| In modern wireless communication system, the communication band has become moreand more crowded. Therefore, more stringent requirements of the linear indicators areproposed. Power amplifier is one of the most important device. Though we can improve thelinearity by simply backing off the input signal, the efficiency of PA will be very bad. Forthis reason, more advanced linearization techniques are needed to improve the linearity andmaintain a moderate efficiency. The commonly used linear technology are introduced, suchas the power back-off technology, negative feedback technology, predistortion technologyand feedforward technology. This paper mostly analyzes the analog predistortion.The design theory and the nonlinearity characteristics of power amplifers are introducedin the first place. Then, several different linearization techniques are analyzed and comparedbriefly.This design uses a cascade of MRF6V2150N and MRF6V2300N to constitute the PAand the output stage uses the structure of balanced amplifier. This article described in detailthe design steps of the main PA meanwhile shown the corresponding simulation results. Inaddition, designed and simulated the analog predistortion modules, including couplers, delaytimer and phase shifter. The result show that the system can achieve52dBm output powerand25%efficiency when frequency changes between259.9MHz and269.4MHz, and theIMD3has been suppressed to be less than-40dBc when the tone spaceing of two-tone inputsignal is6.6MHz.Then, The amplifier is manufactured after designed the PCB layout,considered the cooling of the amplifier and designed the cavity.At last, the overall test of the amplifier gives the test results and analysis of the smallsignal gain and large-signal single-tone test as well as two-tone signal linearity test and thesummary of every problems during the manufactured process. |
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