US3456261A

US3456261A - Slotted waveguide aerial system

Info

Publication number: US3456261A
Application number: US568162A
Authority: US
Inventors: Mervyn James Crumpen
Original assignee: Marconi Co Ltd
Current assignee: BAE Systems Electronics Ltd
Priority date: 1965-08-16
Filing date: 1966-07-27
Publication date: 1969-07-15
Anticipated expiration: 1986-07-15
Also published as: DE1541481A1; SE349901B; GB1142787A

Description

July 15, 1969 M. J. CRUMPEN 3,456,261

SLOTTED WAVEGUIDE AERIAL SYSTEM Filed July 27, 1966 PR/oR ART INVENTOE MQW W TTOENEYJ United States Patent O U.S. Cl. 343-768 6 Claims ABSTRACT OF THE DISCLOSURE A slotted waveguide aerial system includes a length of waveguide having a narrow wall` slotted with in-phase slots on one side of the middle of the length of guide and with anti-phase slots on the other side so that if the guide is fed at the centre point or co-phasially at its two ends the in-phase and anti-phase slots each have the same main direction of beam radiation.

This invention relates to aerial systems and more specically to aerial systems of the slotted waveguide type. Aerial systems of this type are in wide use for directional radio transmission and reception, one very important use being in airborne Doppler navigation systems.

One of the diiculties encountered when a slotted waveguide directional aerial is employed is that the main direction (the direction of the principal lobe in the polar radiation diagram) varies with frequency and if therefore the associated transmitter drifts in frequency there will be a consequent undesired change in directivity. Temperature variations will also cause undesired changes in directivity. It is customary to meet these difficulties by constituting a slotted waveguide aerial system by two slotted waveguides, one an irl-phase guide and the other an anti-phase guide, each fed at one end and suitably loaded at the other, the two guides being so arranged as to have a common main direction. With such a two-guide system frequency drift and temperature variation effects in the two guides practically cancel out so far as the main direction is concerned so that this direction remains praetically constant. However this expedient has the defect of being costly and resulting in a considerable increase in space and weight, because two guides are required. The defects of bulkiness and weight are particularly objectionable in the case of airborne equipments. The object of the present invention is to avoid these defects.

According to this invention a slotted waveguide aerial system comprises a length of waveguide which is provided within-phase slotting on one side of an intermediate point in said length and with anti-phase slotting on the other side of said intermediate point, the slotting being such that if the guide is fed at said intermediate point or is fed cop'nasially at its two ends, the in-phase and antiphase slotting provide a common main direction.

A preferred embodiment comprises a length of rectangularly sectioned waveguide with one narrow wall slotted with in-phase slots on one side of the middle of said length and with anti-phase slots on the other side thereof.

In one arrangement the length of guide is provided with feeder means at said intermediate point and the outer ends of the guide length are reflectionlessly terminated eg. by suitably dimensioned terminating resistances or by short circuiting diodes as known per se. Alternatively means may be provided for feeding the outer ends of the guide length in phase and the guide may be loaded at the intermediate point by a suitable resistance or diode. Obviously the common main direction will be different when the guide is centre fed from what it is when the ice guide is end fed and where it is required to change over the common main direction from one to the other (as will often be the case in an airborne Doppler navigation system) suitable waveguide switch mea-ns may be provided for changing over from centre feed to end feed and vice versa.

The invention is illustrated in and further explained in connection with the accompanying drawings in which:

FIGURE l shows a commonly employed known aerial system with two slotted guides, and

FIGURE 2 shows an embodiment of this invention.

Referring to FIGURE l, one waveguide 1 has in-phase slotting constituted by a plurality of parallel radiating slots 2 in one narrow wall thereof, and the other waveguide 6 has anti-phase slotting constituted by two

sets

7 and 8 each of parallel slots, those of set 7 alternating with and being oppositely inclined with respect to those of set 8 so that each slot in one set is a mirror image of an adjacent slot in the other. The guides are side by side and are fed at opposite ends 3 in the case of guide 1 and 9 in the case of guide 6) in phase from a common source (not shown). The other ends of the guides are terminated by matched loads 4. The two waveguides, fed as described, will have a common direction of principal radiation, indicated by the

arrows

5 and 11 which will remain substantially unchanged by any variation of frequency or temperature likely to be encountered in practice. However the installation involves two guides and to that extent is costly, bulk and heavy.

The embodiment of this invention, shown in FIGURE 2, has only a single guide 12. This guide has one narrow wall slotted with in-phase slots 13 (the counterpart of the slots 2 of guide 1 of FIGURE 1) and anti-phase slots 14 (the counterpart of the

slots

7 and 8 of guide 6 of FIG- URE 1). The in-phase slots are on one side of the middle of the guide `4 and the anti-phase slots are on the other side thereof. As indicated diagrammatically, a central feeder 15 is provided and the

ends

16 and 17 of the guide are terminated by matching loads 4. As indicated by the

parallel arrows

18 and 19 there is a common principal direction for radiation from the two

sets

13, 14 of slots. Alternatively the guides could be fed in phase at their ends from a common source and terminated by a matching load at the centre. This also results in a common principal direction though, of course, it is different from that indicated by the

arrows

18 and 19 and is as indicated by the

broken line arrows

18 and 19. If desired suitable switching means (not shown) may be provided for changing over from centre feed to end feed and vice versa aud thus changing over from one common principal direction to the other.

I claim:

1. A slotted waveguide aerial system comprising a length of waveguide which is provided on one side of an intermediate point in said length with a first plurality of slots which are arrayed along said length and are oriented in-phase with respect to one another, and is further provided on the other side of said intermediate point with a second plurality of slots which are arrayed along said length, some of said second plurality of slots being oriented irl-phase with respect to one another and are oriented anti-phase with respect to others of said second plurality of slots, the slotting being such that the in-phase and anti-phase slotting provides a common main direction when the guide is fed in one of the following ways, namely: (l) fed at said intermediate point, and (2) fed cophasially at its two ends.

2. An aerial system as claimed in claim 1 comprising a length of rectangularly sectioned waveguide with one narrow wall slotted with in-phase slots on one side of the middle of said length and with anti-phase slots on the other side thereof.

3. An aerial system as claimed in claim 1 wherein the length of guide is provided with feeder means at said intermediate point and the outer ends of the guide length are reectionlessly terminated.

4. An aerial system as claimed in claim 1 wherein means are provided for feeding the outer ends of the guide length in phase and the guide is loaded at the intermediate point.

5. A slotted waveguide aerial system comprising a length of waveguide which is provided on one side of an intermediate point in said length with a first plurality of slots which are arrayed along said length and are oriented in-phase with respect to one another, and is further provided on the other side of said intermediate point with a second plurality of slots which are arrayed along said length, some of said second plurality of slots being oriented in-phase with respect to one another and are oriented anti-phase with respect to others of said second plurality of slots, the slotting being such that the in-phase and anti-phase slotting provides a common main direction when the guide is fed at said intermediate point.

6. A slotted waveguide aerial system comprising a length of waveguide which is provided on one side of an intermediate point in said length with a first plurality of slots which are arrayed along said length and are oriented irl-phase with respect to one another, and is further provided on the other side of said intermediate point with a second plurality of slots which are arrayed along said length, some of said second plurality of slots being oriented in-phase with respect to one another and are oriented anti-phase with respect to others of said second plurality of slots, the slotting being such that the in-phase and anti-phase slotting provides a common main direction when the guide is fed cophasially at its two ends.

References Cited UNITED STATES PATENTS 3,293,645 12/1966 Farley et al. 343770 HERMAN K. SAALBACH, Primary Examiner M. NUSSBAUM, Assistant Examiner U.S. Cl. XR.