| Patent Title | A Multimode Primary Feed for Single Offset Reflector Antenna with Wide Cross Polarization Bandwidth |
| Department | Electronics and Comminications |
| Year | 2018 |
| Faculty Name | Balvant Jivabhai Makwana |
| Status | Published |
| Abstract | The performance of the front-fed parabolic reflector antenna arrangement is impaired by the unavoidable blocking of the aperture by feed and supporting structures. Offset parabolic reflector antenna offers significant advantages over a front-fed reflector antenna mainly because of unblocked main aperture, high isolation between the antenna and the primary feed. But, offset configuration suffers from high cross polarization which limits its use in many critical applications. The invention disclosed here improves the performance of offset reflector in terms of circular symmetry of the patterns, improved V.S.WR, high return loss while overcoming the limitations of high cross polarization. This has been done using a horn comprising of cylindrical waveguide followed by an abrupt step and conical corrugation section which uses the concept of conjugate field matching. The higher order mode, TE21 is generated with proper amplitude and phase in relation to fundamental mode, TE11 .This phenomenon further generates HE11 and HE21 modes in corrugated section with proper amplitude and phase at the aperture of horn. This mode mixture at the aperture is conjugate of the focal region field of offset reflector antenna. This field in turn, suppresses the cross polarization field over wide bandwidth. The cross polarization suppression bandwidth of more than 6 percent with reference to centre frequency and an improvement of cross polarization by at least -10 dB as compared to the conventional Gau |