WO1999019939A1 - Dual band phased array antenna - Google Patents

Dual band phased array antenna Download PDF

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Publication number
WO1999019939A1
WO1999019939A1 PCT/GB1998/002953 GB9802953W WO9919939A1 WO 1999019939 A1 WO1999019939 A1 WO 1999019939A1 GB 9802953 W GB9802953 W GB 9802953W WO 9919939 A1 WO9919939 A1 WO 9919939A1
Authority
WO
WIPO (PCT)
Prior art keywords
antenna
aperture
elements
antenna elements
band
Prior art date
Application number
PCT/GB1998/002953
Other languages
French (fr)
Inventor
George Hockham
Original Assignee
The Secretary Of State For Defence
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 The Secretary Of State For Defence filed Critical The Secretary Of State For Defence
Priority to AU92747/98A priority Critical patent/AU9274798A/en
Publication of WO1999019939A1 publication Critical patent/WO1999019939A1/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q21/00—Antenna arrays or systems
    • H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
    • H01Q21/22—Antenna units of the array energised non-uniformly in amplitude or phase, e.g. tapered array or binomial array
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q5/00—Arrangements for simultaneous operation of antennas on two or more different wavebands, e.g. dual-band or multi-band arrangements
    • H01Q5/40—Imbricated or interleaved structures; Combined or electromagnetically coupled arrangements, e.g. comprising two or more non-connected fed radiating elements
    • H01Q5/42—Imbricated or interleaved structures; Combined or electromagnetically coupled arrangements, e.g. comprising two or more non-connected fed radiating elements using two or more imbricated arrays
    • 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
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/06—Systems determining position data of a target
    • G01S13/42—Simultaneous measurement of distance and other co-ordinates
    • G01S13/426—Scanning radar, e.g. 3D radar
    • 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
    • G01S13/87—Combinations of radar systems, e.g. primary radar and secondary radar

Definitions

  • a DUAL BAND PHASED ARRAY ANTENNA This invention relates to a dual band phased array antenna, for example for use in tracking and surveillance radar.
  • a conventional phased array antenna comprises a number of closely spaced individually fed antenna elements which, when excited with a signal having an appropriate phase and amplitude, give rise to a desired total radiation pattern. By changing the phase of individual elements in a defined manner the beam of radiation may be steered electronically in space, thus avoiding mechanical movement of the antenna and improving the system response.
  • a typical array antenna for surveillance radar comprises a plurality of cells each of which contains an individually fed radiating element. Control of the phase and amplitude in each cell is applied to all cells simultaneously to form a beam having a desired shape and direction.
  • the size of the cell is related to the wavelength at a desired operating frequency band. To avoid generation of spurious beams or grating lobes, the cell dimensions are typically chosen to be of the order of about one half the operating wavelength.
  • the total number of elements or cells depends on the angular width of a desired beam of radiated energy, viz. the width of the beam is inversely proportional to the diameter of the array.
  • Commercial ships have a mandatory requirement for radar for navigation and collision avoidance. Usually a ship will have separate tracking and surveillance radar with different operational requirements to satisfy.
  • the long range surveillance radar requires a low frequency of operation for optimum performance, typically D-band; whilst the tracking radar is optimised at a higher frequency band for optimum performance, typically l-band. Conventionally, this has meant using two independent systems in close proximity with one another.
  • a dual band phased array antenna comprises a plurality of apertures; wherein each aperture comprises a first antenna element for operating in a first frequency band; and a plurality of second antenna elements for operating in a second frequency band; the antenna further comprising control means for controlling the phase of the antenna elements within each aperture relative to the phase of antenna elements within each adjacent aperture; wherein each aperture is fully filled with respect to the first antenna element and partially filled with respect to the second antenna elements; wherein the second antenna elements are randomly arranged within each aperture; and wherein the position of the first antenna element is modified in accordance with the random arrangement of the second antenna elements within that aperture.
  • the present invention provides a dual band phased array antenna which is lighter and less expensive than using conventional array antennas and is able to provide adequate performance in either frequency band.
  • the operating frequency of each of the second antenna elements is greater than 3 times that of the operating frequency of each of the first antenna elements. More preferably, the frequency is 10 times, although higher values may be achieved. Preferably, the operating frequency of each of the first antenna elements is 1
  • a dual band phased array radar comprises an array according to the first aspect, wherein the first operating frequency is in the D band and the second operating frequency is in the I band.
  • Figure 1 illustrates an arrangement of apertures in an example of an antenna according to the present invention
  • Figure 2 shows a single aperture of the antenna of Fig. 1 in more detail
  • Figure 3 illustrates examples of random element arrangements for the antenna of Fig. 1 ;
  • Figure 4 illustrates density tapering of the elements across the antenna of Fig. 1 ;
  • Figures 5 shows an example of a pseudo random array of D-band elements in an antenna according to the invention.
  • the example of Fig. 1 represents a 4m diameter array 1 comprising 498 cells 2 on a triangular lattice. The cells are shown in more detail in Fig. 2.
  • Each cell 2 forms an aperture 3 in which a single waveguide 4 is positioned for operating at a first, relatively low, frequency. For surveillance radar this frequency is about 1 GHz, known as D-band.
  • multiple radiating elements 5 which operate at a second, relatively high, frequency are arranged within the aperture. For tracking radar this frequency is about 10 GHz, known as l-band.
  • the radiating elements 4, 5 are driven with a signal having a suitable phase and amplitude from a controller 8.
  • a cell 2 with dimensions suitable for a single waveguide 4 at D-band would, for radiating elements 5 operating at 10 times the frequency, require 10 2 radiating elements to fully fill the aperture.
  • 50,000 radiating elements would be required to fully fill the array, but the operational requirement can be met with only 6000, i.e. 12% population of the array.
  • the elements 5 are randomly distributed across the entire physical aperture 3 of each cell 2. Examples of such random distributions are shown in Fig. 3 which illustrates a selection of positions 6 at which the radiating elements 5 may be placed for apertures at different positions across the whole array.
  • the vertical axis illustrates distance in mm within an aperture and the horizontal axis represents position in mm across the whole array.
  • the present invention overcomes this problem by arranging the l-band elements 5 in a random arrangement in the absence of the D-band elements 4.
  • each of the D-band elements would be located at the same relative position in each cell, but as discussed, this would affect the randomness of the arrangement of the l-band elements. Therefore, a pseudo random perturbation is introduced by positioning the D-band element within the cell 2 where the random arrangement of the l-band elements permits. Although this might be expected to degrade the D-band performance, in practice any degradation is acceptably low.
  • An example of the positions 7 for D-band waveguides over the whole antenna area is illustrated in Fig. 5.
  • the random distribution of the 6000 elements in the 500 cell array results in the elements being generally distributed with an average of 12 elements per cell.
  • a density tapering of elements may be introduced. Density tapering is illustrated in Figs. 4 where the vertical axis represents number of elements in the aperture and the horizontal axes represent rows and columns of the aperture position within the array. Density tapering implies a larger number of elements in cells closer to the centre of the array, than towards the edges, so numbers may vary between 5 and 25 elements per aperture, but still average out as 12.
  • the diameter of the array and number of elements are described for one set of operating frequencies. For other operating frequencies these figures may vary. Likely atmospheric conditions, space constraints and power available influence the frequency of operation, diameter and number of elements in the antenna. Other applications of a dual band phased array antenna are for use in aircraft radar, particularly for fighter aircraft where there are space constraints for fitting an antenna and for radio astronomy.

Abstract

A dual band phased array antenna (1) comprises a plurality of apertures (2). Each aperture comprises a first antenna element (4) for operating in a first frequency band and a plurality of second antenna elements (5) for operating in a second frequency band. The antenna further comprising control means (8) for controlling the phase of the antenna elements (4, 5) within each aperture relative to the phase of antenna elements (4, 5) within each adjacent aperture. Each aperture (2) is fully filled with respect to the first antenna element (4) and partially filled with respect to the second antenna elements (5) and the second antenna elements are randomly arranged within each aperture. The position of the first antenna element (4) is modified in accordance with the random arrangement of the second antenna elements (5) within that aperture.

Description

DUAL BAND PHASED ARRAY ANTENNA This invention relates to a dual band phased array antenna, for example for use in tracking and surveillance radar. A conventional phased array antenna comprises a number of closely spaced individually fed antenna elements which, when excited with a signal having an appropriate phase and amplitude, give rise to a desired total radiation pattern. By changing the phase of individual elements in a defined manner the beam of radiation may be steered electronically in space, thus avoiding mechanical movement of the antenna and improving the system response.
A typical array antenna for surveillance radar comprises a plurality of cells each of which contains an individually fed radiating element. Control of the phase and amplitude in each cell is applied to all cells simultaneously to form a beam having a desired shape and direction. The size of the cell is related to the wavelength at a desired operating frequency band. To avoid generation of spurious beams or grating lobes, the cell dimensions are typically chosen to be of the order of about one half the operating wavelength. The total number of elements or cells depends on the angular width of a desired beam of radiated energy, viz. the width of the beam is inversely proportional to the diameter of the array. Commercial ships have a mandatory requirement for radar for navigation and collision avoidance. Usually a ship will have separate tracking and surveillance radar with different operational requirements to satisfy. The long range surveillance radar requires a low frequency of operation for optimum performance, typically D-band; whilst the tracking radar is optimised at a higher frequency band for optimum performance, typically l-band. Conventionally, this has meant using two independent systems in close proximity with one another.
Proposals have been made to combine surveillance and tracking radar by compromising on the frequency band and using one which is between the two desired frequencies. Another proposal has been to use a single element type and operate it at both frequency bands. However, the resulting performance is only effective if the ratio of the frequencies is no more than 3:1.
In accordance with a first aspect of the present invention, a dual band phased array antenna, comprises a plurality of apertures; wherein each aperture comprises a first antenna element for operating in a first frequency band; and a plurality of second antenna elements for operating in a second frequency band; the antenna further comprising control means for controlling the phase of the antenna elements within each aperture relative to the phase of antenna elements within each adjacent aperture; wherein each aperture is fully filled with respect to the first antenna element and partially filled with respect to the second antenna elements; wherein the second antenna elements are randomly arranged within each aperture; and wherein the position of the first antenna element is modified in accordance with the random arrangement of the second antenna elements within that aperture.
The present invention provides a dual band phased array antenna which is lighter and less expensive than using conventional array antennas and is able to provide adequate performance in either frequency band.
Preferably, the operating frequency of each of the second antenna elements is greater than 3 times that of the operating frequency of each of the first antenna elements. More preferably, the frequency is 10 times, although higher values may be achieved. Preferably, the operating frequency of each of the first antenna elements is 1
GHz.
Preferably, there is an average filling of 12% by the second antenna elements in each aperture.
In accordance with a second aspect of the present invention, a dual band phased array radar comprises an array according to the first aspect, wherein the first operating frequency is in the D band and the second operating frequency is in the I band.
An example of a dual band phased array antenna in accordance with the present invention will now be described with reference to the accompanying drawings in which:-
Figure 1 illustrates an arrangement of apertures in an example of an antenna according to the present invention;
Figure 2 shows a single aperture of the antenna of Fig. 1 in more detail;
Figure 3 illustrates examples of random element arrangements for the antenna of Fig. 1 ;
Figure 4 illustrates density tapering of the elements across the antenna of Fig. 1 ; and,
Figures 5 shows an example of a pseudo random array of D-band elements in an antenna according to the invention. The example of Fig. 1 represents a 4m diameter array 1 comprising 498 cells 2 on a triangular lattice. The cells are shown in more detail in Fig. 2. Each cell 2 forms an aperture 3 in which a single waveguide 4 is positioned for operating at a first, relatively low, frequency. For surveillance radar this frequency is about 1 GHz, known as D-band. In addition, multiple radiating elements 5 which operate at a second, relatively high, frequency are arranged within the aperture. For tracking radar this frequency is about 10 GHz, known as l-band. The radiating elements 4, 5 are driven with a signal having a suitable phase and amplitude from a controller 8. It is known that the relationship of the cell dimensions to the operating wavelength is important to prevent unwanted side lobes forming. A cell 2 with dimensions suitable for a single waveguide 4 at D-band would, for radiating elements 5 operating at 10 times the frequency, require 102 radiating elements to fully fill the aperture.
However, it has been found based on a desired radar cross section for detection, power available and size of the array that the operational requirement of the radar would be met with a much reduced number of radiating elements.
Therefore in the example discussed above, for approximately 500 cells, 50,000 radiating elements would be required to fully fill the array, but the operational requirement can be met with only 6000, i.e. 12% population of the array. To avoid excitation of grating lobes, the elements 5 are randomly distributed across the entire physical aperture 3 of each cell 2. Examples of such random distributions are shown in Fig. 3 which illustrates a selection of positions 6 at which the radiating elements 5 may be placed for apertures at different positions across the whole array. The vertical axis illustrates distance in mm within an aperture and the horizontal axis represents position in mm across the whole array. If low frequency D-band elements 4 are located periodically over the same physical aperture 3, then the l-band elements are unable to occupy the same overlap regions, thus leading to a periodic component in the distribution over the aperture 3 where the l-band elements 5 are precluded. In this case, unacceptable excitation of grating lobes would occur. The present invention overcomes this problem by arranging the l-band elements 5 in a random arrangement in the absence of the D-band elements 4. Generally, each of the D-band elements would be located at the same relative position in each cell, but as discussed, this would affect the randomness of the arrangement of the l-band elements. Therefore, a pseudo random perturbation is introduced by positioning the D-band element within the cell 2 where the random arrangement of the l-band elements permits. Although this might be expected to degrade the D-band performance, in practice any degradation is acceptably low. An example of the positions 7 for D-band waveguides over the whole antenna area is illustrated in Fig. 5.
Over a number of examples, the random distribution of the 6000 elements in the 500 cell array results in the elements being generally distributed with an average of 12 elements per cell. To suppress wide angle side lobes, a density tapering of elements may be introduced. Density tapering is illustrated in Figs. 4 where the vertical axis represents number of elements in the aperture and the horizontal axes represent rows and columns of the aperture position within the array. Density tapering implies a larger number of elements in cells closer to the centre of the array, than towards the edges, so numbers may vary between 5 and 25 elements per aperture, but still average out as 12.
The diameter of the array and number of elements are described for one set of operating frequencies. For other operating frequencies these figures may vary. Likely atmospheric conditions, space constraints and power available influence the frequency of operation, diameter and number of elements in the antenna. Other applications of a dual band phased array antenna are for use in aircraft radar, particularly for fighter aircraft where there are space constraints for fitting an antenna and for radio astronomy.

Claims

1. A dual band phased array antenna (1), the antenna comprising a plurality of apertures (2); wherein each aperture comprises a first antenna element (4) for operating in a first frequency band; a plurality of second antenna elements (5) for operating in a second frequency band; the antenna further comprising control means (8) for controlling the phase of the antenna elements within each aperture relative to the phase of antenna elements within each adjacent aperture; wherein each aperture is fully filled with respect to the first antenna element and partially filled with respect to the second antenna elements; wherein the second antenna elements are randomly arranged within each aperture; and wherein the position of the first antenna element is modified in accordance with the random arrangement of the second antenna elements within that aperture.
2. An antenna according to claim 1 , wherein the operating frequency of each of the second antenna elements is greater than 3 times that of the operating frequency of each of the first antenna elements.
3. An antenna according to claim 1 or claim 2, wherein the operating frequency of each of the second antenna elements is 10 times that of the operating frequency of each of the first antenna elements.
4. An antenna according to any preceding claim, wherein the operating frequency of each of the first antenna elements is 1 GHz.
5. An antenna according to any preceding claim, wherein the average filling of the second antenna elements in each aperture is 12%.
6. A dual band phased array radar, comprising an antenna according to any preceding claim, wherein the first operating frequency is in the D-band and the second operating frequency is in the l-band.
PCT/GB1998/002953 1997-10-11 1998-10-01 Dual band phased array antenna WO1999019939A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU92747/98A AU9274798A (en) 1997-10-11 1998-10-01 Dual band phased array antenna

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9721541.2 1997-10-11
GB9721541A GB2330236A (en) 1997-10-11 1997-10-11 A dual band phased array antenna

Publications (1)

Publication Number Publication Date
WO1999019939A1 true WO1999019939A1 (en) 1999-04-22

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WO (1) WO1999019939A1 (en)

Cited By (1)

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GB2500052A (en) * 2012-03-08 2013-09-11 Univ Antwerpen Target detection

Families Citing this family (2)

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JP6157872B2 (en) * 2013-02-20 2017-07-05 株式会社東芝 Ultrasonic shape measuring apparatus and measuring method
FR3039328B1 (en) * 2015-07-22 2017-08-25 Thales Sa RADIOELECTRIC RADIOELECTRIC WAVE TRANSMIT-RECEIVE DEVICE AND ASSOCIATED RADIO ALTIMETRY SYSTEM

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US3825932A (en) * 1972-06-08 1974-07-23 Int Standard Electric Corp Waveguide antenna
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US5537367A (en) * 1994-10-20 1996-07-16 Lockwood; Geoffrey R. Sparse array structures
US5557291A (en) * 1995-05-25 1996-09-17 Hughes Aircraft Company Multiband, phased-array antenna with interleaved tapered-element and waveguide radiators

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US3623111A (en) * 1969-10-06 1971-11-23 Us Navy Multiaperture radiating array antenna
US3825932A (en) * 1972-06-08 1974-07-23 Int Standard Electric Corp Waveguide antenna
US3761943A (en) * 1972-07-21 1973-09-25 Us Navy Dual-band array antenna
US5168472A (en) * 1991-11-13 1992-12-01 The United States Of America As Represented By The Secretary Of The Navy Dual-frequency receiving array using randomized element positions
US5537367A (en) * 1994-10-20 1996-07-16 Lockwood; Geoffrey R. Sparse array structures
US5557291A (en) * 1995-05-25 1996-09-17 Hughes Aircraft Company Multiband, phased-array antenna with interleaved tapered-element and waveguide radiators

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Title
HAUPT R L: "THINNED ARRAYS USING GENETIC ALGORITHMS", IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, vol. 42, no. 7, 1 July 1994 (1994-07-01), pages 993 - 999, XP000457526 *
MOORE S A W AND HOCKHAM G A: "DUAL FREQUENCY MULTI-FUNCTION RADAR ANTENNA RESEARCH", RADAR 97, 14 October 1997 (1997-10-14) - 16 October 1997 (1997-10-16), EDINGBURGH, pages 50 - 54, XP000776877 *
MOORE S A W AND MOORE A R: "DUAL FREQUENCY MULTI-FUNCTION RADAR ANTENNA RESEARCH", 10TH INTERNATIONAL CONFERENCE ON ANTENNAS AND PROPAGATION (ICAP), vol. 1, 14 April 1997 (1997-04-14) - 17 April 1997 (1997-04-17), EDINBURGH, UK, pages 1.522 - 1.526, XP002087499 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2500052A (en) * 2012-03-08 2013-09-11 Univ Antwerpen Target detection
US9857465B2 (en) 2012-03-08 2018-01-02 Universiteit Antwerpen System and method for target detection

Also Published As

Publication number Publication date
GB2330236A (en) 1999-04-14
GB9721541D0 (en) 1998-05-27
AU9274798A (en) 1999-05-03

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