Dual-mode wide-band and dual-band resonators with Minkowski-island-based fractal patch for WLAN systems

The miniaturized dual-mode band-pass filters (BPF) using Minkowski-island-based (MIB) fractal patch resonator are proposed in this paper. The BPF is mainly formed by a square patch resonator in which a MIB fractal configuration with 2^nd order iteration is embedded in the patch. By the perturbation and the T-couple/inter-digital coupling, the wide-band and dual-band responses are obtained respectively. For wide-band design, at 2.41 GHz it has good measured characteristics including the wide bandwidth of 2.26-2.56 GHz (3-dB fractional bandwidth of 12.4%), low insertion loss of 0.72 dB, high rejection level (-52.5/-44.9 dB), and patch size reduction with 60.6%. For dual-band design, the proposed filter covers the required bandwidths for WLAN band (2.23-2. 98 GHz and 4.79-5.8 GHz) applications.