Ahmed Fayyadh H, Khamas Salam K
Electromagnetics, Wireless Hardware & RF Devices Group, School of Electronic and Electrical Engineering, University of Sheffield, Sheffield S1 3JD, UK.
Sensors (Basel). 2025 Jun 13;25(12):3714. doi: 10.3390/s25123714.
This paper presents a novel switchable branch-line coupler (BLC) designed to achieve variable phase shifts while maintaining a constant output power. The proposed design incorporates low stepwise phase shifters with incremental phase shifts of 10° to 20°, covering phase ranges from -3° to 150°. The initial structure is based on a 3 dB branch-line coupler with arm electrical lengths of 3λ/2. A novel delay line structure is integrated within the BLC arms, consisting of a λ/4 section bridged by a tapered stripline to accommodate a PIN diode switch, thereby altering the current path direction. Additionally, two interdigital capacitors (IDCs), uniquely mounted on a crescent-shaped extension, are implemented alongside the tapered line to elongate the current path when the PIN diode is in the OFF state. By controlling the PIN diode states, the delay time is differentially adjusted, resulting in variable differential phase shifts at the output ports. To validate the functionality, the proposed BLC was integrated with a two-element antenna array to demonstrate differential beam steering. The measurement results confirm that the phased array antenna can switch its main beam between -27° and 25° in the elevation plane, achieving an average realized gain of approximately 7 dBi. The BLC was designed and simulated using CST Microwave Studio and was fabricated on an RO4003C Roger substrate (ε = 3.55, 0.406 mm). The proposed design is well-suited for future Butler matrix-based beamforming networks in antenna array systems, particularly for 5G wireless applications.
本文提出了一种新型的可切换分支线耦合器（BLC），旨在实现可变相移，同时保持输出功率恒定。所提出的设计采用了低阶逐步相移器，相移增量为10°至20°，覆盖的相位范围为-3°至150°。初始结构基于一个3 dB分支线耦合器，其臂的电长度为3λ/2。一种新型延迟线结构集成在BLC臂内，由一个λ/4段和一个渐变带状线桥接而成，以容纳一个PIN二极管开关，从而改变电流路径方向。此外，两个叉指电容器（IDC）独特地安装在一个月牙形延伸部分上，与渐变线一起使用，以便在PIN二极管处于关断状态时延长电流路径。通过控制PIN二极管的状态，可以差分调整延迟时间，从而在输出端口产生可变的差分相移。为了验证其功能，将所提出的BLC与一个二元天线阵列集成，以演示差分波束转向。测量结果证实，相控阵天线可以在仰角平面内将其主波束在-27°和25°之间切换，实现的平均增益约为7 dBi。该BLC使用CST Microwave Studio进行设计和仿真，并制作在RO4003C Roger基板（ε = 3.55，0.406 mm）上。所提出的设计非常适合未来天线阵列系统中基于巴特勒矩阵的波束形成网络，特别是对于5G无线应用。
