EVLA MEMO 69 FOCAL PLANE ARRAY BEAM-FORMING AND SPILL-OVER CANCELLATION USING VIVALDI ANTENNAS

Phased-array feeds are possibly the best option for the 240 to 1200 MHz band on VLA antennas due to their wide bandwidth and relatively small size. One of the greatest assets of these antennas is the ability to produce a shaped beam by appropriately phasing the elements allowing in some cases nearly uniform aperture illumination with minimal ground-directed spillover. The beam-forming properties of Vivaldi focal plane arrays are explored here using detailed calculations that account for the true beam shapes of Vivaldi elements and the geometry of the VLA antennas. We find that the beam-forming properties of Vivaldi arrays are well suited for the VLA. Some additional properties of focal plane array beam-forming are presented as well.