| 11. |
- Gustafsson, Mats, et al.
(författare)
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Sum rules and physical bounds on passive metamaterials
- 2010
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Frequency dependence of the permittivity and permeability is inevitable in metamaterial applications such as cloaking and perfect lenses. In this paper, Herglotz functions are used as a tool to construct sum rules from which we derive physical bounds suited for metamaterial applications, where the material parameters are often designed to be negative or near zero in the frequency band of interest. Several sum rules are presented that relate the temporal dispersion of the material parameters with the difference between the static and instantaneous parameter values, which are used to give upper bounds on the bandwidth of the application. This substantially advances the understanding of the behavior of metamaterials with extraordinary material parameters, and reveals a beautiful connection between properties in the design band (finite frequencies) and the low- and high-frequency limits.
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| 12. |
- Gustafsson, Mats, et al.
(författare)
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Sum rules and physical limitations for passive metamaterials
- 2011
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Konferensbidrag (refereegranskat)abstract
- Bandwidth is an important parameter in many metamaterial applications. It has been shown that Herglotz functions and sum rules offer a powerful methodology to analyze the trade-off between bandwidth and design parameters. Here, this approach is described for the temporal dispersion of constitutive relations and high-impedance surfaces.
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| 13. |
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| 14. |
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| 15. |
- Larsson, Christer, et al.
(författare)
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High temperature waveguide measurements of the permittivity and permeability
- 2010
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Ingår i: ; , s. 1-4
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Konferensbidrag (refereegranskat)abstract
- This paper describes a setup for measurements of the permittivity and the permeability at temperatures from room temperature up to 1000 °C using a single rectangular waveguide. The hardware design of the setup that can handle these temperatures is developed and described. Measurements on a NiZn ferrite sample are performed in order to evaluate the performance of the setup and the procedure that is used to determine the permittivity and permeability from the measured S-parameters.
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| 16. |
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| 17. |
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| 18. |
- Larsson, Christer, et al.
(författare)
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Waveguide measurements of the permittivity and permeability at temperatures up to 1000 C
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper describes a method to measure the permittivity and the permeability at temperatures from room temperature up to 1000 C using a single rectangular waveguide. The hardware design of the setup that can handle these temperatures and the procedure that is required to correct for the thermal expansion is developed. This includes the sample displacement, the displacement of the calibration reference planes, the thermal expansion of the waveguide and the gap between the sample and the waveguide wall. Measurements on Macor\textregistered and NiZn Ferrite samples are performed in order to evaluate the performance of the setup and the procedure that is used to determine the permittivity and permeability from the measured S-parameters.
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| 19. |
- Lau, Buon Kiong, et al.
(författare)
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Career preparation in doctoral education at the departmental level
- 2010
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Ingår i: Proceedings 6:e Pedagogiska inspirationskonferensen 15 december 2010.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Traditionally, doctoral education is designed to train students to become skilled researchers in their respective disciplines. In many cases, however, doctoral graduates find themselves ill-prepared for their career choices. In this paper, we adopt a systematic approach to study the career preparation aspect of doctoral study in our home department. Our findings reveal several shortcomings in the current system and we formulate concrete recommendations to address these issues.
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| 20. |
- Ohlsson, Lars, et al.
(författare)
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Admittance Matching of 60 GHz Rectangular Dielectric Resonator Antennas for Integrated Impulse Radio
- 2010
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Ingår i: [Host publication title missing]. ; , s. 253-256
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Konferensbidrag (refereegranskat)abstract
- Methods to achieve admittance matching of rectangular dielectric resonator antennas intended for 60~GHz impulse radio are reported. The motivation is to find a suitable antenna that may be integrated in the V-band gated tunnel diode wavelet generator, replacing its tank circuit and forming a low complexity transmitter. Probed one- and two-port scattering parameter measurements have been performed to characterise the fabricated antennas. Changing the feed structure from a tapered dipole to an offset fed and tapered slot, a change from capacitive to inductive characteristics is observed, and the matching to the gated tunnel diode is improved. Deembedded admittance resonance frequencies of fabricated antennas were found at 53.6 and 52.2~GHz for dipole and slot fed antennas, respectively. Characterising the transmission link between dipole fed antennas, a maximum antenna gain of 10.5~dBi and a 3~dB power bandwidth of 1.5~GHz were found at 53.3~GHz.
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