Abstract:We introduce two flat graded-index (GRIN) lens designs in this paper. First of these is a thick lens which was designed and fabricated by using the 3D-printing technique. Second, a thin Dial-aDielectric (DaD) lens which uses state-of-the-art artificially engineered dielectric materials for design and will be fabricated in future. Both designs overcome the difficulties faced in finding desired commercial off-the-shelf (COTS) materials for 3D-printing lenses. The lenses comprise of several concentric dielectric rings with bespoke relative permittivities for transforming spherical waves into plane waves and vice versa. The 3D-printed thick flat lens is low-cost and light-weight, but provides broadband and high gain performance. Measurement results show that the realized gain of the thick lens is 9-11 dB over the frequency band of 12-18 GHz. The designed DaD lens has the desirable characteristics of low loss, low reflection and broadband properties.
A cold sintering process (150 °C, 30 min and 200 MPa) was employed to fabricate Na 0.5 Bi 0.5 MoO 4 −Li 2 MoO 4 (NBMO-LMO) composites with up to 96.4% relative density. X-ray diffraction traces, backscattered electron images and Raman spectra indicated the coexistence of NBMO and LMO phases in all composites with no detectable secondary phases. The pemittivity (ε r ) and temperature coefficient of resonant frequency (TCF) decreased, whereas microwave quality factor (Q × f) increased, with increasing weight % LMO. Near-zero TCF was obtained for NBMO-20 wt %LMO with ε r ∼ 17.4 and Q × f ∼ 7470 GHz. Functionally graded ceramics were also fabricated with 5 ≤ ε r ≤ 24. To illustrate the potential of these cold sintered composites to create new substrates and device architecture, a dielectric graded radial index lens was designed and simulated based on the range of ε r facilitated by the NBMO-LMO system, which suggested a 78% aperture efficiency at 34 GHz.
Abstract.Simulated and measured microstrip patch antennas produced using embroidery techniques have been presented. The antennas use a standard microwave substrate material. The effect of stitch direction and stitch density is described and a clear requirement to understand how the currents flow in an antenna so that the stitch direction can be correctly chosen is shown. Two different simulation approaches for these antennas are discussed and one is linked to measurement results, pointing to a simplified model for simulating embroidered patch antennas. 2 1. Introduction.
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