A novel all-metal graded index Gutman lens is proposed. It exploits an interleaved metasurface unit-cell with glide symmetry that can provide high values of equivalent refractive index with low frequency dispersion. The result is a compact lens with broadband performance and a wide field of view up to ±70°. The proposed lens exhibits low loss, directive beams and is an appealing candidate for space applications. The design approach introduced can be applied to other graded index lenses with circular symmetry using rectangular or circular periodic structures.

An ultra-thin compact flexible CPW-fed slot monopole antenna suitable for the Internet of Things (IoT) applications was achieved as a result of exploring the use of Zirconia-based ENrG’s Thin E-Strate® for the antenna’s design. The electromagnetic characterization of the novel material at the frequency range of interest was analyzed. A comparison was made concerning the required dimensions and the simulation results regarding impedance matching and radiation properties, for three different dielectric substrates: Novel flexible ceramic (ENrG’s Thin E-Strate), rigid Arlon 25N, and flexible Polypropylene (PP). Two different metallization techniques—electrotextile-based and inkjet printing—were used in the fabrication of prototypes based on ENrG’s Thin E-Strate. Return losses measured results for the fabricated prototypes with both procedures was compared, as well as with simulation. The best prototype on the ENrG’s Thin E-Strate was compared with one on Arlon 25N, in terms of radiation properties in an anechoic chamber, and conclusions were drawn.

The concept and development of a highly efficient pyramidal horn is described. The radiating element comprises a rectangular radiating aperture fed by two smaller flared square waveguide sections via a bifurcated H-plane surface discontinuity. For the simultaneous feeding of the 2-port radiating element, the total antenna includes a compact H-plane power divider. Properly weighted TEn0 modes (n∈N * ) are excited at the output of the two flared waveguide sections. The bifurcation is responsible for the recombination of the incoming fields. The lowdispersive modal coupling coefficients (or transmission coefficients of the bifurcation's generalized scattering matrix) between the excitation and the aperture modes enable the broadband realization of the targeted aperture modal content. The common waveguide section is responsible for the phase alignment of the aperture modes. The design method targets a pre-optimized model which approximates the amplitude of the aperture modes TEm0 (m = 1, 3, 5, …) in the order of 1/m and minimises their relative phase difference. Finally, maximum aperture efficiency can be achieved by fine tuning and with low computational complexity. Design principles are given and illustrated by means of an example involving an antenna with aperture size of about 2.8λ0×1.4λ0 (λ0 being the free-space wavelength at the central frequency of operation). The antenna exhibits aperture efficiency levels above 95% over the entire Ku-Tx band (10.7 -12.75 GHz), as well as a compact profile (4.1λ0). The measured results of a prototype manufactured through milling verify experimentally the numerically predicted performance.

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