Bandwidth-Enhanced Electrically Large Microstrip Antenna Loaded With SRR Structures

In this letter, microstrip-line-slot feed patch antenna element and array with electrically large property (ELP) are designed and discussed. Periodic three-dimensional split-ring resonator (SRR) structures are introduced as inclusions to realize the ELP. By tuning the structure parameters, their effective permittivity (
ϵ
_eff
<0) and permeability (
u
_eff
>0) could meet the requirement of –1<
u
_eff
ϵ
_eff
<0. The antenna resonates at about 27.7 GHz, which is 4.4 times higher than the original one. Compared with the former ELP design, two resonant modes (TM
₁₀
and antiphase TM
₂₀
mode) are both excited closely with each other, and thus the bandwidth is much improved by joining together. Furthermore, one 1 × 2 array of the SRR-loaded ELP antenna is also designed to confirm the array application. Both the element and array antennas were fabricated for verification. The measured results show that –10 dB impedance bandwidths of 6% and 4.6% with maximum gain of 9.1 and 11.9 dBi were obtained for the element and array, respectively. Larger array could be designed with this method when higher gain is needed.