Realization of an Active Narrow Band Filter with Electronically Controlled Defects in a Microwave Bandgap Structure

Microwave band gap structures (MBG) utilizing fixed defects have received much interest because of their ability to operate as narrow band filters. With the recent interest in reconfigurable wireless devices, the need for electronically controllable narrow band filters is on the rise. By altering the defects in a MBG crystal, the transmission properties of the crystal can be changed. Using this concept, a microwave band gap crystal utilizing PIN diode defect structures has been simulated, fabricated, and tested. Through the control of the PIN 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 FDTD simulation results.