Differential synchronous demodulation for small signal amplitude estimation

Author

Koukourlis, Christos S. ; Trigonidis, Vassilios K. ; Sahalos, John N.

Author_Institution

Dept. of Electr. Eng., Democritus Univ. of Thrace, Xanthi, Greece

Volume

42

Issue

5

fYear

1993

fDate

10/1/1993 12:00:00 AM

Firstpage

926

Lastpage

931

Abstract

A circuit for estimating the amplitude of small signals (in the range of microvolts to a few millivolts) developed initially for an electrical impedance tomography (EIT) data acquisition system is presented. The paper is focused on two points, the accurate demodulation of the difference of two sinewave signals and the common-mode correction of the measurement. The method is oriented for applications in measuring instruments, where a signal source (sinewave oscillator) is assumed to be incorporated. It uses a sample-and-hold circuit, suitably driven, as an amplitude demodulator. One of the advantages of this method is that the realization of the synchronous demodulator (or phase-sensitive detector) does not require a low-pass fitter at the output, resulting in a smaller settling time, that is, in higher speed of measurement. Finally, to improve the accuracy, a self-calibration technique has been developed

Keywords

biomedical electronics; calibration; demodulation; demodulators; electric impedance imaging; sample and hold circuits; voltage measurement; amplitude demodulator; common-mode correction; data acquisition; differential synchronous demodulation; electrical impedance tomography; measuring instruments; phase-sensitive detector; sample-and-hold circuit; self-calibration; settling time; signal source; sinewave oscillator; sinewave signals; Amplitude estimation; Circuits; Data acquisition; Demodulation; Detectors; Impedance; Instruments; Oscillators; Phase detection; Tomography;

fLanguage

English

Journal_Title

Instrumentation and Measurement, IEEE Transactions on

Publisher

ieee

ISSN

0018-9456

Type

jour

DOI

10.1109/19.252529

Filename

252529