Realization of a Compact Branch-line Cou- Pler Using Quasi-fractal Loaded Coupled Transmission-lines

An extremely compact branch-line coupler operating at 900MHz is presented without the use of via-holes, multilayered technique, or air-bridged. The technique presented here uses the concept of fractals to load a coupled transmission-line in order to realize a compact quarter-wavelength transmission-line, which forms the couplers arms. It is shown that the proposed branch-line coupler’s performance is analogous to a conventional branch-line coupler with the benefit of substantially reduced physical dimensions by a factor of 78%. The measured result of the fabricated microstrip branchline coupler is compared with the simulation data. The agreement of the measurement and simulated confirms the theory and validates the proposed coupler design.