The Admittance of Cylindrical Antennas Driven From a Coaxial Line

Otto, D.

doi:10.1002/rds1967291031

Cited by 78 publications

(17 citation statements)

References 8 publications

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“…Wu (1962Wu ( , 1963 also presents a solution but no quantitative results since an integral equation remains to be solved. The recent results obtained by Otto (1967) are in good agreement with those in section 3.2.…”

Section: Admittance Of Gap-excited Infinite Antennasupporting

confidence: 92%

Admittance of Infinite and Finite Cylindrical Metallic

Andersen

1968

Radio Science

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A monopole antenna excited by a coaxial line is studied in detail. The mathematical model of the excitation is a magnetic ring current the radius of which may be larger than the radius of the cylinder. First a study is made of the waves guided by and radiated from an infinite cylinder. Numerical results for the current and the conductance are given. The conductance decreases when the gap width increases.The standing-wave antenna is treated with an assumed effective gap at the antenna ends. A solution of the antenna problem is found by superimposing the !Ilyltiply reflected waves. In the solution,, the effect of the gap and the antenna end separates. Accurate values for the gap admittance and the end admittance are derived from experimental values obtained by Hartig. . IntroductionThe subject of metallic cylindrical antennas has been treated extensively in the past. It suffices here to refer to recent treatments and reviews by King (1956) and Duncan and Hinchey (1960). As soon as the assumption of an infinitely thin antenna is abandoned, a great deal of complexity arises because a finite cylinder cannot be treated in a simple way as a boundary value problem in electrodynamics. Even if this were possible there is still the problem of coupling the isolated cylinder in a meaningful way to a transmission line. This problem is generally known as the gap problem. Almost all existing theories use a delta-function gap which results in an infinity in the susceptance and this infinity is then circumvented in a ~ore or less arbitrary manner (see e.g., Duncan, 1962;Hallen 1953Hallen , 1962.Theories like King-Middleton's second-order theory that forces the current to be a modification of a sinusoidal distribution right into the gap imply a gap of nonzero width. It is often stated that values extrapolated from experiments with decreasing values of gap width should be compared with zero-width theory. Actually the limit does not exist and we see later that King-Middleton's second-order theory implies a width of the order of the radius of the antenna.Solutions based on iterative solutions to an integral equation, Fourier-series solutions, and direct numerical solutions using large computers have their advantages but are difficult to interpret physically. When this is the case, the separation of the source problem from the antenna-end problem is almost impossible;. to foresee what happens is difficult when the antenna is placed in another environment such as a dielectric coating.The concept adhered to in this paper is that of traveling waves along the cylinder. These waves are most easily studied on the infinite cylinder that represents a solvable boundary value problem. To take into account the transmission line antenna coupling, the antenna model chosen is a monopole over a ground plane where the cylindrical antenna is a continuation of the inner conductor in the feeding coaxial line. The true source for the radiated field is then an incoming TEM wave in the coaxial line. From the opening in the ground plane the energy radiates u...

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Section: Admittance Of Gap-excited Infinite Antennasupporting

confidence: 92%

Admittance of Infinite and Finite Cylindrical Metallic

Andersen

1968

Radio Science

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“…The point ζ = k is, once again, a non-integrable singularity and is bypassed in (13). For large, positive ζ, the asymptotic behavior of g(ζ, a) can be found from the large-argument formula [23, 9.7.2] for K 1 to be…”

Section: The Small-frill Limit: General Formulasmentioning

confidence: 99%

“…See, for example, [9][10][11][12][13][14][15][16][17][18][19][20][21][22]; additional references, as well as several reasons motivating such studies are given in [20]. The motivation, purpose and methods of the present paper are different from the above-mentioned references: The specific starting points of the present study are the infinite-antenna results of [1] and [2].…”

Section: Introductionmentioning

confidence: 99%

Input Admittances Arising From Explicit Solutions to Integral Equations for Infinite-Length Dipole Antennas

Fikioris¹,

Valagiannopoulos²

2005

PIER

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Abstract-When one uses integral equations to determine the input admittance of dipole antennas, one must choose between two kernels, the exact and the approximate kernel, and also between (at least) two types of feed, the delta-function generator and the frill generator. For dipole antennas of infinite length, we investigate-analytically and numerically-the similarities and differences between the various admittance values. Particular emphasis is placed on the fact, discussed in detail in recent publications, that certain combinations lead to nonsolvable integral equations.

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“…M ONOPOLE and dipole antennas have been the subject of numerous studies over many years [1]- [5]. Often the popular delta-gap source is employed in a model of the excitation of the structure.…”

Section: Introductionmentioning

confidence: 99%

Feed models for coax-driven monopole and dipole antennas

Lockard

Butler

2006

IEEE Trans. Antennas Propagat.

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A method is presented for accurately modeling a monopole or dipole antenna fed by a coaxial line. The base of the monopole is attached to a conducting plane through which the coaxial feed line extends to the feed. The feed structures considered are easily adaptable to physically rugged forms and are simple to construct. Equivalent models for the three regions of the structure are devised and coupled integral equations for aperture fields and surface currents are formulated to enforce the boundary conditions. Three variations of the feed configuration are discussed and the reflection coefficient of the antenna feed is determined from the data obtained from the solutions of the coupled integral equations. Computed reflection coefficient values are shown to agree well with values measured on laboratory models.

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The Admittance of Cylindrical Antennas Driven From a Coaxial Line

Cited by 78 publications

References 8 publications

Admittance of Infinite and Finite Cylindrical Metallic

Admittance of Infinite and Finite Cylindrical Metallic

Input Admittances Arising From Explicit Solutions to Integral Equations for Infinite-Length Dipole Antennas

Feed models for coax-driven monopole and dipole antennas

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