The Digital Predistortion Method Research Of Power Ampliifer In Baseband Based On Wideband

Under the circumstance of rapid development of mobile communication, the userexperience and data transfer rate became higher and the shortage of spectrum resourcesavailably has become more crucial. Currently, most of the wireless communication systemsadopted the modulation technique based constant envelope, such as Gaussian-filteredMinimum Shift Keying (GMSK). The advantage of this modulation technique is that thenon-linearities in the channel have little effect for signal distortion, the PAs of class B andclass C can be used. However, they have low efficiency and always high-cost. Consequently,it is hoped that raising the efficiency of power amplifier as possible on the premise ofkeeping power amplifier linear.Predistortion technique is a linearization technique of power amplifier which has broadprospects for development. It can correct the non-linearities distortion of power amplifier bysetting a predistorter which has the inverse characteristic of power amplifier before thepower amplifier. This article focuses on the research of digital predistortion, especially thealgorithm of baseband digital predistortion. The major contents are as followed:1. The parameters and methods for measuring the distortion of power amplifier areintroduced systematically. Several common linearization techniques are reviewed andthen the basic principal of predistortion is introduced.2. In the research of digital predistortion for memoryless power amplifier, the memorylesspower amplifier is modeled first, and then the polynomial predistortion and look-uptable predistortion are discussed and simulated respectively. We focus on the implementmethod of predistorter based on look-up table in particular. The performance ofpredistortion system with different indexation techniques is analyzed and compared.And we propose a new segmented uniform LUT which making use of the input signal,the simulated results testify that this method is better that uniform LUT.3. In the research of digital predistortion for memory power amplifier, we focus on theresearch of Hammerstein predistortion based on modeling the memory power amplifier.In order to solve the problem of high time consumption of Hammerstein predistortion, anew memory predistortion method is proposed. This method can shorten the timeconsumption while achieving the almost same performance. The simulated resultsindicate that the new method can correct the non-linearities distortion of memory poweramplifier well, as well as the shorter time consumption than Hammerstein predistortion. 4. To validate the theory proposed in this dissertation by test bench and analyze the resultsexperimentally.