Research On Power Amplifier Based On GaN HEMT Device

With the rapid development of data communications, wireless communications and aerospace systems, the RF power amplifiers have been one of the more important components in the field of phased array radar, point to point wireless communications and electronic warfare systems. High power, high efficiency, low cost and miniaturization have become the current research trends of power amplifiers. As the representative of the third generation of semiconductor material, GaN has gradually replaced the second generation of semiconductor materials such as GaAs, because GaN has the advantage of wide band gap, high electron mobility, high breakdown field, high thermal conductivity, chemical stability and strong anti-radiation. The GaN HEMT power devices with high power density, working frequency, high temperature high pressure, etc., has become an ideal device for solid state power amplifiers.In this thesis, the main research works are focused on the design of high power and broadband amplifiers using GaN HEMT devices, as listed in follows:Firstly, the design of an S-band high-power GaN-based power amplifier (PA) from 2.7GHz to 2.9GHz was carried out. The design of the multi-stage PA and the biasing circuit are investigated seperately, including the four stages of power amplifiers which delivers about 50dBm of saturated output power in class AB and the bias control channel which provides special bias and power sequencing for GaN HEMTs. Overall circuits operating are designed, fabricated and measured. The measured results show that the maximum output power of 100 Watts (pulsed peak power) was expected from 2.7 to 2.9 GHz with resulting gain more than 50 dB and PAE beyond 35%, which match well with simulation.Secondly, the method of broadening the bandwidth of the power amplifiers was investigated. Based on the configuration of balanced amplifier, one wideband GaN power amplifier was designed, including broadband matching network, power divider network, bias circuit, and thermal analysis with GaN HEMT. The simulation results indicated good performace for the broadband power amplifier from 1GHz to 3GHz. The circuits prototyped using printed circuit board were measured. Good agreement betweem the measurements and the theoretical simulations verified the validity of the design strategies.