Automatic digital pre-compensation in IQ modulators

Author

Tuthill, J. ; Cantoni, A.

Author_Institution

Telecommun. Res. Inst., Curtin Univ. of Technol., Perth, WA, Australia

Volume

3

fYear

1999

fDate

15-19 Mar 1999

Firstpage

1621

Abstract

In digital IQ modulators generating continuous phase frequency shift keying (CPFSK) signals, departures from flat-magnitude, linear phase in the pass bands of signal reconstruction filters in the I and Q channels cause ripple in the 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 pre-compensating for the magnitude and phase characteristics of signal reconstruction filters. Optimum digital pre-compensation filters are found using least squares (LS) techniques and we propose a method by which the optimum pre-compensation filters can be estimated using test input signals. This method can be used as part of an automatic compensation process

Keywords

amplitude modulation; band-pass filters; compensation; continuous phase modulation; digital filters; frequency shift keying; least squares approximations; modulators; signal reconstruction; CPFSK signals; FSK signal spectra; IQ modulators; amplitude modulation; automatic digital pre-compensation; continuous phase frequency shift keying signal; digital IQ modulators; least squares techniques; magnitude; nonlinear elements; optimum pre-compensation filters; output signal envelope; pass bands; phase; ripple; sidelobes; signal envelope function; signal reconstruction filters; test input signals; Amplitude modulation; Band pass filters; Chirp modulation; Continuous phase modulation; Digital filters; Digital modulation; Frequency shift keying; Nonlinear filters; Signal generators; Signal reconstruction;

fLanguage

English

Publisher

ieee

Conference_Titel

Acoustics, Speech, and Signal Processing, 1999. Proceedings., 1999 IEEE International Conference on

Conference_Location

Phoenix, AZ

ISSN

1520-6149

Print_ISBN

0-7803-5041-3

Type

conf

DOI

10.1109/ICASSP.1999.756300

Filename

756300