Implementation of a Miniaturized Planar 4-Port Microstrip Butler Matrix for Broadband Applications

In this paper, a miniaturized and broadband 4 × 4 Butler matrix is presented. All components of the presented matrix are designed in a way that, have the broadband impedance bandwidth and compact electrical size as much as possible. Traditional previous Butler matrix composed of phase shifters, while in the presented feeding network dummy crossover role this act, which results to enhance the phase difference bandwidth. The compactness of the optimized and proposed coupler is related to inserting the S-shaped arms instead of ordinary parts. The modified dummy crossover is used to overcome the mismatch phase difference among phase shifter and crossover. Design procedure of miniaturized broadband components such as 3-branch-line coupler, crossover, phase shifter and final design are presented step by step. The results of the simulation and measurement of the desired Butler matrix makes it suitable for the applications of planar multi-beam antennas. The extracted results determine that the bandwidth of the presented network is from 4.5 ~ 6 GHz, that is a good candidate for WLAN applications. The whole size of network is 71.5 × 38.3 mm2.