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Design of a novel corrugated matched feed for an offset parabolic reflector antenna

The antennas for space-borne microwave radiometers have several specific requirements to achieve the specified radiometric accuracies, sensitivity and the desired performance of the radiometer in the space. These include high beam efficiency (≫ 95 %), high gain and low losses, low cross-polarization, low side-lobe levels, etc. [1]. The offset parabolic reflector antennas fulfills most of these requirements due to their inherent advantages of reduced aperture blockage, isolation between the reflector and the feed, lesser spurious radiation and suppressed side-lobes [2]. However, the performance of offset reflectors is satisfactory only when the larger F/D (F/D ≫1) configuration is selected. Generally, in spacecraft antennas, the available space for the antenna structure is limited, and hence the reflector with a large F/D may not be preferred. Alternatively, the use of an offset reflector antenna with a smaller F/D ratio results into high cross-polarization (when illuminated by linearly polarized feed), and beam squinting (when illuminated by a circularly polarized feed) [2]. This high cross-polarization and beam squinting degrade the overall performance of the system and restricts the use of offset reflectors for many practical applications. Thus, to overcome these limitations, an effective cross-pol suppression technique as well as beam squinting minimization technique are to be explored.