| Abstract: | A novel method for designing a multiband rat‐race ring coupler based on a notch filter is proposed. This method realizes dual‐, tri‐, quad‐, penta‐, … band characterizes of coupler using the same structure, two additional branches. So, it has three advantages: (a) simple structure even the number of working bands more than four; (b) achieving the different numbers of working bands with just one structure; (c) useful for almost any kind of wideband passive components because it views them as black boxes. Three prototypes, a tri‐band ring coupler (Global System for Mobile Communications 0.9 GHz, Digital Communication System 1.8 GHz, Industrial Scientific Medical 2.45 GHz), a quad‐band ring coupler (Time Division Long‐Term Evolution 2.3 GHz, Satellite C‐Band Downlink 3.8 GHz, Aeronautical Radio Navigation 4.3 GHz, and Satellite C‐Band Uplink Applications 6.3 GHz) and a penta‐band ring coupler (Frequency Division Long‐Term Evolution LTE‐FDD] 0.9, 1.4, 1.8, 2.3, and 2.6 GHz), are simulated and measured. They all use the same structure but different parameters of the added branch. The results validate the functionality of the coupler. The method of designing multiband devices in this study can be used for other passive devices, and the structure is simple. |
