WO1992016031A1 - A frequency-discriminating dichroic structure with a variable passband and applications thereof - Google Patents

A frequency-discriminating dichroic structure with a variable passband and applications thereof Download PDF

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Publication number
WO1992016031A1
WO1992016031A1 PCT/EP1992/000386 EP9200386W WO9216031A1 WO 1992016031 A1 WO1992016031 A1 WO 1992016031A1 EP 9200386 W EP9200386 W EP 9200386W WO 9216031 A1 WO9216031 A1 WO 9216031A1
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WO
WIPO (PCT)
Prior art keywords
dielectric
dichroic structure
dielectric material
substrate
structure according
Prior art date
Application number
PCT/EP1992/000386
Other languages
French (fr)
Inventor
Daniele Bresciani
Valerio Zingarelli
Original Assignee
Alenia-Aeritalia & Selenia S.P.A.
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
Application filed by Alenia-Aeritalia & Selenia S.P.A. filed Critical Alenia-Aeritalia & Selenia S.P.A.
Publication of WO1992016031A1 publication Critical patent/WO1992016031A1/en

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/204—Filters in which spectral selection is performed by means of a conductive grid or array, e.g. frequency selective surfaces
    • 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
    • H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
    • H01Q15/0013—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
    • H01Q15/002—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective said selective devices being reconfigurable or tunable, e.g. using switches or diodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/44—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the electric or magnetic characteristics of reflecting, refracting, or diffracting devices associated with the radiating element

Definitions

  • the present invention relates to a dichroic structure for the selective attenuation according to frequency of incident electromagnetic waves the frequencies of which fall outside a predetermined passband.
  • the invention concerns a dichroic structure including at least one substrate of dielectric material, at least one face of which bears an orderly and geometrically periodic array of elements of an electrically conductive material or a layer of conductive material having an orderly and geometrically periodic array of holes.
  • such a dichroic structure considerably increases the communication capacity of a system having an antenna with reflectors, enabling it to operate at several frequencies.
  • This drastically ⁇ reduces the weight, bulk and cost of an antenna system, which advantages are of great importance for application to satellite communications systems.
  • frequency-discriminating dichroic structures may be used for forming radomes with well-defined transmission bands.
  • the object of the present invention is to provide a dichroic structure with a variable working (transmission or reflection) band.
  • control means are associated with the substrate of dielectric material for varying the dielectric or magnetic constant of the material so as
  • the dielectric material used has a dielectric or magnetic constant which is variable as a result of the application of a potential difference across the material and the control means are arranged to apply a quasi-static, variable potential difference across the dielectric substrate.
  • the dielectric material used has a dielectric or magnetic constant which can be varied significantly in dependence on its temperature and the control means comprise heating means for changing the temperature of the dielectric material.
  • the heating means may comprise means for generating a high-frequency magnetic field to heat the dielectric material by induction or may be resistive heating means for changing the temperature of the dielectric material by the Joule effect.
  • the dielectric material used has a dielectric or magnetic constant which can be varied as a result of the application of mechanical stress to the material, and the control means are arranged accordingly to apply such mechanical stress to the dielectric substrate material.
  • Figure 1 is a perspective view of a quadrangular portion of a dichroic structure according to a first embodiment of the invention
  • Figure 2 is a perspective view of a quadrangular portion of another dichroic structure according to the invention.
  • Figure 3 is a perspective view of a quadrangular portion of a dielectric material used in a dichroic structure according to the invention, the portion having induction heating means, and
  • Figure 4 is a graph showing schematically the attentuation characteristic of a dichroic structure according to the invention as a function of the frequency shown on the abscissa.
  • a portion of a dichroic structure comprises a substrate 2 of dielectric material with two layers 3 of electrically conductive material, typically metal, on its faces.
  • the layers 3 may be formed in any known manner and each has a respective orderly and geometrically periodic array of holes 4 which, in the embodiment shown by way of example, are cross-shaped.
  • An example of such a material is barium titanate.
  • the terminals of a variable voltage supply are connected to the two conductive layers of the dichroic structure.
  • Variations of the voltage supplied by the supply 5 thus vary the dielectric constant or the magnetic constant of the material constituting the substrate 2, correspondingly shifting the passband of the dichroic structure 1 as shown, for example, in Figure 4.
  • This drawing shows, by way of example, the curve of the attenuation A of the electromagnetic waves incident normally on the dichroic structure, as a function of the frequency f.
  • the dichroic structure shown in the drawing will have an attenuation characteristic, for example, of the type indicated A, in Figure 4 with a central working frequency f, and a bandwidth B. around that frequency.
  • the dichroic structure When the potential difference or voltage supplied by the supply 5 assumes a second value different from the first, the dichroic structure will have an attenuation characteristic with a shifted frequency, such as the characteristic indicated A 2 in Figure 4, which has a passband B 2 centered on a working frequency f 2 .
  • Figure 1 described above relates to an embodiment of the invention in which the passband of the dichroic structure is shifted by the application of a quasi-static voltage, that is, a voltage whose variation with time takes place at a frequency much lower than the working frequency of the dichroic structure.
  • a quasi-static voltage that is, a voltage whose variation with time takes place at a frequency much lower than the working frequency of the dichroic structure.
  • the dichroic structure of Figure 2 includes a substrate 2 of dielectric material whose dielectric or magnetic constant can be varied sensitively as a result of changes in the temperature of the material.
  • a conductive layer 3 applied to at least one face of the dielectric substrate 2 has an orderly and geometrically periodic array of holes 4.
  • at least one face of the dielectric substrate 2 could have a converse conductive structure, that is, an orderly and geometrically periodic array of elements of an electrically conductive material whose shapes are complementary to those of the holes 4 in the layer 3 shown in Figure 2.
  • a resistive element 6 which, in the embodiment illustrated, has a serpentine shape is applied to the face of the substrate 2 opposite that carrying the conductive material 3.
  • the terminals of the resistive element 6 are connected to a variable supply 5. Variations in the current flowing in the resistive element 6 vary the heat dissipated by the Joule effect, correspondingly varying the temperature of the material constituting the substrate 2. The variation thus induced in the dielectric constant and/or the magnetic constant of the material causes a shift in the passband of the dichroic structure 1.
  • devices or systems other than that shown by way of example may be used to heat the substrate 2 of dielectric material by the Joule, effect.
  • Figure 3 shows a portion of a substrate 2 of dielectric material whose dielectric and/or magnetic constant can vary appreciably as a result of a change in the .temperature of the material.
  • a conductive element 7 is wrapped around the substrate 2 as a helix, its terminals conveniently being connected to a high-frequency generator (not shown) .
  • the helix constituted by the element 7 heats the dielectric sheet 2 by induction.
  • the frequency passband of the structure can be shifted at will or when necessary.
  • a material whose dielectric constant can be varied as a result of the application of mechanical stress may be used as a single or layered dielectric substrate.
  • the passband of the dichroic structure can also easily be shifted by the application of.mechanical stress thereto.
  • the dichroic structures with variable passbands according to the invention may conveniently be used in the antennae of telecommunications satellites or for the construction of "stealth" radomes, that is, those which cannot be detected by microwave radar.

Abstract

The structure includes at least one substrate (2) of dielectric material, at least one face of which carries an orderly and geometrically periodic array of elements of electrically conductive material or, in a converse manner, bears at least one layer (3) of conductive material having an orderly and geometrically periodic array of holes (4). The structure is characterised in that control means (5, 6; 7) are associated with the substrate (2) of dielectric material for varying the dielectric or magnetic constant of the material so as correspondingly to modify its passband.

Description

A frequency-discriminating dichroic structure with a variable passband and applications thereof
The present invention relates to a dichroic structure for the selective attenuation according to frequency of incident electromagnetic waves the frequencies of which fall outside a predetermined passband.
More specifically, the invention concerns a dichroic structure including at least one substrate of dielectric material, at least one face of which bears an orderly and geometrically periodic array of elements of an electrically conductive material or a layer of conductive material having an orderly and geometrically periodic array of holes.
For example, such a dichroic structure considerably increases the communication capacity of a system having an antenna with reflectors, enabling it to operate at several frequencies. This drastically ^reduces the weight, bulk and cost of an antenna system, which advantages are of great importance for application to satellite communications systems.
In the avionics field, however, frequency-discriminating dichroic structures may be used for forming radomes with well-defined transmission bands.
The object of the present invention is to provide a dichroic structure with a variable working (transmission or reflection) band.
According to the invention, this object is achieved by a dichroic structure of the type specified above, characterised in that control means are associated with the substrate of dielectric material for varying the dielectric or magnetic constant of the material so as
^correspondingly to modify its working band.
In a first embodiment, the dielectric material used has a dielectric or magnetic constant which is variable as a result of the application of a potential difference across the material and the control means are arranged to apply a quasi-static, variable potential difference across the dielectric substrate.
In a further embodiment, the dielectric material used has a dielectric or magnetic constant which can be varied significantly in dependence on its temperature and the control means comprise heating means for changing the temperature of the dielectric material. The heating means may comprise means for generating a high-frequency magnetic field to heat the dielectric material by induction or may be resistive heating means for changing the temperature of the dielectric material by the Joule effect.
In a further embodiment, the dielectric material used , has a dielectric or magnetic constant which can be varied as a result of the application of mechanical stress to the material, and the control means are arranged accordingly to apply such mechanical stress to the dielectric substrate material.
Further characteristics and advantages of the invention will become clear from the detailed description which follows with reference to the appended drawings, provided purely by way of non-limiting example, in which: Figure 1 is a perspective view of a quadrangular portion of a dichroic structure according to a first embodiment of the invention,
Figure 2 is a perspective view of a quadrangular portion of another dichroic structure according to the invention.
Figure 3 is a perspective view of a quadrangular portion of a dielectric material used in a dichroic structure according to the invention, the portion having induction heating means, and
Figure 4 is a graph showing schematically the attentuation characteristic of a dichroic structure according to the invention as a function of the frequency shown on the abscissa.
In Figure 1, a portion of a dichroic structure, indicated 1, comprises a substrate 2 of dielectric material with two layers 3 of electrically conductive material, typically metal, on its faces. The layers 3 may be formed in any known manner and each has a respective orderly and geometrically periodic array of holes 4 which, in the embodiment shown by way of example, are cross-shaped.
The substrate 2 is made of a dielectric material with a dielectric constant *•=•■ or a magnetic constant U which can be varied as a result of the application of a potential difference across the material. An example of such a material is barium titanate.
The terminals of a variable voltage supply, indicated 5 in Figure 1, are connected to the two conductive layers of the dichroic structure.
Variations of the voltage supplied by the supply 5 thus vary the dielectric constant or the magnetic constant of the material constituting the substrate 2, correspondingly shifting the passband of the dichroic structure 1 as shown, for example, in Figure 4. This drawing shows, by way of example, the curve of the attenuation A of the electromagnetic waves incident normally on the dichroic structure, as a function of the frequency f.
When the potential difference or voltage supplied by the supply 5 assumes a first value, the dichroic structure shown in the drawing will have an attenuation characteristic, for example, of the type indicated A, in Figure 4 with a central working frequency f, and a bandwidth B. around that frequency.
When the potential difference or voltage supplied by the supply 5 assumes a second value different from the first, the dichroic structure will have an attenuation characteristic with a shifted frequency, such as the characteristic indicated A2 in Figure 4, which has a passband B2 centered on a working frequency f2.
Figure 1 described above relates to an embodiment of the invention in which the passband of the dichroic structure is shifted by the application of a quasi-static voltage, that is, a voltage whose variation with time takes place at a frequency much lower than the working frequency of the dichroic structure.
In Figure 2, which shows a variant, the same reference numerals have again been assigned to parts and elements already described.
The dichroic structure of Figure 2 includes a substrate 2 of dielectric material whose dielectric or magnetic constant can be varied sensitively as a result of changes in the temperature of the material. A conductive layer 3 applied to at least one face of the dielectric substrate 2 has an orderly and geometrically periodic array of holes 4. Alternatively, at least one face of the dielectric substrate 2 could have a converse conductive structure, that is, an orderly and geometrically periodic array of elements of an electrically conductive material whose shapes are complementary to those of the holes 4 in the layer 3 shown in Figure 2.
A resistive element 6 which, in the embodiment illustrated, has a serpentine shape is applied to the face of the substrate 2 opposite that carrying the conductive material 3. The terminals of the resistive element 6 are connected to a variable supply 5. Variations in the current flowing in the resistive element 6 vary the heat dissipated by the Joule effect, correspondingly varying the temperature of the material constituting the substrate 2. The variation thus induced in the dielectric constant and/or the magnetic constant of the material causes a shift in the passband of the dichroic structure 1.
Naturally, devices or systems other than that shown by way of example may be used to heat the substrate 2 of dielectric material by the Joule, effect.
Figure 3 shows a portion of a substrate 2 of dielectric material whose dielectric and/or magnetic constant can vary appreciably as a result of a change in the .temperature of the material. In the embodiment of
Figure 3, a conductive element 7 is wrapped around the substrate 2 as a helix, its terminals conveniently being connected to a high-frequency generator (not shown) . The helix constituted by the element 7 heats the dielectric sheet 2 by induction.
With the use of a substrate of the type shown in Figure 3 in a dichroic structure, the frequency passband of the structure can be shifted at will or when necessary.
Other embodiments are possible in addition to tho≤e shown by way of example in Figures 1 to 3.
Thus, for example, a material whose dielectric constant can be varied as a result of the application of mechanical stress may be used as a single or layered dielectric substrate.
Examples of such materials are crystalline and siliceous materials. In • this case, the passband of the dichroic structure can also easily be shifted by the application of.mechanical stress thereto.
The dichroic structures with variable passbands according to the invention may conveniently be used in the antennae of telecommunications satellites or for the construction of "stealth" radomes, that is, those which cannot be detected by microwave radar.
Naturally, the principle of the invention remaining the same, the forms of embodiment and details of construction may be varied widely with respect to those described and illustrated purely by way of non-limiting example, without thereby departing from the scope of the present invention.

Claims

.1. A dichroic structure for the selective attenuation of incident electromagnetic waves the frequencies of which fall outside a predetermined passband (B) , including at least one substrate (2) of dielectric material, at least one face of which carries an orderly and geometrically periodic array of elements of electrically conductive material or, in a converse manner, bears at least one layer of conductive material (3) having an orderly and geometrically periodic array of. holes (4) ,
the structure being characterised in that control means (5, 6; 7) are associated with the substrate (2) of dielectric material for varying the dielectric or magnetic constant of the material so as correspondingly to modify its passband (B) .
2. A dichroic structure according to Claim 1, characterised in that the dielectric material has a dielectric and/or magnetic constant which is variable as a result of the application of a potential difference across the material, and in that the control means (5, Figure 1) are arranged to apply a variable potential difference across the dielectric substrate
(2).
3. A dichroic structure according to Claim 2, including at least one substrate (2) of a dielectric material carrying on each face a layer of electrically conductive material (3) with an orderly and periodic array of holes (4) , characterised in that the control means comprise means (5) for applying a potential difference across the conductive layers (3) on the at least one substrate (2) of dielectric material.
4. A dichroic structure according to Claim 1, characterised in that the control means comprise heating means (5, 6; 7) for varying the temperature of the dielectric material (2) .
5. A dichroic structure according to Claim 4, characterised in that the heating means comprise means (7) for generating a high-frequency magnetic field to heat the dielectric material (2) by induction.
6. A dichroic structure according to Claim 4, characterised in that Joule-effect heating means (5, 6) are associated with the dielectric material (2) .
7. A dichroic structure according to Claim 1, characterised in that the control means are arranged to vary the dielectric and/or magnetic constant of the dielectric material (2) by the application of mechanical stress to the substrate sheet (2) .
8. The use of a dichroic structure according to one or more of the preceding claims for forming a radome which is not detectable by microwave radar.
9. The use of a dichroic structure according to one or more of Claims 1 to 7 for forming an antenna for use on a telecommunications satellite.
PCT/EP1992/000386 1991-02-27 1992-02-24 A frequency-discriminating dichroic structure with a variable passband and applications thereof WO1992016031A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITTO91A000139 1991-02-27
ITTO910139A IT1245423B (en) 1991-02-27 1991-02-27 DICHROIC STRUCTURE DISCRIMINATING IN FREQUENCY WITH VARIABLE BANDWIDTH, AND ITS APPLICATIONS

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Cited By (11)

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Publication number Priority date Publication date Assignee Title
US5386215A (en) * 1992-11-20 1995-01-31 Massachusetts Institute Of Technology Highly efficient planar antenna on a periodic dielectric structure
WO1996000454A1 (en) * 1994-06-27 1996-01-04 The Secretary Of State For Defence Absorbent panel
US5526449A (en) * 1993-01-08 1996-06-11 Massachusetts Institute Of Technology Optoelectronic integrated circuits and method of fabricating and reducing losses using same
FR2761818A1 (en) * 1997-04-03 1998-10-09 Daimler Benz Aerospace Ag PROCESS FOR MANUFACTURING SELECTIVE REFLECTORS IN POLARIZATION
EP0875957A2 (en) * 1997-05-01 1998-11-04 Kitagawa Industries Co., Ltd. Electromagnetic wave absorber
WO1999031759A1 (en) * 1997-12-17 1999-06-24 Baesystems Electronics Ltd. Magnetic beam deflection devices
US5990850A (en) * 1995-03-17 1999-11-23 Massachusetts Institute Of Technology Metallodielectric photonic crystal
EP1049192A2 (en) * 1999-04-26 2000-11-02 Hitachi, Ltd. High-frequency communication device
FR2858469A1 (en) * 2003-07-30 2005-02-04 Univ Rennes Antenna for e.g. motor vehicle obstacles detecting radar, has assembly with two zones of active material layer that are controlled by respective polarization zones defined by metallic patterned layers
EP1936740A1 (en) * 2006-12-22 2008-06-25 Giesecke & Devrient GmbH Antenna for measuring movement information according to the Doppler principle, transponder, system and method
WO2011134666A1 (en) * 2010-04-30 2011-11-03 Thales Compact radiating element having resonant cavities

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108983457B (en) * 2018-08-10 2021-12-03 南方科技大学 Color tunable liquid crystal color filter

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US3309704A (en) * 1965-09-07 1967-03-14 North American Aviation Inc Tunable absorber
US3631501A (en) * 1970-02-16 1971-12-28 Gen Dynamics Corp Microwave phase shifter with liquid dielectric having metallic particles in suspension
WO1990014696A1 (en) * 1989-05-19 1990-11-29 Stefan Johansson Antenna apparatus with reflector or lens consisting of a frequency scanned grating
US4987418A (en) * 1987-12-28 1991-01-22 United Technologies Corporation Ferroelectric panel

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Publication number Priority date Publication date Assignee Title
US3309704A (en) * 1965-09-07 1967-03-14 North American Aviation Inc Tunable absorber
US3631501A (en) * 1970-02-16 1971-12-28 Gen Dynamics Corp Microwave phase shifter with liquid dielectric having metallic particles in suspension
US4987418A (en) * 1987-12-28 1991-01-22 United Technologies Corporation Ferroelectric panel
WO1990014696A1 (en) * 1989-05-19 1990-11-29 Stefan Johansson Antenna apparatus with reflector or lens consisting of a frequency scanned grating

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5386215A (en) * 1992-11-20 1995-01-31 Massachusetts Institute Of Technology Highly efficient planar antenna on a periodic dielectric structure
US5526449A (en) * 1993-01-08 1996-06-11 Massachusetts Institute Of Technology Optoelectronic integrated circuits and method of fabricating and reducing losses using same
WO1996000454A1 (en) * 1994-06-27 1996-01-04 The Secretary Of State For Defence Absorbent panel
US5990850A (en) * 1995-03-17 1999-11-23 Massachusetts Institute Of Technology Metallodielectric photonic crystal
FR2761818A1 (en) * 1997-04-03 1998-10-09 Daimler Benz Aerospace Ag PROCESS FOR MANUFACTURING SELECTIVE REFLECTORS IN POLARIZATION
US6057796A (en) * 1997-05-01 2000-05-02 Kitagawa Industries Co., Ltd. Electromagnetic wave absorber
EP0875957A3 (en) * 1997-05-01 1999-04-28 Kitagawa Industries Co., Ltd. Electromagnetic wave absorber
EP0875957A2 (en) * 1997-05-01 1998-11-04 Kitagawa Industries Co., Ltd. Electromagnetic wave absorber
WO1999031759A1 (en) * 1997-12-17 1999-06-24 Baesystems Electronics Ltd. Magnetic beam deflection devices
US6429803B1 (en) 1997-12-17 2002-08-06 Bae Systems Electronics Limited Magnetic beam deflection devices
EP1049192A2 (en) * 1999-04-26 2000-11-02 Hitachi, Ltd. High-frequency communication device
EP1049192A3 (en) * 1999-04-26 2002-02-06 Hitachi, Ltd. High-frequency communication device
US6862001B2 (en) 1999-04-26 2005-03-01 Hitachi, Ltd. High frequency communication device
FR2858469A1 (en) * 2003-07-30 2005-02-04 Univ Rennes Antenna for e.g. motor vehicle obstacles detecting radar, has assembly with two zones of active material layer that are controlled by respective polarization zones defined by metallic patterned layers
EP1936740A1 (en) * 2006-12-22 2008-06-25 Giesecke & Devrient GmbH Antenna for measuring movement information according to the Doppler principle, transponder, system and method
WO2011134666A1 (en) * 2010-04-30 2011-11-03 Thales Compact radiating element having resonant cavities
FR2959611A1 (en) * 2010-04-30 2011-11-04 Thales Sa COMPRISING RADIANT ELEMENT WITH RESONANT CAVITIES.
US9843099B2 (en) 2010-04-30 2017-12-12 Thales Compact radiating element having resonant cavities

Also Published As

Publication number Publication date
IT1245423B (en) 1994-09-20
ITTO910139A1 (en) 1992-08-27
ITTO910139A0 (en) 1991-02-27

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