New CRLH-Based Planar Slotted Antennas with Helical Inductors for Wireless Communication Systems, RF-Circuits and Microwave Devices at UHF–SHF Bands

Two novel planar slotted-antennas (PSAs) are presented that exhibit good radiation characteristics at the UHF–SHF bands. The proposed antennas are constructed using metamaterial unit-cells constituted from capacitive slots etched in the radiating patch and grounded spiral shaped inductive stubs. The proposed PSA design is fabricated on a commercially available dielectric substrate, i.e. Rogers RO4003 with permittivity of 3.38 and thickness of 1.6 mm. The first PSA comprising five symmetrical unit-cells of slot–inductor–slot configuration operates over a wide bandwidth extending from 1 to 4.2 GHz with a peak gain of 1.5 dBi and efficiency of 35 % at 2 GHz. The second PSA consists of ten asymmetrical unit-cells of slot–inductor configuration on the same size of substrate as the first PSA, enhances the antenna gain by 2 dB and efficiency by 25 % and operates over 0.75–4.5 GHz. The asymmetrical unit-cell effectively increases the aperture size of the antenna without comprising its size. The electrical size of the antenna is 0.083λ₀ × 0.033λ₀ × 0.005λ₀, where free-space wavelength (λ₀) is 1 GHz.