Improvement of spurious responses of coupled-line BPFs using interdigital-type resonators

Out‐of‐band improvement by BPFs with multiple attenuation poles using a condition of variable coupling length of a parallel partially coupled‐line section

“…Also, a novel UWB circular monopole-type notch antenna [3] and a CPW-fed planar UWB antenna with a frequency-band notch function [4] have been studied for UWB applications. Recently, a novel CPW-fed UWB antenna was designed by using a trapezoidal patch and a two-step technique for ultra-wideband impedance matching [5].…”

“…However, optimization is necessary in order to systemize the design methodology and choose the circuit parameters, which will be addressed in a future study. Various UWB antennas with a notch function have been developed for UWB communications [1][2][3][4][5]. Coplanar waveguide (CPW) and microstrip feeds for a half-disk antenna structure have been proposed and compared [1].…”

“…When the I/O ports are on the same side, it is called a parallel coupled-line BPF, and when the I/O ports are on opposite sides, it is called an anti-parallel coupled-line BPF. The characteristics of an anti-parallel partially coupled-line BPF has been investigated [5]. Here, we consider a parallel coupled-line whose basic configuration and characteristics are shown in Figure 1.…”