Flexible Phase-Reconfigurable Branch Line Coupler for Millimeter-Wave Phased Array Antenna

This paper presents a reconfigurable phase-shift branch line coupler (BLC) design. The proposed design is developed based on a defective microstrip line (DML), where all of the conventional microstrip lines of an ordinary BLC are replaced by the DML structure. To realize the phase delay line, four PIN diode switches are used in the DML structure, which redirect the current paths between the input and output ports of the BLC, consequently providing a variety of phase differences at the output ports. Changing PIN diode switch states enables phase shifts between 10
⁰
and 15
⁰
degrees. The proposed design operates millimeter-wave (mmWave) with a resonant frequency of 25.5 GHz. The design parameters are studied and analyzed using the CST Studio Suite software package. The proposed reconfigurable BLC can be employed as phase shifters, offering a flexible, low-cost solution for mmWave phase array antennas.