Antenna Q and stored energy expressed in the fields, currents, and input impedance
(2015) In IEEE Transactions on Antennas and Propagation 63(1). p.240249 Abstract
 Although the stored energy of an antenna is instrumental in the evaluation of antenna Q and the associated physical bounds, it is difficult to strictly define stored energy. Classically, the stored energy is either determined from the input impedance of the antenna or the electromagnetic fields around the antenna. The new energy expressions proposed by Vandenbosch express the stored energy in the current densities in the antenna structure. These expressions are equal to the stored energy defined from the difference between the energy density and the far field energy for many but not all cases. Here, the different approaches to determine the stored energy are compared for dipole, loop, inverted Lantennas, and bowtie antennas. We use Brune... (More)
 Although the stored energy of an antenna is instrumental in the evaluation of antenna Q and the associated physical bounds, it is difficult to strictly define stored energy. Classically, the stored energy is either determined from the input impedance of the antenna or the electromagnetic fields around the antenna. The new energy expressions proposed by Vandenbosch express the stored energy in the current densities in the antenna structure. These expressions are equal to the stored energy defined from the difference between the energy density and the far field energy for many but not all cases. Here, the different approaches to determine the stored energy are compared for dipole, loop, inverted Lantennas, and bowtie antennas. We use Brune synthesized circuit models to determine the stored energy from the input impedance. We also compare the results with differentiation of the input impedance and the obtained bandwidth. The results indicate that the stored energy in the fields, currents, and circuit models agree well for small antennas. For higher frequencies, the stored energy expressed in the currents agrees with the stored energy determined from Brune synthesized circuit models whereas the stored energy approximated by differentiation of input impedance gives a lower value for some cases. The corresponding results for the bandwidth suggest that the inverse proportionality between the fractional bandwidth and Qfactor depends on the threshold level of the reflection coefficient. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/record/4731124
 author
 Gustafsson, Mats ^{LU} and Jonsson, B.L.G
 organization
 publishing date
 2015
 type
 Contribution to journal
 publication status
 published
 subject
 keywords
 antenna Q, stored energy, antennas
 in
 IEEE Transactions on Antennas and Propagation
 volume
 63
 issue
 1
 pages
 240  249
 publisher
 IEEEInstitute of Electrical and Electronics Engineers Inc.
 external identifiers

 wos:000347383500025
 scopus:85016354053
 ISSN
 0018926X
 DOI
 10.1109/TAP.2014.2368111
 project
 EIT_CACOEMD Complex analysis and convex optimization for EM design
 language
 English
 LU publication?
 yes
 id
 64f8eb89f1964fffa9fd61440771cf14 (old id 4731124)
 date added to LUP
 20141028 10:41:03
 date last changed
 20171112 03:41:09
@article{64f8eb89f1964fffa9fd61440771cf14, abstract = {Although the stored energy of an antenna is instrumental in the evaluation of antenna Q and the associated physical bounds, it is difficult to strictly define stored energy. Classically, the stored energy is either determined from the input impedance of the antenna or the electromagnetic fields around the antenna. The new energy expressions proposed by Vandenbosch express the stored energy in the current densities in the antenna structure. These expressions are equal to the stored energy defined from the difference between the energy density and the far field energy for many but not all cases. Here, the different approaches to determine the stored energy are compared for dipole, loop, inverted Lantennas, and bowtie antennas. We use Brune synthesized circuit models to determine the stored energy from the input impedance. We also compare the results with differentiation of the input impedance and the obtained bandwidth. The results indicate that the stored energy in the fields, currents, and circuit models agree well for small antennas. For higher frequencies, the stored energy expressed in the currents agrees with the stored energy determined from Brune synthesized circuit models whereas the stored energy approximated by differentiation of input impedance gives a lower value for some cases. The corresponding results for the bandwidth suggest that the inverse proportionality between the fractional bandwidth and Qfactor depends on the threshold level of the reflection coefficient.}, author = {Gustafsson, Mats and Jonsson, B.L.G}, issn = {0018926X}, keyword = {antenna Q,stored energy,antennas}, language = {eng}, number = {1}, pages = {240249}, publisher = {IEEEInstitute of Electrical and Electronics Engineers Inc.}, series = {IEEE Transactions on Antennas and Propagation}, title = {Antenna Q and stored energy expressed in the fields, currents, and input impedance}, url = {http://dx.doi.org/10.1109/TAP.2014.2368111}, volume = {63}, year = {2015}, }