Dual-Band/Tri-Band/Broadband CPW-Fed Stepped-Impedance Slot Dipole Antennas

摘要

In this study, two multi-band antennas and one broadband antenna using slot stepped-impedance resonators (SIRs) and coplanar waveguide (CPW) feeding have been investigated. All of the proposed antennas are fabricated on 1-mm FR4 substrates with a relative 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 dual-band antenna (antenna A) and a tri-band antenna (antenna B) could be designed at desired bands. Antenna A is implemented with center frequencies $(f _{0}, f _{{rm S}1}) = (1.5 ~{rm GHz}, 3.5 ~{rm GHz})$, and Antenna B is realized with center frequencies $(f _{0}, f _{{rm S}1}, f _{{rm S}2}) = (1.5 ~{rm GHz}, 3.5 ~{rm GHz}, 5.5~{rm GHz})$, where $f _{0}$ is the fundamental frequency. The broadband antenna (antenna C) is designed by allocating the first three resonant frequencies close enough to achieve a 98.7% fractional bandwidth with a return loss of greater than 6 dB from 1.5 GHz to 4.4 GHz. Furthermore, to tackle the null radiation problem at the broadside direction of antennas A and B, parasitic slots are added near the main radiating resonators so as to achieve nearly omni-directional radiation patterns at the high-order mode frequencies.