EP0190927A2 - Antennes guides d'ondes à fentes et réseaux de telles antennes - Google Patents

Antennes guides d'ondes à fentes et réseaux de telles antennes Download PDF

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Publication number
EP0190927A2
EP0190927A2 EP86300779A EP86300779A EP0190927A2 EP 0190927 A2 EP0190927 A2 EP 0190927A2 EP 86300779 A EP86300779 A EP 86300779A EP 86300779 A EP86300779 A EP 86300779A EP 0190927 A2 EP0190927 A2 EP 0190927A2
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EP
European Patent Office
Prior art keywords
slots
radiator
waveguide
septum
slot
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP86300779A
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German (de)
English (en)
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EP0190927A3 (fr
Inventor
Alan John Sangster
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
National Research Development Corp UK
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National Research Development Corp UK
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Filing date
Publication date
Application filed by National Research Development Corp UK filed Critical National Research Development Corp UK
Publication of EP0190927A2 publication Critical patent/EP0190927A2/fr
Publication of EP0190927A3 publication Critical patent/EP0190927A3/fr
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q21/00—Antenna arrays or systems
    • H01Q21/0006—Particular feeding systems
    • H01Q21/0037—Particular feeding systems linear waveguide fed arrays
    • H01Q21/0043—Slotted waveguides

Definitions

  • the present invention relates to slotted waveguide antennas employing waveguide radiators having sidewall slots and arrays of such radiators.
  • slotted-waveguide array antennas which are capable of providing well controlled, very low side lobe, radiation patterns, are well known.
  • two methods of slotting the waveguide are commonly used: namely staggered axial shunt slots in the broad wall, or inclined sidewall slots.
  • arrays formed from slots of this type suffer from two basic radiation pattern errors. These are firstly periodic errors associated with the requirement either to stagger the longitudinal shunt slots or to incline the sidewall slots oppositely, and secondly cross-polarisation errors particularly in the case of the sidewall slots because of their inclination.
  • the slots should be normal to the longitudinal axis of the waveguide in order to prevent cross-polarisation.
  • the slots should also be symmetrical with regard to longitudinal axis to avoid periodic errors. The latter requires means inside the waveguide to ensure that radiation from the symmetrical slots occurs.
  • the radiation patterns of waveguides with symmetrical sidewall slots contain grating lobes because adjacent slots radiate in phase only when separated by a distance equal to one or more wavelengths of the mode within the waveguide and it is an object of the present invention to provide in phase radiation when the sidewall slots are separated by half of the guide wavelength.
  • an elongated waveguide radiator which in cross section is divided into first and second waveguide portions by a septum, having a plurality of first elongated slots in an external wall of the radiator each of which extends on both sides of the septum and is orthogonal to the longitudinal axis of the radiator, and a plurality of elongated second slots, each of which extends from a corresponding one of the first slots into the septum, and has a longitudinal axis which is inclined to a line in the septum normal to the longitudinal axis of the radiator, the direction of the angle of inclination alternating along the radiator.
  • the inclination of the second slots can be as required to provide a desired control of the radiation magnitude from adjacent slots but the second slots must be inclined to said line in the septum (that is second slots must not be parallel to the longitudinal axis of the radiator) or radiation between adjacent slots will not be in phase when they are separated by half of the guide wavelength.
  • Arrays may be constructed using a plurality of radiators according to the first aspect of the invention.
  • an antenna array comprising two or more elongated waveguide radiators each of which in cross section is divided into first and second waveguide portions by a septum, has a plurality of first elongated slots in an external wall of the radiator each of which extends on both sides of the septum and is orthogonal to the longitudinal axis of the radiator, and has a plurality of elongated second slots, each of which extends from a corresponding one of the first slots into the septum, wherein the separation between the first slots in each radiator is substantially equal to 10 times the distance from any first slot in the array to the nearest adjacent first slot.
  • first and second waveguide portions are usually excited in antiphase.
  • a slotted waveguide radiator 10 comprises two waveguides 11 and 12 each of the usual dimensions required to support the TE 10 mode and thus for the X-band the breadth of the waveguide 10 is about two and a quarter centimetres while its overall height is in the region of two and a half centimetres.
  • the radiator 10 can be regarded as being bifurcated along the H plane.
  • the slots 13, 14, 16 and 17 are part of a series of such slots along the radiator 10.
  • the slots are about 0.2 cm wide and spaced at about 4.5 cm along the radiator.
  • slots 13 and 14 are orthogonal to the direction of propagation they would not radiate in a waveguide having no septum and further if the waveguides 11 and 12 were excited in phase the septum 15 would have no effect.
  • the waveguides 11 and 12 are normally excited in antiphase, so that the septum slots 16 and 17 are strongly excited by the "odd" TE 10 mode since they significantly interrupt the septum wall currents of this mode.
  • the fields produced in the slots 16 and 17 if they are each about a quarter of the free space wavelength long induce field patterns in the slots 13 and 14 causing them to radiate parasitically.
  • these slots can vary in length in the range one-eighth to half a free space wavelength.
  • the slots 13 normally have an overall length of half the free space wavelength at the centre of the band to be propagated in the waveguides 11 and 12, although they may be as short as a quarter of the free space wavelength.
  • the slots 13 and 14 are resonant as are each upper half of the slots 13 and 14 together with the corresponding slots 16 and 17, and each lower half of the slots 13 and 14 together with the corresponding slots 16 and 17.
  • Non- resonant slot lengths may be used if some pattern shaping is desired; for example a cosine distribution or other tapering of field strength across the antenna aperture. Other out of phase excitations than antiphase can sometimes prove useful for the waveguides 11 and 12.
  • the waveguide radiator 10 generates horizontal polarisation when the radiator is mounted horizontally, and as the slots 13 and 14 are orthogonal to the axis of the radiator, significant cross-polarisation does not occur.
  • the slots 13 and 14 are regularly spaced and symmetrical with respect to the wall of the radiator 10 so periodic errors are avoided.
  • the grating lobe problem can be largely overcome by the waveguide of Figure 2.
  • This waveguide also has slots 13 and 14 but these slots radiate in phase when separated axially by half of one guide wavelength and so reduces the problem of grating lobes.
  • septum slots 25 and 26 extend axially along the radiator 10 from the slots 13 and 14, respectively, and are configured to provide the required phase reversal.
  • the direction in which the slots 25, 26 extend in the axial direction of the radiator 10 is reversed.
  • FIG 3 where currents in the septum 15 are indicated by chain dashed arrows 27, the electric fields parasitically excited in the slots 25 and 26 are as shown by the arrows 28 and 29, respectively.
  • the slots are separated by half a guide wavelength and one due to the directions of the slots 25 and 26. It can be seen that the electric field directions excited in the slots 13 and 14 are in phase due to these two reversals and at half guide wavelength spacing, therefore, the slots radiate in phase. Again the slots 25 and 26 are each approximately a quarter of a free space wavelength long at the centre of the band of frequencies to be propagated and other dimensions are the same as those of the waveguide of Figure 1.
  • the septum slots 25 and 26 may be inclined to the longitudinal axis of the waveguide at angles up to, but not including, 90 0 (when they become equivalent to the slots 16 and 17). Traversing the waveguides in the longitudinal direction the slots are inclined first in the 'forward' direction and then in the 'backward' direction for adjacent slots.
  • Such slots provide only partial phase reversal and although such a phase change is usually a disadvantage, it can sometimes be useful to give control of radiation strength if it is required to keep the lengths of the sidewall slots and septum slots invariant; for example in constructing a narrow-band resonant array.
  • Figure 5 shows three possible ways 20, 21 and 22 of stacking, on a background of equilateral triangles each having sides d. Schemes 20 and 21 are particularly suitable for this purpose.
  • slots as indicated by lines transverse to the waveguides are separated by a distance d.
  • the object of stacking is to create a planar array in which slots radiate in phase and are spaced by less than 0.7 ⁇ o , where A 0 is the free space wavelength.
  • the array 20 is made up of three radiators 10 of the type shown in Figure 1 while the arrays 21 and 22 are each formed by two such radiators but, in practice, arrays of this type usually comprise many more radiators. Corresponding waveguides in the radiators making up the arrays are fed in phase.
  • the separation between adjacent slots in the same waveguide radiator is d 10 and thus the separation d between slots in the stacked array is just over a third of the guide wavelength ( ⁇ g ). Since the A is greater than ⁇ o , d is, as required, approximately equal to ⁇ o/2 . If the waveguide width is chosen to be that of a standard waveguide the direction of the beam is almost broadside. However as is apparent from Figure 5 this increase in slot separation is achieved at the expense of the sidewall dimension (b) of the waveguide radiator. As a consequence the sidewall dimension has to be reduced to less than 0.2 of a free space wavelength. After provision is made for wall thickness and the septum, the inside dimension of each waveguide 11 and 12 is such that manufacture is difficult.
  • the array 21 overcomes this problem but requires the addition of phase compensation between adjacent slots to reduce ⁇ g to be equal to or a little larger than ⁇ o in order to place the main beam close to broadside.
  • the separation between the slots in each waveguide radiator making up the array is about A giving the required array slot separation of about ⁇ o/2 .
  • Phase compensation can be obtained for example by dielectric loading (this is partially or completely filling the waveguide with dielectric), the use of periodically spaced metallic fins or irises, oversize waveguides or discrete phase shifters. The latter is usually preferable in view of attenuation loss, weight associated with dielectric or periodic loading and overmoding associated with an oversize waveguide.
  • the required additional phase shift between slots which is needed to ensure approximately broadside radiation is of the order of 90°. Since the separation between adjacent slots is approximately one free space wavelength, sufficient space is available for the insertion of an inductive post phase shifter between slots.
  • the sidewall dimension b is enlarged to normal size.
  • this arrangement requires that the waveguide radiator be even more heavily loaded so that ⁇ g approaches ⁇ o/2 . While radiators as used in the arrays 20 and 21 are not suitable for use individually those of the array 22 may be used singly.
  • a feed waveguide 31 has three slots which couple into bifurcated waveguides 32, 33 and 34 by way of 3dB power splitters 35, 36 and 37. Since the power splitters introduce a 90° phase shift between the two portions of each bifurcated waveguide, the upper portions include phase shifters 38, 39 and 40 to give the 180 phase difference to induce the "odd" mode in the waveguides.
  • the phase shifters may comprise shaped dielectric inserts providing 90° of phase shift at the centre-band frequency but which are also matched to the waveguides. Matched loads 42 to 48 are provided for the waveguides 31 to 34.
  • Other radiators according to the invention can be fed in similar ways.
  • Arrays 21 and 22 are more easily implemented with waveguide radiators of the type shown in Figures 2 and 4 since loading is not required.
  • the distance S between slots in each radiator is, in effect, ⁇ g/2 , and for the array 21 ⁇ g should equal about twice ⁇ o . This condition can easily be met for example by operating close to the cut-off frequency of the waveguide.
  • ⁇ g should be approximately 1.4 ⁇ o which again can easily be arranged.
  • the slots in the septum between the waveguides can be of other shapes provided, as far as the arrangement similar to Figure 3 are concerned, the electric field and adjacent slots are in opposite directions.
  • the waveguides may be filled with dielectric or may be periodically loaded to reduce the guide wavelength, thus minimising the grating lobe problem and also permitting frequency scanning of the main radiated beam.
  • the sidewall slots and the septum slots may be considerably shorter than their 'resonant' values if a particular aperture field shaping is desired.
  • the slots in the waveguide walls may extend from the narrow walls into the broad walls.

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  • Waveguide Aerials (AREA)
  • Variable-Direction Aerials And Aerial Arrays (AREA)
EP86300779A 1985-02-07 1986-02-05 Antennes guides d'ondes à fentes et réseaux de telles antennes Withdrawn EP0190927A3 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB8503055 1985-02-07
GB8503055 1985-02-07
GB8505198 1985-02-28
GB8505198 1985-02-28

Publications (2)

Publication Number Publication Date
EP0190927A2 true EP0190927A2 (fr) 1986-08-13
EP0190927A3 EP0190927A3 (fr) 1988-08-24

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EP86300779A Withdrawn EP0190927A3 (fr) 1985-02-07 1986-02-05 Antennes guides d'ondes à fentes et réseaux de telles antennes

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EP (1) EP0190927A3 (fr)
GB (1) GB2170959A (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0329079A2 (fr) * 1988-02-19 1989-08-23 Asahi Kasei Kogyo Kabushiki Kaisha Antenne guide d'ondes à fentes
EP1122813A2 (fr) * 2000-02-04 2001-08-08 Hughes Electronics Corporation Terminal à réseau d'antennes à commande de phase pour constellations de satellites équatoriales
US7068733B2 (en) 2001-02-05 2006-06-27 The Directv Group, Inc. Sampling technique for digital beam former

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5311200A (en) * 1991-06-18 1994-05-10 Malibu Research Associates, Inc. Millimeter wave variable width waveguide scanner

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1441741A1 (de) * 1962-05-10 1969-10-09 Lab For Electronics Inc Mikrowellenantenne
US3720953A (en) * 1972-02-02 1973-03-13 Hughes Aircraft Co Dual polarized slot elements in septated waveguide cavity

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1573604A (en) * 1977-02-18 1980-08-28 Nat Res Dev Aerial arrays

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1441741A1 (de) * 1962-05-10 1969-10-09 Lab For Electronics Inc Mikrowellenantenne
US3720953A (en) * 1972-02-02 1973-03-13 Hughes Aircraft Co Dual polarized slot elements in septated waveguide cavity

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
IEE PROC., vol. 129, Pt. H, no. 6, December 1982, pages 299-306; A.J.SANGSTER et al.: "Moment method analysis of a T-shaped slot radiator in bifurcated waveguide" *
IEEE TRANSACTIONS OF ANTENNAS AND PROPAGATION, vol. AP-22, no. 2, March 1974, pages 196-200, IEEE, New York, US; J.AJIOKA et al.: "Arbitrarily polarized slot radiators in bifurcated waveguide arrays" *
IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, vol. AP-32, no. 3, March 1984, pages 247-251, IEEE, New York, US; J.S.AJIOKA et al.: "Slot radiators in septated waveguide" *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0329079A2 (fr) * 1988-02-19 1989-08-23 Asahi Kasei Kogyo Kabushiki Kaisha Antenne guide d'ondes à fentes
EP0329079A3 (en) * 1988-02-19 1990-06-13 Asahi Kasei Kogyo Kabushiki Kaisha Slotted waveguide antenna
EP1122813A2 (fr) * 2000-02-04 2001-08-08 Hughes Electronics Corporation Terminal à réseau d'antennes à commande de phase pour constellations de satellites équatoriales
EP1122813A3 (fr) * 2000-02-04 2004-03-10 Hughes Electronics Corporation Terminal à réseau d'antennes à commande de phase pour constellations de satellites équatoriales
US7339520B2 (en) 2000-02-04 2008-03-04 The Directv Group, Inc. Phased array terminal for equatorial satellite constellations
US7068733B2 (en) 2001-02-05 2006-06-27 The Directv Group, Inc. Sampling technique for digital beam former

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Publication number Publication date
GB8602840D0 (en) 1986-03-12
EP0190927A3 (fr) 1988-08-24
GB2170959A (en) 1986-08-13

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