Dual-band and multiband CPW fed strip antennas for wireless applications

In this study, A multi band and dual band antenna using slot stepped-impedance resonators(SIR) and coplanar waveguide (CPW) feeding have been investigated. All of the proposed antennas are fabricated on 1-mm FR4 substrates with a dielectric constant of 4.4 and a loss tangent of 0.02. In comparison to the conventional uniform — impedance resonator (UIR), the SIR shows a better control over spurious response. In this way a multiband could be designed at desired bands. The multiband antenna is designed by allocating the resonating frequencies close enough to achieve a 98.7% fractional bandwidth with a return loss greater than 12 dB from 1 GHz to 12 GHz with multiple bands. Furthermore, to tackle the null radiation problem at the multiband. Parasitic slots are added near the main radiating resonators so as to achieve nearly omnidirectional radiation patterns at higher order mode frequencies.