A Miniaturized Solid-state Power Amplifier For FM Broadcasting

As an important part of the transmitter,the RF power amplifier plays an indispensable role in improving the communication quality.More and more Solid-state power amplifiers have been adopted by various RF microwave systems,because of their advantages of high reliability,long lasting,wide bandwidth,simple power supply,etc.The power amplifiers which used by FM radio transmitters have been basically completed the transition from tubes,klystrons,and other vacuum amplifiers to transistors(solid state).The output power is increased by combining the outputs of several identical transistor RF power amplifiers using power synthesis techniques.In order to increase the total output power,the output power of each transistor RF power amplifier was gathered by power synthesis technology.However,in the FM band,the size of power divider/combiner is very large which directly leads to the solid-state power amplifier occupies most of the space of the FM transmitter.Therefore,it is important to reduce the size of solid-state power amplifiers.The main works of the thesis as follow:(1)A miniaturized Wilkison power divider is designed and realized which is being used to distribute the input power.In order to reduce the size of wilkison power divider,the ?/4 transmission line was replaced by a new type of asymmetric impedance transformer.At the same time,the design formula of the asymmetric impedance transformer was given.The circuit is simulated with HFSS and then fabricated and tested.At the center frequency 98MHz,|S11|=-44.7dB,|S21|=-3.28dB,IS23|=-31.5dB.The size of the circuit is 0.034?g×0.034?g and the design realizes miniaturization.(2)A power amplifier operating at FM band is designed and realized,which is based on the MRF6V2010N.The power amplifier is used as a unit in the whole power amplification system.The circuit is simulated with ADS and then fabricated and tested.At the center frequency 98MHz,the gain is 23.5dB,output power up to 40.3 dBm,the PAE up to 58%.The design meets the requirements.(3)In order to gather the output power,a miniaturized Gysel power divider is designed and realized based on lumped component.The circuit is simulated with ADS and then fabricated and tested.The RF resistor which has high-power capacity was used as the isolation resistor.Besides,a heat sink is mounted under the resistor.Therefore,the Gysel power divider can work in a high power environment.The measured results show that |S11|=-31dB,|S21|=-3.28dB,|S23|=-42dB.The size of the circuit is 0.09?g×0.1?g and the design realizes miniaturization.(4)Assembling the designed units and the miniaturized solid state power amplifier was completed.The test results display that at At the center frequency 98MHz,|S11|=-44.7dB,the gain is 23.1dB,output power up to 20 W and the PAE up to 55.2%.The design meets the requirements of liaoning putian digital co.,LTD.