Synthesis of a dielectric rod array for a multiple beam reflector antenna
At the Delft University of Technology a new transportable atmospheric radar (TARA), having a sophisticated antenna system, is under construction. The antenna of TARA has multiple beams pointing in different directions. The beams are switched electronically by means of a parabolic dish fed by a dielectric rod array located in the focal plane. Moumen and Ligthart (1999) showed that an array consisting of two dielectric rods separated by 0.77/spl lambda/, where /spl lambda/ stands for the wavelength, is needed in order to achieve a well focused beam at 15/spl deg/ with low side-lobes. However, due to this small separation distance, degradation of the radiation pattern and mismatches, due to mutual coupling, become a serious problem. This paper presents a method to synthesise the dielectric rod array (amplitude and phase distribution) that takes into account mutual coupling effects.
TARA: Transportable Atmospheric Radar
In this article, a new atmospheric profiler is described. The system is mobile in the sense that it can be disassembled and built up at a different location. Some specific characteristics of the antenna system and transportability are highlighted. Less attention is paid to the transmitter and receiver systems as they are of more conventional FM-CW design. A description of the data acquisition and processing system is given.
Evaluation of focal fields and radiation characteristics of a dual-offset reflector antenna
A receive-mode analysis of a dual-offset reflector antenna consisting of an offset paraboloid and an offset hyperboloid is presented. In this analysis the field scattered from the offset paraboloid is determined using a g.t.d. formulation involving two edge points and a reflection point, if one exists. A method is described for deciding whether there is a reflection point from the gradient of the path length at the edge points. The focal-region fields and the radiation characteristics are computed by numerical integration of the physical optics current on the offset hyperboloid. An experimental antenna operating at 35 GHz is described Results of measurements of radiation patterns and of the power coupled into a circular waveguide array feed are compared with theory. In each cae reasonable agreement is achieved for copolarised directed components. However, the experimental antenna produced higher crosspolarisation than expected.