Radiation ${Q}$-Factors of Thin-Wire Dipole Arrangements

Abstract

In this letter, we present an investigation of the radiation -factors of two coupled thin dipole antennas with sinusoidal current distribution. The approach is based on novel rigorous equations for radiated power and stored energies recently derived by Vandenbosch. First, we study the validity of the used thin-wire approximation with a reduced kernel. Good agreement between the assumed sinusoidal current distribution and the real cylindrical antenna modeled with the full-wave method of moments (MoM) is observed. Then, radiation -factors are evaluated for half-wave side-by-side coupled dipole antennas with different feeding configurations. It is found that every such combination of studied coupled dipoles presents minimum for specific feeding arrangement and separation distance.

A Method for the Evaluation of Radiation Q Based on Modal Approach

“…Again, the total is an oscillating function with an absolute minimum of . While the case of out-of-phase currents was analytically verified in [11] , for in-phase currents a similar study is more complicated.…”

“…Note that for wavelength the angular wavenumber and the charge density is defined as . In most studied cases the domains and are equal , for see [11].…”

“…Physically, gives the scattered electric field intensity. Therefore, has the characteristics of impedance (11) The solution of (11) can be treated directly (12) as usually employed in the method of moments (MoM) [17] or by the superposition of the characteristic currents [12], [18]. This knowledge is important for our later expectations.…”

“…The Q factor based on total current density from MoM has already been successfully calculated in [10] and [11] (MoM in Matlab with a thin-wire reduced kernel). However, to the knowledge of the authors, modal Q factors and stored energies have never been rigorously computed.…”

“…The derived expressions are rigorous, widely usable and easy to implement. They have been verified and successfully tested for simple examples in [11]. We extend this theory for modal analysis purposes, based on the theory of characteristic modes (TCM) [12] and then utilize them for the investigation of radiation Q for some canonical antennas.…”