Modeling and Design of Nonresonant-Node-Based Filtenna for Triband Wi-Fi Application

The triband wireless Wi-Fi router radiated by series-fed antennas suffers from serious mutual coupling, resulting in throughput degradation. To reduce the mutual coupling, the filtering antennas (filtennas) are designed with nonresonant node (NRN) radiators and series-fed antennas. The NRN filtering radiators are characterized by the NRN filtering circuits, which includes the capacitance and inductance NRNs. These NRNs realize a parallel resonance and radiation zero simultaneously. The radiation zero frequency is smaller or larger than the resonant frequency in the capacitance and inductance NRN, respectively. As the mechanism to manipulate the resonant frequency and radiation zero is figured out, the NRN filtering radiators are designed, and the above analysis is validated. Then, the series-fed antenna equivalent to a parallel resonance is fed by the NRN filtering radiator, and a second-order bandpass filtering network is formed. Its filtering response with the radiation zero realizes a high out-of-band rejection to reduce the mutual coupling. For demonstration, a cross-coupling NRN filtenna is designed to work at 2.4–2.5 GHz [low band (LB)], while the inductance and capacitance NRN filtennas operate at 5.17–5.33GHz [mid band (MB)] and 5.735–5.835 GHz [high band (HB)], respectively. Herein, the radiation zero of the MB antenna is designed at HB, while the HB radiation zero operates at MB. The measurement results exhibit that the mutual coupling is reduced, and the throughput of the triband wireless Wi-Fi router is improved.