Transdirectional Coupled-Line Couplers Implemented by Periodical Shunt Capacitors.

Transdirectional coupled-line couplers have the benefit of perfect input/output isolation. However, for a coupled-line coupler to operate in transdirectional mode, both phase- and impedance-coupling are required, which is difficult to meet by traditional coupled lines. To overcome this problem, this paper presents a novel transdirectional coupled-line coupler implemented by periodically loaded coupled lines. Two. 3-dB 90° hybrids are designed and built to verify this concept. The first one was built on FR-4 substrates and operated at 3.6 GHz. The second one was built on Roger RTlDuroid 5870 substrates with length reduced and operated at 3.6 GHz. A good agreement with simulated results is reached. [ABSTRACT FROM AUTHOR]