Compact Ultra-Wideband (UWB) Bandpass Filters With Multiple Notched Bands

A novel asymmetric coupling strip is presented, which can be used in the ultra-wideband (UWB) bandpass filter (BPF) to generate multiple notched bands within the passband. The proposed structure can provide two main paths for the signals, which makes it possible to generate multiple transmission zeroes. The center frequencies and bandwidths of the notched bands can be controlled by tuning the structural parameters. The asymmetric coupling strip has been integrated into a circular disc resonator to construct a compact UWB BPF with multiple notched bands. The measured results agree with the predicted ones closely. These two notched bands centered at 4.3 and 8 GHz have 10-dB rejection fractional bandwidths of about 4.2% and 3.8%, respectively.