Compact Gaussian Beam System for S-Parameter Characterization of Planar Structures at Millimeter-Wave Frequencies

This paper describes the design and implementation of a compact quasi-optical Gaussian beam system for measuring the frequency response of millimeter-wave materials, frequency-selective surfaces, and antenna elements in the array environment. The core components of this system are two wideband millimeter-wave focusing array antennas that act as adapters between the coaxial ports of the network analyzer and the wave ports defined at the input and output planes of the device under test. The use of planar focusing arrays for generating the Gaussian beams leads to very compact measurement setups with a total length of only a few centimeters. This paper addresses the design of the Ka/Q-band focusing arrays and demonstrates the utility of the proposed system through experiment. A useful method that allows reproducing two-port S-parameters from one-port measurements will also be introduced.