Vhf Broadband Power Amplifier Is Developed

According to the development of wireless communication, Software-Defined Radio (SDR) has been proposed as new communication architecture in recent years. Because its high agility and opening, it has become the focus of the research on the design of wireless communication systems. Research of radio frequency wide-band power amplifier, which is one of the keys of Software-Defined Radio, has become more and more important. The development of SDR provides new ideas of design and higher demands to power amplifiers, and high performance power amplifiers have promote the development of SDR.The dissertation designs a wide-band power amplifier in view of the characteristic and demands of SDR. Firstly, several theories which we need to design wide-band power amplifiers are illuminated and researched in detail. There are three steps for the design: the selection of the first stage power amplifier, the research of the drive stage power amplifier and the last stage power amplifier. At first, biasing point is determined and stability is judged. The next step is to analyze the matching network of input and output according to S-parameters method, and get a suitable topological. By the technology of negative feedback and power back-off, stability and linearity are improved. System is simulated and optimized using Agilent ADS. Besides, DC power supply circuit is design to provide electrical source, on the other hand, filter the harmful high frequency and low frequency signals. Heat protection circuit is developed for cool the power amplifier. After debugging, the power amplifier achieves perfect performance.Finally, a VHF wide-band power amplifier is designed. A bandwidth of 108MHz—175MHz, a maximum output power of 40dBm with fluctuation of <±1dB, an input VSWR <2:1, an output VSWR <2:1, PAE of 50% has been achieved with 28V supply. All measurement results agree highly with design request.