Mutual coupling between parallel half-mode substrate integrated waveguides

This paper presents an experimental study on the mutual coupling between pairs of parallel half-mode substrate integrated waveguides (HMSIWs) in three different configurations. The three different arrangements correspond to the cases where, firstly the open sides of the two HMSIWs face each other; secondly they share the linear array of metallic vias at their closed side; and thirdly the open side of one HMSIW faces the closed side of the second one. As a reference, the mutual coupling between pairs of parallel microstrip lines is also measured and compared to corresponding HMSIWs. The investigation shows that the best isolation can be achieved for the third configuration. The presented results and comparisons are of importance to the application of HMSIWs in the design of microwave integrated circuits (MICs) and array antenna feeds.