| With the development of the wireless communication technology, the request for the design of the wireless communication equipment is getting higher and higher. While with the unceasing promotion of the 3G technology, to design a base depot power amplifier of high efficiency, high power, and high linearity has been a big challenge. And the RF power amplifier is the radio RF transmitter's terminal, whose duty is to complete the baseband signal's modulation to the carrier, make it pass band signal, remove it to the needed frequency, and have enough power to launch the signal. The main function of RF power amplifier is to enlarge the RF signal, which is aimed at the high efficient output. The RF power amplifier is mainly applied to different kinds of wireless transmitter. The essences of the amplification of RF signal is conversing current power into high frequency power under the control of RF signal's input. As one of transmitter's most important parts, the quality of the RF power amplifier influences the entire communications system's performance. The RF power amplifier is the most important component in the communications system, and also the core equipment of base-station system.In this article the author mainly used the MRF621100H chip to design a RF power amplifier using 2140MHz center frequency. Because of its high request of gain and output power, this design adopted the method of three levels of cascades. To guarantee a better match and the isolation effect, the author put the Pi attentuator between the second level and the third level to carry out the adjustment. In order to improve the linearity of this RF power amplifier, in this article the author has carried out some theoretical summary research to common behavioral models of RF power amplifiers.The power amplifier is composed of three levels. The RF power amplifier's preamplifier of infrared system uses the ALM1322 chip to carry out the design, which may realize reaches as high as 29dB the gain; the output IP3 reaches as high as 35.6dBm, which lays solid foundation for the entire power amplifier system to achieve high gain of 56dB; The RF power amplifier's actuation level uses the highest linearity design, and use the ALM31222 chip in here to carry out the design, whose linearity is quite high. Besides, the output IP3 reaches as high as 47.9dBm, and also has the power to attach the efficiency to be quite high. All of these have a crucial effect on linearity enhancement of the entire power amplifier. The last stage power amplifier uses the design of big power tubes and big signals, which guarantees the high efficiency, the high power, the high linearity of the entire power amplifier in the working band. The author used the MRF621100H chip to carry out the design, which can achieve a gain of 16dB, and have a high output and the linearity. All the three levels of power amplifiers were strictly carried out according to the design procedures of the RF power amplifier. These procedures such as deciding design targets, choosing components, simulation and optimization and so on were carried out separately. The author used an attenuator as a disconnector to cascade, that is, to constitute the entire power amplifier, and the simulation result satisfied the design requirements completely. |
