The Study Of S-band Gan Hemt Balance Power Amplifier

GaN wide Bandgap Semiconductor microwave power devices and circuits have a broad application prospects in phased array radar system and other military and civilian fields of microwave power, because of its high current density, high power density, low noise and excellent frequency characteristics. Nowadays many research works are underway from material improvement fabrication development to device optimization. An increasing number of microwave power amplifier based on GaN HEMTs have been demonstrated. The object is a part of the research objective"Wide-adaptive-dynamic-range-matched Power Amplifiers Based on Wide-gap Power Devices"which is to develop high-performance S-band power amplifier based on GaN HEMT devices. In this dissertation the studies were focused on the development of S band HMIC power amplifiers based on the GaN High Electron Mobility Transistor bought from Nitronex.Several research results are introduced in the following:The key design technologies were researched about the HEMT power amplifier,such as circuit topology,efficiency mode,large signal optimization design,and circuit stability.A circuit design flow was set up.In addition ,the mainly studies in this paper were the multi-stage power amplifier cascading technology, the power synthes was technology and the circuit stability technologies: According to the impedance characteristics of HEMT devices,a new two-stage cascade structure of power amplifier was proposed in this paper.That was matching the input impedance of the first-stage power amplifier and the output impedance of second-stage power amplifier to 30 ohms which was close to the output impedance of the first-stage power amplifier. Using this method, the size of the matching circuit was reduced evidently. The application of Lang coupler and Wilkinson power divider were researched to power synthesis. An effective method for eliminating low-frequency oscillation is proposed, that is, a complex lossy LCR absorbing network is placed between gate electrode of GaN HEMT and ground. The high gain of lower frequencies is reduced outside of working band and low frequency oscillation is eliminated. Besides, the gain and VSWR performance change unobviously in working frequency band.A S-Band Balanced Power Amplifier was developed successfully which was coupled with Lange coupler. With the gate bias of-1.75V and the drain bias of 28V, the small-signal S parameter test shows that from 2.7 ~ 3.5GHz, the linear gain is 21~22.5dB, VSWRin<1.2, VSWRout<1.8. At 3.5GHz, pulse signal test, the maximum power is46dBm, the maximum PAE is 33.2% .A S-Band single-stage Balanced Power Amplifier was developed successfully which was coupled with Wilkinson coupler. With th gate bias of-1.6V and the drain bias of 28V, the small-signal S parameter test shows that from 2.7 ~ 3.5GHz, the linear gain is9.6~12 dB, VSWRin<1.8, VSWRout<1.6. At 3.5GHz ,the maximum pulsed-output power is 45.6dBm, the maximum PAE is 30%.