A Study on Linearization of Intermodulation Distortion for WCDMA

Jeon, Joong-Sung; Kim, Dong-il

Journal of Navigation and Port Research 2004;28(2):149-154.
Published online March 31, 2004.

A Study on Linearization of Intermodulation Distortion for WCDMA

Abstract

A linear power amplifier is particularly emphasized on the system using a linear modulations, such as 16QAM and QPSK with pulse shaping, because intermodulation distortion which causes adjacent channel interference and co-channel interference is mostly generated in a nonlinear power amplifier. In this paper, parameters of a linearization loop, such as an amplitude imbalance, a phase imbalance and a delay mismatch, are briefly analyzed to get a specific cancellation performance and linearization bandwidth. Experimental results are presented for IMT-2000 frequency band. The center frequency of the feedforward amplifier is 2140 ㎒ with 60 ㎒ bandwidth. When the average output power of feedforward amplifier is 20 Watt, the intermodulation cancellation performance is more than 28 ㏈. In this case, the output power of feedforward amplifier reduced 3.5 ㏈ because of extra delay line loss and coupling loss The feedforward amplifier efficiency is more than 7％ for multicarrier signals.

Key Words: Linearization;Feedforward;Delay line;Intermodulation