Measurements at 140 GHz using a multistate reflectometer

The authors describe the design of a measurement system which enables measurements for device characterisation at 140 GHz. Because there is currently no equipment available which can perform measurements and also allows a vectorial indication of the reflection coefficient at these frequencies, a dielectric multistage reflectometer (DMR) has been built and will be used in future to measure the scattering parameters of on-wafer devices. The hardware of the DMR is much simpler in comparison to a conventional network analyser requiring frequency converters, local oscillators and phase detectors which makes this relatively complicated design quite expensive. The simplicity in the hardware configuration of the DMR on the one side certainly has its tradesoff on the other side in the numerical involvement to acquire out of several scalar power readings a vectorial indication of the measured reflection coefficient. Although a lot of work has been done in recent years to realise and design 6 port and then 4 port reflectometers they were built in metallic waveguide technology and operated below 100 GHz. To avoid the disadvantages of metallic waveguide which occur above 100 GHz, the DMR has been built using components in dielectric waveguide technology.