Gain and Q Bounds for Coupled TM-TE Modes

Thal, H.L.

doi:10.1109/tap.2009.2021930

Cited by 26 publications

(9 citation statements)

References 13 publications

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“…We showed in [11] that the Q in (1), which depends on the definition of the internal energy in (3) or (7), was approximately equal to twice the inverse of the matched VSWR half-power fractional bandwidth (FBW hp ), that is…”

Section: General Expressions For Quality Factormentioning

confidence: 99%

“…When P e = P m , the spherical antenna radiates equal power in the electric and magnetic dipole fields and both Q nc,sph e,lb and Q nc,sph m,lb become equal to one half the minimum Q of a single electric or magnetic dipole because the two spherical dipoles form a self-tuned antenna requiring no external tuning capacitor or inductor. (As mentioned in the Introduction, for cophasal electric and magnetic dipole moments forming a Huygens source, Thal [7] has shown that extra internal tuning, which adds to the Q-energy, is required to feed these Huygens-source electric and magnetic dipole moments with a common electric current. )…”

Section: Minimization For the Quasi-static Magnetic Field Of The Magnmentioning

confidence: 99%

“…This circuit-model approach to finding the minimum Q has the advantage of reducing a complex problem in electromagnetic theory to the systematic investigation of a ladder network of RLC circuits [6,7]. However, the circuit models were restricted to representing spherical and circular cylindrical modes and thus the lower bounds on Q were for spheres or circular cylinders circumscribing the antennas.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, Gustafsson and Nordebo [17] have obtained lower bounds on Q for larger antennas using the "convex optimization" of current distributions [18]. Also, Thal [7] has obtained lower bounds on the Q of spherical electric and magnetic dipole antennas under subsidiary conditions that maximize the gain of the antenna and increase the lower bounds by requiring extra internal tuning to maintain the proper phase between the single-port electric currents that feed the electric and magnetic dipoles. For example, Thal has shown that the lower-bound formula for the Q of an electrically small spherical Huygens source (equal-power, perpendicular, cophasal † In the paragraph preceding Section 2.1 of [13], it was erroneously stated that the Q of an electric dipole moment perpendicular to the plane of a thin oblate spheroid approaches ∞, whereas it actually approaches 9π/[4(ka s ) 3 ], where a s is the radius of the oblate spheroid.…”

Section: Introductionmentioning

confidence: 99%

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Minimum Q for Lossy and Lossless Electrically Small Dipole Antennas

Yaghjian¹,

Gustafsson²,

Jonsson³

2013

PIER

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Abstract-General expressions for the quality factor (Q) of antennas are minimized to obtain lower-bound formulas for the Q of electrically small, lossy or lossless, combined electric and magnetic dipole antennas confined to an arbitrarily shaped volume. The lowerbound formulas for Q are derived for dipole antennas with specified electric and magnetic dipole moments excited by both electric and magnetic surface currents as well as by electric surface currents alone. With either excitation, separate formulas are found for the dipole antennas containing only lossless or "nondispersive-conductivity" material and for the dipole antennas containing "highly dispersive lossy" material. The formulas involve the quasi-static electric and magnetic polarizabilities of the associated perfectly conducting volume of the antenna, the ratio of the powers radiated by the specified electric and magnetic dipole moments, and the efficiency of the antenna.

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Section: General Expressions For Quality Factormentioning

confidence: 99%

Section: Minimization For the Quasi-static Magnetic Field Of The Magnmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Minimum Q for Lossy and Lossless Electrically Small Dipole Antennas

Yaghjian¹,

Gustafsson²,

Jonsson³

2013

PIER

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“…Chu [14] used circuit models of spherical modes to compute the stored energy and Q-factor for spherical geometries. The results obtained from circuit models have been generalized to mixed modes and non-magnetic sources by Thal [109,110].…”

Section: Background and Overviewmentioning

confidence: 99%

Physical Bounds of Antennas

Gustafsson¹,

Tayli²,

Cismasu³

2015

Handbook of Antenna Technologies

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Design of small antennas is challenging because fundamental physics limits the performance. Physical bounds provide basic restrictions on the antenna performance solely expressed in the available antenna design space. These limits offer antenna designers a-priori information about the feasibility of antenna designs and a figure of merit for different designs. Here, an overview of physical bounds on antennas and the development from circumscribing spheres to arbitrary shaped regions and embedded antennas are presented. The underlying assumptions for the methods based on circuit models, mode expansions, forward scattering, and current optimization are illustrated and their pros and cons are discussed. The physical bounds are compared with numerical data for several antennas.

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