Implementation of automatic digital compensation in IQ modulators

Author

Tuthill, J. ; Cantoni, A.

Author_Institution

Telecommunications, Electronics and Networking (TEN) Research Group, Department of Electrical and Electronic Engineering, University of Western Australia, Nedlands, WA, 6907, Australia

fYear

2000

fDate

4-8 Sept. 2000

Firstpage

1

Lastpage

4

Abstract

We consider Digital Signal Processor (DSP) based IQ modulators generating Continuous Phase Frequency Shift Keying (CPFSK) signals. Departures from a flat-magnitude, linear phase frequency response in the pass bands of signal reconstruction filters in the / and Q channels cause ripple in the modulator output signal envelope. Amplitude Modulation (AM) in the signal envelope function produces undesirable sidelobes in the FSK signal spectrum when the signal passes through nonlinear elements in the transmission path. A structure is developed for digitally compensating for the magnitude and phase characteristics of the signal reconstruction filters. Optimum digital compensation filters are found using least squares (LS) techniques. We propose a method by which the optimum compensation filters can be estimated using test input signals thus allowing the compensation process to be automated. We describe the implementation of the automatic digital compensation technique on a DSP platform and present experimental results.

Keywords

Band-pass filters; Digital signal processing; Finite impulse response filters; Modulation; Optimization; Radio frequency; Vectors;

fLanguage

English

Publisher

ieee

Conference_Titel

Signal Processing Conference, 2000 10th European

Conference_Location

Tampere, Finland

Print_ISBN

978-952-1504-43-3

Type

conf

Filename

7075314