The crow´s nest antenna-experimental results

The experimental radar system CNA-512 is introduced. Its core is a spatial array consisting of 512 statistically distributed microstrip antennas. The object is to demonstrate radar operation over 360° without need for mechanical antenna rotation. The CNA-512, working at X-band, is designed for a look-direction-independent beamwidth of 2.7°. The positions of the single elements (microstrip loop antennas) were determined via a 3D-Taylor density distribution. Each antenna element is to be equipped with a separate T/R-module, from which 60 have been realized in the first step. The array is subdivided into 32 subgroups with combination on the RF level; the individual signal outputs are down-mixed and digitized, allowing monopulse operation and adaptive null steering. Phase calibration for beamforming is achieved by the measurement of relative phases at a few reference elements inside the sphere. First experiments with the CNA-512 showed that transmit-receive operation and phase-steering work as projected