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The SKA dishes will be used with single pixel feeds (resulting in a single on-axis main beam) as well as phased array feeds that will generate multiple offset beams. The final optics will be shaped to improve the performance of the single pixel systems. This shaping may, however, be to the detriment of the offset beams of the multi-beam systems. It is important to understand the extent of this. A...
Aperture array technology is one of the candidate technologies for the 500 MHz to 1500 MHz frequency range of the SKA. The feasibility and low noise potential of aperture arrays have been demonstrated with small test systems before, e.g. with a 50 K system noise temperature, measured on a 1 m2 prototype tile in 2010. However, further reduction of the array noise temperature is essential to optimize...
An extension of the radio astronomy technique of aperture synthesis imaging into novel near-field three-dimensional microscopy is discussed. The basics of near-field aperture synthesis imaging are overviewed and results of demonstrators and simulations are presented. Spatial variations in the phase of near-field aperture synthesis signals are examined, to illustrate possible sub-wavelength instrument...
We describe the demonstration of a ¼ VGA format long-wavelength infrared focal plane array based on an InAs/GaSb superlattice absorber surrounded by an electron-blocking and a hole-blocking unipolar barrier. An 8.8 µm cutoff focal plane without antireflection coating based on this complementary barrier infrared detector design has yielded noise equivalent differential temperature of 18.6 mK at operating...
Instrumentation for radio astronomical observations is currently undergoing a transition from large reflectors with single-pixel feeds to multi-pixel phased arrays. Research efforts aimed at realizing the benefits of phased arrays for highly sensitive, calibrated astronomical measurements have opened up interesting challenges for antenna designers. This paper surveys recent theoretical and experimental...
We report the small-range strain characterization of anisotropic fiber Bragg gratings (FBGs) written by high-intensity femtosecond UV pulses. The FBGs are characterized with applied strain of 0-300 muepsiv using a high-speed Czerny-Turner spectrometer. The strain response slope is comparable to typical FBGs.
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