Sensitivity of a correlation radiometer

Faris, John J.

doi:10.6028/jres.071c.016

Cited by 15 publications

(8 citation statements)

References 2 publications

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“…In this section we develop a simple model for the WMAP instrument using Jones matrices (Jones 1941;Montgomery et al 1948;Blum 1959;Faris 1967;Sault et al 1996;Tinbergen 1996;Hu et al 2003). In the following we assume that all circuit elements are matched and ignore additive noise terms.…”

Section: Radiometer Modelmentioning

confidence: 99%

Three‐Year Wilkinson Microwave Anisotropy Probe ( WMAP ) Observations: Polarization Analysis

Page

Hinshaw

Komatsu

et al. 2007

ASTROPHYS J SUPPL S

834

616

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The Wilkinson Microwave Anisotropy Probe (WMAP) has mapped the entire sky in five frequency bands between 23 and 94 GHz with polarization-sensitive radiometers. We present 3 year full-sky maps of the polarization and analyze them for foreground emission and cosmological implications. These observations open up a new window for understanding how the universe began and help set a foundation for future observations. WMAP observes significant levels of polarized foreground emission due to both Galactic synchrotron radiation and thermal dust emission. Synchrotron radiation is the dominant signal at l < 50 and P 40 GHz, while thermal dust emission is evident at 94 GHz. The least contaminated channel is at 61 GHz. We present a model of polarized foreground emission that captures the large angular scale characteristics of the microwave sky. After applying a Galactic mask that cuts 25.7% of the sky, we show that the high Galactic latitude rms polarized foreground emission, averaged over l ¼ 4Y6, ranges from %5 K at 22 GHz to P0.6 K at 61 GHz. By comparison, the levels of intrinsic CMB polarization for a ÃCDM model with an optical depth of ¼ 0:09 and assumed tensor-to-scalar ratio r ¼ 0:3 are %0.3 K for E-mode polarization and %0.1 K for B-mode polarization. To analyze the maps for CMB polarization at l < 16, we subtract a model of the foreground emission that is based primarily on a scaling WMAP's 23 GHz map. In the foregroundcorrected maps, we detect l(l þ 1)C EE l¼ 2Y6 h i /2 ¼ 0:086 AE 0:029 (K) 2 . This is interpreted as the result of rescattering of the CMB by free electrons released during reionization at z r ¼ 10:9 þ2:7 À2:3 for a model with instantaneous reionization. By computing the likelihood of just the EE data as a function of we find ¼ 0:10 AE 0:03. When the same EE data are used in the full six-parameter fit to all WMAP data ( TT, TE, EE), we find ¼ 0:09 AE 0:03. Marginalization over the foreground subtraction affects this value by < 0:01. We see no evidence for B modes, limiting them to l(l þ 1)C BB l¼ 2Y6 h i /2 ¼ À0:04 AE 0:03 (K) 2 . We perform a template fit to the E-mode and B-mode data with an approximate model for the tensor scalar ratio. We find that the limit from the polarization signals alone is r < 2:2 (95% CL), where r is evaluated at k ¼ 0:002 Mpc À1 . This corresponds to a limit on the cosmic density of gravitational waves of GW h 2 < 5 ; 10 À12 . From the full WMAP analysis, we find r < 0:55 (95% CL) corresponding to a limit of GW h 2 < 1 ; 10 À12 (95% CL). The limit on r is approaching the upper bound of predictions for some of the simplest models of inflation, r $ 0:3. Subject headingg s: cosmic microwave background -cosmology: observations -polarization Online material: color figure

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Section: Radiometer Modelmentioning

confidence: 99%

Three‐Year Wilkinson Microwave Anisotropy Probe ( WMAP ) Observations: Polarization Analysis

Page

Hinshaw

Komatsu

et al. 2007

ASTROPHYS J SUPPL S

834

616

View full text Add to dashboard Cite

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“…The equation relating rotation to field and length is (1) where is the axial magnetic field, is the gyromagnetic ratio rad/s Oe (where is 2.11 for TT2-111), is the ferrite length, is the speed of light, and is the dielectric constant of the ferrite 12.5. This formula is correct only in the limit where the frequency is well above resonance as follows: (2) which at saturation is 14 GHz. From (1), the minimum length for 45 rotation at a saturated field of 5000 G is 1.35 mm.…”

Section: Rotator Microwave Designmentioning

confidence: 95%

“…Ferrite switches based on a Y-junction circulator geometry have low loss and sufficient speed, but also limited bandwidth. The correlation receiver geometry [2] is complex, and the required hybrids, phase switches, and phase matching limit the bandwidth. In the application motivating this study, a dual-polarized receiver using monolithic microwave integrated circuit (MMIC) HEMT amplifiers was required to cover 74-110 GHz with 31-MHz spectral resolution [3], and achieve true radiometric noise across the full band.…”

Section: Introductionmentioning

confidence: 99%

A Low-Loss 74–110-GHz Faraday Polarization Rotator

Erickson

Grosslein

2007

IEEE Trans. Microwave Theory Techn.

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We have developed a switchable Faraday polarization rotator for 74-110 GHz with a typical room-temperature insertion loss of 0.6 dB and a maximum of 1.3 dB. The device uses a cylindrical ferrite rod in the HE 11 mode with an axial magnetic field applied by a solenoid. The ports are square metallic waveguides transitioning to ceramic tapers, which then couple to the ferrite rod. The device is designed for use at a temperature of 20 K, where typical loss is 0.5 dB. The design rotation is 45 about the zero-bias value, but up to 90 is possible. The switching time is 10 s.

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“…The situation is different when the amplifier gain fluctuations are differential-mode instead of common-mode for the two amplifier chains. Faris [12] calculates the effect of a varying gain imbalance between the two chains for g 2 (f, t) = [1 + a(t)]g 1 (f ), where g 1,2 (f ) are the complex amplifier voltage gains of the two chains and a(t) is a zero-mean random variable that describes the differential-mode fluctuations. Fluctuations increase the output variance by a factor of (1 + a 2 (t) ) compared with the case of purely common-mode gain fluctuations between the two arms.…”

Section: Choice Of Hybridmentioning

confidence: 99%

“…[2,3,4,5,6]). A number of authors have described specific architectures and examined the operation and sensitivity of correlation radiometers in absolute terms and their suppression of effects from the 1/f noise common to amplifiers [4,7,8,9,10,11,12,13,14]. In the following, Section II contains a general discussion of correlation and Section III gives an analysis of the choice of hybrid phase, information that is not readily available elsewhere.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopy with multichannel correlation radiometers

Harris

2005

Review of Scientific Instruments

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*Correlation radiometers make true differential measurements in power with high accuracy and small systematic errors. This receiver architecture has been used in radio astronomy for measurements of continuum radiation for over 50 years; this article examines spectroscopy over broad bandwidths using correlation techniques. After general discussions of correlation and the choice of hybrid phase experimental results from tests with a simple laboratory multi-channel correlation radiometer are shown. Analysis of the effect of the input hybrid's phase shows that a 90• hybrid is likely to be the best general choice for radio astronomy, depending on its amplitude match and phase flatness with frequency. The laboratory results verify that the combination of the correlation architecture and an analog lag correlator is an excellent method for spectroscopy over very wide bandwidths.

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Sensitivity of a correlation radiometer

Cited by 15 publications

References 2 publications

Three‐Year Wilkinson Microwave Anisotropy Probe ( WMAP ) Observations: Polarization Analysis

Three‐Year Wilkinson Microwave Anisotropy Probe ( WMAP ) Observations: Polarization Analysis

A Low-Loss 74–110-GHz Faraday Polarization Rotator

Spectroscopy with multichannel correlation radiometers

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