Novel Uniplanar Tandem Couplers

Novel tight uniplanar directional couplers are developed by connecting two loosely coupled coplanar-waveguide (CPW) couplers in tandem configuration. In this study, two uniplanar tandem couplers are implemented on the FR4 substrate. These tandem couplers are carefully examined theoretically and experimentally, and good match between simulated and measured results is observed. The proposed tandem coupler is also compared with the 3dB Lange coupler, and the comparison shows that the tandem coupler has the merits of smaller area, better return loss, better isolation, and more relaxed fabrication requirement.