Mutual Coupling of Microbump Antennas: Theory, Experiment, and Application

A theory based on the dyadic Green’s function and the sphere model is developed to analyze the coupling characteristics between two microbump antenna elements. The formula for the mutual impedance according to the rection theorem is obtained, which can accurately calculate the coupling caused by the disks and the balls and can also consider the surface-wave effect. Measurements were conducted for the mutual impedance and mutual coupling between the two microbump antenna elements at 3GHz. Measured results are in excellent agreement with the calculations and simulations. Further, a 4×4 millimeter-wave microbump antenna array was designed, fabricated, and measured. Results shows that the microbump antenna array is superior to the microstrip antenna array, especially in the radiation efficiency, which is increased by 21.2% at the resonant frequency of the microbump antenna.