US2917739A - Corner reflector - Google Patents

Corner reflector Download PDF

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US2917739A
US2917739A US641353A US64135346A US2917739A US 2917739 A US2917739 A US 2917739A US 641353 A US641353 A US 641353A US 64135346 A US64135346 A US 64135346A US 2917739 A US2917739 A US 2917739A
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reflector
microwave radiation
incident
reflecting
disc
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US641353A
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Halpern Otto
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/75—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors
    • G01S13/751—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors wherein the responder or reflector radiates a coded signal
    • G01S13/756—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors wherein the responder or reflector radiates a coded signal using a signal generator for modifying the reflectivity of the reflector

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  • This invention relates to an identification device and more particularly to a reflector for reflecting radio microwave radiation having a surface which is periodically made reflectingand non-reflecting of incident microwave radiation.
  • This invention provides a novel means for identifying a radio microwave reflector by modulating reflected signals from the reflector in such a manner as to provide an automatic recognition device which is operative at preselected wave lengths of incident microwave radiation.
  • An objectof this invention isto provide an identification device comprising a radio microwave reflector having means for automatically modulating radio microwave radiation impinging upon the reflector.
  • Another object of this invention is to provide a radio microwave reflector having means responsive to a preselected wave length of incident radio microwave radiation for modulating the signals reflected by the reflector.
  • Still another object of this invention is to provide a radio microwave reflector having one surface which is periodically made reflecting and non-reflecting of incident radio microwave radiation.
  • a particular object of this invention is to provide a radio microwave reflector having means responsive to a preselected wave length of incident radio microwave radiation for causing one surface of the reflector to be periodically reflecting and non-reflecting of such incident radio microwave radiation.
  • Fig. 1 is a plan view of the reflector as contemplated by this invention.
  • Fig. 2 is a front view of a reflector as shown in Fig. 1.
  • radar signals radio microwave radiation
  • radar signals reflected by moving objects show intensity modulation which has characteristic and more or less constant frequencies.
  • radar signals reflected from a three-bladed propeller show a modulation which has a frequency equal to three (number of blades) times the propeller shaft frequency and its harmonics.
  • This invention provides an identification device comprising a radio microwave reflector having means for automatically modulating radio microwave radiation reflected by the reflector.
  • a metallic trihedral corner reflector 20 having two fixed intersecting triangular surfaces 21 and 22 which preferably include an angle of 60 therebetween in the vertical plane and an angle of 90 therebetween in the horizontal plane.
  • the third side of the reflector consists of a sector of a rotating disc 23 which is rotated about the axis of a shaft 24 by means of a suitable motor 25.
  • Surfaces 21 and comprise a pair of identical triangularly shaped sur- 2,917,739 Patented Dec. 15, 1959 faces which intersect along the edge oppositely disposed from disc 23, thereby forming a corner reflector having only. a single open end 29 for admission and reflection of incident radio microwave radiation.
  • the plane of the open end '29 is normal to the plane of the disc 23.
  • a yoke 26 is provided tomaintain surfaces 21 and 22 in a fixed orientation with respect to motor 25, and at the same time to permit disc 23 to rotate with respect to surfaces 21 and 22.
  • disc 23 is provided in certain sectors with a coating of material which is non-reflective of incident radio microwave radiation.
  • two opposite quadrants 27 and 28 are covered with the nonreflecting material while the remaining opposite quadrants 30 and 31 are left reflective and the corner reflector will thus modulate reflected signals with a fre-- quency equal to twice that of the rotational speed of the disc; That is to say, in a reflector constructed as shown, the radar signals reflected by the reflector will show a modulation which has a frequency equal to two times the disc shaft frequency.
  • disc 23, comprising the third surface of the corner reflector and being related will be alternately reflective and non-reflective of incident microwave radiation of the wavelengthfor which the coating is made resonant. 7
  • Harp material which is responsive only to a preselected wave length or band of wave lengths for whichit is designed to be resonant.
  • Harp material is composed of myriads of finely divided electrically conductiveparticles dispersed quasi-insulated in a neutral binder. Such finely divided particles preferably include aluminum, graphite, copper, and permalloy flakes, although other electrically conductive particles may be used. Examples of such binders include waxes, resins, polystyrene vistanex, and synthetic rubbers among others. Such a material is fully disclosed and described in my copending application Serial Number 581,179, filed March 5, 1945.
  • Harp material is a high dielectric constant, and in the case where ferromagnetic flakes are used, a high magnetic susceptibility, properties which give a high index of refraction for electro-magnetic waves.
  • the physical principle underlying these applications is the construction of a' coating of material having a high index of refraction and a thickness equal to a quarter-wave length or odd multiple there- I i of, as measured inside the coating, of the incident microwave radiation for which it is designed to be resonant.
  • Such a coating being a resonant device, has a reflection coefficient which increases rapidly on both sides of the resonant wave length. However, there is very little reflection of incident microwave radiation of the wave length for which the coating is designed to be resonant. It is therefore possible to obtain an arbitrarily sharp resonance effect which is selective to a particular microwave frequency and wave length.
  • quadrants 27 and 28 are covered with a coating of Harp material as heretofore described, the thickness of the layer being equal to a quarter-wave length, or odd multiple thereof, as measured inside the coating, of the incident microwave radiation for which it is designed to be resonant.
  • an electrical dissymmetry which is effective only at the particular radiation frequency for which the coating is made resonant is introduced between the coated and uncoated portions of disc 23.
  • Incident microwave radiation of the resonant frequency of the coating, being reflected by corner reflector 20, is modulated in accordance with rotation of disc 23, while microwave radiation of other fre modulation signals other than that equal to twice the ro-.
  • An identification device comprising a corner reflector for reflecting incident radio microwave radiation, said reflector having a plurality of inclined surfaces, one of said surfaces being rotatable with respect to the remainder of. said surfaces and having sectors thereof non-reflective of incident radio microwave radiation ofa predetermined wave length.
  • An identification device comprising a corner reflector having a plurality of inclined metallic surfaces for reflecting incident radio microwave radiation, .one of said surfaces being rotatable with respect to the remainder of .said surfaces and having various sectors thereof coated with a layer for preventing reflection of incident radio microwave radiation of a preselected frequency therefrom, said layer consisting of myriads of finely-divided electrically conductive particles dispersed quasi-insulated, in a binder, the thickness of said layer being predeterminedly limited to anodd multiple of one-quart r Wave length of the incident microwave radiation of preselected frequency, as measured inside the layer.
  • a reflector comprising a plurality of reflecting surfaces, at least one of said surfaces being rotatable with respect to the remainder of said surfaces and having selected sectors thereof absorptive of radiation of a preselected wave length.
  • a reflector comprising a plurality of reflecting surfaces, at least a portion of one of said reflecting surfaces having a coating of material absorptive of radiation of a predetermined wave length.
  • a reflector comprising a plurality of reflecting surfaces, at least one of said surfaces being rotatable with respect to the remainder of said surfaces and having first selected sectors absorptive of radiation of preselected wave lengths and second selected sectors reflective of radiation of said preselected wave lengths.
  • a reflector comprising a plurality of reflecting surfaces, at least one of, said surfaces being rotatable with respect to the remainder of said surfaces and having preselected successive;se.ctors alternately reflective and absorptive of radiation of preselected wave lengths.

Description

Dec. 15, 1959 o. HALPERN 2,917,739
CORN
Unite States Patent 2,917,739 CORNER REFLECTOR Otto Halpern, Pacific Palisades, Calif., assignor, by mesn'e assignments, to the United States of America as represented by the Secretary of the Navy This invention relates to an identification device and more particularly to a reflector for reflecting radio microwave radiation having a surface which is periodically made reflectingand non-reflecting of incident microwave radiation.
-,In the operation of radar equipment it is frequently desirable to be able to identify a target appearing upon the screen of the indicator scope. This invention provides a novel means for identifying a radio microwave reflector by modulating reflected signals from the reflector in such a manner as to provide an automatic recognition device which is operative at preselected wave lengths of incident microwave radiation.
An objectof this invention isto provide an identification device comprising a radio microwave reflector having means for automatically modulating radio microwave radiation impinging upon the reflector.
Another object of this invention is to provide a radio microwave reflector having means responsive to a preselected wave length of incident radio microwave radiation for modulating the signals reflected by the reflector.
Still another object of this invention is to provide a radio microwave reflector having one surface which is periodically made reflecting and non-reflecting of incident radio microwave radiation.
A particular object of this invention is to provide a radio microwave reflector having means responsive to a preselected wave length of incident radio microwave radiation for causing one surface of the reflector to be periodically reflecting and non-reflecting of such incident radio microwave radiation.
Further objects and advantages of this invention, as well as its construction, arrangement, and operation will be apparent from the following description and claims in connection with the accompanying drawings, in which:
Fig. 1 is a plan view of the reflector as contemplated by this invention; and
Fig. 2 is a front view of a reflector as shown in Fig. 1.
It is known that radar signals (radio microwave radiation) reflected by moving objects show intensity modulation which has characteristic and more or less constant frequencies. For example, radar signals reflected from a three-bladed propeller show a modulation which has a frequency equal to three (number of blades) times the propeller shaft frequency and its harmonics. This invention provides an identification device comprising a radio microwave reflector having means for automatically modulating radio microwave radiation reflected by the reflector.
Referring 'to Figs. 1 and 2, there is shown a metallic trihedral corner reflector 20 having two fixed intersecting triangular surfaces 21 and 22 which preferably include an angle of 60 therebetween in the vertical plane and an angle of 90 therebetween in the horizontal plane. The third side of the reflector consists of a sector of a rotating disc 23 which is rotated about the axis of a shaft 24 by means of a suitable motor 25. Surfaces 21 and comprise a pair of identical triangularly shaped sur- 2,917,739 Patented Dec. 15, 1959 faces which intersect along the edge oppositely disposed from disc 23, thereby forming a corner reflector having only. a single open end 29 for admission and reflection of incident radio microwave radiation. As shown in the drawings the plane of the open end '29 is normal to the plane of the disc 23. A yoke 26 is provided tomaintain surfaces 21 and 22 in a fixed orientation with respect to motor 25, and at the same time to permit disc 23 to rotate with respect to surfaces 21 and 22.
In order to modulate the reflected microwave radiation, disc 23 is provided in certain sectors with a coating of material which is non-reflective of incident radio microwave radiation. In the particular design shown, two opposite quadrants 27 and 28 are covered with the nonreflecting material while the remaining opposite quadrants 30 and 31 are left reflective and the corner reflector will thus modulate reflected signals with a fre-- quency equal to twice that of the rotational speed of the disc; That is to say, in a reflector constructed as shown, the radar signals reflected by the reflector will show a modulation which has a frequency equal to two times the disc shaft frequency. It will of course be readily understood that disc 23, comprising the third surface of the corner reflector and being related, will be alternately reflective and non-reflective of incident microwave radiation of the wavelengthfor which the coating is made resonant. 7
Various materials may be used to coat portions of disc 23, among them being Harp material which is responsive only to a preselected wave length or band of wave lengths for whichit is designed to be resonant. Harp material is composed of myriads of finely divided electrically conductiveparticles dispersed quasi-insulated in a neutral binder. Such finely divided particles preferably include aluminum, graphite, copper, and permalloy flakes, although other electrically conductive particles may be used. Examples of such binders include waxes, resins, polystyrene vistanex, and synthetic rubbers among others. Such a material is fully disclosed and described in my copending application Serial Number 581,179, filed March 5, 1945. The characteristic property of Harp material is a high dielectric constant, and in the case where ferromagnetic flakes are used, a high magnetic susceptibility, properties which give a high index of refraction for electro-magnetic waves. The physical principle underlying these applications is the construction of a' coating of material having a high index of refraction and a thickness equal to a quarter-wave length or odd multiple there- I i of, as measured inside the coating, of the incident microwave radiation for which it is designed to be resonant. Such a coating, being a resonant device, has a reflection coefficient which increases rapidly on both sides of the resonant wave length. However, there is very little reflection of incident microwave radiation of the wave length for which the coating is designed to be resonant. It is therefore possible to obtain an arbitrarily sharp resonance effect which is selective to a particular microwave frequency and wave length.
As shown in Fig. l, quadrants 27 and 28 are covered with a coating of Harp material as heretofore described, the thickness of the layer being equal to a quarter-wave length, or odd multiple thereof, as measured inside the coating, of the incident microwave radiation for which it is designed to be resonant. In this manner, an electrical dissymmetry which is effective only at the particular radiation frequency for which the coating is made resonant is introduced between the coated and uncoated portions of disc 23. Incident microwave radiation of the resonant frequency of the coating, being reflected by corner reflector 20, is modulated in accordance with rotation of disc 23, while microwave radiation of other fre modulation signals other than that equal to twice the ro-.
tational speed of the disc as explained above. While a particular embodiment of this invention has been disclosed and described, it is to be understood that various changes and modifications may be made in this invention without departing from the spirit and scope thereof as setforth in the appended claims.
What is claimed is:
1, An identification device comprising a corner reflector for reflecting incident radio microwave radiation, said reflector having a plurality of inclined surfaces, one of said surfaces being rotatable with respect to the remainder of. said surfaces and having sectors thereof non-reflective of incident radio microwave radiation ofa predetermined wave length.
2. An identification device comprising a corner reflector having a plurality of inclined metallic surfaces for reflecting incident radio microwave radiation, .one of said surfaces being rotatable with respect to the remainder of .said surfaces and having various sectors thereof coated with a layer for preventing reflection of incident radio microwave radiation of a preselected frequency therefrom, said layer consisting of myriads of finely-divided electrically conductive particles dispersed quasi-insulated, in a binder, the thickness of said layer being predeterminedly limited to anodd multiple of one-quart r Wave length of the incident microwave radiation of preselected frequency, as measured inside the layer.
3, A reflector comprising a plurality of reflecting surfaces, at least one of said surfaces being rotatable with respect to the remainder of said surfaces and having selected sectors thereof absorptive of radiation of a preselected wave length.
4. A reflector comprising a plurality of reflecting surfaces, at least a portion of one of said reflecting surfaces having a coating of material absorptive of radiation of a predetermined wave length.
5. A reflector comprising a plurality of reflecting surfaces, at least one of said surfaces being rotatable with respect to the remainder of said surfaces and having first selected sectors absorptive of radiation of preselected wave lengths and second selected sectors reflective of radiation of said preselected wave lengths.
6. A reflector comprising a plurality of reflecting surfaces, at least one of, said surfaces being rotatable with respect to the remainder of said surfaces and having preselected successive;se.ctors alternately reflective and absorptive of radiation of preselected wave lengths.
References Cited in the file of this patent UNITED STATES PATENTS 4 1,384,014 Fessenden July 5, 1921 2,212,110 Beuermann Aug. 20, 1-940 2,432,984 Budenbom Dec. 23, 1947 2,443,643 Schelleng June 22, 1948 2,472,782 Albersheim June 14, i949 FOREIGN PATENTS 422,659 Great Britain Jan. 16, 1935 694,523 Germany July 4, 1940 OTHER REFERENCES The Corner Reflector Antenna, Proceedings of ;I. R LE., vol. 28, No. 11, November 19.40, pp. 513 519.
The Square-Comer Reflector, Radio for March 1939, pp. 19-23.
US641353A 1946-01-15 1946-01-15 Corner reflector Expired - Lifetime US2917739A (en)

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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3310804A (en) * 1963-06-18 1967-03-21 Joseph B Brauer Isotropic microwave reflector
US4763361A (en) * 1986-02-13 1988-08-09 The United States Of America As Represented By The Secretary Of The Army System and device for recognition or IFF use
US4972192A (en) * 1989-11-06 1990-11-20 Georgia Tech Research Corporation Constant amplitude doppler producing radar reflector
US20080290087A1 (en) * 2007-05-21 2008-11-27 Rf Dynamics Ltd. Electromagnetic heating
EP2006708A1 (en) * 2007-06-15 2008-12-24 Robert Bosch GmbH Localising system for a robotic vehicle
US7994962B1 (en) * 2007-07-17 2011-08-09 Drosera Ltd. Apparatus and method for concentrating electromagnetic energy on a remotely-located object
US8207479B2 (en) 2006-02-21 2012-06-26 Goji Limited Electromagnetic heating according to an efficiency of energy transfer
US8492686B2 (en) 2008-11-10 2013-07-23 Goji, Ltd. Device and method for heating using RF energy
US8653482B2 (en) 2006-02-21 2014-02-18 Goji Limited RF controlled freezing
US8839527B2 (en) 2006-02-21 2014-09-23 Goji Limited Drying apparatus and methods and accessories for use therewith
US9131543B2 (en) 2007-08-30 2015-09-08 Goji Limited Dynamic impedance matching in RF resonator cavity
US9215756B2 (en) 2009-11-10 2015-12-15 Goji Limited Device and method for controlling energy
US10674570B2 (en) 2006-02-21 2020-06-02 Goji Limited System and method for applying electromagnetic energy

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Publication number Priority date Publication date Assignee Title
US1384014A (en) * 1918-01-14 1921-07-05 Submarine Signal Co Method and apparatus for signaling and otherwise utilizing radiant impulses
GB422659A (en) * 1933-02-08 1935-01-16 Pintsch Julius Ag Improvements in or relating to ultra-short wave transmitting arrangements
DE694523C (en) * 1933-02-09 1940-08-02 Julius Pintsch Kom Ges and receiving arrangements
US2212110A (en) * 1936-08-15 1940-08-20 Telefunken Gmbh Radio beacon system
US2432984A (en) * 1940-04-05 1947-12-23 Bell Telephone Labor Inc Electromagnetic wave reflection system
US2443643A (en) * 1945-09-07 1948-06-22 Bell Telephone Labor Inc Wave modifying device
US2472782A (en) * 1945-09-07 1949-06-14 Bell Telephone Labor Inc Wave modifying reflector

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1384014A (en) * 1918-01-14 1921-07-05 Submarine Signal Co Method and apparatus for signaling and otherwise utilizing radiant impulses
GB422659A (en) * 1933-02-08 1935-01-16 Pintsch Julius Ag Improvements in or relating to ultra-short wave transmitting arrangements
DE694523C (en) * 1933-02-09 1940-08-02 Julius Pintsch Kom Ges and receiving arrangements
US2212110A (en) * 1936-08-15 1940-08-20 Telefunken Gmbh Radio beacon system
US2432984A (en) * 1940-04-05 1947-12-23 Bell Telephone Labor Inc Electromagnetic wave reflection system
US2443643A (en) * 1945-09-07 1948-06-22 Bell Telephone Labor Inc Wave modifying device
US2472782A (en) * 1945-09-07 1949-06-14 Bell Telephone Labor Inc Wave modifying reflector

Cited By (32)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3310804A (en) * 1963-06-18 1967-03-21 Joseph B Brauer Isotropic microwave reflector
US4763361A (en) * 1986-02-13 1988-08-09 The United States Of America As Represented By The Secretary Of The Army System and device for recognition or IFF use
US4972192A (en) * 1989-11-06 1990-11-20 Georgia Tech Research Corporation Constant amplitude doppler producing radar reflector
US10674570B2 (en) 2006-02-21 2020-06-02 Goji Limited System and method for applying electromagnetic energy
US8759729B2 (en) 2006-02-21 2014-06-24 Goji Limited Electromagnetic heating according to an efficiency of energy transfer
US11729871B2 (en) 2006-02-21 2023-08-15 Joliet 2010 Limited System and method for applying electromagnetic energy
US8207479B2 (en) 2006-02-21 2012-06-26 Goji Limited Electromagnetic heating according to an efficiency of energy transfer
US11523474B2 (en) 2006-02-21 2022-12-06 Goji Limited Electromagnetic heating
US11057968B2 (en) 2006-02-21 2021-07-06 Goji Limited Food preparation
US8653482B2 (en) 2006-02-21 2014-02-18 Goji Limited RF controlled freezing
US9078298B2 (en) 2006-02-21 2015-07-07 Goji Limited Electromagnetic heating
US8839527B2 (en) 2006-02-21 2014-09-23 Goji Limited Drying apparatus and methods and accessories for use therewith
US8941040B2 (en) 2006-02-21 2015-01-27 Goji Limited Electromagnetic heating
US9040883B2 (en) 2006-02-21 2015-05-26 Goji Limited Electromagnetic heating
US10492247B2 (en) 2006-02-21 2019-11-26 Goji Limited Food preparation
US10080264B2 (en) 2006-02-21 2018-09-18 Goji Limited Food preparation
US9167633B2 (en) 2006-02-21 2015-10-20 Goji Limited Food preparation
US9872345B2 (en) 2006-02-21 2018-01-16 Goji Limited Food preparation
US8389916B2 (en) 2007-05-21 2013-03-05 Goji Limited Electromagnetic heating
US20080290087A1 (en) * 2007-05-21 2008-11-27 Rf Dynamics Ltd. Electromagnetic heating
EP2006708A1 (en) * 2007-06-15 2008-12-24 Robert Bosch GmbH Localising system for a robotic vehicle
US7994962B1 (en) * 2007-07-17 2011-08-09 Drosera Ltd. Apparatus and method for concentrating electromagnetic energy on a remotely-located object
US9131543B2 (en) 2007-08-30 2015-09-08 Goji Limited Dynamic impedance matching in RF resonator cavity
US11129245B2 (en) 2007-08-30 2021-09-21 Goji Limited Dynamic impedance matching in RF resonator cavity
US10687395B2 (en) 2008-11-10 2020-06-16 Goji Limited Device for controlling energy
US8492686B2 (en) 2008-11-10 2013-07-23 Goji, Ltd. Device and method for heating using RF energy
US9374852B2 (en) 2008-11-10 2016-06-21 Goji Limited Device and method for heating using RF energy
US11653425B2 (en) 2008-11-10 2023-05-16 Joliet 2010 Limited Device and method for controlling energy
US9609692B2 (en) 2009-11-10 2017-03-28 Goji Limited Device and method for controlling energy
US10999901B2 (en) 2009-11-10 2021-05-04 Goji Limited Device and method for controlling energy
US10405380B2 (en) 2009-11-10 2019-09-03 Goji Limited Device and method for heating using RF energy
US9215756B2 (en) 2009-11-10 2015-12-15 Goji Limited Device and method for controlling energy

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