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Your search keyword '"Vardaxoglou, Yiannis"' showing total 91 results
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91 results on '"Vardaxoglou, Yiannis"'

3. Frequency selective surface with a bistable auxetic geometry.

Author

Vardaxoglou, Yiannis and Alexandridis, Antonis A.

Subjects
*FREQUENCY selective surfaces, *GEOMETRY
Abstract

Two bistable auxetic array geometries have been considered as FSS arrays of conducting elements. A square base form auxetic array with a combination of vertical and horizontal IT‐poles and a triangular one with three legged elements. Both of these have exhibited FSS reflection and transmission band characteristics with close band ratios. [ABSTRACT FROM AUTHOR]

Published
2024
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4. Simulations and Measurements of dual-band 2-d Periodic Leaky Wave Antenna

Author

Kelly, James, Passalacqua, Giovanni, Feresidis, Alexandros P, Capolino, Filippo, Albani, Matteo, and Vardaxoglou, Yiannis C

Subjects
Communications Engineering, Engineering, Electronics, Sensors and Digital Hardware
Abstract

A dual band 2-D leaky wave antenna is presented. The antenna is constructed from a double layer partially reflective surface suspended above a metallic ground plane, forming two Fabry Perot cavities corresponding to the two different resonant frequencies. The paper demonstrates the successful operation of the antenna through simulation and measurement. ©2007 IEEE.

Published
2007

9. Multi-material additive manufacturing of low sintering temperature Bi2Mo2O9 ceramics with Ag floating electrodes by selective laser burnout

Author

Gheisari, Reza, primary, Chamberlain, Henry, additional, Chi-Tangyie, George, additional, Zhang, Shiyu, additional, Goulas, Athanasios, additional, Lee, Chih-Kuo, additional, Whittaker, Tom, additional, Wang, Dawei, additional, Ketharam, Annapoorani, additional, Ghosh, Avishek, additional, Vaidhyanathan, Bala, additional, Whittow, Will, additional, Cadman, Darren, additional, Vardaxoglou, Yiannis C., additional, Reaney, Ian M., additional, and Engstrøm, Daniel S., additional

Published
2020
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10. Laser-assisted manufacture for performance-optimized dielectrically loaded GPS antennas for mobile telephones

Author

Leisten, Oliver, Fieret, Jim, Stassen Böhlen, Ines, Rumsby, Phil T., McEvoy, Patrick, Vardaxoglou, Yiannis, Leisten, Oliver, Fieret, Jim, Stassen Böhlen, Ines, Rumsby, Phil T., McEvoy, Patrick, and Vardaxoglou, Yiannis

Abstract

The use of ceramic cores of high dielectric constant is an essential part of a strategy to miniaturize GPS antennas for mobile telephones. The core reduces the guide wavelength of the conducting structures on the antenna, thereby creating a need for high-resolution imaging to maintain very accurate dimensions. It is for this principal reason that a novel laser imaging technology has been developed using a positive electrophoretic photoresist and UV excimer laser mask imaging to produce the conducting features on the surface of the antenna. Furthermore, a significant process challenge in producing this type of antenna concerns the reproducibility of the right-hand circular polarization performance and the bandwidth over which this can be achieved - which becomes progressively smaller as antenna size is reduce. It is therefore a vital requirement that the antennas have the point to be tuned by a laser trimming process at an automatic RF testing station. A galvanometer controlled Nd:YAG laser spot is used to trim the conductive pattern on the top of the antenna following an RF measurement to characterize the resonant frequencies of the four helical conductors. Results demonstrate the laser imaging and trimming techniques ensure a high-speed method of guaranteeing the antenna performance. The technique is appropriate for other antenna types such as GSM, Bluetooth and Wireless LAN.

Published
2019

12. Multi-material additive manufacturing of low sintering temperature Bi2Mo2O9 ceramics with Ag floating electrodes by selective laser burnout.

Author

Gheisari, Reza, Chamberlain, Henry, Chi-Tangyie, George, Zhang, Shiyu, Goulas, Athanasios, Lee, Chih-Kuo, Whittaker, Tom, Wang, Dawei, Ketharam, Annapoorani, Ghosh, Avishek, Vaidhyanathan, Bala, Whittow, Will, Cadman, Darren, Vardaxoglou, Yiannis C., Reaney, Ian M., and Engstrøm, Daniel S.

Subjects
LOW Temperature Cofired Ceramic technology, LOW temperatures, CERAMICS, MICROWAVE communication systems, PERMITTIVITY, MANUFACTURING processes, SINTERING, MOLYBDENUM disilicide
Abstract

Additive manufacturing (AM) of co-fired low temperature ceramics offers a unique route for fabrication of novel 3D radio frequency (RF) and microwave communication components, embedded electronics and sensors. This paper describes the first-ever direct 3D printing of low temperature co-fired ceramics/floating electrode 3D structures. Slurry-based AM and selective laser burnout (SLB) were used to fabricate bulk dielectric, Bi2Mo2O9 (BMO, sintering temperature = 620–650°C, εr = 38) with silver (Ag) internal floating electrodes. A printable BMO slurry was developed and the SLB optimised to improve edge definition and burn out the binder without damaging the ceramic. The SLB increased the green strength needed for shape retention, produced crack-free parts and prevented Ag leaching into the ceramic during co-firing. The green parts were sintered after SLB in a conventional furnace at 645°C for 4 h and achieved 94.5% density, compressive strength of 4097 MPa, a relative permittivity (εr) of 33.8 and a loss tangent (tan δ) of 0.0004 (8 GHz) for BMO. The feasibility of using SLB followed by a post-printing sintering step to create BMO/Ag 3D structures was thus demonstrated. [ABSTRACT FROM AUTHOR]

Published
2020
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18. 3D-printed lens antenna

Author

Arya, Ravi Kumar, primary, Zhang, Shiyu, additional, Vardaxoglou, Yiannis, additional, Whittow, Will, additional, and Mittra, Raj, additional

Published
2017
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19. Guest Editorial

Author

Antoniades, Marco, primary, Skrivervik, Anja K., additional, and Vardaxoglou, Yiannis C., additional

Published
2016
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33. 3D-printed planar graded index lenses.

Author

Shiyu Zhang, Arya, Ravi Kumar, Pandey, Shaileshchandra, Vardaxoglou, Yiannis, Whittow, Will, and Mittra, Raj

Subjects
GRADIENT index optics, PLANE wavefronts, THREE-dimensional printing, DIELECTRIC devices, PERFORMANCE evaluation
Abstract

The authors introduce two flat graded-index (GRIN) lens designs in this study. First of these is a thick lens, which was designed and fabricated by using the three-dimensional (3D)-printing technique. Second, a thin dial-a-dielectric (DaD) lens, which uses state-of-the-art artificially engineered dielectric materials for design and for which they present only the simulated results, with plans to fabricate it in the future. Both designs overcome the difficulties faced in finding desired commercial off-the-shelf materials, either for 3D-printing or for fabricating conventional GRIN 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 realised 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. [ABSTRACT FROM AUTHOR]

Published
2016
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