Switchable and Tunable Notch in Ultra-Wideband Filter Using Electromagnetic Bandgap Structure

A simple technique to reconfigure a notch filter employing a 1-D electromagnetic bandgap (EBG) structure, which is capacitively coupled to a microstrip line, is presented in this letter. The resonant nature of the EBG creates a notch in the transmission band. The notch filter is made reconfigurable/tunable by introducing an additional capacitive structure to change the size (geometry) of the EBG unit cell. The structure is connected or disconnected to the main structure (unit cell) by means of a PIN diode or varactor diode. Its application in notched-band ultra wideband (UWB) filter is demonstrated. A 450 MHz change in notch frequency is observed using PIN diode, and 340 MHz tuning range is observed using varactor diode.