Microstrip antenna array controlled with active phase shifter

A two-element microstrip antenna array controlled by active phase shifters is described. It can be mounted on aircraft or missiles and be used in direction finder or adaptive array systems. The mutual coupling between microstrip patches is studied experimentally, and it is found that the self-impedence and resonant frequency are affected significantly when the separation is less than 0.4 wavelengths; they remain almost constant when the separation is greater than 0.5 wavelengths. The effect of mutual coupling in the E-plane is less prominent than in the H-plane.