Comparison of three cross-polarisation prediction methods for reflector antennas

Bach, H.; Viskum, H.-H.

doi:10.1049/ip-h-2.1986.0058

Cited by 9 publications

(6 citation statements)

References 2 publications

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“…The conversion of I into Q and U seen here is produced by the reflector alone. Currents near the reflector rim dominate cross‐polarization performance [ Bach and Viskum , 1986], and polarization performance could be improved by reducing the edge illumination.…”

Section: Results Of Calculationsmentioning

confidence: 99%

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Polarization properties of reflector antennas used as radio telescopes

Ng¹,

Landecker

Cazzolato

et al. 2005

Radio Science

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The distribution of cross polarization across the main beam and near sidelobes of a reflector antenna is calculated. Results are expressed in terms relevant to imaging in radio astronomy, using Stokes parameters, as plots of instrumental polarization Q/I, U/I, and V/I, showing conversion of total intensity of a signal which is unpolarized into apparent linear and circular polarization. The calculations use GRASP8, software that is based on physical optics and the physical theory of diffraction. For purposes of calculation, the symmetrical paraboloidal reflector (diameter ∼40 wavelengths) is fed at the prime focus with a linearly polarized signal. Computed radiation patterns at a number of feed orientations are averaged to establish the antenna response to an unpolarized radio astronomy signal. The results of the computations are consistent with measurements of instrumental polarization of the Dominion Radio Astrophysical Observatory Synthesis Telescope at 1420 MHz made using unpolarized radio sources. For this telescope, the dominant source of instrumental polarization across the field is the cross polarization of the feed. The next most significant effect is scattering by the feed struts; both three‐strut and four‐strut configurations are examined. Struts affect performance in linear polarization but also introduce some instrumental circular polarization. The contribution to instrumental polarization from the reflector itself is comparatively small. Roughness of the reflector surface has relatively little effect in the main beam in Q and U but introduces V and also randomizes the polarization of the sidelobes. In all cases considered, the computations show that the first and subsequent sidelobes are highly polarized, with levels of instrumental polarization up to 50%.

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Section: Results Of Calculationsmentioning

confidence: 99%

“…PO derives currents on the surface of the reflector from the incident field. PTD models the current near the reflector rim; these currents are strong determinants of cross‐polarization performance [ Bach and Viskum , 1986].…”

Section: Calculation Of Instrumental Polarizationmentioning

confidence: 99%

Polarization properties of reflector antennas used as radio telescopes

Ng¹,

Landecker

Cazzolato

et al. 2005

Radio Science

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show abstract

“…Specifically, we have from (9a) and (9b) A(,. 4) A [4) cos (,,1 9 (A similar substitution was used by Mitzner in Section 3.2.1 of Ref. 17 for the special case of the wedge.)…”

Section: Kterniination Of the Rectanguar Components Of And In Terms Of Kmentioning

confidence: 95%

“…13 ". 4 In 1950. Braunbek" developed further these two basic ideas of the modrrn theories of diffraction and applied them in detail to the circwjlar erture and disc.…”

Section: Introductionmentioning

confidence: 99%