Design and Free-Space Measurements of Broadband, Low-Loss Negative-Permeability and Negative-Index Media

We present the design and measurement of broadband, volumetric negative-permeability and negative-refractive-index (NRI) media. Both of these media are fabricated using standard printed-circuit-board techniques and operate at X-band frequencies. The S-parameters of four-cell slabs of the negative-permeability and NRI media are measured, and the material parameters of the NRI lens are extracted. The four-cell-thick (λ₀/3) NRI lens exhibits a backward-wave bandwidth of 41.2% and a total loss of 0.67 dB at the operating frequency (where μr ≈ -1). Super-resolved focusing in free space is also demonstrated, and spatial frequencies beyond the free-space wavenumber are recovered over a bandwidth of 7.4%. A focus with a half-power beamwidth of 0.27λ₀ is achieved at 10.435 GHz.