A Coupled Resonator Decoupling Network With Source-Load Coupling for Antennas of the Same Band and in Adjacent Bands

A second-order coupled resonator decoupling network (CRDN) with source-load coupling is proposed in this article. Based on the characteristic analysis of different types of coupled antennas, a general decoupling theory from the network point of view for the CRDN with source-load coupling is developed, in which the coupling coefficients of all couplings in the CRDN can be analytically obtained. To demonstrate the effectiveness of the proposed theory, two design examples are elaborated. Two identical triangular sheet antennas of the same frequency, as well as two monopoles operating in adjacent frequency bands, are decoupled by a CRDN with the source-load coupling realized by coupled microstrip lines. Two prototypes and their counterparts in which antennas are strongly coupled without CRDNs are fabricated and measured. The measurement results show that in both cases, the CRDN with the source-load coupling can suppress the mutual couplings between antennas to below <inline-formula> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula>20 dB within the band of interest while maintaining key performances such as matching, radiation patterns, total efficiencies as well as envelope correlation coefficients (ECCs) and available throughput in a given propagation channel. The proposed decoupling design shows great potential to be applied to antenna coexistence problems with broader bandwidth demand.