A Transmission Line-Based Notch Structure With a Wide Range of Variation Notch Bandwidth

In this letter, a novel method is proposed to realize a wide range of variation notch bandwidth in a notch structure by changing the height of the mushroom-like resonator that is embedded in the dielectric layer of the transmission line (TL). The resonator consists of narrow strips and rectangular patches and is connected to the ground through metal vias, and a detailed analysis of its working mechanism and key parameters is provided based on the equivalent circuit. The Q value of the resonant circuit shows that the notch bandwidth is relevant to the equivalent capacitance ratio, which explains that the notch bandwidth can be flexibly adjusted by adjusting the height of the resonator. Its applicability to other TLs is also discussed. Furthermore, the notch structure can be applied to various antennas without affecting their radiation characteristics. Three validation structures are fabricated: narrowband and broadband notched microstrip lines, and a dual-band notched antenna with low cross-polarization, all the measured results show effects consistent with simulation predictions.