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K a -band reflector antennas are of interest for satellite-based synthetic aperture radar (SAR) Earth observation missions. In practice, the antenna performance may decrease due to mutual coupling within the feed and with the reflector. Here, the impact of mutual coupling in K a -band reflector antennas is presented in terms of the active reflection coefficients, the accepted power and the radiation patterns. Mutual coupling in a center-fed and an offset-fed reflector antenna is investigated over the Ka-band range allocated for Earth exploration satellites.

Array-fed reflector antennas are being considered for various synthetic aperture radar (SAR) satellites. Mutual coupling between the array elements, as well as with the reflector, impact the antenna performance significantly. The impact of this coupling is assessed for an L-band antenna. Two different feedings and two different element spacings are considered. The impact of the mutual coupling versus frequency is assessed through extensive full-wave simulations in HFSS. Two methods to reduce the impact of mutual coupling are analyzed.

In this paper, we propose a new beamforming scheme for pulse-based signals, particularly, for ultra wideband pulses, by employing a random array geometry and an orientation matching of the arrays. Unlike conventional directional beamforming, the introduced scheme forms an array beam, being independent of a signal impinging direction for both near-fields and far-fields. As a consequence, it is advantageous to suppress unwanted interferences having same frequency contents and coexisting in the same arrival direction with reference to the desired signal. The proposed beamforming concept is analyzed together with the definitions of the −3dB beamwidth and restlobe level. Besides, the orientational beampatterns are compared with the directional beampatterns, and observed that the array responses are different according to the respective spatial processing domains.

The article explains the orientational beamforming concept from a perspective of spread-spectrum communication not in the frequency domain but in the spatial domain. In the orientational beamforming concept, radiated signal energy is spread over a certain part of or the entire angular range by a transmit array with randomly (practically pseudo-random) distributed antennas. At the receiving end, an identical pseudo-random array is employed so that the matching of the antenna distributions between the transmit and receive arrays spatially collects and recovers the signal of interest. An orientational alignment of identical arrays is exploited to perform the beamforming. We have observed that the newly discovered spatial domain can eliminate the necessity of knowing the signal direction to obtain beamforming. Consequently, the matched array processing system improves the interference suppression capability, especially when directional interfering signals exist. The concept is also applicable to the near-field scenario without being affected by spherical wavefront delays in forming an array beam. In this article, proposed orientational beamforming in combination with conventional directional beamforming is also discussed.

Synthetic Aperture RADAR (SAR), with its all-time and all-weather operation capability, is nowadays one of the most important surveillance techniques. The multi-rotor UAV [1] can be used as a cheap and flexible platform for new concept SAR system test. However, since the multi-rotor is of small size and light weight, it is easily prone to motion error caused by air turbulence. The platform movement error of a multi-rotor UAV is studied and motion compensation is performed in two steps: coarse motion compensation and fine motion compensation. The coarse motion errors are estimated based on the DGPS (Differential Global Positioning System) information. Fine phase correction is performed by combination of PGA (Phase Gradient Autofocus) and prominent point processing algorithms. Final results prove that the multi-rotor SAR image quality is comparable with the airborne one.