Last modified: 2014-02-22
Abstract
Controlling antenna pattern (AP) of a millimeter wave phased antenna array in a wide scanning sector, by means of the necessary amplitude and phase distributions on antenna surface, is limited by a considerable increasing of the number of feeds and their density. When using the optically controlled antennas, it is also limited by the feed construction complexity and by the total radiated power. In the optical wave band the control of the reflected signal phase can be performed by using piezoelements. Here, for a phase variation from 0 to π, it is necessary to have extremely small shifts of reflecting element. In the millimeter wave band, the needed shifts are of the order of several millimeters, that is hardly realizable with usual piesoelements. However the needed shift value can be decreased considerably, provided that electromagnetic wave is propagating in the material with dielectric permittivity ε > 1.
In the paper, the method of AP scanning sector widening, for the same values of reflecting element shifts, is considered. It is based on passing the electromagnetic wave through the material with a high e value. Modelling of the reflecting surface part has been carried out. The results show that one has to use a liquid dielectric as a material with high dielectric constant The dependences of the AP scanning sector on the reflecting surface inclination angle have been obtained for different liquids. The effects of the dielectric permittivity and microwave absorption were taken into account in the wave propagation through dielectric. The experiments on the scanning sector changing and the wave damping measurements with various liquid dielectrics were carried out.
As a result, good agreement between the simulated and experimentally measured data was observed. This confirms the possibility of widening AP scanning sector by means of using a material with a high dielectric permittivity.