The ALMA Front End Optics—System Aspects and European Measurement Results

Rudolf, H.; Carter, M.; Baryshev, A.

doi:10.1109/tap.2007.908556

Cited by 22 publications

(21 citation statements)

References 6 publications

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“…This problem is often circumvented by splitting the wide band into multiple sub-bands, each with its own feed horn; but then a complex set-up is required to minimize aberrations due to off-axis positioning of the multiple horns [12]. The ideal reflector feed should present a frequency stable radiation pattern with moderate gain and stable phase center position across the whole band.…”

mentioning

confidence: 99%

Broadband Integrated Lens for Illuminating Reflector Antenna With Constant Aperture Efficiency

Fernandes

Lima

Costa

2010

IEEE Trans. Antennas Propagat.

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Abstract-A new integrated shaped lens antenna configuration is described with frequency stable radiation pattern and phase center position across a broad 1:3 frequency band, which can be used for focal plane reflector feeding in quasi-optical radio telescope systems. The lens is compatible with the integration of ultrawideband uniplanar printed feeds at its base and equally broadband mixing devices, like the Hot Electron Bolometer (HEB), although these are not used in the present work. Measurements on a scaled mm-wave lab prototype have confirmed stable performance versus frequency, with only 1 dB directivity variation, and better than 94% Gaussicity, thanks to the possibility to impose a predefined output radiation pattern template. Simulations were performed to test the illumination of an off-set parabolic reflector by the lens radiation pattern, which confirmed reasonably constant aperture efficiency in the order of 78% across the 100% bandwidth.Index Terms-Broadband stable radiation pattern, broadband stable phase center position, integrated lens antennas, millimeterand submillimeter wave antennas, reflector feed.

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mentioning

confidence: 99%

Broadband Integrated Lens for Illuminating Reflector Antenna With Constant Aperture Efficiency

Fernandes

Lima

Costa

2010

IEEE Trans. Antennas Propagat.

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“…The receiver's front end can be understood as two orthogonal dipoles, one horizontal (the X-axis) and one vertical (the Y-axis), in the frame of the antenna mount (although there could also be a generic rotation of the XY plane on a third antenna axis, parallel to the source direction). The Atacama Large Mm/submm Array (ALMA) is a good example of an interferometer that uses linear-feed polarization receivers (e.g., Rudolf et al 2007). …”

Section: Introductionmentioning

confidence: 99%

“…For instance, most of the stations of the Global Mm-VLBI Array (GMVA), which use circular polarizers at 86 GHz, suffer from polarization leakages as high as 2−6% (Martí-Vidal et al 2012); the reported leakage of the circular polarizers at the SubMillimeter Array (SMA) can also reach values up to 4% (Marrone & Rao 2008). In contrast, the leakage from the linear polarizers at ALMA reach amplitudes of ∼1% (e.g., Rudolf et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Calibration of mixed-polarization interferometric observations

Martí-Vidal

Roy

Conway

et al. 2016

A&A

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Heterodyne receivers register the sky signal on either a circular polarization basis (where it is split into left-hand and right-hand circular polarization) or a linear polarization basis (where it is split into horizontal and vertical linear polarization). We study the problem of interferometric observations performed with telescopes that observe on different polarization bases, hence producing visibilities that we call "mixed basis" (i.e., linear in one telescope and circular in the other). We present novel algorithms for the proper calibration and treatment of such interferometric observations and test our algorithms with both simulations and real data. The use of our algorithms will be important for the optimum calibration of forthcoming observations with the Atacama Large Mm/submm Array (ALMA) in very-long-baseline interferometry (VLBI) mode. Our algorithms will also allow us to optimally calibrate future VLBI observations at very high data rates (i.e., wide bandwidths), where linear-polarization feeds will be preferable at some stations, to overcome the polarimetric limitations due to the use of quarter-wave plates.

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“…ALMA is a mm/sub-mm radio-interferometer instrument consisting of 50+ antennas [1]. Each of the Cassegrain antennas will host an individual cryostat housing 10 independent cartridges, each of them containing a dedicated heterodyne receiver for a selected band of interest [1].…”

Section: Introductionmentioning

confidence: 99%

“…Each of the Cassegrain antennas will host an individual cryostat housing 10 independent cartridges, each of them containing a dedicated heterodyne receiver for a selected band of interest [1]. The ALMA band 9 cartridge, which covers the range 600-720 GHz, is cryogenically cooled and contains a dual polarised front-end with local oscillator quasi-optical coupling system.…”

Section: Introductionmentioning

confidence: 99%

Quasi-optical assessment of the ALMA band 9 front-end

Candotti

Baryshev

Trappe

2009

Infrared Physics & Technology

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a b s t r a c tThe ALMA band 9 (600-720 GHz) receiver is a dual channel heterodyne system which is capable of detecting orthogonally polarised signals utilising a wire grid beam splitter. Two Superconductor-Insulator-Superconductor (SIS) mixers mounted behind hybrid mode corrugated horns are coupled to the 12 m Cassegrain antenna via a wavelength independent configuration of two off-axis elliptical mirrors.We outline an approach involving accurate physical optics simulations in conjunction with precise experimental measurements of the complete optical front-end which guarantees the highest performances. This practical verification approach can be generalised to all quasi-optical receivers to validate system performance. In this paper, we verify the optical design and estimate antenna system efficiency. Comparison between measurement and simulation indicates precise information is achievable in estimating system performance allowing potential improvements in ALMA instrument calibration accuracy.

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The ALMA Front End Optics—System Aspects and European Measurement Results

Cited by 22 publications

References 6 publications

Broadband Integrated Lens for Illuminating Reflector Antenna With Constant Aperture Efficiency

Broadband Integrated Lens for Illuminating Reflector Antenna With Constant Aperture Efficiency

Calibration of mixed-polarization interferometric observations

Quasi-optical assessment of the ALMA band 9 front-end

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