Dense focal plane arrays for pushbroom satellite radiometers

Abstract

Sammendrag-Performance of a dense focal plane array feeding an offset toroidal reflector antenna system is studied and discussed in the context of a potential application in multi-beam radiometers for ocean surveillance. We present a preliminary design of the array feed for the 5-m diameter antenna at X-band. This array is optimized to realize high antenna beam efficiency (∼ 95%) over a wide scan range (±20 • ) with very low side-lobe and cross-polarization levels.Index Terms-reflector antenna feeds, multi-beam antennas, microwave radiometry.

Fast and Accurate Analysis of Reflector Antennas With Phased Array Feeds Including Multiple Reflections Between Feed and Reflector

“…Among these feeds, one can distinguish between a cluster of horns yielding one beam per feed [1], [2], and the more densely packed beamforming array antennas commonly referred to as Phased Array Feeds (PAFs) capable of providing a continuous FoV of simultaneous beams. Examples that benefit from these technologies are radars and terrestrial communications; while since recently, PAFs have also been developed for astronomical and geoscientific instruments, as well as for commercial satellite communication terminals [3]- [6]. Thanks to their electronic beamforming capabilities, these new systems potentially enable much faster studies of the Earth and Space than currently possible and are an attractive alternative to bulky mechanically beam steered antennas.…”

Future spaceborne ocean missions using high sensitivity multiple-beam radiometers

“…The distanceto-coast requirement translates into the need for a very fine antenna beam with low side-lobes and high beam efficiency -not very compatible with a traditional feed horn. Instead, a dense array of a large number of smaller antenna elements can be used, and by summing the outputs from clusters of those, adjusted properly in phase and amplitude, the individual beams can be generated [4]. Figure 2 illustrates the concept, and Figure 3 shows how signals from different elements (*) contribute to more than one beam.…”

Multibeam Focal Plane Arrays With Digital Beamforming for High Precision Space-Borne Ocean Remote Sensing

“…It is important to note that the required numbers of elements, determined through this optimization procedure, are almost twice smaller than when applying a conventional conjugatefield-matching optimization approach (see Table 3 in [12]). For both systems, the optimal d el is near 0.75λ; this value satisfies the grating-lobe free condition [13] and also minimizes the active impedance variation of antenna elements due to their non-identical excitation [31], [32].…”

“…The main requirements for the array radiating element are that (i) it should be small enough to design the array with interelement spacing less than 0.75λ in order to avoid the grating lobes [13]; and (ii) it should be possible to use in a dualpolarization configuration. Since the relative bandwidth required for the ocean remote sensing do not exceed 5 .…”