New uniplanar transitions for circuit and antenna applications

New uniplanar microstrip-to-slotline, microstrip-to-coplanar strips (CPS) and microstrip-to-coplanar waveguide (CPW) transitions for MIC/MMIC and slotline antennas for phased array applications are described. Such transitions are compact and suitable to be used in an open environment or inside a package or a multichip module. The transitions share the concept of using a balun which consists of two microstrip lines connected to a slotline through a pair of coupled microstrips. In this paper, the transitions are studied theoretically using the Finite Difference Time Domain (FDTD) technique and measured experimentally using an HP8510C Network Analyzer. For a back-to-back microstrip-to-slotline transition, an insertion loss of less than 1.3 dB per transition is achieved over a 49% bandwidth with a minimum of 0.6 dB around the design frequency.