A new approach to the design of super-directive aerial arrays

Bloch, A.; Medhurst, R.G.; Pool, S.D.

doi:10.1049/pi-3.1953.0062

Cited by 55 publications

(6 citation statements)

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“…For these cases, the currents in the non-contributing subspace can only be used to tune the currents into self resonance. Hence, they are quiescent in the externally tuned case (8) and determined by the eigenvectors associated with the largest eigenvalues of the eigenvalue problems in (20), where the matrices X, R r , and R Ω are restricted to the non-contributing subspace.…”

Section: Appendix D Numerical Evaluation Of Qcqpmentioning

confidence: 99%

“…The optimization problems (8) and (16) are solved analytically for spherical structures using spherical waves [48]. The matrices in the eigenvalue problems (13) and (18) are diagonalized for spherical modes offering closed-form solutions of the eigenvalue problems.…”

Section: Appendix F Maximum Gain For a Spherementioning

confidence: 99%

“…A series of works starting in the 1940s revealed the fact that the directivity is unbounded [3] but also predicted the enormous cost in other antenna parameters, namely in Q-factor [4], related sensitivity of feeding network [5], and radiation efficiency in case that the antenna is made of lossy material [6]. Consequently, as pointed out by Hansen [7], the superdirective aperture design requires additional constraint, replacing fixed spacing in array theory [8], [9].…”

Section: Introductionmentioning

confidence: 99%

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Maximum Gain, Effective Area, and Directivity

Gustafsson

Čapek

2019

IEEE Trans. Antennas Propagat.

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Fundamental bounds on antenna gain are found via convex optimization of the current density in a prescribed region. Various constraints are considered, including self-resonance and only partial control of the current distribution. Derived formulas are valid for arbitrarily shaped radiators of a given conductivity. All the optimization tasks are reduced to eigenvalue problems, which are solved efficiently. The second part of the paper deals with superdirectivity and its associated minimal costs in efficiency and Q-factor. The paper is accompanied with a series of examples practically demonstrating the relevance of the theoretical framework and entirely spanning wide range of material parameters and electrical sizes used in antenna technology. Presented results are analyzed from a perspective of effectively radiating modes. In contrast to a common approach utilizing spherical modes, the radiating modes of a given body are directly evaluated and analyzed here. All crucial mathematical steps are reviewed in the appendices, including a series of important subroutines to be considered making it possible to reduce the computational burden associated with the evaluation of electrically large structures and structures of high conductivity.

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Section: Appendix D Numerical Evaluation Of Qcqpmentioning

confidence: 99%

Section: Appendix F Maximum Gain For a Spherementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Maximum Gain, Effective Area, and Directivity

Gustafsson

Čapek

2019

IEEE Trans. Antennas Propagat.

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“…Let us now see whether it is possible to obtain a jet without the use of a high-frequency source. In this connection I am much indebted to Mr. R. G. Medhurst for correspondence about the theory of supergain in electromagnetic aerial arrays as developed by Bloch, Medhurst and Pool [3], [4] (the second reference contains a bibliography).…”

Section: Gravitational Radiationmentioning

confidence: 99%

Untitled

1968

Quart. Appl. Math.

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This paper deals with radiation (scalar, electromagnetic, or gravitational) produced by an extended source. The object is to construct a model source the radiation from which is concentrated in a jet of small angle with an assigned target direction. This is done by taking for the source an infinite train of high-frequency plane waves travelling in the target direction with the basic speed of propagation, the amplitude falling off exponentially with distance. The critical number, to be made large in this model, is the ratio a/A, where a is a typical radius of the source and X the wave length. However, it is also shown that a jet of scalar radiation may be obtained from a source which possesses no frequency but consists of a single shock wave. □ p = Pt.t ,(2.2) where P, is a body-force per unit volume constituting the source. This differs from (2.1) only in that the right-hand side is the divergence of a vector field. We shall proceed with (2.1) and return to (2.2) later.The retarded potential solution of (2.1), observed at the event X, iŝReceived June 2, 1967.

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“…A rather surprising conclusion was reached by Uzkov 17 who showed that as the length of the linear endfire array tends to zero, the directivity increases as the square of the number of elements in the array. Gain maximisation for a finite number of elements of any linear array was performed by Bloch et al 18 and by Uzsoky and Solymar 19 who also introduced auxiliary conditions defining both an array-Q and tolerance sensitivity. Directivity maximisation for a linear array of dipoles was done by Tai.…”

Section: Introductionmentioning

confidence: 99%