An investigation of the effects of mutual coupling on the performance of microstrip radiation

As system requirements dictate that antenna arrays achieve extremely low side lobe levels and that beam formation is well known, the effect of mutual coupling between array elements cannot be ignored. This is true even if the coupling between elements is small. At the time this investigation was initiated quantitative mutual coupling data was not available (either experimental or theoretical) for use of the microstrip array designer. Hence, one was forced to employ expensive cut-and-try techniques to achieve the final array design. The goal of this investigation was to quantitatively determine mutual coupling between microstrip radiators and to determine operating parameters of circular ring microstrip antennas which are particularly useful for microstrip array applications. To achieve the first goal a transmission line model of a pair of coupled rectangular microstrip radiators was developed. This model was then programmed on the NCSU IBM 370 computer. The model can handle two basic geometries the H-plane or parallel coupled and the E-plane or gap coupled radiators.