A Miniaturized UWB Microwave Dual-Comb Dielectric Spectroscopy System

Abstract

This article presents a miniaturized microwave dual-comb spectroscopy (DCS) system for the characterization of materials in an ultrawideband (UWB) frequency range. The proposed UWB DCS system consists of two comb generators, a sensor, a mixer, a low-pass filter, and an oscilloscope. The output of the DCS system is generated by mixing of two frequency combs with slightly different repetition rates, while one of the combs contains UWB dielectric properties of the material under test (MUT). Thus, the microwave UWB properties of the MUT is mapped to the baseband frequency significantly reducing the receiver complexity. All the sources and the oscilloscope are phase-locked to enable the measurement of both magnitude and phase of the system output. To decrease the averaging time and increase the system calibration accuracy while maintaining the system sensitivity, only nine samples of the system output in the time domain are captured and used for calibration. Through calibration, the DCS system behavior is described with the magnitude and phase responses of 13 reference MUTs. Using such system description, $\epsilon '$ and $\epsilon ''$ of six unknown MUTs are estimated with errors less than $0.055|\epsilon ^{*}|$ in the frequency range from 3 to 10 GHz. This proposed DCS system is accurate, fast, and low cost with the possibility of being self-sustained and independent of the laboratory facility.