Quasi-Millimeter-Wave UWB Bandpass Filter with Sharp Notch at Restricted Band

This paper presents a bandpass filter for ultra-wideband (UWB) radio systems at quasi-millimeter-wave frequencies (22 - 29 GHz) with a sharp notch at the restricted band. The developed bandpass filters are based on edge-coupled line structure, and designed by using electromagnetic simulation software and fabricated using wet-etching process. The sharp notch at the restricted band is realized by introducing an in-line open stub structure into the bandpass filter, which is embedded in the input and output lines, keeping the whole filter very compact. The measured results demonstrate good filter performance of the developed filters, including the insertion loss: about 2.7 dB over the passband, and a sharp notch to stop the restricted band with attenuation larger than 25 dB.