Directional radiation properties of two impedance monopoles mounted on a perfectly conducting rectangular screen

Subject and Purpose. Two impedance resonant monopoles of electric length 0.2 £ l / l £ 0.3 are mounted on a rectangular screen perpendicularly to the screen surface and studied for the directional radiation properties (directive gain and radiation patterns) depending on the monopole separation and the side length and aspect ratio of the screen.

 Methods and Methodology. A three-dimensional diffraction vector problem of two impedance monopoles mounted on a perfectly conducting rectangular screen is solved in terms of the uniform geometric theory of diffraction. Allowances are made for the diffracted field asymptotics of the secondary diffraction at the screen edges and for the electric current distribution asymptotics of a thin impedance dipole in the free space.

Results. For a lattice of two impedance monopoles mounted on a rectangular screen, 3-D programs have been developed for calculating its radiation patterns, directive gain D_max at a radiation maximum, and radiation resistance in view of the secondary diffraction at the screen edges. The radiation pattern shaping for the diffraction and total fields and the directive gain D_max have been analyzed depending on the monopole separation x / l  0.1...1, the screen side length x / l  1.2…4, and the screen aspect ratio W / L  0.5…3. It has been shown that the so obtained optimum separation x _opt  0.65, optimum length L_opt and optimum ratio (W / L) _opt make D_opt three times greater than the lowest D_max value.

Conclusions. The three-dimensional vector problem of field diffraction of two impedance monopoles mounted on an ideally conducting rectangular screen has been solved. It is of interest that given an optimum monopole separation x_opt and an optimum side length L_opt of the square screen, a lattice of two monopoles offers a greater radiation resistance and a two times larger D_opt than a single monopole on the same screen does. The developed computational programs and the obtained numerical results enable efficient actual wireless communication systems to be modelled for both ideally conducting and impedance resonant monopoles.