A novel Technique for Linearizing Digital Pre-distortion in Power Amplifiers for OFDM Applications

In this paper, a novel technique is proposed for linearizing digital pre-distortion in poweramplifiers for OFDM systems. For this purpose, a hybrid technique comprising search tablemethod and polynomial method is employed such that as few as hardware are utilize inimplementation in order to not only decreases computational complexity but also leads to afast response capability. Furthermore, least mean square (LMS), as a competitive method,was employed in the proposed technique. Coefficients of look-up table are estimated by LMSmethod as a forward program with the least error amount in order to estimate modulatoroutput of OFDM. In addition, designing of several RF power amplifiers and theirlinearization unit in ADS software results in elimination of non-linear distortions of theseamplifiers by linearizing unit, and yet various realistic involved phenomena in base-bandpre-distortion system design, including memory effect, antenna mismatch, and etc., arestudied. Measures such as ACPR were adopted for the purpose of linearizationmeasurement and comparison. High The peak-to-average power ratio (PAPR) is one of thebiggest problems in OFDM systems that by combining these techniques, we improve it. Theobtained results of the proposed technique are presented both by look-up table andfrequency spectrum of output signal. The results also indicate appropriate performance ofthe proposed technique. Simulations were carried out on ADS software, while final signaloutput was extracted by MATLAB.

Keywords:

Digital Pre-distortion , Power amplifier , Linearization , OFDM , Look-up table method , Polynomial method