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17 February 2003 Heterodyne spectrometers with very wide bandwidths
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Abstract
New astronomical and remote-sensing instruments require microwave spectrometers with modest spectral resolution over many gigahertz of instantaneous bandwidth. Applications include millimeter-wave searches for distant objects with poorly known redshifts, submillimeter and far-infrared observations of Doppler-broadened spectral lines from galaxies, and observations of pressure-broadened atmospheric lines. Wide bandwidths and the consequent stability requirements make it difficult to use general-purpose receiver and spectrometer architectures in these applications. We discuss analog auto- and cross-correlation lag spectrometers that are optimized for these observations. Analog correlators obtain their wide bandwidths by a combination of transmission line delays and direct voltage multiplication in transistor or diode mixers. We show results from a new custom transistor multiplier with bandwidth to 25 GHz. Stability becomes increasingly important as bandwidths broaden. We discuss system requirements for single-dish correlation radiometers, which have intrinsic high stability, and present results showing that analog cross-correlators are suitable backends for these receivers.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Andrew I. Harris "Heterodyne spectrometers with very wide bandwidths", Proc. SPIE 4855, Millimeter and Submillimeter Detectors for Astronomy, (17 February 2003); https://doi.org/10.1117/12.459150
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