An adaptive direct conversion transmitter

Author

Hilborn, Derek S. ; Stapleton, Shawn P. ; Cavers, James K.

Author_Institution

Sch. of Eng. Sci., Simon Fraser Univ., Burnaby, BC, Canada

Volume

43

Issue

2

fYear

1994

fDate

5/1/1994 12:00:00 AM

Firstpage

223

Lastpage

233

Abstract

An adaptive direct conversion transmitter is presented, in which adjacent channel power measurements are used to simultaneously compensate for both power amplifier (PA) nonlinearity and quadrature modulator (QM) errors. Three main contributions are given. First, analysis is presented which shows that adjacent channel power is a quadratic function of power amplifier nonlinearity as well as quadrature modulator errors. Quadrature modulator errors are gain imbalance, phase splitter error, and DC offset errors. Second, a new optimization method is given which uses the predicted adjacent channel power surface to obtain fast convergence. Third, simulation and measured results are given for an adaptive system using offset QPSK modulation. The measured results confirm the analysis and show that a 20-dB reduction in adjacent channel power is achievable. In general, the adaptive direct conversion transmitter has applications in any system where power efficiency and spectral efficiency are important, and allows the use of smaller more efficient power amplifiers in a direct conversion architecture

Keywords

adaptive systems; mobile radio systems; modulators; phase shift keying; power amplifiers; power measurement; radio transmitters; radiofrequency amplifiers; DC offset errors; adaptive direct conversion transmitter; adaptive system; adjacent channel power measurements; direct conversion architecture; gain imbalance; measured results; mobile radio communication; offset QPSK; optimization method; phase splitter error; power amplifier nonlinearity; power efficiency; quadratic function; quadrature modulator errors; simulation; spectral efficiency; Adaptive systems; Control systems; Error correction; Feedback; Frequency; Phase modulation; Power amplifiers; Power measurement; Predistortion; Transmitters;

fLanguage

English

Journal_Title

Vehicular Technology, IEEE Transactions on

Publisher

ieee

ISSN

0018-9545

Type

jour

DOI

10.1109/25.293640

Filename

293640