Research On Q-band Solid State Amplifier

The solid state power amplifier is widely used in the preceding stage drive of electronic vacuum power amplifier,like traveling-wave tube,klystron and carcinotron,as well as electronic countermeasure,specified test system,wireless communication system and various military and civil satellites.Restricted by its semiconductor materials,the output power of MMIC is not high.In order to meet the system's demand for middle and high power,the most common way is to use power combiner technology to improve out power.This paper aims at design of unit solid state power amplifier in Q-band,as well as design of power combiner network.As for the design of unit solid state power amplifier,transiting the waveguide to microstrip is the first step.For the frequently used waveguide-microstrip transition structures,the author conducts modeling,simulation,optimization on them in the HFSS,the electromagnetic simulation software,and measure these transition structures.The result shows that within 42-46 GHz working band,the transition loss of waveguide-ridge waveguide-microstrip transition structure is less than 0.55 dB,and its reflection coefficient of input port is less than-17 dB.However,the connecting of ridge waveguide and microstrip,there is a large discrepancy among those test results.For transition structure of waveguide-microstrip H plane,its reflection coeffient is less than-18 dB and transition loss less than 0.6 dB within 42-46 GHz working band.It has simple equipment and small error.After analyzing the advantages and disadvantages of those transition structure,transition structure of waveguide-microstrip H plane is chosen to design the unit solid state power amplifier.Based on four-port network basic theory of magic T power divider,two high-isolated power dividers are designed,which within 42-46 GHz working band,their reflection coefficient of input port is less than-17 dB,and the amplitude of the two output ports is quite coherent,Within 0.2 dB,the isolation of the two output ports is less than-20 dB.According to the radial waveguide theory,a 8-way power divider is designed based on rectangular waveguide-coaxial waveguide transform structure and characteristics of coaxial waveguide TEM mode.Within 42-46 GHz working band,its reflection coeffieent is less than-25 dB,and amplitude consistency of the output port for every way is less than-0.18 dB.The radial waveguide is based on coaxial TEM mode,which regards the narrow side of waveguide as the shared port.Thus,the increase of ways of power divider would lead to the increase of its volume.Radical waveguide based on Circle Waveguide TE01 mode is put forward,which regards the longer side as the shared port.So 20-way power divider is designed,whose reflection coefficient is less than-15 dB,and the amplitude consistency of output port for each way is less than 0.15 dB,within the 42.5-45.5GHz working band.Based on the waveguide-microstrip H plane transition structure,unit solid state power amplifier is designed.The test results show that within 42-46 GHz working band,the maximum output power is 1.78 W.There is some gap between the maximum power and the saturate output power,as indicated on the microarray handbook,2W.Finally,this paper analyzes the cause.