Compact Low Profile Dual Linear Ku-band Feed for Multi-beam Satellite Characterization at CATF

A compact, low profile Ku-band feed is designed and realized successfully for characterization of multi-beam satellite payloads at Compact Antenna Test Facility (CATF). Transponder characterization of integrated spacecraft (S/C) is generally carried out using uplink (U/L) and downlink (D/L) CATF feeds mounted on twin feed plate positioner of CATF. By giving appropriate azimuth and elevation angle to spacecraft positioner, In Orbit Test (IOT) location is brought parallel to facility reference axis, for payload characterization. This method is suitable for spacecraft's with single and sufficiently broad beam coverage. But this same method cannot be used for S/C with multiple high gain beams, because any time either U/L or D/L beam can be in focus of CATF geometry and other beam will be away from the focus. As the beams are very narrow (0.8 deg 3 dB beam width) it may not be possible to saturate the transponder if the spatial separation is high. To meet this critical requirement, geometrical analysis of CATF is done to find out corresponding feed locations at CATF focal plane for each beam. In this paper in next four sections design aspects, methodology and measurement validation of compact low profile Ku band feeds, which meet all the illumination requirements of CATF are discussed in details. This developed feeds latter used for payload characterization of integrated multi-beam spacecraft GSAT 19, GSAT 11 and GSAT 29 in CATF.