Harmonic-Suppressed Dual-Resonance Decoupling Network With Near-Zero Insertion Loss for Patch Antenna Arrays

To suppress the coupling among patch antenna arrays and reduce out-of-band spurious, a feeding-decoupling network with harmonic suppression is proposed. The decoupling method is achieved by generating two decoupling paths between the feeding of an antenna and the radiating patch of an adjacent antenna, through a slotline-based lowpass filter and a miniaturized coupled line coupler. Despite no decoupling operation between non-adjacent elements, the coupling among them is also reduced. The decoupling and harmonic suppression are realized by sharing the same structures, making the physical layout compact. For demonstration purposes, a design of a $1\times $ 8 patch antenna array working at 4.9 GHz, integrated with the proposed decoupling structure is developed. The results indicate that within the impedance bandwidth from 4.8 to 5.1 GHz, the coupling between both adjacent and non-adjacent elements is suppressed to less than −25 dB. Besides, spurious of up to 12 GHz is well suppressed. The in-band total efficiency of the decoupled array is higher than 80%. There is nearly no insertion loss resulting from only $50 \Omega $ transmission lines utilized with very few discontinuities, as expected.