WO2015072953A1 - An antenna signal absorber - Google Patents

An antenna signal absorber Download PDF

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Publication number
WO2015072953A1
WO2015072953A1 PCT/TR2014/000452 TR2014000452W WO2015072953A1 WO 2015072953 A1 WO2015072953 A1 WO 2015072953A1 TR 2014000452 W TR2014000452 W TR 2014000452W WO 2015072953 A1 WO2015072953 A1 WO 2015072953A1
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WO
WIPO (PCT)
Prior art keywords
antenna signal
signal absorber
enables
absorber
antenna
Prior art date
Application number
PCT/TR2014/000452
Other languages
French (fr)
Inventor
Niyazi Korkut ULUAYDIN
Original Assignee
Bogazici Universitesi
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 Bogazici Universitesi filed Critical Bogazici Universitesi
Publication of WO2015072953A1 publication Critical patent/WO2015072953A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems
    • H01Q17/008—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems with a particular shape
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems
    • H01Q17/001—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems for modifying the directional characteristic of an aerial

Definitions

  • the present invention relates to an antenna signal absorber which enables, for all kinds of dipole-based telecommunication antennas, to reduce the general network noise; to focus service on to closer ⁇ distance ⁇ clients for higher data throughput rates especially in networks employing new generation modulation technologies such as UMTS, WCDMA, OFDMA; to use band width more efficiently; and the general data throughput to be used at higher spectral efficiency without the need for breathing cell features causing unwanted coverage losses.
  • new generation modulation technologies such as UMTS, WCDMA, OFDMA
  • barriers disposed on the back of the antennas either do not provide a significant benefit or cause reflections that create resonance and harmful interference particularly in the case of use of metal plates. Therefore, since barriers disposed on the back of antennas provide limited benefit and are difficult to estimate the side effects, they have never come into general use.
  • the Japanese patent document no. JP2008304219 an application in the state of the art, discloses about suppression of the unnecessary signals received by the antenna.
  • the unnecessary signal absorber can suppress clutter by spatiotemporal adaptation signal processing without using another means and easily even when the Doppler frequency of a target is unknown.
  • the unnecessary signal absorber can suppress unnecessary signal components included in a reflection signal received by a plurality of elementary antennas which are installed on a mobile unit.
  • the unnecessary signal absorber has a load calculating section for calculating a load coefficient.
  • the Japanese patent document no. JP2000131420 discloses about effectively suppressing unwanted signals contained in a coherent video for the same spatial coordinates in a radar system.
  • the absorber comprises an arithmetic unit for approximating the time variation of an input signal using a coherent video in the same spatial coordinates in a radar system.
  • the system also comprises a second arithmetic unit. After approximating the equations in these arithmetic units and making the necessary calculations, the device suppresses the signal.
  • the Japanese patent document no. JP2000266837 an application in the state of the art, discloses about suppression of unnecessary wave components. In this system, unnecessary waves can be suppressed even when desired waves and unnecessary waves come from the same direction.
  • the device has horizontal and vertical polarizing elements.
  • the device also comprises transmission reception modules.
  • the modules are connected to the said elements respectively. Additionally, transmission and reception polarizations can vary.
  • a polarization- operating means obtains from a received signal a polarization state of an unnecessary wave included in the received signal. Radar transmission pulses are transmitted and radar reflection pulses are received by polarized waves orthogonal to the unnecessary waves. Thus even the unnecessary waves coming from equal directions can be suppressed.
  • an adaptive weight/bias and the polarization state of unnecessary waves are operated for each pulse cycle period to update values.
  • ferrite and similar metal plates or mixtures have a weight of 60-90% of the antenna's weight and this imposes a significant static load on the polar pipes to which the antennas are mounted and to their fundamental points. Additionally, since thickness also significantly increases, wind load differs significantly as well.
  • An objective of the present invention is to provide an antenna signal absorber which enables, for all kinds of dipole-based telecommunication antennas, to reduce the overall network noise; to focus service on to closer clients for higher data throughput rates especially in networks employing new generation modulation technologies such as UMTS, WCDMA, OFDMA; to use band width more efficiently; and the general data throughput to be used at higher spectral efficiency without the need for breathing cell features causing unwanted coverage losses.
  • new generation modulation technologies such as UMTS, WCDMA, OFDMA
  • Another objective of the present invention is to provide an antenna signal absorber, which suppresses the signals going towards the back in specific fields when any dipole-based antenna is concentrating its signal towards the front according to the degree of directionality such that it will not cause a change to the antenna pattern in the front, and which also prevents signals coming from other sources from the back from reaching the antenna.
  • Figure 1 is the side view of the Antenna Signal Absorber.
  • FIG. 2 is the graphical view of the Antenna Signal Absorber.
  • the components shown in the figures are each given reference numbers as follows:
  • the antenna signal absorber (1) which enables, for dipole-based antennas, to reduce overall network noise and to use the general data throughput at higher spectral efficiency without losing coverage, basically comprises
  • At least one base (3) which is located in the body (2) and enables the antenna signal absorber (1) to be connected to the antenna back lobe contact surface, at least one protrusion (4) which is located on the body (2) and enables to absorb signals,
  • At least one recess (5) which is located on the body (2) and enables to absorb signals
  • At least one surface (4) which is located on the protrusion (4) and recess (5) and enables signal absorption.
  • the antenna signal absorber (1) includes thereon a base (3) which is located in the body (2) and enables connection of the antenna signal absorber (1) to the antenna back lobe contact surface; a protrusion (4) which is located on the body (2) and enables to absorb signals; and a recess (5) which is located on the body (2) and enables to absorb signals.
  • the antenna signal absorber (1) of the present invention includes a surface (6) which is located on the protrusion (4) and recess (5), and enables signal absorption.
  • the antenna signal absorber (1) provides 5 times and more reduction in weight to provide an electromagnetic isolation value at the same level. Besides, since the isolation provided by the antenna signal absorber (1) does not cause undesirable reflections, there is no need to deal with any side effects.
  • the antenna signal absorber (1) of the present invention can be protected by a radome having the same features with the antenna radome and/or can be used without radome in antennas which are concealed for camouflage purposes such that they will not be exposed to external factors. When used without radome, it may be located in near field or Fresnel zone, but this does not have a significant effect on the antenna pattern.
  • the desired electromagnetic absorption, scattering and isolation values can be adjusted both according to the frequency and, if there is use of multiple frequency, can be adjusted for an overall absorption.
  • Rapid solutions are produced with the ability of automated production by means of the adjustments to be made in the material sizes, thickness, content and composition with respect to the purpose and place of use. Furthermore, for antennas propagating multiple frequencies/technologies, production can be made so as to focus on an overall absorption or on more specific absorption of one of the technologies.
  • the antenna signal absorber (1) of the present invention can be used without an outer radome at the narrow places of camouflages such as water tanks and chimneys used in general GSM and UMTS applications.
  • camouflages such as water tanks and chimneys used in general GSM and UMTS applications.
  • the material since the material is completely elastic, it can cover any kind of antenna. Additionally, by using it at the back of mobile antennas such as radars, both the receiver sensitivity can be increased and its electromagnetic shielding properties can be taken advantage of.
  • the antenna signal absorber (1) can also be used such that it will cover both one and two sides of the antennas or their back and one or all sides at places such as gulfs, channels and valleys which create planning difficulties geologically for providing coverage and signal quality at the same time.
  • the antenna signal absorber (1) is adjusted firstly by the gradual change of the dielectric properties of the materials from the point nearest to the antenna to the point farthest to the antenna.
  • the antenna signal absorber (1) of the present invention is preferably made of carbon black and similar absorbent materials which basically have weak reflection.
  • the materials such as graphite, thin metal fibers or flakes which are not very conductive, which are of larger size and which have average dielectric properties but have sizes in micrometer to millimeter level form the antenna signal absorber (1) such that their density increases as they are farther away from the antenna.
  • a good conductive knitted/woven material is used at a distance of approximately factor ⁇ /4 on the antenna signal absorber (1) according to the frequency and the dielectric property of the material that it is made from. The reason for using knitted material is both to create Eddy currents (currents induced by alternative currents in the electric circuits and on the metallic conductors in the vicinity of the said circuits) and to enable scattering of the electromagnetic waves that leak from here.
  • the antenna signal absorber (1) of the present invention can be adjusted according to the situation and the desired electromagnetic response.
  • antenna isolation When antenna isolation is required to be kept high both at the back and towards the sides, it can be used partially linearly and helical good conductors and magnetic materials can be used. Additionally, preferably silver materials are used in terms of lightness. This property may be called chirality.
  • the macro, midi or mini scattering media on the antenna signal absorber (1) of the present invention are sprinkled into the material. These scattering media may be two or three dimensional and the varying dimensions change the effects of the scattering media. Furthermore, producing the materials in different ways by external geometries is a complementary aspect of the product. Here, dielectric properties of structures which are pyramid, conical, etc.
  • the antenna signal absorber (1) of the present invention if the wide frequency band absorption and suppression effects of the antenna towards the farther layers are needed to be increased particularly at specific frequencies, plane continuous structures similar to inner geometries are added in between. These repeating structures can be adjusted to a specific frequency and/or frequencies like in the transmission model. This way, if a specific frequency is desired, in addition to this general impact, suppression of over 90 dB can be obtained by being supported by a frequency selective surface.
  • x axis shows time and y axis shows the signal size value in dB.

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  • Aerials With Secondary Devices (AREA)

Abstract

An antenna signal absorber (1), which enables, for dipole-based antennas, to reduce overall network noise and to use the general data throughput at higher spectral efficiency without losing coverage, basically characterized by at least one body (2), at least one base (3) which is located in the body (2) and enables the antenna signal absorber (1) to be connected to the antenna back lobe contact surface, at least one protrusion (4) which is located on the body (2) and enables to absorb signals, at least one recess (5) which is located on the body (2) and enables to absorb signals, at least one surface (4) which is located on the protrusion (4) and recess (5) and enables signal absorption.

Description

DESCRIPTION
AN ANTENNA SIGNAL ABSORBER
Field of the Invention
The present invention relates to an antenna signal absorber which enables, for all kinds of dipole-based telecommunication antennas, to reduce the general network noise; to focus service on to closer {distance} clients for higher data throughput rates especially in networks employing new generation modulation technologies such as UMTS, WCDMA, OFDMA; to use band width more efficiently; and the general data throughput to be used at higher spectral efficiency without the need for breathing cell features causing unwanted coverage losses.
Background of the Invention
The need for suppressing signals at the back of antennas has, in the beginning, led the telecommunication sector to mount the antennas to the wall or to cover the antennas generally by placing metal pieces at the back thereof. Although wall mounting is a simple and effective method, since rear signals increase Rayleigh attenuations in near fields, it may have negative effects on the cell {signal} quality. Additionally, electromagnetic power densities may exceed the regulation values against living areas behind the walls to which the antennas are mounted. For this reason, wall mounting is not allowed by Information Technologies and Communications Authority (BTK) in Turkey.
On the other hand, barriers disposed on the back of the antennas either do not provide a significant benefit or cause reflections that create resonance and harmful interference particularly in the case of use of metal plates. Therefore, since barriers disposed on the back of antennas provide limited benefit and are difficult to estimate the side effects, they have never come into general use. The Japanese patent document no. JP2008304219, an application in the state of the art, discloses about suppression of the unnecessary signals received by the antenna. In this system, the unnecessary signal absorber can suppress clutter by spatiotemporal adaptation signal processing without using another means and easily even when the Doppler frequency of a target is unknown. The unnecessary signal absorber can suppress unnecessary signal components included in a reflection signal received by a plurality of elementary antennas which are installed on a mobile unit. The unnecessary signal absorber has a load calculating section for calculating a load coefficient.
The Japanese patent document no. JP2000131420, an application in the state of the art, discloses about effectively suppressing unwanted signals contained in a coherent video for the same spatial coordinates in a radar system. In this system, the absorber comprises an arithmetic unit for approximating the time variation of an input signal using a coherent video in the same spatial coordinates in a radar system. The system also comprises a second arithmetic unit. After approximating the equations in these arithmetic units and making the necessary calculations, the device suppresses the signal. The Japanese patent document no. JP2000266837, an application in the state of the art, discloses about suppression of unnecessary wave components. In this system, unnecessary waves can be suppressed even when desired waves and unnecessary waves come from the same direction. The device has horizontal and vertical polarizing elements. The device also comprises transmission reception modules. The modules are connected to the said elements respectively. Additionally, transmission and reception polarizations can vary. A polarization- operating means obtains from a received signal a polarization state of an unnecessary wave included in the received signal. Radar transmission pulses are transmitted and radar reflection pulses are received by polarized waves orthogonal to the unnecessary waves. Thus even the unnecessary waves coming from equal directions can be suppressed. Moreover, an adaptive weight/bias and the polarization state of unnecessary waves are operated for each pulse cycle period to update values.
Applications other than the above are ferrite barriers and use of laminated metal coatings. These can partially reduce reflections.
The problems of wall mounting and thin metal barriers are mentioned hereinbefore. Four problems occur in the thicknesses used for the ferrite barriers and laminated metal coatings to achieve the desired electromagnetic isolation values:
- Due to the nature of the materials that are used, ferrite and similar metal plates or mixtures have a weight of 60-90% of the antenna's weight and this imposes a significant static load on the polar pipes to which the antennas are mounted and to their fundamental points. Additionally, since thickness also significantly increases, wind load differs significantly as well.
- Even if these materials achieve the suppression rates and isolation targets, they still cause undesirable reflections.
- As ferrite isolators used within the material are of high cost, they significantly increase the solution's total cost.
- Since these materials are not elastic, their mounting in the field are very difficult or impossible, and they cannot be variable much in terms of thickness. Summary of the Invention
An objective of the present invention is to provide an antenna signal absorber which enables, for all kinds of dipole-based telecommunication antennas, to reduce the overall network noise; to focus service on to closer clients for higher data throughput rates especially in networks employing new generation modulation technologies such as UMTS, WCDMA, OFDMA; to use band width more efficiently; and the general data throughput to be used at higher spectral efficiency without the need for breathing cell features causing unwanted coverage losses. Another objective of the present invention is to provide an antenna signal absorber, which suppresses the signals going towards the back in specific fields when any dipole-based antenna is concentrating its signal towards the front according to the degree of directionality such that it will not cause a change to the antenna pattern in the front, and which also prevents signals coming from other sources from the back from reaching the antenna.
Detailed Description of the Invention
An antenna signal absorber developed to fulfill the objectives of the present invention is illustrated in the accompanying figures, in which:
Figure 1 is the side view of the Antenna Signal Absorber.
Figure 2 is the graphical view of the Antenna Signal Absorber. The components shown in the figures are each given reference numbers as follows:
1. Antenna Signal Absorber
2. Body
3. Base
4. Protrusion
5. Recess
6. Surface The antenna signal absorber (1), which enables, for dipole-based antennas, to reduce overall network noise and to use the general data throughput at higher spectral efficiency without losing coverage, basically comprises
at least one body (2),
- at least one base (3) which is located in the body (2) and enables the antenna signal absorber (1) to be connected to the antenna back lobe contact surface, at least one protrusion (4) which is located on the body (2) and enables to absorb signals,
at least one recess (5) which is located on the body (2) and enables to absorb signals,
at least one surface (4) which is located on the protrusion (4) and recess (5) and enables signal absorption.
In a preferred embodiment of the invention, the antenna signal absorber (1) includes thereon a base (3) which is located in the body (2) and enables connection of the antenna signal absorber (1) to the antenna back lobe contact surface; a protrusion (4) which is located on the body (2) and enables to absorb signals; and a recess (5) which is located on the body (2) and enables to absorb signals. Additionally, the antenna signal absorber (1) of the present invention includes a surface (6) which is located on the protrusion (4) and recess (5), and enables signal absorption.
In one embodiment of the invention, the antenna signal absorber (1) provides 5 times and more reduction in weight to provide an electromagnetic isolation value at the same level. Besides, since the isolation provided by the antenna signal absorber (1) does not cause undesirable reflections, there is no need to deal with any side effects.
In one embodiment of the invention, the antenna signal absorber (1) of the present invention can be protected by a radome having the same features with the antenna radome and/or can be used without radome in antennas which are concealed for camouflage purposes such that they will not be exposed to external factors. When used without radome, it may be located in near field or Fresnel zone, but this does not have a significant effect on the antenna pattern. In one embodiment of the invention, by means of the antenna signal absorber (1) of the present invention, the desired electromagnetic absorption, scattering and isolation values can be adjusted both according to the frequency and, if there is use of multiple frequency, can be adjusted for an overall absorption. Rapid solutions are produced with the ability of automated production by means of the adjustments to be made in the material sizes, thickness, content and composition with respect to the purpose and place of use. Furthermore, for antennas propagating multiple frequencies/technologies, production can be made so as to focus on an overall absorption or on more specific absorption of one of the technologies.
In one embodiment of the invention, the antenna signal absorber (1) of the present invention can be used without an outer radome at the narrow places of camouflages such as water tanks and chimneys used in general GSM and UMTS applications. In this case, since the material is completely elastic, it can cover any kind of antenna. Additionally, by using it at the back of mobile antennas such as radars, both the receiver sensitivity can be increased and its electromagnetic shielding properties can be taken advantage of.
In another embodiment of the invention, the antenna signal absorber (1) can also be used such that it will cover both one and two sides of the antennas or their back and one or all sides at places such as gulfs, channels and valleys which create planning difficulties geologically for providing coverage and signal quality at the same time. In one embodiment of the invention, the antenna signal absorber (1) is adjusted firstly by the gradual change of the dielectric properties of the materials from the point nearest to the antenna to the point farthest to the antenna. The antenna signal absorber (1) of the present invention is preferably made of carbon black and similar absorbent materials which basically have weak reflection. Furthermore, in the antenna signal absorber (1), the materials such as graphite, thin metal fibers or flakes which are not very conductive, which are of larger size and which have average dielectric properties but have sizes in micrometer to millimeter level form the antenna signal absorber (1) such that their density increases as they are farther away from the antenna. In another embodiment of the invention, a good conductive knitted/woven material is used at a distance of approximately factor λ/4 on the antenna signal absorber (1) according to the frequency and the dielectric property of the material that it is made from. The reason for using knitted material is both to create Eddy currents (currents induced by alternative currents in the electric circuits and on the metallic conductors in the vicinity of the said circuits) and to enable scattering of the electromagnetic waves that leak from here.
The antenna signal absorber (1) of the present invention can be adjusted according to the situation and the desired electromagnetic response. When antenna isolation is required to be kept high both at the back and towards the sides, it can be used partially linearly and helical good conductors and magnetic materials can be used. Additionally, preferably silver materials are used in terms of lightness. This property may be called chirality. The macro, midi or mini scattering media on the antenna signal absorber (1) of the present invention are sprinkled into the material. These scattering media may be two or three dimensional and the varying dimensions change the effects of the scattering media. Furthermore, producing the materials in different ways by external geometries is a complementary aspect of the product. Here, dielectric properties of structures which are pyramid, conical, etc. or which can fit into each other without leaving any gap in between are prepared such that they are opposite to each other. For example, while the first pyramid is adjusted such that its impedance increases from the base to the end, the second pyramid is adjusted such that its impedance increases from the end to the base. When these two pieces are fitted to each other face to face, gradual change of the dielectric properties is enabled from both material density and geometric property, and back reflections are prevented. The greatest advantage of this structure is that it is of a thickness that is less than the thickness of free space λ/4 (λ: Wavelength) thickness due to the fact that the wavelength is shorter in this type of materials and reaches the minimum reflection value. For this reason, the difference between the main beam radiated by the antenna to the front and the residual signal that is reflected from the material remains at 70 dB and higher.
Thanks to the antenna signal absorber (1) of the present invention, if the wide frequency band absorption and suppression effects of the antenna towards the farther layers are needed to be increased particularly at specific frequencies, plane continuous structures similar to inner geometries are added in between. These repeating structures can be adjusted to a specific frequency and/or frequencies like in the transmission model. This way, if a specific frequency is desired, in addition to this general impact, suppression of over 90 dB can be obtained by being supported by a frequency selective surface. In the graphic provided in Figure 2, x axis shows time and y axis shows the signal size value in dB.

Claims

An antenna signal absorber (1), which enables, for the dipole-based antennas to which it is mounted, to reduce general network noise and to use the general data throughput at high efficiency without losing content, basically characterized by
at least one body
(2),
at least one base
(3) which is located in the body (2) and enables the antenna signal absorber (1) to be connected to the antenna back lobe contact surface,
- at least one protrusion (4) which is located on the body (2) and enables to absorb signals,
at least one recess (5) which is located on the body (2) and enables to absorb signals,
at least one surface (4) which is located on the protrusion
(4) and recess (5) and enables signal absorption.
An antenna signal absorber (1) according to Claim 1, characterized by the body (2) which provides 5 times and more reduction in weight to provide an electromagnetic isolation value at the same level.
An antenna signal absorber (1) according to Claim 1, characterized by the body (2) which enables the desired electromagnetic absorption, scattering and isolation values to be adjusted according to the frequency.
An antenna signal absorber (1) according to Claim 1, characterized by the body (2) which can also be mounted such that it will cover both one and two sides of the antennas or their back and one or all sides at places such as gulfs, channels and valleys which create planning difficulties geologically for providing coverage and quality at the same time.
5. An antenna signal absorber (1) according to Claim 1, characterized by the body (2) which is preferably made of carbon black and similar absorbent materials that basically have weak reflection.
6. An antenna signal absorber (1) according to Claim 1, characterized by the body (2) which is preferably made of a conductive knitted material at a distance of approximately factor λ/4 according to the frequency and the dielectric property of the material that it is made from.
7. An antenna signal absorber (1) according to Claim 1, characterized by the body (2) which, thanks to its knitted structure, both creates Eddy currents and enables scattering of the electromagnetic waves that leak from here.
8. An antenna signal absorber (1) according to Claim 1, characterized by the body (2) into which macro, midi or mini scattering media that can be two or three dimensional are sprinkled.
9. An antenna signal absorber (1) according to Claim 1, characterized by the protrusion (4) which is preferably in the form of a triangular pyramid.
10. An antenna signal absorber (1) according to Claim 1, characterized by the recess (5) which is preferably in the form of a triangular pyramid.
11. An antenna signal absorber (1) according to Claim 1, characterized by the protrusion (4) which, in alternative embodiments, can be conical, cylindrical or in the form of a rectangular prism.
12. An antenna signal absorber (1) according to Claim 1, characterized by the recess (5) which, in alternative embodiments, can be conical, cylindrical or in the form of a rectangular prism.
13. An antenna signal absorber (1) according to Claim 1, characterized by the protrusion (4) and recess (5) which can fit into each other and form a flat structure preferably without leaving any gap in between and which thus enable to increase the number of layers.
PCT/TR2014/000452 2013-11-15 2014-11-14 An antenna signal absorber WO2015072953A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
TR201313320 2013-11-15
TR2013/13320 2013-11-15

Publications (1)

Publication Number Publication Date
WO2015072953A1 true WO2015072953A1 (en) 2015-05-21

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024098666A1 (en) * 2022-11-11 2024-05-16 河海大学 Three-dimensional special-shaped wave-absorbing structure-based antenna array

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2464006A (en) * 1944-04-28 1949-03-08 Philco Corp Radio wave absorption device
US2870439A (en) * 1950-12-29 1959-01-20 Western Union Telegraph Co Microwave energy attenuating wall
US2977591A (en) * 1952-09-17 1961-03-28 Howard A Tanner Fibrous microwave absorber
US4164718A (en) * 1976-07-09 1979-08-14 California Institute Of Technology Electromagnetic power absorber
US5872547A (en) * 1996-07-16 1999-02-16 Metawave Communications Corporation Conical omni-directional coverage multibeam antenna with parasitic elements
US6025803A (en) * 1998-03-20 2000-02-15 Northern Telecom Limited Low profile antenna assembly for use in cellular communications
US6744412B1 (en) * 2002-10-29 2004-06-01 Bae Systems Information And Electronic Systems Integration Inc. High up/down ratio GPS antennas with serrated absorber

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2464006A (en) * 1944-04-28 1949-03-08 Philco Corp Radio wave absorption device
US2870439A (en) * 1950-12-29 1959-01-20 Western Union Telegraph Co Microwave energy attenuating wall
US2977591A (en) * 1952-09-17 1961-03-28 Howard A Tanner Fibrous microwave absorber
US4164718A (en) * 1976-07-09 1979-08-14 California Institute Of Technology Electromagnetic power absorber
US5872547A (en) * 1996-07-16 1999-02-16 Metawave Communications Corporation Conical omni-directional coverage multibeam antenna with parasitic elements
US6025803A (en) * 1998-03-20 2000-02-15 Northern Telecom Limited Low profile antenna assembly for use in cellular communications
US6744412B1 (en) * 2002-10-29 2004-06-01 Bae Systems Information And Electronic Systems Integration Inc. High up/down ratio GPS antennas with serrated absorber

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024098666A1 (en) * 2022-11-11 2024-05-16 河海大学 Three-dimensional special-shaped wave-absorbing structure-based antenna array

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