Multimode and Wideband Printed Loop Antenna Based on Degraded Split-Ring Resonators

In this paper, a compound multimode printed loop antenna based on degraded spilt-ring resonators (SRRs) for broadband wireless applications is proposed. The proposed antenna consists of an outer split ring and one inner closed ring with a big difference in size, which can be considered as degraded SRRs. By virtue of the orthogonal radiating mode of two rings, the compound multimode loop antenna can achieve multi-band resonances. Collaborating with the two coupled rings, a parasitic strip is placed close to the feed gap of the inner ring, which not only induces a new resonant frequency at upper band but also greatly improves the impedance matching in all high-frequency bands. The proposed antenna not only covers the first split ring mode at 816 MHz but also exhibits a broadband property covering from 2.3 to 4.6 GHz (reflection coefficient |S11|0x 0.11λ0(λ0is the wavelength at the lowest operating frequency), uniplanar and simple printed structure and wide bandwidth characteristics make it suitable for a wide range of wireless applications.