Super-Compact Planar Ultra-Wideband (UWB) Bandpass Filter Composed of Capacitor-Loaded E-shaped Electrodes

This paper newly proposes a super-compact planar ultra-wideband (UWB) bandpass filter composed of capacitor-loaded E-shaped electrodes. This capacitor supplies additional capacitance to the tightly-coupled electrodes, leading to relax the fabrication difficulties. By introducing the capacitor to the gap, response of the UWB passband is drastically improved. In the experiment, with a 0.5 pF capacitor, a clear UWB passband from 3.1 GHz to 11.4 GHz (FBW 114%) was obtained with small ripples of less than 0.5 dB and minimum insertion loss of 0.4 dB, which results show good agreement with the theory. Using this method, planar UWB filters can be made much more compact.