GaN HEMT Low Noise Device Modeling With High Efficiency Amplifier Design

Wide gap semiconductor gallium nitride （GaN） material posseses the advantagesof high density of two-dimensional electron gas and high breakdown voltage. It isideally suitable for power amplifier. Another advantage of GaN HEMT is that it is ableto withstand higher input power. It can be used to simplify the limiter circuits for lownoise amplifier in transceiver front-end. So low noise amplifiers and power amplifierscould be integrated in a single MMIC chip. The thesis contains the following works:1. Firstly briefly analyzing the working mechanism of GaN HEMT. GaN HEMTnumerical physical model is researched and then the traditional structure of GaNHEMT’s numerical physical model is established and comparisoned with the measureddata. On the basis of our model, we studied:（1） the influence of an aluminum nitride（AlN） inserted layer to the high frequency noise performance of the device. At8GHzHEMT with AlN Interlayer demonstrated that minnimum noise figure (NFmin)reducedby0.5dB, the noise conductance recuced by50%, and the current cut-off frequencyincreased by17%.（2） The noise performance of GaN HEMT with a recessed gatestructure at mm-wave band. At80GHz GaN HEMT with a recessed gate demonstratedthat NFmin reduced by1.2dB, the current cut-off frequency increased by10%,maximum oscillation frequency （fmax） increased by11%, and transconductanceincreased approximately40%.2. Secondly the traditional noise equivalent circuit model is changed method toovercome the disadvantage that it need enormous sets of test data for low-noiseamplifier noise equivalent circuit modeling. The model took gate-drain feedbackcapacitance into consideration to increase the high-frequency accuracy of the model.Empirical parameters were excluded form the model. No parameter fitting to predict thenoise performance of the device. A GaN HEMT low noise amplifier （LNA） isdesigned with this model and fabricated with domestic process line. Test results indicatethe gain more than13dB, gain flatness better than±0.5dB, and noise figure less than2.5dB from1.5GHz to4GHz.3. Thirdly designing an inverse Class F power amplifier (PA) with the output capacitance considered. The larger output capacitance of GaN HEMT prevent it fromachieving second harmonic open characteristers of inverse F PA. This article takes thecompensation of the external circuit design a GaN inverse class F power amplifier.Co-simulation results show that a power added efficiency better than60%, a gaingreater than6dB, and a output power greater than41dBm in the range of800MHzbandwidth at the center frequency of3.1GHz. The test results demonstrated a smallsignal gain greater than8dB from1.8GHz to2.35GHz, drain efficiency greater than65%, a output power greater than43.5dBm from1.95GHz to2.25GHz. The amplifierachieved maximum output power greater than45dBm and drain efficiency of70.03%at2.0GHz. It achieved maximum efficiency of75.68%and output power of44.7dBm at2.2GHz.