Lindgren Quadridge Feeds

S. Weinreb and W. Imbriale

SKA Antenna Working GroupMay 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 = 0.6F/D = 0.5F/D = 0.4

Comparison of GAVRT design with a front fed parabola

Assumes no surface RMS loss

GAVRT

F/D = 1.0F/D = 0.9F/D = 0.8

Lindgren feed with shaped 12-meter Cassegrain antenna

Return Loss

Physical Optics

Overall

Comparison of GAVRT with Shaped design

Shaped designGAVRT