Correction to: Scientific Reports https://doi.org/10.1038/s41598-018-37787-x, published online 20 February 2019

This Article contains errors in two of the Figures. In Figure 2, the shapes in the first row (a-d) are incorrectly all shown as the same shape. In Figure 8, there is a pixel-shift distortion of the graphics. The correct Figures 2 and 8 appear below as Figures 1 and 2 respectively.

Figure 1
figure 1

An example of a basic geometric method to achieve stepped corner perturbation inside a dual-mode square resonator. Feeds are assumed to be aligned with the x and y axes, but are not shown. The idealized switches here are small conductive strips that are switched on/off by being present/absent. As the perturbation gets larger, the eigenmode splitting is increased. Cases (a–d) are equivalent to configurations (A–D).

Figure 2
figure 2

A square resonator design that applies the internal-aperture frequency-tuning concept, alongside mode-splitting.