BROAD-BAND UNIPLANAR HYBRID-RING AND BRANCH-LINE COUPLERS

Novel uniplanar 180-degrees and 90-degrees hybrids suitable for MIC and MMIC are described. The new uniplanar crossover hybrid-ring magic-T coupler using a coplanar waveguide (CPW) and slotline provides substantially improved amplitude and phase characteristics over a broad bandwidth compared to conventional microstrip hybrid-ring couplers. Experimental results show that the uniplanar crossover hybrid-ring coupler has a bandwidth of more than one octave from 2 to 4 GHz with +/-0.4 dB power dividing balance and +/-1-degrees phase balance. A uniplanar two-branch directional coupler using a coupled rectangular slotline ring has also been developed that has over 20 dB isolation over a bandwidth of more than 40% centered at 3 GHz with +/-1 dB power dividing balance. To fully utilize the advantages of uniplanar structures, transitions from CPW to slotline and coplanar strip (CPS) using uniform and nonuniform CPWs, slotlines, or CPSs are discussed. These transitions are uniplanar and simple to fabricate. No via holes are needed for ground connections, and integration with solid-state devices is easy. A pair of broad-band transitions using CPW shorts and slotline radial stubs is demonstrated with a 1 dB bandwidth of more than 5.2:1. The CPW-CPS transition shows a 1 dB bandwidth of more than two octaves.