| The power amplifier is an integral part of modern mobile communication, whoseperformance has a direct impact on the transmission quality. In order to make the poweramplifier work with high efficiency, the power amplifier must work within the linearregion usually nearby the1dB compression point. With the wide application of signalspossessing the characteristics of broadband and high peak-to-average ration, thenonlinear distortion of the amplifier is more serious, which means increasingout-of-band spectrum and the bit error rate. The new signal transmission technology andthe new modulation mode both require the power amplifier has a large linear dynamicrange. Therefore, a variety of linearization techniques have been extensively researched.This paper conducts a systematic study of digital baseband predistortion techniques,and goes as follows:First of all, an introduction about the nonlinearity and memory effects of poweramplifier, with various power amplifier models of memoryless and memory, ispresented. After that, various kinds of linearization techniques are analyzed andcompared. Based on above analysis, an adaptive base band digital predistortion methodis deeply researched. Then the paper gives the simulation of this method based on theLMS and RLS algorithm and memory polynomial, also based on the LMS algorithmand different models.At last, the digital predistortion is realized in FPGA and applied in digital TVtransmitter. Digital up and down converter, compels parameters are implemented in theFPGA. This single-FPGA architecture avoids additional digital signal processor, reducesthe difficulty and complexity of the whole digital system. In the physical test, the inputsignal is8MHz; the power amplifier’s rated output power is280W. The test result showthat the digital predistortion system has a good linearization performance, which canreduce MER14.98dB, reduce side lobe about16dB. What’s more, the transmittersystem is of low-cost and good performance. |
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