Compact Single and Dual-Band Branch-Line Coupler with Effective Fractional Bandwidth for Wireless Communication Systems

Multiple wireless communication systems make use of a branch-line coupler (BLC), which is a passive microwave component. For the purpose of splitting and combining microwave signals, as well as providing a 90-degree phase shift between the output ports, this 4-port device is made from four quarter-wavelength (λ/4) transmission lines. Having recently developed a dual-band branch-line coupler (DBBLC), there has been a lot of attention paid to this development. When it comes to getting dual-band (DB) functioning of a BLC, one of the most common approaches is stub loaded transmission lines. For the BLC, stubs may be positioned either in the center of the arms or at the input of the arms. Stepped-impedance stubs, orthogonal coupled branches, and coupled lines are some of the strategies that have been shown to be effective in achieving DB functioning of a coupler. Through the utilization of the Elongated T-Shape Transmission Line (ETSTL), this work presents a one-of-a-kind design for each single-band branch-line coupler (SBBLC) and DBBLC that is of a compact proportion. Based on the information presented in this article, the SBBLC operates at a frequency of 0.9 GHz, whereas the DBBLC operates at 0.9 and 2.4 GHz. Using a fractional bandwidth (FBW) of 44%, the coupler that has been proposed is able to function at both 0.9 GHz (GSM) and 2.4 GHz (wireless). Efforts are done on reducing the size of the coupler to be ready forfabrication.