Antenna models

Array pattern multiplication of phased array antennas

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Antenna models — reading order Maxwell’s equations Retarded potentials Near-field / far-field boundary Far-field retarded potentials Array pattern multiplication (this article) Dipole power gain patterns Introduction Take one element’s radiation vector \(\mathbf{F}\), place \(N\) identical copies at positions \(\mathbf{l}_i\) with weights \(a_i\), and the far-field total factors as \(\mathbf{F}\,A\). That is pattern multiplication: the step … Read more

Far-field retarded potentials

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Antenna models — reading order Maxwell’s equations Retarded potentials Near-field / far-field boundary Far-field retarded potentials (this article) Array pattern multiplication Dipole power gain patterns Introduction In the Fraunhofer region the amplitude goes as \(1/r\), and the phase is \(e^{-jkr}\) times a linearised path through the source. The angular part factors into a radiation vector … Read more

Near-field – far-field : Where is the boundary ?

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Antenna models — reading order Maxwell’s equations Retarded potentials Near-field / far-field boundary (this article) Far-field retarded potentials Array pattern multiplication Dipole power gain patterns Introduction Antenna fields change character with distance: reactive storage near the element, Fresnel diffraction at intermediate range, and spherical-wave radiation farther out. Link-budget and pattern formulas almost always assume that … Read more

From Maxwell’s equations to antenna array – part 1

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Antenna models — reading order Maxwell’s equations (this article) Retarded potentials Near-field / far-field boundary Far-field retarded potentials Array pattern multiplication Dipole power gain patterns Introduction Antenna theory is Maxwell’s equations plus boundary conditions and a far-field approximation. Before retarded potentials and array factors, write the four laws carefully—especially Ampère’s law with Maxwell’s displacement current. … Read more

Normalized power gain of dipole antennas

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Antenna models — reading order Maxwell’s equations Retarded potentials Near-field / far-field boundary Far-field retarded potentials Array pattern multiplication Dipole power gain patterns (this article) Introduction You have almost certainly seen the short-dipole pattern: nulls along the wire, maximum broadside. We will derive the normalised power patterns for the Hertzian dipole, the half-wave dipole, and … Read more