Decoupling of Antennas with Adjacent Frequency Bands Using Cascaded Decoupling Network

This communication presents a novel decoupling device called a cascaded power dividing decoupling network (C-PDDN). It is cascaded with two antennas operating in adjacent or even contiguous frequency bands to reduce the mutual coupling. To achieve high isolations at $n$ desired frequency points, an $n$ -order C-PDDN can be accordingly designed. Each order PDDN consists of two power dividers (PDs), two sections of transmission lines, and one reactive component. Explicit design formulas are presented to calculate the design parameters of the C-PDDN to meet the required isolation criteria. To validate the decoupling concept, a two-order C-PDDN is designed and applied to a testing array that consists of two base-station dipole antennas, one of which serves the time-division long-term evolution (2300–2400 MHz) and the other for wireless fidelity system (2400–2483.5 MHz). The simulated and measured results demonstrate that the proposed two-order C-PDDN could decrease the mutual coupling by over 20 dB, verifying the decoupling methodology.