Broadband, low-loss negative-permeability and negative-index media for free-space applications

We present broadband negative permeability and negative-refractive-index (NRI) media that operate in free space. Both of these media operate at X-band frequencies and are fabricated using standard printed-circuit-board techniques. The S-parameters of four-cell slabs of the negative permeability and NRI media are measured using a quasi-optical Gaussian beam measurement system. Using these data, the material parameters of the NRI lens are calculated. The four-cell-thick (lambda₀/3) lens exhibits a backward-wave bandwidth of 41.2% and a total loss of 0.67 dB at the operating frequency. Super-resolved focusing in free space is also demonstrated over a bandwidth of 8.4%. A focus with a half-power beamwidth of 0.27 lambda₀ is achieved at 10.435 GHz.