Figure 2

(a) Schematic diagram: the resonators are embedded into a rigid wall to achieve tunable surface impedance. (b) Surface impedance (red solid line) and reflection coefficient (blue dashed line) along with \(Q_{\mathrm{loss}}^{-1}\) at \(Q_{\mathrm{leak}}^{-1}=0.025\). (c) 2D schematics of CSR (left panel) and 3D photograph of a sample fabricated by 3D printing (right panel). (d) Surface impedance at resonant frequency (red symbol lines) of CSRs with different \(w_1\). The blue symbol line indicates the variation of L to keep the resonant frequency at 236 Hz. (e) Retrieved loss and leakage factors.