Coherent Multibeam Arrays Using a Cold Aperture Stop
| Autor: | James Di Francesco, Stephane Claude, Lewis B. G. Knee, Doug Henke |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Heterodyne
Physics Noise temperature Radiation Aperture business.industry Point source Detector Astrophysics::Instrumentation and Methods for Astrophysics 020206 networking & telecommunications 02 engineering and technology 01 natural sciences 010309 optics Optics Sampling (signal processing) 0103 physical sciences 0202 electrical engineering electronic engineering information engineering Nyquist–Shannon sampling theorem Truncation (statistics) Electrical and Electronic Engineering business Astrophysics::Galaxy Astrophysics |
| Zdroj: | IEEE Transactions on Terahertz Science and Technology. 6:601-610 |
| ISSN: | 2156-3446 2156-342X |
| Popis: | To increase the mapping speed of a given area-of-sky, multibeam heterodyne arrays may be used. Since typical heterodyne arrays are spatially arranged sparsely at approximately 4· Nyquist sampling (i.e., two full-width-half-maximum beam widths), many pointings are required to sample fully the area of interest. A cold aperture stop may be used to increase the packing density of the detectors, which results in a denser instantaneous spatial sampling on-sky. Combining reimaging optics with the cold stop, good aperture efficiency can be obtained. As expected, however, a significant amount of power is truncated at the stop and the surrounding baffling. We analyze the consequence of this power truncation and explore the possibility of using this layout for coherent detection as a multibeam feed. We show that for a fixed area-of-sky, a “twice-Nyquist” spatial sampling arrangement may improve the normalized point source mapping speed when the system noise temperature is dominated by background or atmospheric contribution. |
| Databáze: | OpenAIRE |
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