Electronically controlled microwave band gap filter structures

Microwave band gap structures (MBG) utilizing fixed defects have received m uch interest because of their ability to operate as narrow band filters. Wi th the recent interest in reconfigurable wireless devices, the need for ele ctronically controllable narrow band filters is on the rise. By altering th e defects in an MBG crystal, the transmission properties of the crystal can be changed. Using this concept, two controllable defect structures have be en studied. Microwave band gap crystals utilizing single and dual p-i-n dio de defect structures have been simulated, fabricated, and tested. Through t he control of the p-i-n diode bias current, the transmission effects caused by the crystal defects can be altered. Experiments demonstrating contrasts of more than 30 dB between the diode-on and diode-off states are presented along with the corresponding finite difference time domain simulation resu lts. (C) 2001 American Institute of Physics.