A Rigorous Multimodal Analysis and Design Procedure of a Uniplanar 180 ^ Hybrid

• Published in: IEEE transactions on microwave theory and techniques Vol. 57; no. 7; pp. 1832 - 1839
• Main Authors: Llamas, M.A., Ribo, M., Girbau, D., Pradell, L.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.07.2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: 180 ^{\circ} hybrid; Applied sciences; Bandwidth; Circuit analysis; Circuit properties; Circuit simulation; Coplanar waveguide (CPW) cross; Coplanar waveguides; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Frequency; Image analysis; magic T; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; multimodal models; Performance analysis; Performance loss; Phased arrays; Slotline; uniplanar circuit; Performance evaluation; Return loss; 180° hybrid; Phase shift; magic T; Implementation; Frequency shift; Simulation; Coplanar waveguide (CPW) cross; Coplanar waveguides; uniplanar circuit; multimodal models; Quantitative analysis; Planar technology
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2009.2022881

Uniplanar 180deg hybrids are basic building blocks in uniplanar technology. In this paper, a new rigorous analysis of a uniplanar 180deg magic-T hybrid based on an air-bridged coplanar cross is performed. The analysis proposed is multimodal since it takes into account the coplanar even and odd fundamental modes simultaneously. From this analysis, a complete circuit model for the hybrid is extracted, and the conditions for ideal performance are derived. This new multimodal model is necessary for the design of the hybrid, and allows a quantitative analysis of its performance, notably bandwidth, isolation, and return loss under any actual loading condition. It has been used to design and implement a 180deg hybrid on alumina with a working frequency of 15 GHz. A very good agreement between simulation and measurement is obtained. The experimental results prove a frequency-independent phase-shift behavior with a measured phase error less than plusmn 2deg.