Bandwidth properties of odd mode resonances in frequency selective surfaces

Previous findings show that frequency selective surfaces (FSS) can have resonances of arbitrarily narrow bandwidths. The reason why the bandwidth of certain resonances is necessarily very narrow is shown. We prove that if the current distribution at resonance is mostly odd, then the current magnitude must approach infinity when the angle of incidence approaches normal (0/spl deg/). Since infinite currents cannot physically exist, the resonant bandwidth must approach 0/spl deg/ in order to suppress the infinite currents.