Effective negative-ε stopband microstrip lines based on complementary split ring resonators

In this letter a super-compact stopband microstrip is proposed. The frequency gap is produced by an array complementary split ring resonators (CSRRs)-a concept prohere for the first time-etched on the ground plane. This behaviour is interpreted as due to the presence of a negative effective permittivity in the vicinity of resonance. The resulting device produces a deep rejection frequency band with sharp cutoff, and a pass band that exhibits very low losses and good matching. Due to the sub-lambda operation of CSRRs, the electrical size of the device is very small.