Electromagnetic characterisation of MM-wave transitions

Integrated circuit techniques are even more attractive at millimetre-wavelengths than for microwaves, since waveguide of a very small cross-section is used extensively, requiring very accurate machining of components. The photolithographic technique for producing microstrip, fin-line and suspended strip-line circuits has thus a clear advantage offering very high resolution in a simple mass-producible technique. Inter-connection between subsystems and with test instruments is however realised in waveguide. Knowledge of the characteristics of the transitions between these media though accurate CAD of these components is thus essential, if meaningful comparison is to be made between measured and modelled circuit parameters. The author discusses a number of approaches to the analysis of printed structures, including the transmission line matrix (TLM) method and the determination of two-port scattering parameters