A Non-Contact Submillimeter-Wave $S$-Parameters Measurement Technique for Multiport Micromachined Devices

This paper presents a novel non-contact broadband on-wafer S-parameter measurement technique for submillimeter-wave and terahertz applications. The proposed method enables S-parameters measurement of multi-port micromachined devices using a two-port measurement setup. In this method, a small fraction of the signal at each waveguide port is weakly coupled to free space using a small array of reflection-canceling slots which are then measured by an open-ended waveguide probe. The S-parameters of the device-under-test are calculated from the measured signals obtained from each port and from that of a reference match waveguide. A broadband waveguide slot array antenna with high return loss is designed as a matched load to terminate all ports of the device except the input port. To assess the reliability and accuracy of the proposed measurement method, three different micromachined waveguide directional couplers are designed, fabricated, and tested. Multiple apertures on the common wall between the adjacent waveguides are designed and optimized to achieve high directivity couplers over a broad frequency range. The measured S-parameters of the couplers are shown to be in good agreement with the simulations, which indicates the accuracy of the proposed measurement method.