Metamaterials Show Promise for RF Circuits

Researchers explored the capabilities of metamaterials as microwave circuit substrates.

Artificially created composite materials, also known as metamaterials, promise behavior beyond what is normally found in nature, such as dielectric materials with negative permeability and permittivity. In search of potential circuit applications for metamaterials, researchers from Australia’s Queensland University of Technology and Malaysia’s Universiti Kebangsaan Malaysia investigated the use of microstrip transmission lines and dual-star, split-ring resonators (DSSRRs) fabricated on metamaterials to achieve circuit sizes much smaller than normally dictated by quarter- and half-wavelength structures. They explored left-handed (LH) and right-handed (RH) metamaterial media to better understand some potential capabilities of metamaterials for RF and microwave circuits.

The researchers designed a DSSRR with metallic rings on top of a metamaterial substrate. Two opposite rings were formed, with a small gap to obtain a negative resonance. The bandwidth of the resonator can be enhanced by gap tuning. A DSSRR is fabricated in microstrip technology by etching the rings just below the surface of the substrate. The performance of this periodic unit-cell resonator was measured by vector network analysis and S-parameters. The first resonance was detected at 8.9 GHz, and the second–at about 16 dB less in amplitude—at 10 GHz. The same period unit-cell DSSRR was fabricated on commercial circuit material with dielectric constant of 10.2, RT6010 laminate from Rogers Corp., so as to verify the basic performance of the resonator.

The experimenters closely matched their numerical predictions with measured results as part of a study to better understand the properties of composite right-handed/left-handed (CRLH) metamaterials as microwave substrates. It confirmed a great deal of metamaterial theory as applied to RF/microwave circuits.

See “Making Meta Better,” IEEE Microwave Magazine, Vol. 17, No. 8, August 2016, p. 52.

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