A study of hybrid ring and branch line couplers utilizing uniplanar asymmetric coplanar stripline

Abstract

This thesis introduces four new uniplanar 3-dB hybrid couplers using asymmetrical coplanar striplines (ACPS) for microwave integrated circuit (MIC) and monolithic microwave integrated circuit (MMIC) applications. The ACPS transmission line is characterized using Sonnet Software, and its characteristic impedance is graphed for a particular substrate. These graphs serve as building blocks for the design process. ACPS transmission lines eliminate the plating of the inner conducting ground plane and also lessen the number of bond wires as compared to coplanar waveguide (CPW) hybrid couplers. A standard uniplanar 180' hybrid ring and reverse-phase hybrid ring coupler are designed and fabricated. The advantages of the reverse-phase hybrid ring are wider bandwidth and smaller size. A reduced size reverse-phase hybrid ring coupler is also designed and fabricated, and its advantage is smaller size while maintaining the performance of the reverse-phase hybrid ring coupler. A new 3-dB 90' branch-line hybrid coupler is also designed and constructed. These circuits will be shown to meet or exceed the performance of similar microstrip and CPW hybrid couplers while at the same time maintaining the advantages previously mentioned.