Corrigendum to “A novel quadband ultra miniaturized planar antenna with metallic vias and defected ground structure for portable devices” [Heliyon 7 (3) (March 2021) e06373]

In the original published version of this article, Equation 2 incorrectly displayed a subtraction sign (−) between the first and second terms, where there should have been an addition sign (+). The correct version of Equation 2 can be found below. The authors apologize for the errors. Both the HTML and PDF versions of the article have been updated to correct the errors.

$${\epsilon }_{eff}=\frac{{\epsilon }_r+1}{2}+\frac{{\epsilon }_r-1}{2}{\left[1+12\frac{h}{\left(3.414a\right)}\right]}^{-0.5}$$