Back-to-Back Reflector Antennas With Reduced Moment of Inertia for Spacecraft Spinning Platforms

Abstract

A back-to-back reflector antenna system with reduced moment of inertia is proposed in order to address the demanding problem of supporting large reflector antennas on spinning platforms. The configuration provides additional potential advantages, such as reducing the spinning speed by half for a given sampling rate when both back-to-back reflectors are utilized. Geometrical parameters of the reflector are determined such that the moment of inertia of the rotating system is reduced. It is shown that these back-to-back reflectors suffer from a high cross-pol level in the asymmetrical plane due to the large feed offset angle. Two different methods are explored to alleviate the high cross-pol level problem. In the first method, a sub reflector is utilized to minimize the cross-pol level by satisfying the Mizugutchi condition. In the second method, a tri-mode matched feed horn is suggested to achieve a similar result. The suppressed cross-pol level puts forward the gravitationally balanced back-to-back reflector antenna systems as a potential candidate for future spacecraft antennas on spinning platforms.

Investigation of Asymmetric Phase Errors of an Optimized Dual-Mode Primary Feed on the Cross Polarization of Offset Reflector Antennas

“…With the primary feed model defined by (4) and linear phase errors given by (2), in (2) changes from 0 to 1 with a step of 0.25 to include the phase errors in both TE and TE modes. The secondary far-field crosspolar components are numerically calculated at both diagonal and asymmetry planes, i.e., and 90 .…”

“…This case can be interpreted as a dual-mode feed having different phase center locations for each individual mode. With the linear phase errors described by (2), the secondary cross polarization levels are calculated at both and 90 planes as before. The results are depicted in Fig.…”

“…Essentially, the primary feed should conjugately match the focal region of the reflector to reduce or cancel the cross polarization. The tri-mode feed [1] is the most popular example of such matched feeds that have been recently revisited in [2]. Another example is the dual-mode feed analytically modeled by trigonometric functions to exclude the feed imperfections existing in practice [3].…”

A transmit/receive twin‐horn feed for spinning remote sensing reflector antennas

“…A novel approach to overcome the aforementioned drawbacks is to use the back-to-back reflector structure [7][8][9], as shown in Figure 1. This gravitationally balanced configuration utilizes two identical reflectors, mounted back-to-back on a spinning platform.…”

A Simplified Feed Model for Investigating the Cross Polarization Reduction in Circular- and Elliptical-Rim Offset Reflector Antennas

“…Later, Jacobson [6] presented two solutions: one a dual-mode rectangular horn and the other a linear array of small aperture round waveguide feeds, with their axes parallel to the optical axis of the offset reflector, to reduce cross polarization in the offset reflector antenna. The tri-mode feed design has been recently revisited by [7] for balanced back-to-back reflectors with a reduced moment of inertia.…”