Wide band microstrip to microstrip vertical coaxial transition for radar & EW applications

Abstract

A wide band DC-18 GHz microstrip to microstrip vertical transition for Microwave Integrated Circuits (MICs) using coaxial design approach for Radar & EW applications, is being explained in this paper. A simple, flexible, self-supporting and economical solution for wideband vertical coaxial transition with respect to Microstrip lines for MICs has been brought out in this paper to avoid RF cross overs. It consist of coaxial structure which in turn connected to two microstrip lines in top and bottom side of two different pcbs. The signal is going through two transitions: a) Quasi TEM mode to pure TEM mode and b) TEM mode to Quasi TEM mode. The challenge of this transition is to provide better matching at the transitions to ensure better input and output VSWR, and hence minimum insertion loss for the required frequency band. Insertion loss of max 0.5dB @ 18GHz and return loss more than 20dB for DC-18 GHz frequency band was targeted. Also, the size (length & diameter) of the vertical transition can be customized as per requirement compared to RF glass bead which are available of standard size.