an output power density up to 3.48 W/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> over the chip area and up to 4.55 W/mm over the active periphery.

A novel large-signal gallium nitride (GaN) high electron mobility transistor (HEMT) model that focuses on and improves analysis and design of switching-mode power amplifiers (PAs) is presented in this letter. The proposed model can be constructed using standard DC and AC characterization measurements and easily implemented in any computer-aided design (CAD) software to simulate and design switching-mode amplifiers. The model can predict the behavior of a switching-mode PA accurately at saturation and, due to the proposed approach, also well in the weak compression region. Using the developed model, an inverse class-F PA is designed and fabricated for validation purposes. The prototype developed using the proposed model achieved power-added efficiency (PAE) of 67% for an output power of 36.7 dBm at 2.35 GHz. Comparison between simulation and measured results of the manufactured PA proves the validity and accuracy of the proposed model.

This paper proposes Microstrip non-Foster circuit (NFC) enhanced high efficiency high power class-J GaN HEMT (gallium nitride high electron mobility transistor) amplifier. The NFC enhances the performance of the power amplifier (PA) by cancelling the power transistor's input parasitic capacitance. The PA was designed based on Cree's CGHV40030FP GaN HEMT biased with drain supply voltage of 50 V at quiescent drain-to-source current (I DSq ) of 15 mA. The NFC is part of the input matching network and contains two GaN HEMTs biased with drain supply voltage of 20 V at IDSq of 3 mA. The PA operates from 2.0 to 2.2 GHz. The NFC negative capacitance at 2.1GHz center frequency stood at −2.4 pF. The NFC PA has output power of 43.9 dBm (24.5 W), 69.3% drain efficiency, 66.4% power added efficiency (PAE) and transducer power gain of 11.9 dB.

In order to meet the application requirements of radar networks for high efficiency and high second harmonic suppression (SHS) of power amplifiers, this paper proposes a C-band 30 W power amplifier (PA) microwave monolithic integrated circuit (MMIC) based on 0.25 μm gallium nitride (GaN) high electron mobility transistor (HEMT) process. The proposed PA uses a two-stage amplifier structure to achieve high power gain. A topology with SHS is designed in the output-matching network. Besides, the large signal model load pull simulation and the harmonic control technology in the output stage are used to improve efficiency. The high-power additional efficiency (PAE) and high SHS of the PA MMIC are achieved simultaneously. In the 5–6 GHz frequency range, multiple indicator measurements of the proposed PA show that output power is over 45 dBm, the PAE is more than 57%, the SHS exceeds 45 dBc, the power gain is greater than 24 dB, which are conducted under the condition of 100 μs pulse width and 10% duty cycle. In addition, the size of the PA MMIC, including bonding pads, is 3.3 × 3.1 mm2.

A new design approach of Rat-Race coupler based compact GaN HEMT power amplifier towards flat high efficiency over broadband