S-parameter Characterisation of Sub-Millimetre Membrane Circuits

Abstract: In this thesis, a thru-reflect-line (TRL) calibration technique enabling full S-parameter characterisation for membrane circuits has been demonstrated in the WR-03 waveguide band (220 to 325 GHz). The designed membrane TRL kit is packaged in E-plane split blocks. An improvement of beam lead to ground connection was utilized by recessing the block surface. The proposed calibration provides the reference planes right at device under tests, thus reduces an extra de-embedding step. Membrane circuits such as stub filter, thin film resistors, thin film capacitor were characterised by applying the presented method. The simulated and measured results agree well, showing the validity of this approach. Furthermore, the measurement uncertainties such as temperature variation, time drift, system noise, power level fluctuations, connection repeatability and assembly tolerance were systematically investigated. For the connection repeatability study, the amplitude response of transmission coefficient varies within +/-(0.1) dB while that of reflection coefficient is below -30 dB across the frequency band. In addition, the result of the membrane circuit is not sensitive to circuit mounting tolerance. These analysis prove that this technique is applicable in the WR-03 band. However, it is also very crucial to have a setup with good cables because of the significant impact of the cables on the characterisation result.