RF signal crossover across PTH (Via)

A microstrip Via or Plated Through Hole is encountered in case of (a) Component grounding and (b) when the signal is expected to change a layer on a Printed Circuit Board (PCB). Case (b), i.e. Crossover of signal through a 'Via' is an important and interesting phenomenon as the discontinuity presents a step change in characteristic impedance! Requirement of Miniaturization of circuitry means that Signal Cross-Over Vias (SCOV) find a place quite often in RF and Microwave Boards. Engineers often avoid them due to lack of understanding and sacrifice a lot of board space or end up implementing expensive alternate solutions. Reasonably accurate model of the Via is available and is used in the study carried out in this paper. An attempt has been made to minimize the effect of the inductive reactance of the microstrip via with the help of an open wire stub of small (appropriate) length, interchangeably termed as monopole in the following passages. The study has been carried on PCBs with different via sizes and configurations. The frequency range has been purposely restricted up to 4GHz. Substrate chosen is commercial Rogers 4003C. It is low loss substrate even in Millimetre Wave Range and will not contribute to absorptive losses in the PCB. Conclusions are drawn from the comparison between the observed and the theoretical results.