Study On Key Technology Of The Rf Power Amplifier

With the rapid speed development of the communication, the increasing larger number users and limited spectrum recourse require higher and higher spectrum exploited and higher date ratio. RF Power amplifier, as one of the important components for the wireless communication base station systems, has a very important effect on the communication quality of the systems. The relative high power to average ratio which caused by the use of the multi-carriers, acquires that the RF power amplifier should have high linearity strongly, while the base stations acquire high efficiency as well as the terminal users. To improve the communication quality, RF power amplifiers are faced with the very severe challenges for higher linearity and efficiency. Therefore, more and more linearization and efficiency enhancement techniques have been adopted for RF power amplifier to settle these key problems.The dissertation study the methods to minimize the the eletrical memory and video bandwidth of the RF power amplifier. The first key work was focused on the Doherty power amplifier, which has a distinguished feature of active load pull effect as one of the efficiency enhancement techniques. Doherty RF power amplifier is characterized by its high efficiency for a wide range output power back off without using additional circuits. This is due to its special biases setup for the carrier amplifier and peaking amplifier which results in different kinds of working modes according to the input signal lever. The dissertation also study the outband rejection of the RF power amplifier.The dissertation theoretical analysis of the 2-way Doherty, N-way Doherty, Multiple -stage Doherty, On the analysis of the N-way Doherty, set different gate voltage of the peak amplifiers, and give the relationship of the impendence, current, voltage, efficiency, power between the normoalized input voltage. On the analysis of the 3-stage Doherty ,a novel 3-stage Doherty work principles and the requirements of working patterns in the low and high lever range are presented. Also gave the theoretical analysis the relationship of impendence, current, voltage, efficiency, power between the normoalized input voltage, gives the design of the novel 3-stage Doherty . On the theoretical analysis of the 3-way Doherty amplifier and inverted 2-way Doherty amplifier, an inverted 3-way Doherty structure is proposed, also gives the design of the inverted 3-way Doherty.Using the phase and impendence, a novel 3-stage Doherty with 52% efficiency for WCDMA systems is constructed in the dissertation with the help of the ADS'simulation, which can get high linear characteristics with the pre-digital distortion system. An inverted 3-way Doherty structure is used as last stage in a four stages cascaded Doherty power amplifier, which is constructed for CDMA mobile base station system, and which get high gain and high efficiency with the pre-digital distortion system in the dissertation.RF and microwave bandpass filter with wide band rejection is studied. On the theoretical analysis of interdigital capacitor, the dissertation gives the size of the structure calculate formulas. With the calculation formula and CST soft ware, the dissertation designes band pass filter with ultra-wide Stopband.