Measurement Method for Imbalance Factors in Direct-Conversion Quadrature Radar Systems

• Published in: IEEE microwave and wireless components letters Vol. 17; no. 5; pp. 403 - 405
• Main Authors: Byung-Kwon Park, Yamada, S., Lubecke, V.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.05.2007; Institute of Electrical and Electronics Engineers
• Subjects: Amplitudes; Applied sciences; Baseband; Circuit properties; Circuits; Digital communication; Digital signal processing; Direct-conversion; Doppler radar; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Exact sciences and technology; imbalance factor; Integrated circuits; Integrated circuits by function (including memories and processors); Measurement methods; Microwaves; Performance evaluation; Phase measurement; Phase shifters; quadrature receiver; Quadratures; Radar; Radar measurements; Radiocommunications; Radiolocalization and radionavigation; Receivers; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Signal convertors; Signal generators; Telecommunications; Telecommunications and information theory; Transmitters. Receivers; Direct convertor; Q factor; Base band; Receiver; Digital processing; imbalance factor; Output signal; Phase shifter; Accuracy; Direct-conversion; Linear transformation; Integrated circuit; quadrature receiver; Signal processing; Measurement method; Doppler radar; Digital signal processor; Non ideality
• ISSN: 1531-1309
• DOI: 10.1109/LMWC.2007.895742

In quadrature direct-conversion Doppler radar systems, the I and Q receiver channels are subject to amplitude and phase imbalance factors caused by circuit and component imperfections. This nonideality results in an undesired linear transformation of the baseband output signals which degrades output accuracy and sensitivity. With known imbalance factors, compensation can be achieved through digital signal processing, but accuracy is affected by circuit modifications required to determine those factors. Presented here is a new measurement method for I/Q imbalance factors that can be performed without significant modification to the radar system, allowing more precise imbalance correction to be achieved. A phase shifter is introduced at the receiver input to simulate a target approaching with constant velocity, resulting in sinusoidal outputs which can be easily compared to determine phase and amplitude imbalance