Wideband Spectrometer Development in the Astronomy Department of the University of Maryland

Wideband spectrometers are becoming increasingly important for astronomy at millimeter and submillimeter wavelengths.  Applications include molecular line searches for primordial galaxies at unknown redshifts and extragalactic submillimeter spectroscopy of galaxies, whose spectral lines are very wide because of the Doppler effect's scaling with frequency. 

A review paper (pdf) from the SOFIA/NASA Far-IR, Sub-mm, and mm Detector Workshop provides an overview of different wideband heterodyne spectrometers and some of their applications to astronomy.  Another paper, from the 2002 SPIE Astronomical Telescopes and Instrumentation meeting (pdf), describes broadband analog correlator technology and suitable receiver architectures in more detail. 

Technical information is available below on the WASP2,WASP3, APHID analog lag correlators and their software. These are spectrometer systems that we have been developing in the High Frequency Radio Astronomy Laboratory at the University of Maryland.

WASP2 Analog Lag Correlator

of multiplier chain WASP2 is a 3.8 GHz bandwidth lag correlator spectrometer optimized for heterodyne astronomical spectroscopy with moderate resolution. This image shows three of the multipliers and the resistive taps to the transmission lines.

Some useful reference documents are:

WASP3 Ultra-wideband Multiplier

Custom multiplier MMIC WASP3 is a 25 GHz bandwidth Gilbert cell multiplier project for very broadband correlators and spectrometers.   Stephen Maas of Nonlinear Technologies, Inc. designed this custom MMIC for this project, with testing in the High Frequency Radio Astronomy Laboratory of the University of Maryland's Laboratory for Millimeter-wave Astronomy

A number of memos and images summarize measurements of the chips and associated components:

APHID Correlator for Phase Correction

APHID module In its current incarnation, APHID uses a single WASP2 board as an auto- or cross-correlator to test ideas for atmospheric phase correction for the BIMA and OVRO millimeter wave interferometers.

Some references:

Software documentation for the spectrometers

big computer Software is key to spectrometer operation.

A preliminary set of references for the spectrometer control, data reduction pipeline, and archiving software:

Questions or comments?   Please contact Andrew Harris.