Compact Single- and Dual-Band Filtering 180° Hybrid Couplers on Circular Patch Resonator
Gang Zhang, Fei Jiao, Shicheng Liu, Lei Zhu, Shiyan Wang, Qiyun Zhang, Jiquan Yang
Abstract
In this article, an effective approach is proposed to design of compact single and dual-band patch filtering 180° hybrid couplers based on circular patch resonator. Without an additional circuit, the prescribed in-phase and out-of-phase specifications of the coupler are achieved by elaborately studying and utilizing the electric field distributions of the degenerate resonant modes in the unslotted/slotted patch resonators. Meanwhile, the desired single-/dual-band filtering responses are attained by virtue of the coupling extent between the two designed patch resonators in the back-to-back form. In our design, a pair of TM11-modes at first makeup a single passband for single-band operation, and a pair of TM11-like modes and a pair of TM12-like modes then construct the two separate passbands for dual-band operation, respectively. After the working principle is explained, the design procedure based on the coupling matrix is provided. For demonstration, two prototypes for single- and dual-band patch filtering 180° hybrid couplers are implemented, respectively. Measured results coincide well with simulated ones, verifying the proposed design concept.