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| 2. |
- Cismasu, Marius
(författare)
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Antenna Analysis and Design Using Stored Energies and Physical Limitations
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A method to estimate Q and QZ' of antennas from single-frequency current distributions is described. This single-frequency method and the concepts of physical bounds on antenna parameters and optimum current distributions are applied to different analysis and design situations of two-dimensional and three-dimensional radiating structures (i.e., antennas). The situations considered are: antenna optimization using a genetic algorithm and the single-frequency Q computation for single or multi-band operation, antenna placement optimization in a wireless device using physical bounds, and antenna optimization that includes QZ' in the objective function. Antenna performance is compared with physical bounds or optimum-current performance in the situations studied. The results presented in this thesis suggest that single-frequency methods may reduce the time necessary to optimize automatically, e.g., using a computer, some antenna parameters such as bandwidth. Furthermore, physical bounds and optimum current distributions are tools that provide valuable information for the processes of antenna analysis and design.
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| 3. |
- Cismasu, Marius, et al.
(författare)
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Antenna Bandwidth Optimization by Genetic Algorithms with Single Frequency Simulation
- 2013
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Ingår i: 2013 7th European Conference on Antennas and Propagation (EuCAP). - 2164-3342. - 9781467321877 ; , s. 2781-2782
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Konferensbidrag (refereegranskat)abstract
- Antenna Q optimization by a genetic algorithm with method of moments simulation at a single frequency is described. The optimized antennas may have arbitrary shapes within a rectangular region. Simulations using a commercial tool show good agreement between the predicted and realized Q factor. Furthermore, comparison with the physical bound shows that the optimized antennas perform close to the optimum for many electrically small dimensions.
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| 4. |
- Cismasu, Marius, et al.
(författare)
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Antenna Bandwidth Optimization with Single Frequency Simulation
- 2014
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 62:3, s. 1304-1311
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Tidskriftsartikel (refereegranskat)abstract
- A method to compute antenna Q using an electromagnetic simulation at a single frequency is described. This method can easily be integrated into global optimization algorithms. In this way the optimization time of some antenna parameters, e.g., bandwidth, may be significantly reduced. The method is validated by direct comparison with the physical bound of the analyzed structure. Numerical examples for rectangular antennas and antennas with a rectangular ground plane illustrate the integration of the method into a genetic algorithm. The results predicted by optimization agree very well with those obtained using a commercial electromagnetic solver. These results suggest that the method can be used to yield antennas with Q factors within 20% of their corresponding physical bound.
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| 5. |
- Cismasu, Marius, et al.
(författare)
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Antenna Bandwidth Optimization with Single Frequency Simulation
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A method to compute antenna Q using an electromagnetic simulation at a single frequency is described. This method can easily be integrated into global optimization algorithms. In this way the optimization time of some antenna parameters, e.g., bandwidth, may be significantly reduced. The method is validated by direct comparison with the physical bound of the analyzed structure. Numerical examples for rectangular antennas and antennas with a rectangular ground plane illustrate the integration of the method into a genetic algorithm. The results predicted by optimization agree very well with those obtained using a commercial electromagnetic solver. These results suggest that the method can be used to yield antennas with Q factors within 20% of their corresponding physical bound.
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| 6. |
- Cismasu, Marius, et al.
(författare)
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Illustration of mobile terminal antenna optimization by genetic algorithms with single frequency simulation
- 2013
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Ingår i: Proceedings of 2013 URSI International Symposium on Electromagnetic Theory (EMTS). - 2163-405X. - 9781467349390 ; , s. 84-87
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Konferensbidrag (refereegranskat)abstract
- An antenna Q optimization procedure using single frequency method of moments simulation integrated into a genetic algorithm is presented. This procedure is applied to a simplified model that describes the geometry of many mobile terminals in use nowadays. The predicted Q factors show good agreement with those obtained by simulation with a commercial tool. Furthermore, the results are close to the physical bound for many common electrical dimensions.
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| 7. |
- Cismasu, Marius, et al.
(författare)
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Illustrations of Physical Bounds on Directive Antennas
- 2010
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Ingår i: 2010 Conference Proceedings ICECom, 20th International Conference on Applied Electromagnetics and Communications. - 9781612849980 - 9789536037582
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Konferensbidrag (refereegranskat)abstract
- Applications of physical bounds for electromagnetic radiators can be used to derive a priori estimates for antenna parameters in terms of the directivity-bandwidth product. These estimates relate the static electric and magnetic polarizability of the radiating structure to its dynamic properties. The results have previously been illustrated for dipole radiators with good agreement. Here, the bounds are illustrated for some antennas with complex radiation patterns, i.e., directivity greater than 3/2 and narrow beams. The a priori estimates show good agreement with the realized antenna parameters.
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| 8. |
- Cismasu, Marius, et al.
(författare)
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Multiband Antenna Q Optimization using Stored Energy Expressions
- 2014
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1548-5757. ; 13, s. 646-649
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Tidskriftsartikel (refereegranskat)abstract
- A method to compute antenna Q from a single frequency current distribution is applied to the optimization of multiband radiating structures. A genetic algorithm produces suboptimal structures in the sense of simultaneous multiband minimum Q. These structures model in a simplified manner common wireless communication devices. The comparison with the physical bounds for the considered situations shows that the suboptimal structures perform close to their limitations. Matching networks are designed using real component models with a commercial tool. These networks have less than three components and provide less than -6.5dB reflection coefficient magnitude in all considered bands. The results show that the single frequency Q estimation method may be useful for antenna design
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| 9. |
- Cismasu, Marius, et al.
(författare)
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Optimal Charges and Currents on Small Wire Antennas
- 2012
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Ingår i: IEEE Antennas and Propagation Society International Symposium (APSURSI), 2012. - 1522-3965 .- 1947-1491. - 9781467304610 ; , s. 1-2
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Konferensbidrag (refereegranskat)abstract
- The optimum surface charge on a thin wire antenna is computed using a variational formulation in the low-frequency limit. This charge and its corresponding current are compared with simulation results for self resonant structures. The comparison shows that the currents and charges on self resonant structures resemble those in the static limit to a great extent.
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