Tuning and widening of stop bands of microstrip photonic band gap ring structures

We show that the characteristics of microstrip ring structures exhibiting stop bands can be varied by mounting reactive components on the gap of the ring. The presence of capacitor (inductor) on the gap decreases (increases) the center frequency and the frequency range of the stop band. We also show that the stop band can be widened by modifying the structure of the ring. These properties can be useful in the applications to the compact microwave circuits, tunable filters, and microwave switches.