Common Mode Suppression Technique for Dual-Band Array Environment

A method for mutual coupling reduction is proposed and demonstrated for a dual band array environment which operates from 698–960 MHz and 1.695-2.700 GHz. Upon the excitation of the low-band (LB) dipole in the baseline design, common mode (CM) currents are induced on the mid-band (MB) dipole feed stems which lead to unwanted radiated emissions. The proposed design technique improves the LB radiation characteristics in the presence of the MB sub-arrays by suppression of the CM currents. Improvements in beamwidth stability, cross-polar radiation, front-to-back ratio, and gain are demonstrated through simulation and measurement. The proposed technique improves the measured LB system gain from 4.33 dBi to 6.92 dBi at 805 MHz, a 2.59 dB improvement.