L-band Broadband Amplifier Research

Multi -octaves broadband power amplifier is key component of broadband RF front end, which is widely used in Software Radio, active phase-controlled radar array and synthesized aviation electronic equipments. The 4W power amplifier in this research, with bandwidth of 400～2000MHz, comes from a national defense project about software radio. Generally, 1000MHz is interface in RF circuits because circuits before and after it have different forms. The design difficulty of power amplifier in this paper is rapidly increase for its bandwidth covers low frequency and microwave. There is no report in both home and abroad. The researcher studied widely and deeply in power device, large signal, broadband matching networks and nonlinear analysis technique. Main work includes: ■Nonlinear model of power transistor ■Design method of broadband matching network ■Harmonic balance nonlinear analysis technique ■Load pull measurement and its realization in software ■Broadband Lange coupler design Finally, a 4W broadband power amplifiers were designed. A bandwidth of 400～2000MHz, a maximum output power of 36dBm with fluctuation of ±1dB,.a input VSWR <2.4:1, a second harmonics restraint of -20.15dBc and PAE of 29% at 1.5HGz has been achieved with 8V supply. All measurements results agree highly with design ones to testify that the design approaches in this paper is feasible and accurate. Critical technique the project starves for was achieved. Experts in the institute speaked highly on it.