Swept-frequency near millimeter wave characterisation of samples in an international sample exchange

The instrumentation used to characterize the exchange consists of an Automated Scalar Network Analyzer System (ASNAS) operating on the 90 to 100 GHz frequency range coupled to a pseudooptical antenna arrangement for making free space transmission measurements on the samples. The ASNAS involves a computer controlled scalar network analyzer and a swept frequency IMPATT source feeding into a W band waveguide. Two different pairs of W band horn lens antennas (95 GHz center frequency) are employed in the measurements. They were mounted in transmitter receiver configurations. One pair of antennas provides a free space near millimeter wave beam focussed in space at the sample position. The other pair of antennas provides a collimated free space beam incident on the samples. The sample mount is on the same optical track as the antenna mounts. The sample is mounted at an angle and attenuating sheets are inserted before and after the sample to minimize multiple reflection resonance effects between the sample and the antennas. A carbonized foam aperture is used to prevent leakage around the sample and suppress multipath signals. The whole quasioptical apparatus is mounted on a 4 inch thick honeycomb optical table to provide rigidity and vibration isolation.