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ALMA MEMO #393
DSB versus SSB and Bandwith/Sensitivity tradeoff
S.Guilloteau (IRAM/ESO)
2002/05/14
Keywords: Receiver, Correlator
The ALMA performances will depend on the receiver design and performances. Conflicting requirements on cost, reproducibility, maintainability, bandwidth and noise temperature affect the receiver design, and the capabilities of ALMA. This memo reviews the possible tradeoff between receiver complexity and ALMA performances, considering DSB vs SSB and Bandwidth vs Receiver noise tradeoffs. Realistic scientific applications are considered.
This memo reproduces the numerical results obtained in memo 304 using a different approach. However, the conclusion differ because I also account for a scheduling strategy in which high frequency observations are made only when the weather allows. Combined with a reasonable assumption on the distribution of continuum (or dual-line) observations vs single spectral line cases, this assumption favors DSB mixers at high frequencies. DSB receivers may provide a 10 % advantage above 500 GHz, while SSB receivers would provide a
10 % advantage below that frequency.
Analysis of the Bandwidth/Receiver noise trade-off indicate that reduction of a factor 2 in detection bandwidth can be compensated by improvement by 25 -- 30 % in Receiver noise.
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Last modified: 2002-05-14
alma-memos@nrao.edu