Alireza Kazemipour

Design and Calibration of a Compact Quasi-Optical System for Material Characterization in Millimeter/Submillimeter Wave Domain

A compact quasi-optical setup based on conventional rectangular horn antennas and two symmetrical parabolic mirrors is designed to provide a plane wave on the material under test. To measure the scattering parameters at millimeter/submillimeter wavelengths, a commercial vector network analyzer and waveguide frequency extension units are used. The calibration of the system is performed with a simple practical deembedding process to determine the S-parameters on the material surface without using high-cost micrometer positioners. A reliable extraction method is presented to derive the material permittivity and calculate the errors and uncertainties as direct functions of the sample and setup geometry and their physical characteristics. Several materials are measured and the complex permittivity is presented together with a detailed uncertainty budget.

A reliable simple method to extract the intrinsic material properties in millimeter/sub-millimeter wave domain

A simple method is presented to extract the material characteristics from the scattering parameters in the frequency domain. The method is based on “transmission” measurement data only and can give the complex permittivity and/or the absorption and refraction index via easy arithmetic operations with closed-form formulas. Therefore, a parametric error analysis will be feasible for metrological aspects to show important uncertainty contributions. The actual measurements have been performed with a compact quasi-optical free-space setup in the frequency band from 50 GHz to 500 GHz and the detailed results are presented to show the performance of the method.

Design and calibration of a compact quasi-optical system for material characterization in millimeter/sub-millimeter wave domain

A compact spectrometer setup based on conventional rectangular horn antennas and two symmetrical parabolic mirrors is designed to provide a plane wave on the material-under-test. A commercial Vector Network Analyzer (VNA) and waveguide frequency extension units are used to measure the scattering parameters. A simple practical calibration process is used to determine the S-parameters on the material surface without need of high-cost micrometer positioners. Several materials are measured and the complex permittivity is presented.

A Simple New Method to Calibrate Millimeter-Wave Mixers

This paper presents a novel method to test the conversion loss of fully reciprocal millimeter-wave mixers without measuring the absolute signal power at the radio-frequency port. The authors utilize the reciprocal feature of the mixer and obtain conversion loss based on relative power measured by a network analyzer.

Novel method to measure the conversion-losses (C.L.) of microwave and mm-wave mixers

Classic methods to measure the mixer conversion-losses (C.L.) usually need an absolute RF and IF power-measurement at the mixers ports. However, absolute power-measurement cannot be achieved with a low uncertainty level for the higher frequencies and mm-waves because of non-available standards and source & load mismatch problems. A new method is proposed (for reciprocal mixers) based on relative-power measurement at IF-port when the RF-port is fed/measured by VNA. Therefore, the C.L. can be evaluated for the mm-wave mixers by using a suitable VNA and its relevant frequency-converters up to 325GHz. The setup is described and preliminary results are presented for a microwave-mixer and a mm-wave one.

Analytical study of mm-wave and THz beams, application to RF metrology

Using mm-wave and THz radiation as a reliable measurement tool in spectroscopy and remote-sensing requires accurate beam characterization. Gaussian approximation is a practical model to describe the radiated beam of Laser sources and high-directivity THz/mm-wave horn antennas. The radiated beam is analytically studied in this paper and a simple closed-form formula is presented for the wave-front phase distribution. Analytical results are compared with measurements and good agreement is observed for mm-wave horns. The closed-form formula is used for a parametric error-analysis and uncertainty evaluation as needed in RF metrology. Therefore, the contribution of all the source characteristics and its geometrical parameters to the phase deviation can be shown.