A QUASI-OPTICAL FREE-SPACE S-PARAMETERS MEASUREMENT SYSTEM FOR MATERIAL CHARACTERIZATION IN W AND KA BANDS

Several quasi-optical measurement systems based on lensand/or reflector configurations have been used to characterizethe optical properties of materials by extracting theS-parameters using a four-port Vector Network Analyser(VNA). This paper describes the modelling and performancesof a compact quasi optical free-space test benchoperated both in Ka (26.5-40 GHz) and W bands (75-110 GHz). A test set-up based on two fully reflectiveCompact Test Range (CTR) systems have been chosenin order to create a quiet zone region with low crosspolarizationand low aberration where samples under testwill be located. The predicted quiet zone ripples in theWband are within 2 dB for the amplitude and 3 degree forthe phase while they are 3 dB and 15 degree respectivelyin the Ka band. This system will be used to characterizematerials and also to investigate instrumental systematiceffects introduced by quasi-optical components such asinterference filters and half-wave plates.