Bandwidth and radiation specifications enhancement of monopole antennas loaded with split ring resonators

New broadband antennas loaded with split ring resonators (SRR) are proposed and investigated. The results illustrate that by loading the conventional monopole antennas with an asymmetrical meander lines SRR, a lower resonance frequency mode can be excited. The dimensions of the SRR have been selected to provide a resonance close the resonance of the monopole antennas. The results illustrate that when both resonance coincide the antennas bandwidths and radiation properties can be enhanced. The length and width of the antennas are 25 × 10^-2λ₀ × 11 × 10^-2λ₀ and 25 × 10^-2λ₀ × 21 × 10^-2λ₀ at 4 GHz for monopole antennas, and 29 × 10^-2λ₀ × 21 × 10^-2λ₀ at 2.9 GHz for both monopole antennas loaded with SRR. For antennas without SRR loading, maximum of measured gains and efficiencies are 3.6 dBi and 78.5% for F-antenna, and 3.9 dBi and 80.2% for T-antenna, hence they appear at 5 GHz. For antennas with SRR loading, these parameters are 4 dBi and 81.2% for F-antenna, and 4.4 dBi and ~83% for T-antenna, which appeared at 6 GHz. By implementing the meander lines SRR as a matching load on the monopole antennas, the resulted antennas cover the measured frequency bandwidths of 2.9-6.41 GHz and 2.6-6.6 GHz (75.4 and ~87% fractional bandwidths), which are ~2.4 and 2.11 times more than monopole antennas with an approximately same in size.