PhD Defense: "Non-Linear MMIC Design using AlGaN/GaN HEMT Technology"

Valiallah Zomorrodian

July 1st (Friday), 10:00am
Materials Research Lab (MRL), Rm 2053

High output power and high efficiency are two desirable factors for RF/microwave power amplifiers. Higher power added efficiency (PAE) leads to less DC power consumption by the circuit, increasing the battery life and also relaxing the heat dissipation requirements, while high power density results in smaller, simpler circuitry. Monolithic Microwave Integrated Circuits (MMICs) are of great interest in RF/Microwave application due to their much smaller size compared to the hybrid circuit technology. Among the existing microwave device technologies, AlGaN/GaN high electron mobility transistor (HEMT) technology is rapidly emerging as a high-power, high-frequency device of choice for future wireless applications. AlGaN/GaN HEMTs have superior power-density and much higher breakdown voltage compared with other technologies and excellent power performance has been reported for devices as well as for MMIC power amplifiers.

The goal of this thesis is focused on demonstration of state of the art performance from highly non-linear MMICs using AlGaN/GaN HEMTs. In the area of high efficiency power amplifier design, we will study the limitations of the high frequency performance of class E and Class F MMIC power amplifier topologies, and demonstrate the work done in improving the circuit performance compared to the previous results. We will show the limitations of the class E power amplifier topology in achieving high efficiency power amplification at microwave, and demonstrate state of the art performance achieved from a MMIC class F power amplifier in C band.

In the area of frequency conversion circuits, we will demonstrate a state of the art frequency doubler MMIC designed at C band, and discuss the design challenges regarding the large signal modeling of the device and the implementation of the high Q resonant passives required to achieve high performance from this circuit.

The ability to successfully implement the AlGaN/GaN HEMTs into working circuits depends greatly on the accuracy of the available device model and the ability to accurately model and design the passive matching networks and tuning elements. In this work, a scalable non-linear large signal model was extracted for AlGaN/GaN HEMTs for use in circuit design and excellent match between simulations and measurements was obtained for the DC, small signal and power performance including load-pull and source-pull power and PAE contours. A systematic method for design of complex matching networks and tuning elements using Sonnet electromagnetic (EM) simulations was developed and excellent agreement between the equivalent circuit models, Sonnet simulations and measured s-parameter data from fabricated resonators and matching networks was demonstrated. We will show that these tools, along with our design approach in optimizing the performance of each circuit are the key to the high performance of the circuits presented in this work.

Host: Professor Robert York

Hosted by: Professor Robert York