Offset balancing in pseudo-correlation radiometers for CMB measurements

Abstract

Radiometeric CMB measurements need to be highly stable and this stability is best obtained with differential receivers. The residual 1/f noise in the differential output is strongly dependent on the radiometer input offset which can be cancelled using various balancing strategies. In this paper we discuss a software method implemented in the Planck-LFI pseudo-correlation receivers which uses a tunable "gain modulation factor, r, in the sky-load difference. Numerical simulations and experimental data show how proper tuning of the parameter r ensures a very stable differential output with knee frequencies of the order of few mHz. Various approaches to calculate r using the radiometer total power data are discussed with some examples relevant to Planck-LFI. Although the paper focuses on pseudo-correlation receivers and the examples are relative to Planck-LFI, the proposed method and its analysis is general and can be applied to a large class of differential radiometric receivers.

12 pages, 8 figures, accepted for publication in A&A (updated version with few editorial changes)

References in corpus (4)

• The Microwave Anisotropy Probe (MAP) Mission
• Design, Implementation and Testing of the MAP Radiometers
• 1/f noise and other systematic effects in the Planck-LFI radiometers
• PLANCK: systematic effects induced by periodic fluctuations of arbitrary shape

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• Spectroscopy with Multichannel Correlation Radiometers
• Scanning strategy for mapping the Cosmic Microwave Background anisotropies with Planck
• Planck pre-launch status: Low Frequency Instrument calibration and expected scientific performance
• Planck-LFI: Design and Performance of the 4 Kelvin Reference Load Unit
• Design, development and verification of the 30 and 44 GHz front-end modules for the Planck Low Frequency Instrument
• Noise Properties of the Planck-LFI Receivers
• The linearity response of the Planck-LFI flight model receivers
• Planck pre-launch status: calibration of the Low Frequency Instrument flight model radiometers
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• Planck-LFI radiometers tuning
• An Integrated System at the Bleien Observatory for Mapping the Galaxy
• In-flight calibration and verification of the Planck-LFI instrument
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