US2639383A - Microwave antenna - Google Patents

Microwave antenna Download PDF

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Publication number
US2639383A
US2639383A US216717A US21671751A US2639383A US 2639383 A US2639383 A US 2639383A US 216717 A US216717 A US 216717A US 21671751 A US21671751 A US 21671751A US 2639383 A US2639383 A US 2639383A
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US
United States
Prior art keywords
slots
waveguide
antenna
wavelength
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.)
Expired - Lifetime
Application number
US216717A
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English (en)
Inventor
Gruenberg Harry
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 Council of Canada
Original Assignee
National Research Council of Canada
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
Priority to NL7506610.A priority Critical patent/NL162753B/nl
Priority to NL77126D priority patent/NL77126C/xx
Application filed by National Research Council of Canada filed Critical National Research Council of Canada
Priority to US216717A priority patent/US2639383A/en
Priority to GB15686/51A priority patent/GB681697A/en
Priority to DEN4217A priority patent/DE884970C/de
Priority to FR1114807D priority patent/FR1114807A/fr
Application granted granted Critical
Publication of US2639383A publication Critical patent/US2639383A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
    • H01Q13/20—Non-resonant leaky-waveguide or transmission-line antennas; Equivalent structures causing radiation along the transmission path of a guided wave
    • 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 invention relates to directive antennas for microwaves, that is for electro-magnetic waves having lengths in free space of less than one meter.
  • Watson appearing at pages 747 to 777 of volume 93, part IIIA, Number 4 of the Journal of the Institution of Electrical Engineers, and the book The Physical Principles of Wave Guide Transmission and Antenna Systems, by W. H. Watson, 1947, Oxford, at the Clarendon Press) there is disclosed an antenna structure comprising a waveguide formed with an array of radiators consisting of slots in special arrangements.
  • the present invention is concerned with the arrangement in which adjacent slots are located on opposite sides of the centre line of a broad face of the waveguide and in the present application, an antenna with this arrangement of slots will be called the Watson and Guptill antenna.
  • the Watson and Guptill antenna takes into account the well-known design considerations for linear arrays of radiators and the fact that the wavelength in the guide differs from that in free space.
  • the radiators must radiate in phase, This could be achieved by spacing the radiators along the axis of the array at intervals equal to the wavelength in the guide (by) of the wave to be radiated, but, owing to the higher phase velocity in the guide, at least in the usual case where the dielectric is air, such a spacing would, in a guide having a normal width of about of the wavelength in free space (is), be equal to the spacing of about 1.
  • a spacing of /2Ag is, in the normal case of a guide of a width of about AM, equivalent to a spacing of about %is, and is consequently satisfactory from the point: of view of the radiation pattern.
  • the spacing of the radiators coupled in reverse phase relation is different from /zkg, the angle of the beam tothe axis of the array becomes acute and decreases with increasing departure from /gky spacing, the beam being directed in the direction of wave propagation in the guide when the spacing is greater than 180 and in the opposite direction when the spacing is less than 180.
  • the present invention resulted from the discovery that even when the above conditions are observed in the design 'of a slotted waveguide antenna such as the Watson and Guptill antenna, there remain second order beams making angles of approximately 50 with the main beam and having levels of about 10 per cent of that of the main beam.
  • this spurious radiation is not troublesome, for example in the ease of navigation on open waters where the radar equipment is not ordinarily used to locate nearby objects.
  • the radar equipment is not ordinarily used to locate nearby objects.
  • second order beams cause reflections from these nearby objects, serious errors in interpretation of the'radar patterns may result.
  • the second order beams may cause the patterns to be blurred and unreadable. It isthought'that the reason these second order beams have remained undiscovered, prior to the present invention, is that, as mentioned above, they are not noticeable except in the presence of nearby objects and moreover they occur in planes in which radiation patterns are not usually taken.
  • a directive antenna obtained by spacing the slots about a guide wavelength on one side of the centre line and exciting them approximately in phase would result in large second order beams due to the slot spacing being greater than a free space wavelength, it was generally thought that this defect was overcome and at the sametime the directive feature of the array was retained by spacing the slots approximately half a guide wavelength apart and re* versing the phase of alternate slots by staggering them about the centre line.
  • these second order beams from a slotted waveguide antenna are reduced to an amount dependent only on a asymmetries in excitation of the slots and on the limits in the accuracy of construction of the slotted waveguide by having the longi tudinal centre lines of the slots in a broad face: of the waveguide collinear and the narrow faces of the waveguide shaped so that the centre linebetween them in the plane of said broad face of the waveguide is sinuous and lies between each. slot and the next adjacent slots.
  • a microwave antenna comprises a waveguide of substantially rectangular cross-section having two opposite narrow faces and two relatively broad faces, thewaveguide having formed in a broad face thereof a series of slots substantially resonant for a wave of given wavelength and of substantially greater length than width, the centres of the slots of the series being spaced along the waveguide at intervals of less than substantially seven-eighths of said wavelength in free space, the longitudinal centre lines of the slots being substantially collinear, the narrow faces of the waveguide being shaped so that the centre line between the narrow faces is sinuous and lies on opposite sides of adjacent slots, and the distance of substantially every slot from the centre line between the narrow faces being at least substantially the same as said distance for either adjacent slot.
  • Figure 1 is a perspective diagrammatic view of a slotted waveguide micowave antenna according to the prior art
  • Figure 2 is a perspective representation of second order beams produced by a prior art antenna as shown in Figure 1;
  • Figure 3 is a perspective view of a section of a slotted waveguide microwave antenna ac cording to the present invention,- with its rear broad face removed;
  • Figure 4 is typical radiation patterns for a prior art antenna and for an antenna according to the present invention
  • FIG. 1 A prior Watson and Guptill slotted waveguide antenna is shown in Figure 1, where a slotted rectangular waveguide lll has longitudinal slots H in one of its broad faces l2. Adjacent slots II are staggered about the centre line l3 of the broad face l2. As explained in the Watson and Guptill copending application, as well as in the paper and book by W. H. Watson, referred to above, the dimensions of the slots II should be such that they are resonant for the wavelength of the microwave to be radiated and are of substantially greater length than width. It is also explained in the references mentioned that the distance of the slots I I from the centre line 13 controls the amount of radiation from the slots H.
  • the prior art antenna of Figure 1 is shown in dotted line in Figure 2 with the second order beams l6 and I! shown in full line.
  • the second order beams l6 and I! have, respectively, broad maxima 18, I9 and 20, 2
  • the maxima are at (0 and 5 as indicated in Figure 1):
  • a is a weighted mean slot offset. This weighted mean is close to the amount of offset of the slot which is most strongly excited.
  • the second order beams l6 and I! may be ten per cent of the main beam.
  • a slotted waveguide antenna according to the present invention is shown in Figure 3.
  • a series of slots II are arranged with their longitudinal centre lines collinear and with their centres spaced along a broad face I2 of a waveguide.
  • the spacing between the centres of adjacent slots H must be less than substantially seven-eighths of the wavelength in free space of the microwave to which the slots II are resonant.
  • the slots H are spaced at one-half the wavelength in the waveguide.
  • the rear broad face of the waveuide is not shown so that the inner construction of the waveguide can be seen.
  • the rear broad face can be secured in position by screws which are driven into tapped holes 22 and the rear broad face is then sweated to the edges 23 of the narrow faces 24 to secure good electrical contact throughout the lengths of the faces.
  • the front broad face [2 is mounted in the same manner.
  • the narrow faces 24 are each corrugated so that the sinuous centre line 25 lies on opposite sides of adjacent slots as shown in Figure 3, where a depression 25 in one of the narrow faces 24 is directly opposite a protuberance 21 in the other narrow face 24.
  • the complete antenna would be terminated by a reflectmg plunger, or other similar device, arranged in the waveguide at a distance, equal to one-quarter of the wavelength in the waveguide of the wave to which the slots l I are resonant, from the centre of the slot 1 l in the waveguide furthest from the point at which the waveguide is to be fed with a microwave.
  • the slots H are all in line and are excited at the desired amplitude and phase by the displacement of the sidewalls (narrow faces 24) from the collinear longitudinal centre lines of the slots II.
  • the corrugations in the side walls may be relatively shallow.
  • very close mechanical tolerances are required since small asymmetries in the excitation of every alternate slot may cause small second order beams in the axial plane of the main beam.
  • Figure 4 shows typical radiation patterns for a prior art slotted waveguide type of antenna and for a slotted waveguide type of antenna according to the present invention.
  • Each of the graphs is relative field strength plotted against the angle ( Figure 1) and each of the graphs for the same antenna is for a different angle 4: ( Figure 1). It is clear, from a comparison of the field strengths of the two antennas for the same angle it, that, with an antenna according to the invention, the undesirable second order beams I6 and I! are greatly reduced although the main beam 26 is practically unchanged.
  • a directive antenna for microwaves comprising a waveguide of substantially rectangular cross-section with two opposite narrow faces and two relatively broad faces, the waveguide having formed in a broad face thereof a series of slots substantially resonant for a wave of a given wavelength and of substantially greater length than width, the centres of the slots of the series being spaced along the waveguide at intervals of less than substantially seven-eighths of said wavelength in free space, the longitudinal centre line-s of the slots being substantially collinear, the narrow faces of the waveguide being shaped so that the centre line between the narrow faces in the plane of the broad face containing the series of slots is sinuous and lies on opposite sides of adjacent slots, and the distance of substantially every slot from the centre line between the narrow faces being at least substantially the same as said distance for either adjacent slot.
  • a directive antenna as claimed in claim 1 in which the centres of the slots are spaced along the waveguide at intervals of half the wavelength in the waveguide of the wave to which the slots are resonant.
  • a directive antenna as claimed in claim 1 in which the narrow faces of the waveguide are corrugated, each depression in one of said narrow faces being directly opposite a protuberance in the other narrow face, and the longitudinal centre lines of the slots are substantially collinear with a centre line between straight lines joining the innermost projections of the protuberances of said narrow faces into the waveguide.
  • a directive antenna as claimed in claim 3 in which the centres of the slots are spaced along the waveguide at intervals of half the wavelength in the waveguide of the wave to which the slots are resonant.
  • each corrugation in each of the narrow faces of the guide is rectangular in shape having its longer side substantially parallel and opposite to the longitudinal centre line of a slot and of substantially the same length as said slot.
  • a directive antenna as claimed in claim 5 in which the centres of the slots are spaced along the waveguide at intervals of half the wavelength in the waveguide of the wave to which the slots are resonant.

Landscapes

  • Waveguide Aerials (AREA)
  • Aerials With Secondary Devices (AREA)
US216717A 1951-03-21 1951-03-21 Microwave antenna Expired - Lifetime US2639383A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
NL7506610.A NL162753B (nl) 1951-03-21 Werkwijze voor het opbrengen van een bekledingslaag op een draagband, alsmede inrichting voor het toepassen van deze werkwijze.
NL77126D NL77126C (nl) 1951-03-21
US216717A US2639383A (en) 1951-03-21 1951-03-21 Microwave antenna
GB15686/51A GB681697A (en) 1951-03-21 1951-07-02 Microwave antennas
DEN4217A DE884970C (de) 1951-03-21 1951-07-25 Richtantenne fuer Mikrowellen
FR1114807D FR1114807A (fr) 1951-03-21 1951-07-27 Antenne pour ondes ultra-courtes

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US216717A US2639383A (en) 1951-03-21 1951-03-21 Microwave antenna

Publications (1)

Publication Number Publication Date
US2639383A true US2639383A (en) 1953-05-19

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Family Applications (1)

Application Number Title Priority Date Filing Date
US216717A Expired - Lifetime US2639383A (en) 1951-03-21 1951-03-21 Microwave antenna

Country Status (5)

Country Link
US (1) US2639383A (nl)
DE (1) DE884970C (nl)
FR (1) FR1114807A (nl)
GB (1) GB681697A (nl)
NL (2) NL162753B (nl)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3100300A (en) * 1956-10-10 1963-08-06 Carlyle J Sletten Antenna array synthesis method
US5028933A (en) * 1988-03-21 1991-07-02 Unisys Corporation Radial waveguide channel electronic scan antenna
CN106058476A (zh) * 2016-06-17 2016-10-26 中国人民解放军国防科学技术大学 高功率微波密布缝隙波导天线
WO2017220631A1 (fr) * 2016-06-22 2017-12-28 Universite De Rennes 1 Guide metallique d'ondes electromagnetiques a fentes, ayant une forme generale de serpentin

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1557601A (nl) * 1958-04-08 1969-02-21
GB1212556A (en) * 1968-07-01 1970-11-18 Marconi Co Ltd Improvements in or relating to slotted wave guide aerials

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2567748A (en) * 1943-10-02 1951-09-11 Milton G White Control of wave length in wave guides
US2574433A (en) * 1943-10-01 1951-11-06 Roger E Clapp System for directional interchange of energy between wave guides and free space
US2573746A (en) * 1945-09-19 1951-11-06 Honorary Advisory Council Sci Directive antenna for microwaves

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2574433A (en) * 1943-10-01 1951-11-06 Roger E Clapp System for directional interchange of energy between wave guides and free space
US2567748A (en) * 1943-10-02 1951-09-11 Milton G White Control of wave length in wave guides
US2573746A (en) * 1945-09-19 1951-11-06 Honorary Advisory Council Sci Directive antenna for microwaves

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3100300A (en) * 1956-10-10 1963-08-06 Carlyle J Sletten Antenna array synthesis method
US5028933A (en) * 1988-03-21 1991-07-02 Unisys Corporation Radial waveguide channel electronic scan antenna
CN106058476A (zh) * 2016-06-17 2016-10-26 中国人民解放军国防科学技术大学 高功率微波密布缝隙波导天线
CN106058476B (zh) * 2016-06-17 2018-12-21 中国人民解放军国防科学技术大学 高功率微波密布缝隙波导天线
WO2017220631A1 (fr) * 2016-06-22 2017-12-28 Universite De Rennes 1 Guide metallique d'ondes electromagnetiques a fentes, ayant une forme generale de serpentin
FR3053163A1 (fr) * 2016-06-22 2017-12-29 Univ Rennes Guide metallique d'ondes electromagnetiques a fentes, ayant une forme generale de serpentin

Also Published As

Publication number Publication date
FR1114807A (fr) 1956-04-17
DE884970C (de) 1953-07-30
NL77126C (nl)
GB681697A (en) 1952-10-29
NL162753B (nl)

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