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Doherty Feed-Forward Amplifier Performance Using a Novel Crest Factor Reduction Technique
Kim, Wan-Jong,Cho, Kyoung-Joon,Stapleton, Shawn P.,Kim, Jong-Heon THE INSTITUTE OF ELECTRICAL ENGINEERS 2007 IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS Vol. No.
<P>This letter describes a novel iterative crest factor reduction (CFR) technique applied to a Doherty feedforward linear power amplifier (DFFLPA). This novel CFR technique is based on repeated peak cancellations and uses a scaling factor to reduce complexity. According to our results, only three iterations result in over 4-dB reduction for a two carrier WCDMA signal. Experimental results demonstrate that the proposed algorithm was able to enhance the DFFLPA system efficiency from 11.5% to 18.3%</P>
기지국 안테나 배열을 이용한 FDD 방식의 무선통신 시스템에서 송신 빔 형성을 위한 주파수 변환 방식
오성근,Shawn P.Stapleton 대한전자공학회 1997 電子工學會論文誌, S Vol.s34 No.5
We consider transmission beamforming techniques for frequency-division-duplex (FDD) wireless communication systems using adaptive arrays to improve the signal quality of the array transmission link. We develop a simple effective transmission beamforming technique based on an approximated frequency tranlsation (AFT) to derive the tranmsiion beamforming weights from the uplink channel vector. This technique exploits the invariance of the short-time averaged fast fading statistics to small frequency translations. A simple approximate relationship that relates the transmission channel vector to the reception channel vector is derived. We have developed its practical alternative in which the frequency translation of the channel vector is performed at the principal angle of arrival (AOA) of the u;link synthestic angular spectrum instead of the mean AOA. To analyze the performance of the proposed methods, we consider the power loss incurred by applying the estimated channel vector instead of the true downlink channel vector. The performance is analyzed as a function of the mean AOA, the angular spread, the number of elements, frequncy difference between the uplink and the downlink, and the angle distribution. Their performance is also compared with that of the direct weight reuse method and the AOA based methods.
Design of RF Pre-Distortion Linearizer for Various Transfer Characteristics of Power Amplifiers
Dong-Hee Jang,Kyoung-Joon Cho,Sang-Hee Kim,Jong-Heon Kim,Shawn P. Stapleton 한국전자파학회JEES 2003 Journal of Electromagnetic Engineering and Science Vol.3 No.2
We propose a diode-based RF pre-distorter with various gain and phase characteristics, for non-linearity compensation of RF power amplifiers. This pre-distorter results in the removal of the diode- and configuration-characteristics in the conventional diode-based RF pre-distorters. We have analyzed the operation principle of the proposed pre-distorter. The results show that gain and phase characteristics of the pre-distorter in all four quadrants are achieved. Several power amplifiers and test signals are used for verifying the performance of the proposed diode-based RF pre-distorter.