Open slot antenna in a small groundplane at the second resonance

The open slot at second resonance in a small groundplane makes a simple, wideband antenna. The wider slot has a wider theoretical bandwidth as expected, but the best 50Ω impedance bandwidth calls for a given slot width. When the groundplane is small (<;λ2), the pattern retains a single lobe at each side of the groundplane with directivity over 6.2dBi. For a given slot width, the minimum groundplane size to retain the antenna 50Ω impedance performance is small, e.g., for the slot width w=0.06L=0.04λ (L=0.8λ), the required groundplane size is about 0.32λ by 0.83λ. The depth of the slot can range from 0.008/. to 0.167/. without significantly changing the performance.