Project supported by the National Natural Science Foundation of China(Grant Nos.U2141232,62071221,and 62071442);the Aeronautical Science Foundation of China(Grant No.2019ZA037001)。
An ultra-wideband bandpass filter(BPF)with a wide out-of-band rejection based on a surface plasmonic waveguide(SPW)slotline with ring grooves is designed and analyzed.A paired microstrip-to-slotline transition is desi...