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A Digital Correction Method for Increased Dynamic Range in Interferometric Six-Port Radars

S. Krause1, F. Michler2, A. Kölpin3, M. Rudolph4, and W. Heinrich1

Published in:

IEEE Microwave Wireless Compon. Lett., vol. 31, no. 8, pp. 997-1000 (2021).


In this letter, we demonstrate a digital correction method for extending the dynamic range of a six-port radar system based on detector diodes. An individual diode gain is considered to depend on output voltage, which can be approximated as a linear function in order to extrapolate the diode’s square-law response to higher input powers. The individual diode coefficients are extracted during an initial calibration measurement utilizing the interferometric working principle. A six-port junction in combination with power detectors based on Si Schottky diodes operating at 24 GHz has been employed to validate the concept. Reduction of the third- and fifth-order harmonics of up to 35 and 22 dB, respectively, has been achieved at the highest input power of 8 dBm. The correction was applied for a wide range of operating conditions. As a result, the increase in phase error under large-signal and high power operation is effectively compensated and remains low under small-signal conditions. Thus, phase accuracy is maintained beyond the classical dynamic range of detector diodes in six-port applications so far.

1 Ferdinand-Braun-Institute for High Frequency Technology, 12489 Berlin, Germany
2 Department of Electrical-Electronic-Communication Engineering, Friedrich-Alexander-University Erlangen-Nuremberg, 91054 Erlangen, Germany
3 Institute of High-Frequency Technology, Technical University Hamburg-Harburg, 21073 Hamburg, Germany
4 Radio Frequency and Microwave Techniques, Brandenburg Technical University, 03013 Cottbus, Germany

Index Terms:

Calibration technique, digital correction, displacement measurement, six-port radar.

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