Derivation and application of the equivalent paraboloid for classical offset Cassegrain and Gregorian antennas

Rusch, W.; Prata, A.; Rahmat-Samii, Y.; Shore, Robert A.

doi:10.1109/8.56949

Cited by 76 publications

(53 citation statements)

References 12 publications

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“…More detailed discussions were given by Mizugutch [5], Dragone [6], Rusch et al [7], Noethe et al [8], Chang and Prata [9], and Chang [10]. Certain conditions have to be met for an optimized off-axis system to avoid unacceptable linear astigmatism and cross polarization in an off-axis system.…”

Section: Introductionmentioning

confidence: 96%

Field scanner design for MUSTANG of the Green Bank Telescope

Cheng¹,

Li²,

Li³

et al. 2011

Sci. China Phys. Mech. Astron.

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MUSTANG (Multiplex SQUID TES Array at Ninety GHz) is a bolometer camera for the Green Bank Telescope (GBT) working at a frequency of 90 GHz. The detector has a field of view of 40 arcsec. To cancel out random emission change from atmosphere and other sources, requires a fast scanning reflecting system with a few arcminute ranges. In this paper, the aberrations of an off-axis system are reviewed. The condition for an optimized system is provided. In an optimized system, as additional image transfer mirrors are introduced, new aberrations of the off-axis system may be reintroduced, resulting in a limited field of view. In this paper, different scanning mirror arrangements for the GBT system are analyzed through the ray tracing analysis. These include using the subreflector as the scanning mirror, chopping a flat mirror and transferring image with an ellipse mirror, and chopping a flat mirror and transferring image with a pair of face-to-face paraboloid mirrors. The system analysis shows that chopping a flat mirror and using a well aligned pair of paraboloids can generate the required field of view for the MUSTANG detector system, while other systems all suffer from larger off-axis aberrations added by the system modification. The spot diagrams of the well aligned pair of paraboloids produced are only about one Airy disk size within a scanning angle of about 3 arcmin.

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Section: Introductionmentioning

confidence: 96%

Field scanner design for MUSTANG of the Green Bank Telescope

Cheng¹,

Li²,

Li³

et al. 2011

Sci. China Phys. Mech. Astron.

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“…This approximate optical equivalence of paraboloidal and ellipsoidal reflectors was used by the authors for the fist time in [24] where a compensated Gregorian system with reduced cross-polarization was designed. Its primary utility is that existing design rules for far field systems (for example, the low cross-polarization dual-reflector system [21] and general design rules [22], [23]) can be readily applied to the near field.…”

Section: Near Field Focusingmentioning

confidence: 99%

Confocal Ellipsoidal Reflector System for a Mechanically Scanned Active Terahertz Imager

Llombart

Cooper

Dengler

et al. 2010

IEEE Trans. Antennas Propagat.

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Abstract-We present the design of a reflector system that can rapidly scan and refocus a terahertz beam for high-resolution standoff imaging applications. The proposed optical system utilizes a confocal Gregorian geometry with a small mechanical rotating mirror and an axial displacement of the feed. For operation at submillimeter wavelengths and standoff ranges of many meters, the imaging targets are electrically very close to the antenna aperture. Therefore the main reflector surface must be an ellipse, instead of a parabola, in order to achieve the best imaging performance. Here we demonstrate how a simple design equivalence can be used to generalize the design of a Gregorian reflector system based on a paraboloidal main reflector to one with an ellipsoidal main reflector. The system parameters are determined by minimizing the optical path length error, and the results are validated with numerical simulations from the commercial antenna software package GRASP. The system is able to scan the beam over 0.5 m in cross-range at a 25 m standoff range with less than 1% increase of the half-power beam-width.

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“…These include the focus fed paraboloid, as well as Cassegrain and Gregorian dual reflector systems [1]. All these systems may be symmetrical or offset, with GO based design details available in the open literature [2,3,4,5,6], and sketches of some of the configurations shown in Fig. 1.…”

Section: Reflector Antenna Systems Backgroundmentioning

confidence: 99%

Recent Advances in Surrogate Modelling of Reflector Antenna Systems

Villiers¹

2016

Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016)

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Abstract. This paper discusses some of the recent advances in the surrogate based modeling and optimization of reflector antenna systems, and presents several examples. Much of the focus is on the design of reflector systems for radio astronomy applications, where especially tight specifications are placed on some of the important performance metrics. In several cases the response surfaces of these performance metrics are computationally expensive to compute, and, as an added complication, they are often conflicting and need to be optimized in a multiobjective (MO) or Pareto framework. The large numbers of function evaluations required in these optimization loops make direct full wave simulation in the loop intractable, and surrogate based methods may in these cases lead to reliable global MO optimizations. Two main characteristics of reflector antenna responses of interest are exploited, namely their slow (or periodic) variation with design parameters, as well as the availability of a computationally cheap geometric optics approximation. 4302

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Derivation and application of the equivalent paraboloid for classical offset Cassegrain and Gregorian antennas

Cited by 76 publications

References 12 publications

Field scanner design for MUSTANG of the Green Bank Telescope

Field scanner design for MUSTANG of the Green Bank Telescope

Confocal Ellipsoidal Reflector System for a Mechanically Scanned Active Terahertz Imager

Recent Advances in Surrogate Modelling of Reflector Antenna Systems

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