arXiv subjects

Pavel Hazdra

Publications and source records attributed to Pavel Hazdra.

3 recordsLinked to original sources

arXiv2018

On the End-Fire (Super) Directivity of an Array of Two Elementary Dipoles

The concept of source currents of a radiating source can be employed to express directivity in some particular cases analytically. For an antenna array, this concept can be combined with concepts of mutual radiation intensity and the mutual power of array elements. Using these approaches, we treat the evaluation of the directivity for an elementary dipole, and its end-fire array, which is of special attention due to superdirective properties. A closed form expression for the directivity of this array with out-of-phase excitation is derived. It is observed that end-fire directivity can be further enhanced by optimizing the excitation currents of the array. Their optimal relative phase and corresponding increased directivity are also found analytically. The results are validated by a full-wave simulator.

physics.class-ph↗

arXiv2016

Analytical Representation of Characteristic Modes Decomposition

Aspects of the theory of characteristic modes, based on their variational formulation, are presented and an explicit form of a related functional, involving only currents in a spatial domain, is derived. The new formulation leads to deeper insight into the modal behavior of radiating structures as demonstrated by a detailed analysis of three canonical structures: a dipole, an array of two dipoles and a loop, cylinder and a sphere. It is demonstrated that knowledge of the analytical functional can be utilized to solve important problems related to the theory of characteristic modes decomposition such as the resonance of inductive modes or the benchmarking of method of moments code.

physics.class-ph↗

arXiv2014

On the Functional Relation Between Quality Factor and Fractional Bandwidth

The functional relation between the fractional band-width and the quality factor of a radiating system is investigated in this note. Several widely used definitions of the quality factor are compared on two examples of RLC circuits that serve as a simplified model of a single resonant antenna tuned to its resonance. It is demonstrated that for a first-order system, only the quality factor based on differentiation of input impedance has unique proportionality to the fractional bandwidth, whereas e.g. the classical definition of the quality factor, i. e. the ratio of the stored energy to the lost energy per one cycle, is not uniquely proportional to the fractional bandwidth. In addition, it is shown that for higher-order systems the quality factor based on differentiation of the input impedance ceases to be uniquely related to the fractional bandwidth.

physics.class-ph↗