Cylindrical Antennas and Arrays

Abstract

Cylindrical arrays lie at the heart of the antenna systems of most major radio communication systems, including broadcasting networks, cellular 'phone systems and radar. In this book, the authors present practical theoretical methods for determining current distributions, input admittances and field patterns of a wide variety of cylindrical antennas, including the isolated antenna, the two-element array, the circular array, curtain arrays, Yagi and log-periodic arrays, planar arrays and three-dimensional arrays. Coverage includes analysis of horizontal antennas over, on and in the earth and sea, large resonant arrays of electrically short dipoles and a chapter on the theory and techniques of experimental measurement. Written by three of the leading engineers in the field, and based on world-class research carried out at Harvard over the last forty years, Cylindrical Antennas and Arrays is destined to become established as the basic reference for practising engineers and advanced students for many years to come.

Resonance Splitting in Two Coupled Circular Closed-Loop Arrays and Investigation of Analogy to Traveling-Wave Optical Resonators

“…We choose to excite only one of the dipoles, the one on the azimuthal position θ = 180 • in the left array, so that only symmetrical modes with respect to the x-axis are excited on the coupled system (N is assumed to be even). From the problem of the single array [1][2][3][4][5], it is known that, for resonances to occur, one must properly select the inter-element spacing d, as well as the dipoles' length 2h and radius a. Dipole arrays can be effectively analyzed by the semi-analytical approach of "two-term" theory, originally developed by R. W. P. King (see [4] for original references). The method is based on an approximate solution to the N coupled integral equations for the currents of N mutually coupled dipoles, under the hypothesis that each current can be expressed as the sum of two terms.…”

“…This system can be written in matrix form as [D] {t} = [P ] {V } where the components of the matrices D and P depend on the characteristics of the dipoles (length and radius) and on the inter-dipole distance [4]. For our numerical experiments, we consider perfectly conducting dipoles with length 2h = 1.42 and radius a = 0.058 and circular arrays consisting of N = 72 elements arranged around a circle with radius R = 11.46, which gives an inter-element spacing d = 2R sin(π/N) = 1.…”

“…The diagram is characterized by a set of distinct sharp peaks corresponding to the resonances (freespace wavelength λ m ) of the circular array with an azimuthal order that increases with decreasing wavelength. These resonances have been well studied both theoretically and experimentally in previous works [1][2][3][4][5][6][7][8][9][10][11][12]. We have subsequently built the linear system (2) of "two-term" theory for two coupled arrays ( Fig.…”

“…It is the result of theoretical and experimental research [1][2][3][4][5][6][7][8][9][10][11][12] that large circular arrays (consisting of many elements N and having a circumference of many wavelengths) of identical, parallel and nonstaggered cylindrical dipoles possess a series of very narrow resonances, when the inter-element spacing d, the length and the radii of the identical dipoles are properly selected. Resonance means that the driving-point conductance has a maximum with a very large value, while the driving-point susceptance is zero.…”

“…. , N [2,4,10]. The circumference C of the array is always an integer multiple of the effective wavelength λ m of the wave that is supported by the array [9,10], i.e., C = |m| λ m .…”