| 1. |
- Cheng, Shi, et al.
(författare)
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T-matched dipole antenna integrated in electrically small body-worn wireless sensor node
- 2009
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Ingår i: IEE Proceedings - Microwaves Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1350-2417 .- 1359-706X. ; 3:5, s. 774-781
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Tidskriftsartikel (refereegranskat)abstract
- A 2.4 GHz antenna for an electrically small body-worn sensor node is presented. Usually, unbalanced antennas are used in such applications. Implementing a balanced antenna in a small node deployed on the body is problematic from the points of view of both design and characterisation. A solution using a T-matched dipole integrated in the node housing is presented. Techniques for characterisation both in free space and on the body are described. Besides antenna port impedance and radiation efficiency, radiated power and radiation patterns of the active antenna fed by a transceiver in a fully functional sensor node are measured. The benefits and drawbacks of the chosen antenna design and characterisation techniques are discussed.
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| 2. |
- Eriksson, Anders, 1971, et al.
(författare)
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Mode chart of electrically thin parallel-plate circular resonators
- 2001
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Ingår i: IEE Proceedings: Microwaves, Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1350-2417 .- 1359-706X. ; 148:1, s. 51 - 55
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Tidskriftsartikel (refereegranskat)abstract
- Modes in electrically thin circular parallel-plate resonators are discussed in detail. It is shown that the widely used mode indices (found from the field solutions) do not indicate the radial numbers of the field maximums in a straightforward manner. The diameter of the disc, not the radius, accommodates integer numbers of the field maximums (antinodes). These diametrical numbers are expressed in terms of radial mode indices. Emphasis is placed on the first axially symmetric mode TM020, which was incorrectly regarded as TM010 in the past. Some applications of the mode chart, including interpretation of experimental observations, are also discussed. Comparison is made with microstrip and annular resonators.
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| 3. |
- Gevorgian, Spartak, 1948, et al.
(författare)
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Modelling of thin-film HTS/ferroelectric interdigital capacitors
- 1996
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Ingår i: IEE Proceedings: Microwaves, Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1350-2417 .- 1359-706X. ; 143:5, s. 397 - 401
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Tidskriftsartikel (refereegranskat)abstract
- The model of the interdigital capacitor (IDC) has been used for monitoring and analysing the dielectric properties of thin ferroelectric films. The dielectric properties of the film are correlated to its crystalline structure using a simple model of STO. The results of the analysis may be used for optimisation of growth and annealing processes of the films and reducing the effects of the electrode ferroelectric interface. The model can be used to optimise the design of IDCs in the sense of minimum losses and maximum controllability by selecting finger width and gapwidth of the IDC. Further improvement of the model suggests a comprehensive study of all possible mechanisms affecting the dielectric constant and the losses of STO films
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| 4. |
- Gevorgian, Spartak, 1948, et al.
(författare)
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Simple and accurate dispersion expression for the effective dielectric constant of coplanar waveguides
- 1997
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Ingår i: IEE Proceedings: Microwaves, Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1350-2417 .- 1359-706X. ; 144:2, s. 145-148
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Tidskriftsartikel (refereegranskat)abstract
- A conformal mapping based analytic formula is proposed for computation of the frequency dependent effective dielectric constant, ɛeff, of coplanar waveguides (CPW). This formula is correct in a wide frequency band and for wide range of CPW parameters, and models both negative and positive slopes in the frequency dependence of ɛeff. The results are especially useful for modeling microwave/millimetrewave and ultrahigh speed digital interconnects.
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| 5. |
- Olsson, Torbjörn, et al.
(författare)
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Robustness comparison of bow-tie and dipole antennas
- 2005
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Ingår i: IEE Proceedings - Microwaves Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1350-2417 .- 1359-706X. ; 151:6, s. 525-529
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Tidskriftsartikel (refereegranskat)abstract
- The paper describes the application of a computer intensive methodology to evaluate antenna susceptibility to random physical damage for a dipole and a bow-tie antenna. For each randomly generated damage pattern antenna parameters are simulated and a statistical comparison is performed. Computer intensive statistical methods like the Bootstrap, used here for postprocessing, make fewer initial assumptions than classical statistical methods when modelling a problem, and are robust against small deflections from these assumptions. The bias-corrected and accelerated (BCa) Bootstrap method is used for confidence interval estimates. The dipole antenna is found to be more robust to numbers of small (similar to 100th of a wavelength) circular holes penetrating the structure than the bow-tie antenna.
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| 6. |
- Sipus, Z., et al.
(författare)
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Moment method analysis of circular cylindrical array of waveguide elements covered with a multilayer radome
- 2006
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Ingår i: IEE Proceedings - Microwaves Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1350-2417 .- 1359-706X. ; 153:1, s. 29-37
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Tidskriftsartikel (refereegranskat)abstract
- An analysis of ail array of rectangular waveguide openings in a circular cylindrical groundplane covered with a radome is presented. The analysis method is based oil the modal solution, i.e. on the superposition of one-dimensional spectral solutions, and on the method of moments. The modal approach requires the summation of a large number of terms in the Fourier series For structures with large radii. Furthermore. highly oscillating integrals occur when the wavegulde openings are axially separated. Both problems are treated with special care: asymptotic formulas are used for calculating the Green's functions, and the integration contour for calculating the Inverse Fourier transformation is carefully selected. Measurements oil ail 18 x 3 waveguide array oil a circular cylindrical structure covered with a radome have been used for verification of the theoretical results. The effect of an airgap between the waveguide openings and the radome is discussed. The agreement between calculated and measured values of mutual coupling, input admittance and radiation patterns is very good.
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| 7. |
- Warrington, EM, et al.
(författare)
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Directional diversity of HF signals received over high latitude paths, and the possibility of improved data throughput by means of spatial filtering
- 2000
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Ingår i: IEE Proceedings - Microwaves Antennas and Propagation. - 1350-2417 .- 1359-706X. ; 147:6, s. 487-494
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Tidskriftsartikel (refereegranskat)abstract
- The high latitude ionosphere is a dynamic propagation medium in which HF radio signals associated with each propagation mode may arrive at the receiver over a range of angles in both azimuth and in elevation. Furthermore, ionospheric movements at the reflection points impose Doppler shifts and Doppler spreads onto the signals. Large Doppler spreads and multipath propagation in which the delay spread is large are particularly prevalent at these northerly latitudes and can result in a significant degradation in the performance of digital communication systems. This investigation suggests that the application of spatial filtering from simple antenna arrays comprising pairs or triplets of antennas can significantly reduce the level of apparent Doppler spreading, frequently to levels at which modern, high speed modems are expected to operate satisfactorily. The investigation concentrated on Doppler spread since this was the most significant factor in the data employed in this study: however, it is noted that reductions in effective multipath delay spread are also possible.
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| 8. |
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| 9. |
- Gevorgian, Spartak, 1948, et al.
(författare)
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Electrically Controlled HTSC/Ferroelectric Coplanar Waveguide
- 1994
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Ingår i: Microwave and Optical Technology Letters. - : Institution of Engineering and Technology (IET). - 1098-2760 .- 0895-2477. ; 141:6, s. 501 - 503
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that in an integrated YBa2Cu3O7SrTiO3 structure coplanar waveguide (CPW) electrical control of microwave propagation characteristics is possible. Microwave losses of less than 0.2 dB/cm at 10 GHz can be achieved at liquid nitrogen temperatures, provided ferroelectric films with perfect crystalline structures are used. Electrically controlled changes in effective dielectric permittivity of more than 40% are predicted at 77 K and 10 GHz. Sections of these CPWs can be used in electrically controlled phase shifters and resonators.
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| 10. |
- Kristensson, Gerhard, et al.
(författare)
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Radiation efficiency and surface waves for patch antennas on inhomogeneous substrates
- 2003
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Ingår i: IEE Proceedings - Microwaves Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1350-2417. ; 150:6, s. 477-483
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Tidskriftsartikel (refereegranskat)abstract
- Surface wave characteristics and radiation efficiency are calculated for a patch antenna with a given current distribution and located on top of an inhomogeneous, isotropic substrate. The substrate is infinite in the lateral directions and inhomogeneous with respect to the height coordinate. The surface waves in the substrate are analysed using the propagator technique and residue calculus. The propagators and the residues are found by solving two sets of systems of ordinary differential equations (ODEs). Several dispersion curves of the surface waves for inhomogeneous substrates are calculated. The radiation efficiency is compared with the corresponding quantities of a printed antenna on a homogeneous substrate.
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