Quadrature Errors and DC Offsets Calibration of Analog Complex Cross-Correlator for Interferometric Passive Millimeter-Wave Imaging Applications

Autor:	Zhiping Li, Jungang Miao, Chao Wang, Bingyuan Liang, Xin Xin
Rok vydání:	2018
Předmět:	0211 other engineering and technologies Phase (waves) 02 engineering and technology lcsh:Chemical technology millimeter-wave imaging Biochemistry Noise (electronics) Article Analytical Chemistry analog correlator cross correlation interferometric imaging security sensing 0202 electrical engineering electronic engineering information engineering Electronic engineering Calibration lcsh:TP1-1185 Electrical and Electronic Engineering Instrumentation 021101 geological & geomatics engineering Electronic circuit Physics Cross-correlation System of measurement 020206 networking & telecommunications Atomic and Molecular Physics and Optics Quadrature (mathematics) Interferometry
Zdroj:	Sensors; Volume 18; Issue 2; Pages: 677 Sensors (Basel, Switzerland) Sensors, Vol 18, Iss 2, p 677 (2018)
ISSN:	1424-8220
DOI:	10.3390/s18020677
Popis:	The design and calibration of the cross-correlator are crucial issues for interferometric imaging systems. In this paper, an analog complex cross-correlator with output DC offsets and amplitudes calibration capability is proposed for interferometric passive millimeter-wave security sensing applications. By employing digital potentiometers in the low frequency amplification circuits of the correlator, the outputs characteristics of the correlator could be digitally controlled. A measurement system and a corresponding calibration scheme were developed in order to eliminate the output DC offsets and the quadrature amplitude error between the in-phase and the quadrature correlating subunits of the complex correlator. By using vector modulators to provide phase controllable correlated noise signals, the measurement system was capable of obtaining the output correlation circle of the correlator. When injected with −18 dBm correlated noise signals, the calibrated quadrature amplitude error was 0.041 dB and the calibrated DC offsets were under 26 mV, which was only 7.1% of the uncalibrated value. Furthermore, we also described a quadrature errors calibration algorithm in order to estimate the quadrature phase error and in order to improve the output phase accuracy of the correlator. After applying this calibration, we were able to reduce the output phase error of the correlator to 0.3°.
Databáze:	OpenAIRE
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