WO2001048549A1 - Obturateur d'antenne de poursuite de satellites - Google Patents

Obturateur d'antenne de poursuite de satellites Download PDF

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Publication number
WO2001048549A1
WO2001048549A1 PCT/AU2000/001363 AU0001363W WO0148549A1 WO 2001048549 A1 WO2001048549 A1 WO 2001048549A1 AU 0001363 W AU0001363 W AU 0001363W WO 0148549 A1 WO0148549 A1 WO 0148549A1
Authority
WO
WIPO (PCT)
Prior art keywords
lens
refractive index
shutter
array
radiation
Prior art date
Application number
PCT/AU2000/001363
Other languages
English (en)
Inventor
Patrick Michael Conrick
Colin Rudolph
Original Assignee
Alcatel
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from AU65420/99A external-priority patent/AU6542099A/en
Priority claimed from AUPQ6433A external-priority patent/AUPQ643300A0/en
Application filed by Alcatel filed Critical Alcatel
Priority to AU12561/01A priority Critical patent/AU1256101A/en
Publication of WO2001048549A1 publication Critical patent/WO2001048549A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
    • H01Q19/06—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using refracting or diffracting devices, e.g. lens
    • H01Q19/062—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using refracting or diffracting devices, e.g. lens for focusing
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B3/00—Simple or compound lenses
    • G02B3/0087—Simple or compound lenses with index gradient
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/005—Diaphragms
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/02—Refracting or diffracting devices, e.g. lens, prism
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/02—Refracting or diffracting devices, e.g. lens, prism
    • H01Q15/08—Refracting or diffracting devices, e.g. lens, prism formed of solid dielectric material

Definitions

  • This invention relates to a device for selectively blocking or passing electromagnetic radiation.
  • the device may be used to form a matrix of cells which can be activated individually or in groups.
  • a specific application of the invention is the selective opening of the cells of such an array to form the tracking mechanism for a LEO satellite communication system.
  • the invention will be described in the context of an antenna arrangement for tracking LEO satellites.
  • a pair of independently controllable mechanical tracking dish antennas are used so that, while a first antenna is tracking a first satellite within the communication window, the second antenna can lock on to a second satellite in preparation for a hand-over.
  • a tracking antenna may have a beam width of the order of a few degrees, often one degree or less.
  • a LEO satellite may be "in view” for only a few minutes and continuous use causes ware of precision components, making accurate tracking difficult.
  • the tracking mechanism is switched off during "quiescent" traffic periods, or the antenna may be turned on only when the user wishes to transit or receive.
  • increasingly there is a demand for "off-line" data push services where an agency needs to supply data to a subscriber. This can be done in a cost effective manner by transmitting the data during quiescent periods.
  • LEO satellite systems may use the same band as geo-stationary satellite. Thus it is necessary to prevent interference between the two systems which may occur when a LEO passes between a ground based transceiver and a geo-stationary satellite. Disclosure of the Invention
  • an e-m beam shutter including a controllable element having a first state and a second state and control means to selectively switch the shutter between the first state and the second state, - wherein in the first state, the shutter deflects incident radiation along a first path, and in the second state, the shutter permits or causes incident radiation to follow a second path.
  • the specification also discloses an array of shutters as claimed in any one of claims 1 to 4, the array including a programmable controller programmed with the locus of one or more moving sources of e-m radiation; e-m focussing means to focus e-m radiation from a moving source in a focal plane to produce a corresponding locus; the array being located at or near to the focal plane to block or pass the e-m radiation; - the shutters of the array in the locus being opened sequentially by the controller to permit the passage of radiation as the focal point approaches the shutter.
  • the specification also discloses a paralleling lens adapted to convert input radiation into substantially parallel output radiation, the lens having a refractive index increasing from input to output .
  • Figure 1 shows a prior art arrangement of a pair of dish antennas using mechanical tracking.
  • Figure 2 shows an array of cells making up a tracking shutter embodying the invention.
  • Figure 3 to 6 show various embodiments of tracking antennas utilising a tracking shutter.
  • Figure 7 shows the function of a paralleling lens.
  • Figure 8 shows an analysis of the beam path through the paralleling plate
  • Figure 9 is a graph showing the angle of refraction for differing values of relative refractive index of the paralleling plate.
  • Figure 10 shows an implementation of a LEO tracking antenna including a paralleling plate embodying the invention.
  • Figure 1 1 shows a section through a modified paralleling plate adapted to receive radiation over a wide input range.
  • Figure 1 2 shows a further development of the embodiment of figure 1 1 which can be used to produce a concentration of the input radiation on to a target area. Best mode of carrying out the Invention
  • FIG 1 illustrates the dual mechanical tracking antenna arrangement of the prior art.
  • a pair of dish antennas, 1 and 2 are mounted on universal mountings 3 and
  • the antennas l and 2 are electrically connected to a transceiver 9 by connections 7 and 8.
  • the antennas 1 and 2 are programmed and controlled to track different satellites, one antenna locking on to a satellite newly arrived in the window while the other antenna tracks an earlier satellite.
  • a hand-over of the communication is arranged as the earlier satellite moves out of range, e.g. as it approaches 10° above the horizon.
  • Figure 2 illustrates an array of cells, 20, which are individually controllable to block or enable the passage of the e-m beam, such as the microwave band used by LEO systems.
  • the array is shown as circular because the tracking antenna may have to track satellites within a spherical field of view of _+ 1 60° .
  • the shape of the array may be chosen to suit the particular application.
  • the array may be rectangular if a narrow scanning zone is required.
  • a controller 21 is connected to the array to open or close cells as required.
  • the controller 21 may be programmed to open a sequence of adjacent cells, to mirror the path of a LEO satellite. Two or more satellites may be tracked simultaneously.
  • the cells are opened in sequence on an "open-before-close" basis so that a newly opened cell is opened before the preceding cell is closed.
  • the cells may be miniaturized flip-disc type cells, being a scaled shown vision of the flip-disc public display systems, the discs being made of a material which reflects the e-m beam when the cell is closed, the disc being rotated to be substantially parallel to the e-m beam when the cell is open.
  • the discs may be of a material which has a refractive index such that when the angle of incidence of the e- m beam is greater than a critical angle, the beam is reflected, and when the angle is less than the critical angle, the beam passes through the disc. The disc is thus controlled to tilt it mechanically to pass the beam to a target, or reflect or refract the beam away from the target.
  • the cells may be composed of material whose refractive index or other optical or quasi-optical properties can be changed, e.g. by the application of light, or an electric field, or heat, or a magnetic field.
  • the e-m beam can be deflected towards or away from a path which leads to or away from an antenna.
  • Photonic Spectra August 1 997 discusses non-linear optical materials whose properties, including refractive index, can be changed by electrical or optical energy (see abstract at ww . lau ⁇ n . com/content /aug97 /tec vbr ⁇ d . html ) .
  • a magnetic field may be used to alter characteristics of the material, such as optical transparency (Photonics Spectra, December 1 997, www . laurin . com . dec 97 / techma . html ) .
  • FIG. 3 shows ⁇ first arrangement for a tracking antenna utilizing a shutter embodying the invention.
  • the arrangement includes a first e-m lens such as a Luneberg Lens 30, a tracking array 31 , a second e-m lens means 32 (e.g. a Fresnel lens), and an antenna 33.
  • the first lens 31 focuses the incident beams onto a focal plane.
  • the shutter array 31 is located at or near the focal lane.
  • the beam 34a, 34b is focussed onto cell 35 of the shutter array.
  • the lens traces its locus on the focal plane so that a sequence of cells are illuminated, mirroring the passage of the satellite. A satellite moving from right to left will illuminate a locus moving a left to right.
  • the controller may be programmed with the orbit information of the constellation of satellites to enable it to track the projected locus.
  • the controller may only be programmed to track those satellites in the constellation which are within the window of the tracking system.
  • the information on the satellite orbits may be updated periodically to maintain the accuracy of the tracking.
  • Figure 3B shows the locus 100 of a satellite illuminating cells 101 to 1 10 in sequence.
  • the controller 21 (not shown in Figure 3B) opens the cells 101 to 1 10 in sequence, each cell being opened as the locus of the satellite approaches the cell, and being closed after the satellite locus has passed over the cell.
  • the second lens is used to focus the beams to (received beam) or from (transmitted beam) the antenna 33. In this way, only beams to or from satellites within the aperture of the open cells can be transmitted or received via the antenna 33.
  • the controller 21 begins tracking a second satellite e.g. locus 1 1 1 .
  • cell 1 20 or one of the subsequent cells (121 to 1 27) is activated before communication is lost with the first satellite, and a hand-over to the new satellite is initiated.
  • Figure 4 shows an arrangement similar to Figure 3, in which the lens 32 is replaced by a series of concentric annular reflectors 36 which deflect the beams to the antenna 33.
  • the reflectors are arranged to collect beams from the corresponding cells and direct the beams to the antenna 33.
  • the embodiment shown in Figure 5 is similar to the embodiment shown in figures 3 and 4, but the second "quasi-optical" device, 37, is a seifoc lens having a radially graded index to focus the beams on the antenna 33.
  • the embodiment of Figure 6 has an additional element, paralleling lens 38.
  • the paralleling lens has the characteristic that, whatever the angle of incidence of the beam entering the lens, the output beam has a decreased divergence and is bent towards the normal to the refractive index gradient, (assuming transmision from less to greater refractive index) independent of where the incident beam strikes the lens. This differs from a normal convex lens where beams from any specific point on the focal plane exit in parallel to a line between the centre of the lens and the specific point on the focal plane.
  • a paralleling lens may be flat rather than lenticular and have a stepped or progressively increasing refractive index from the input to the output. This may be manufactured simply by laminating two or more layers having progressively increasing refractive indices. The increasing refractive index causes the incident beams to be deflected towards the normal. Thus whatever the incidence angle, all beams can be made to exit with a decreased divergence.
  • the use of the paralleling lens in conjunction with the shutter array simplifies the operation of the shutter array and the subsequent handling of the output beam, because all the beams incident on the array arrive at substantially the same angle. This averts or reduces the need to make significant geometric or refractive index adjustments for the cells in accordance with the location of the cells in the array. Thus the cells may not need to be inclined at significantly different angles within the array, and the same refractive index materials can be used in all cells. Depending on the configuration and operating conditions, the use of the paralleling lens means that little or no adjustment to these characteristics is necessary.
  • the paralleling lens located in the focal plane of a normal lens has the effect of transforming the groups of intersecting rays focussed on a specific focal point into a cohesive group of substantially parallel rays rather than continuing to diverge after passing through the focal point.
  • the groups of rays corresponding to different focal points retain the relative geometric relationships with each other corresponding to the relative geometric relationship between the focal points. In other words the relative positions of the input points map across to the output.
  • the paralleling lens should be located close to the array and/or have a matching refractive index material.
  • Figure 7 shows the transformation of non-parallel rays intersecting at a point, 71 , on the input surface of a paralleling lens 70, to a first group of substantially parallel rays, 72, at the output of the lens.
  • the inset depth (d) / refractive index ( ⁇ ) graph, 77 indicates that refractive index increases with depth.
  • the first and second groups of substantially parallel rays are shown projected onto a plane, 76, which represents the shutter array.
  • the intersecting rays on the incident face of the lens represent the focussed rays from a satellite at different points on its orbit, after the rays have been focussed by a focussing lens.
  • the relative geometric positions of the rays are maintained after passing through the paralleling lens. This means that the rays strike the cells of the array at substantially the same angle, simplifying the construction and operation of the cells, as it reduces or avoids the necessity to correct for the non-parallel nature of the rays emerging from the focussing lens.
  • the paralleling lens can be used to deflect the angle of the existing rays simply by tilting the paralleling lens, because the rays leaving the lens are deflected towards the normal to the refractive index contour of the lens.
  • the paralleling lens may be used as the array element, as tilting the element deflects the rays.
  • the array may have all its elements "open" except for the elements directed to the geo-stationary satellite or, if there is more than one geo-stationary satellite, the cells directed to the geo-stationary satellites are occluded. In this way, the array can transmit and receive in all directions except in the direction of the geo-stationary satellites, so that interference between the ground based terminal and the geo-stationary satellites is prevented.
  • the control system monitors the locus of the LEOs in relation to the position of the known geo-stationary satellites, and initiates a hand-over when the LEO locus approaches intersection with an occluded cell. Due to the fact that the angle of incidence can vary between + 10° to + 1 70° above the horizon, the paralleling lens may be modified to function better over the 1 60° range.
  • the paralleling effect can be reinforced in a concentric fashion to better maintain the parallel nature of the output, while also reducing the reflection of energy due to the low angle of incidence, ie, the nearer the incident beam is to being parallel to the surface, the more energy is reflected.
  • the edges of the paralleling lens raised to present a concave surface to the incident beam more of the incident energy can be captured.
  • the paralleling plate has a radial graduation of its refractive index whereby incident radiation beams at large angles of incidence strike the plate near its periphery and are refracted more than the beams striking nearer the centre.
  • the radial graduation is achieved by laminating a series of concentric annuli having progressively increasing refractive indices and increasing inner radii.
  • the interface surfaces between the rings are sloped to optimize the refraction of the beams, so that, for example, the output beams all travel in substantially the same direction.
  • the sloping of the interface surfaces may be used to focus the beams to a target area.
  • Figure 8 shows an optical or quasi-optical arrangement including a lens 83, conceptually illustrated as a straight line and a paralleling plate 86.
  • the paralleling plate has a first layer 84 having a refractive index N A at the wavelength of interest, and a second layer 85 having a refractive index N B , where :
  • Lens 83 focuses incoming parallel rays 81 and 82 at the interface between layers 84 and 85. Ray 81 , after passing through lens 83, strikes the interface at an angle 01 to the normal to the interface and is refracted into layer 85 at an angle ⁇ .
  • S ⁇ n refraction is proportional to the sine of the angle of incidence.
  • the graph in Figure 9 shows, the consequence of this is that the deflection is proportionally greater than the angle of incidence, due to the flattering of the sinusoid curve.
  • the graph of Figure 9 has a Y axis representing the sine of an angle and an X axis graduated in degree of angle and shows a first curve, Sin A, representing the sine of the incident angle, and four other curves representing the sines of the corresponding angles of refraction for values of N equal to 1 .1 , 1 .2, 1 .4, and 1 .8, the curves being progressively lower as N increases.
  • the graph can be used to determine the sine of the angle of refraction for a given angle of incidence and a given value of N.
  • the first column represents angles in degrees and column 2 represents the sine of these angles.
  • Columns 3 to 9 represent the sines of the corresponding angles of refraction for the values of N ranging from 1 .1 for 1 .8 appearing at the head of the corresponding columns.
  • the sine an angle of refraction can be determined for a known value of N for a given angle of incidence.
  • the angle of refraction can be determined from its sine.
  • the graph of Figure 9 or Table 1 can be used to determine the angle of refraction. For instance, referring to figure 9 and Table 1 , suppose that:
  • the beam divergence angle for the beam bounded by ray 81 and ray 82 has thus been reduced from 0 2 - ⁇ to ⁇ 2 - ⁇ ⁇ , ie from 30° to 21 ° .
  • This narrowing of the beam divergence increases with the value of N.
  • FIG. 10 shows an implementation of a LEO tracking antenna using the quasi-optical characteristics of microwaves.
  • a focussing lens 83 eg. a Luneberg lens, conceptually shown as a straight line, focuses microwave radiation (rays 81 & 82) onto a paralleling plate 86, also shown as a straight line.
  • a controllable array of microwave gates 1 10 is located under the paralleling plate. The gate array may be controlled by control means 103 to track the locus of a LEO as it transits the field of view. Cells of the array are opened in sequence to permit the signals to pass while cells pointing (via lens 83) to unwanted sources of radiation remain closed.
  • the paralleling plate 86 narrows the beam and facilitates its passage through the cells of the array, which may be sensitive to the incident angle of the radiation.
  • the narrowing of the beam facilitates the focussing of the radiation onto the target area (antenna 1 12) by the collecting lens 1 1 1 , also shown conceptually as a line.
  • Figure 1 1 shows a cross-section through a paralleling plate made up of two or more annular elements 1 21 , 1 22, 123.
  • Annulus 122 has a triangular shape and its major sides are designed to interface with annulus (in this example, disc) 1 21 , and annulus 123 which also has a triangular section.
  • the refractive index of 1 23 is less than the refractive index of 1 22, which is less than the refractive index of 1 21 .
  • the interfaces between at least some of the rings are sloped, to accentuate the angle of incidence.
  • the radiation output may be kept substantially parallel irrespective of the elevation of the LEO. While it may be possible to buiid up a single plate having the appropriate Rl profile, e.g. using CVD, this would be a complex operation, but is still within the scope of this invention. However, the manufacture of such a plate is simplified by the use of the triangular sectioned annulus technique illustrated in Figure 1 1 .
  • the plate of figure 1 1 may also be extended to produce a focussing lens by having a further stack of such rings on the lower side of disc 21 , with the refractive indices continuing to increase in the same direction.
  • the triangular sectioned rings can be used to achieve both a narrowing of the beam and a change of direction, because the change of angle of the interface between the rings effectively increases the angle of incidence and hence produces a greater change in the angle of refraction.

Abstract

La présente invention concerne un obturateur (20) contrôlable de poursuite par faisceau électromagnétique et un dispositif de poursuite de satellites en orbite basse terrestre (LEO). On utilise une lentille de Lüneberg (30) afin de projeter la position d'un satellite LEO sur l'obturateur de poursuite constitué d'un réseau de cellule (31) contrôlées au moyen d'un contrôleur (21) afin qu'elles laissent passer les signaux recherchés et qu'elles arrêtent les signaux indésirables. Ce contrôleur peut être programmé à l'aide des informations d'orbite d'une constellation de satellites LEO. L'invention concerne également une lentille cylindrique (84, 85) permettant d'améliorer l'efficacité de l'obturateur.
PCT/AU2000/001363 1999-12-23 2000-11-06 Obturateur d'antenne de poursuite de satellites WO2001048549A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU12561/01A AU1256101A (en) 1999-12-23 2000-11-06 Shutter for satellite tracking antenna

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
AU65420/99A AU6542099A (en) 1999-12-23 1999-12-23 Shutter for satellite tracking antenna
AU65420/99 1999-12-23
AUPQ6433A AUPQ643300A0 (en) 2000-03-27 2000-03-27 Shutter for satelite tracking antenna
AUPQ6433 2000-03-27

Publications (1)

Publication Number Publication Date
WO2001048549A1 true WO2001048549A1 (fr) 2001-07-05

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Application Number Title Priority Date Filing Date
PCT/AU2000/001363 WO2001048549A1 (fr) 1999-12-23 2000-11-06 Obturateur d'antenne de poursuite de satellites

Country Status (1)

Country Link
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102012011789A1 (de) * 2012-06-15 2013-08-14 Deutsches Zentrum für Luft- und Raumfahrt e.V. Freistrahl-Kommunikationsterminal zur mobilen optischen Freistrahlkommunikation
US20180219285A1 (en) * 2017-02-02 2018-08-02 The Boeing Company Spherical dielectric lens side-lobe suppression implemented through reducing spherical aberration

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102012011789A1 (de) * 2012-06-15 2013-08-14 Deutsches Zentrum für Luft- und Raumfahrt e.V. Freistrahl-Kommunikationsterminal zur mobilen optischen Freistrahlkommunikation
US20180219285A1 (en) * 2017-02-02 2018-08-02 The Boeing Company Spherical dielectric lens side-lobe suppression implemented through reducing spherical aberration
EP3358677A1 (fr) * 2017-02-02 2018-08-08 The Boeing Company Suppression des lobes latéraux d'une lentille diélectrique sphérique mise en oeuvre par réduction de l'aberration sphérique
CN108390159A (zh) * 2017-02-02 2018-08-10 波音公司 通过减小球面像差所实现的球面电介质透镜旁波瓣抑制
JP2018174517A (ja) * 2017-02-02 2018-11-08 ザ・ボーイング・カンパニーＴｈｅ Ｂｏｅｉｎｇ Ｃｏｍｐａｎｙ 球面収差の低減を通して実現される球面誘電体レンズのサイドローブの抑制
US10714827B2 (en) 2017-02-02 2020-07-14 The Boeing Company Spherical dielectric lens side-lobe suppression implemented through reducing spherical aberration
JP7049118B2 (ja) 2017-02-02 2022-04-06 ザ・ボーイング・カンパニー 球面収差の低減を通して実現される球面誘電体レンズのサイドローブの抑制

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