| In this paper an L-band pulse power is designed based on Agilent ADS RF simulation software module for a radar transmitter system within the operating frequency range of 960 ~ 1225 MHz,its external dimensions are 124×45×25mm,the average output power is 25 W,it operates in a pulsed mode,the duty cycle is 10 %.The RF power amplifier basis is firstly described,including amplifier types,S-parameters,key performance indicators and the like. Then the main content of the pulse amplifier design:the bias circuit,pulse power technology were introduced and analyzed.This thesis focuses on describing pulse amplifier design process. RFPA system design is divided into two blocks including enlarge link and power supply module. The enlarge link consists of four levels of amplifier circuit, each amplifier circuit consists mainly by amplifier chip and its bias circuit and its matching network.The first three amplifiers do not work in saturation,so the small-signal S-parameter approach is used to design the matching circuit. The last amplifier has two choices: the first choice is a LDMOS amplifier,which works in saturation,and load traction approach is used to design its matching circuit;the second choice is an internally matched GaN amplifier. After the design of each amplifier,the resistive attenuator network was added to take away the excess gain in the front of the every input matching circuit of first three amplifiers,the isolator was added at the output port of the last amplifier to protect the amplifiers from unmatching loads.The power supply module of the former three amplifier consists of DC-DC circuit and 5V power modulation circuit,the power supply circuit of the LDMOS amplifier is consists of DC-DC circuit(generating positive gate voltage) and 50 V power supply modulation circuit,and the GaN power supply circuit is mainly consists of DC-DC circuit(generate negative gate voltage),temperature compensation circuit and 50 V power power modulation circuit.Finally,the design of PCB layout and cavity structure of the amplifier system were finished. In order to meet the dimensions of miniaturization design requirements, the paper finally select GaN as the final amplifier. a three-cavity structure was adopted as cavity structure, the upper chamber placed the final amplifier and temperature compensation circuit and a ring isolator,the middle layer of the cavity place the system power supply module,the lower chamber place the fomer three amplier circuit. |
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