Lindgren Quadridge Feeds S. Weinreb and W. Imbriale SKA Antenna Working Group May 6, 2009

Peak Gain On-axis Gain Peak Cross-pol On-axis cross-pol Lindgren Quadridge Feed measured performance (0,45,90,135 cuts - amplitude, phase, principle and cross polarizations)

Freq = 5.3 GHz Principle Pol

Freq = 5.3 GHz Cross Pol

Freq = 10.0 GHz – Principle Pol

Freq = 10.0 GHz – Cross Pol

DSS-28 Geometry 60 degree offset design Parabola at vertex Geometry of Tertiary

Two Feeds with switchable optics

Predicted GAVRT performance (with no geometry errors) Return Loss Strut Blockage RMS Loss Overall Physical Optics

Comparisons of measured (Venus) versus calculated (with geometry errors) Measured (blue dots) Calculated (red line)

Comparison of GAVRT design with a front fed parabola Assumes no surface RMS loss GAVRT F/D = 0.6 F/D = 0.5 F/D = 0.4

Comparison of GAVRT design with a front fed parabola Assumes no surface RMS loss GAVRT F/D = 1.0 F/D = 0.9 F/D = 0.8

Lindgren feed with shaped 12-meter Cassegrain antenna Return Loss Physical Optics Overall

Comparison of GAVRT with Shaped design Shaped design GAVRT