Changsi Wang

An Electrothermal Model for Empirical Large- Signal Modeling of AlGaN/GaN HEMTs Including Self-Heating and Ambient Temperature Effects

Accurate modeling of electrothermal effects of GaN electronic devices is critical for reliability design and assessment. In this paper, an electrothermal model for large signal equivalent circuit modeling of AlGaN/GaN HEMTs including self-heating and ambient temperature effects is presented. To accurately describe the effect of ambient temperature, two separate electrothermal networks (Idiss, Rdiss, and Cdiss for self-heating, and Iamb, Ramb, and Camb for ambient temperature effect) are used to describe drain-source current slump due to self-heating and ambient temperature effects, respectively. A temperature-dependent thermal resistance and thermal capacitance model is proposed and implemented in the electrothermal network. The extraction of the thermal parameters is fulfilled by using numerical finite-element method. Single tone on wafer load-pull measurements at two operating frequencies (3 and 14 GHz) are carried out for verification purposes. The results show that good agreements on fundamental output power, the second and third harmonics output power, and power added efficiency have been achieved between simulations and measurements over a wide range of -55 °C to 175 °C.

A scalable GaN HEMT large-signal model for high-efficiency RF power amplifier design

This paper presents a large-signal empirical model for GaN HEMT devices using an improved Angelov drain current formulation with self-heating effect and a modified non-linear capacitance model. The established model for small gate-width GaN HEMTs is validated by on-wafer load-pull measurements up to 14 GHz. Moreover, a scalable large-signal model is presented by adding scalable parameters to drain-source current and non-linear capacitance equations. The scalable model of a 1.25 mm GaN HEMT has been employed to design a class-AB power amplifier for validation purposes. The results show that good agreement has been achieved between the simulated and measured results with 37.2 dBm saturation output power (Psat) and 58% maximum power-added-efficiency at 3 GHz.

A Large-Signal Statistical Model and Yield Estimation of GaN HEMTs Based on Response Surface Methodology

A novel nonlinear large-signal equivalent circuit statistical model of GaN HEMTs based on response surface methodology (RSM) is proposed in this letter. Thirty-four GaN HEMTs from 10 batches are measured and all the parameters in the large-signal equivalent circuit model are extracted by an in-house parameters extraction program. We choose the four most sensitive parameters of the drain-source current model and the gate charge model. The statistical method is modeled by using response surface methodology to change the range of the four parameters. The statistical model is implemented in Agilent-ADS and three S-band GaN HEMT power amplifier are designed by using the established statistical model for validation. The results show that good accuracy has been achieved by comparing measured and simulated output power (Pout) and power added efficiency (PAE). This method is simple and accurate for GaN HEMT power amplifier design and yield estimation.

Flexible microwave filters on ultra thin Liquid Crystal Polymer substrate

In this paper, investigations about the applications of ultra thin Liquid Crystal Polymer (LCP) in flexible microwave filters are carried out. The LCP substrate of 50μm substrate thickness was offered as a double copper clad laminate with 18μm copper laminate thickness. First, a microstrip line are fabricated and measured to show the microwave transmission characterization at flat and bending condition. Then, for demonstration purpose, a X band band-pass filter and a stepped impedance low pass filter were designed and tested with overall LCP dimensions of 5.4 × 3.2 mm2 and 15.7×2 mm2,respectively. For the filters, good agreement between the simulated and measured S-parameters and compact sizes are obtained. The bending effects of the microstrip line and the band-pass filter are also measured and the measured data shows a very low susceptibility to the S-parameters due to bending behavior. The results show that ultrathin LCP substrate is a promising candidate for the miniaturization and flexibility applications in microwave devices.

Analysis of the Energy Output System for 5.8 GHz Magnetron

In this paper, a kind of microwave energy-output system of the 5.8 GHz 18-vane magnetron was designed and discussed. The QL of the anode was calculated by MAGIC3D. The impact on the energy output system by coaxial impedance converter and short plane of the waveguide was discussed and simulated by CST Microwave Studio. At last we give the structure size of the energy output system for engineering design reference.

A ultra-wideband empirical large-signal model for AlGaAs/GaAs HEMTs

An accurate large-signal GaAs HEMT modeling is very important for microwave and millimeter wave power MMIC amplifier design. This paper presents a complete GaAs HEMT model suitable for ultra-wide band application. The model is realized with an improved drain current (Ids) formulation with self-heating and charge trapping modification. This large-signal GaAs HEMT modeling is validated for a wideband frequency from 12GHz to 40GHz and can predict fundamental output power, gain, and power added efficiency accurately.

A novel compact Ka band fourth-harmonic image rejection mixer

Wth the commercial 0.15-μm pseudomorphic high electron mobility transistor (pHEMT) process, a novel compact Ka-band fourth-harmonic image rejection resistive FET mixer is designed in this paper. A compact Balun with two scale-down Lange couplers used for the impedance transformation is proposed for LO signal pump. The results show that less than 19.5 dB Conversion Loss (CL) in 32~38 GHz, more than 21 dB Image Rejection Ration (IRR) in 32~36.5 GHz, and better than 30 dB and 42 dB high isolation, from LO to RF and 4LO to RF, respectively, can be achieved by the proposed configuration. The chip size is minimized to 1.8 mm×1.4 mm.