Novel Decoupling Concept for Strongly Coupled Frequency-Dependent Antenna Arrays

This paper presents a novel wideband decoupling network for strongly frequency-dependent antenna couplings. The network consists of directional couplers, a transmission line, and a parallel resonant circuit. It cancels mutual coupling by the superposition of a designed coupling with the same magnitude as the original coupling but the opposite phase. Further, the proposed approach accommodates variations in the coupling magnitude and large group delays in the coupling phase. Therefore, it is easy to apply the approach to wideband applications. The design formulas are also derived. With these formulas, the computational results show that the resultant coupling with the proposed technique is 26.4 dB smaller than that of the original coupling at 12.2% bandwidth with a large group delay. Moreover, this paper also describes a technique for practical implementation using short stubs. The resultant coupling with the fabricated multiantenna is 12.6 dB smaller than the original, over the entire 12.2% frequency range. The degradation of radiation efficiency by the proposed circuit is sufficiently small and the enhancement of signal-to-noise ratio is demonstrated.