Decoupling for microstrip antenna array based on characteristic mode analysis

A new decoupling method for microstrip antenna arrays has been proposed in this paper, which is based on characteristic mode analysis. This method works by suppressing the nonworking mode that contributes the most to mutual coupling. An eight-element microstrip antenna array is designed as the reference antenna, and for this antenna, mode suppression is achieved by etching gaps on the patch and adding metal columns between the patch and the ground. The antenna array after the mode suppression is fabricated and measured. The results show that the measured S₃₄ after the mode suppression is below −21 dB, whereas the simulated S₃₄ of the reference antenna array is about −15 dB. This indicated a 7–10.5 dB reduction in coupling across the band. Additionally, the measured ActiveS₃ after the mode suppression is still below −11 dB. Besides, the measured and simulated normalized array patterns after the mode suppression agree well at different frequencies.