Xiaoming Liu

Bio: Xiaoming Liu is an academic researcher from Queen Mary University of London. The author has contributed to research in topics: Dielectric & Permittivity. The author has an hindex of 1, co-authored 1 publications receiving 5 citations. Previous affiliations of Xiaoming Liu include Anhui Normal University.

Characterization of the dielectric properties of water and methanol in the D-band using a quasi-optical spectroscopy

Abstract: This work presents the measurement of the permittivities of water and methanol in the D-band. Water is a reference medium for dielectric measurement. The dielectric permittivity of water in the millimeter wave range is a fundamental parameter in many applications, and needs to be investigated systematically. The measurement is conducted using a quasi-optical spectroscopy, which is an improved free-space method more suitable for the millimeter wave range. The theoretical formulae are derived using the signal-flow chart method, which is developed specially for multi-layer operation. This model enables one measure liquid samples. A non-calibration method has been developed to retrieve the permittivity. Water and methanol are measured at several temperatures. The measured results agree with published results in a 4% discrepancy. This work will add new measured data to the permittivities of water and methanol over the whole D-band.

Calibrated and Frequency Traceable D-Band FMCW Radar for VNA-like S-Parameter Measurements

Abstract: In this paper a D-band frequency modulated continuous wave (FMCW) radar system and a signal processing chain for vector network analyzer(VNA)-like S-parameter measurements are presented. The radar sensor covers an ultra-wide 56GHz (126GHz–182GHz, 36.4%) sweep bandwidth and can be equipped with a standard WM-1651 [1] (WR-6.5) waveguide flange. To achieve measurement-grade phase stability a cascaded multi-phase-locked-loop (PLL) frequency traceable reference clock concept is introduced and system stability measurements are presented. Finally, a FMCW radar calibration concept is provided to allow complex (magnitude and phase) S-parameter measurements with cost-effective wide-band FMCW radar sensors. To demonstrate the achieved system performance and the potential of this approach, material characterization measurements are presented and compared to conventional VNA measurement equipment with waveguide extenders.

Broadband Quasi-Optical Dielectric Spectroscopy for Solid and Liquid Samples

Abstract: Dielectric materials play a supporting role for electronic circuits. With the development of 5G millimeter wave communication, precision measurement of dielectric property becomes increasingly important. This paper introduces a free-space quasi-optical spectroscopy for complex dielectric property measurement. This spectroscopy can work in both transmission and reflection modes to accommodate both low-loss and high-loss materials. By applying the transfer matrix theory, both solid and liquid samples can be characterized using this system. In addition, the system employs a Gaussian telescope design, giving a possibility of broadband operation. Furthermore, this system is much simpler in calibration compared to other systems. A detailed description of the quasi-optical system is presented. Four materials are measured in the E-band (60–90 GHz). De-ionized water is also measured to represent liquid substrates in electronic circuits. The measurement is in good agreement with published data within a discrepancy of 5%.

Single-Substrate Double-Side High Selectivity Frequency Selective Surface

Abstract: Frequency selective surface is a key component in applications such as communication antenna and remote sensing radiometer. One of the core parameters is selectivity, which is usually realized using a multi-layer structure or through a complicated 3D structure. These methods, however, would impose much challenge on alignment or fabrication. This paper proposes a single-substrate and combined-united array to realize a high selectivity frequency selective surface. The unit cell is a combined pattern of cross dipole and square loop to generate double transmission zeroes out of the passband. Both sides of the substrate are printed with the same pattern to enhance the selectivity. Such a structure enables easy fabrication and assembly by avoiding using multi-substrates. A prototype in the Ku-band demonstrates that both sides of the passband show high selectivity.