Articles | Volume 15
25 Oct 2017
 | 25 Oct 2017

A 24 GHz Waveguide based Radar System using an Advanced Algorithm for I/Q Offset Cancelation

Christoph Will, Sarah Linz, Sebastian Mann, Fabian Lurz, Stefan Lindner, Robert Weigel, and Alexander Koelpin

Abstract. Precise position measurement with micrometer accuracy plays an important role in modern industrial applications. Herewith, a guided wave Six-Port interferometric radar system is presented. Due to limited matching and discontinuities in the radio frequency part of the system, the designers have to deal with DC offsets. The offset voltages in the baseband lead to worse relative modulation dynamics relating to the full scale range of the analog-to-digital converters and thus, considerably degrade the system performance. While common cancelation techniques try to estimate and extinguish the DC offsets directly, the proposed radar system is satisfied with equalizing both DC offsets for each of the two differential baseband signal pairs. Since the complex representation of the baseband signals is utilized for a subsequent arctangent demodulation, the proposed offset equalization implicates a centering of the in-phase and quadrature (I/Q) components of the received signal, which is sufficient to simplify the demodulation and improve the phase accuracy. Therefore, a standard Six-Port radar system is extended and a variable phase shifter plus variable attenuators are inserted at different positions. An intelligent algorithm adjusts these configurable components to achieve optimal I/Q offset cancelation.

Short summary
This paper presents a guided wave Six-Port interferometric radar system with integrated I/Q offset cancelation. An intelligent algorithm is proposed which optimally adjusts three voltage controlled attenuators and one voltage controlled phase shifter in the radio frequency part of the system. By minimizing the I/Q offset, the standard deviation as well as the relative error are decreased in comparison to an uncompensated measurement setup.