Wideband microstrip-to-CPS transitions

Abstract

A microstrip-to-Coplanar Stripline (CPS) transition to cover the ultra-wideband (UWB) band from 3.1GHz to 10.6GHz is proposed in this report. The transition structure was formed by three sections, which are the microstrip mode section, the CPS mode section and the transition mode section in between. The transition mode section is constructed using a coupled-line structure to realize both impedance matching and field matching. In addition, a UWB bandpass filter was incorporated into the transition structure in the microstrip mode to reduce the overall size of microwave integrated circuits. The proposed transition has the advantages of compact size, wide bandwidth, and ease of design and fabrication. The single microstrip-to-CPS transition has a 3dB insertion loss bandwidth from 2.9GHz to 10.7GHz and a 10dB return loss bandwidth from 3.3GHz to 10.75GHz. The 3dB insertion loss bandwidth from 3.7GHz to 11.3GHz is achieved for the back-to-back microstrip-to-CPS transition.