A new procedure for the design of multi-band branch-line couplers utilizing microstrip non-uniform transmission lines with Fourier-based profiles is presented in this article. The general method is accomplished by replacing the quarter-wave uniform transmission lines of a conventional coupler with multi-band non-uniform transmission lines of the same lengths, without including additional transmission lines or matching networks. The design of non-uniform transmission line couplers is performed using even- and odd-mode analysis. The proposed structure is relatively simple and is fabricated on a single-layered microstrip board. Two design examples of dual- and triple-band branch-line couplers suitable for global system mobile (GSM), wireless local area networks, and WiFi communications are designed, fabricated, and experimentally evaluated to validate the proposed methodology.
- branch-line coupler
- multi-band 3-dB couplers
- non-uniform transmission line
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering