The Research Of Satellite-based X Band GaN Solid-state Power Amplifier Technology

With the development of space technology, satellite communication has higher demands on transmitters. Power amplifier, as a key module of a transmitter, the higher efficiency, broader bandwidth, smaller size, good stability are its eternal design goals. TWTA and GaAs SSPA, as popular amplifiers used in X band, which are either expensive in price, large in volume, or low in output power and efficiency, could not combine the requirements stated above. GaN power devices, due to the development of GaN semiconductor technology, are of properties of high output power, high gain, broad bandwidth, high efficiency, good stability, which are suitable for high power and broad bandwidth design applications. The purpose of the thesis is to develop a x-band 30-W-output-power Ga N solid state power amplifier principle prototype.This thesis firstly introduced the characteristics of GaN amplifier devices, GaN’s advantages compared with GaAs device, the present development situation at home and abroad, and puts forward the design goal of the thesis. Then thesis introduced the basic theory of power amplifier designing, as well as the main design indexes. In chapter 3, thesis introduced the load-pull test technology that used for actual working characteristics’ extraction under large signal state, the deembedding technology using for small signal extraction and the principles of TRL calibration technology that relevant to those technologies. This thesis mainly accomplished the following work in PA designing:(1) through the analysis of demands and performance comparison of multiple devices, the paper made the three-level PA scheme, where SGK7785-30 A is used as the GaN device;(2)Accomplished the design of fixture, TRL calibration kit, and the load-pull test which determined the working impedance of the PA, then designed and simulated matching network, bias network, circuit principle and the whole circuit in turn;(3)designed and optimized layouts, test cavity of the PA then manufactured the PA, then tested PA and analyzed the results.Test results showed that the PA achieved 30 W output power with the GaN’s PAE over 35%,PA’s efficiency over 30% and the gain over 36 dB under CW operation, while its gain flatness less than 1 dB from 7.7-8.5GHz. The PA’s physical size is only of 150 x 100 x 26 mm3. The GaN SSPA demonstrated obvious advantages over GaAs SSPA of the same frequency band on output power, efficiency, gain and bandwidth.