US3803620A

US3803620A - Continuous scanning waveguide antenna

Info

Publication number: US3803620A
Application number: US00353129A
Authority: US
Inventors: D Young
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-04-20
Filing date: 1973-04-20
Publication date: 1974-04-09
Anticipated expiration: 1991-04-09

Abstract

A repeated scanning of a given beam pattern from a waveguide antenna is accomplished by passing metallic material transversely through the waveguide in a repetitive manner to vary the phase velocity of electromagnetic energy propagated along the waveguide. This type of scanning is carried out by providing alternate segments of conductive and dielectric material on a plurality of rings coaxially arranged and uniformly spaced in positions such that the rings all pass through a series of longitudinally spaced openings in opposite walls of the waveguide. By rotating the rings in synchronism, the entering and leaving of the conductive segments or slugs in the interior of the waveguide in a direction transverse to the waveguide axis effects the repetitive type scanning. The advantage of the arrangement is that the scanning can be very fast and is essentially linear throughout the entire angular sweep of the beam pattern.

Description

United States Patent [191 Young [451 Apr. 9, 1974 CONTINUOUS SCANNING WAVEGUIDE ANTENNA [76] Inventor: David W. Young, 4033 Via Marina Apt. G316, Marina Del Rey, Calif.

[22] Filed: Apr. 20, 1973 [21] Appl. No.: 353,129

[52] US. Cl 343/768, 343/771, 343/778, 343/854 [51] Int. Cl. H0lq 3/26, l-lOlq 13/20 [58] Field of Search 343/767, 768, 770, 777, 343/778, 854, 771

[56] References Cited UNITED STATES PATENTS 3,568,208 3/1971 Hatcher et al. 343/768 Primary Examiner--James W. Lawrence Assistant Examiner-Marvin Nussbaum Attorney, Agent, or Firm-Ralph B. Pastoriza, Pastoriza and Kelly [5 7] ABSTRACT A repeated scanning of a given beam pattern from a waveguide antenna is accomplished by passing metallic material transversely through the waveguide in a repetitive manner to vary the phase velocity of electromagnetic energy propagated along the waveguide. This type of scanning is carried out by providing alternate segments of conductive and dielectric material on a plurality of rings coaxially arranged and uniformly spaced in positions such that the rings all pass through a series of longitudinally spaced openings in opposite walls of the waveguide. By rotating the rings in synchronism, the entering and leaving of the conductive segments or slugs in the interior of the waveguide in a direction transverse to the waveguide axis effects the repetitive type scanning. The advantage of the arrangement is that the scanning can be very fast and is essentially linear throughout the entire angular sweep of the beam pattern.

6 Claims, 7 Drawing Figures CONTINUOUS SCANNING WAVEGUIDE ANTENNA This invention relates generally to waveguide type antennas and more particularly to an improved waveguide beam scanning antenna providing an essentially linear sweep scan with continuous motion.

BACKGROUND OF THE INVENTION Scanning type waveguide antennas are known in the art and include both mechanical and electrical phase shift systems for effecting the scanning operation. The most frequent use for such waveguide type scanners is in radar systems.

Mechanical type scanning of a beam from a waveguide has been accomplished by either introducing conductive surfaces into the interior of the waveguide or changing the cross section dimensions of the waveguide, both actions serving to shift the phase velocity of electromagnetic energy propagated down the guide in a manner to effect a scanning of the output beam. Normally the output beam is provided by resonating slots in a side wall of the waveguide.

In my co-pending patent application Ser. No. 353,201 filed Apr. 20, i973 and entitled RIDGE SCAN ANTENNA there is described and shown a greatly improved radar waveguide scanning antenna wherein a ridge member is mechanically moved into and out from a longitudinal side wall of the antenna resulting in a back and forth scanning of the coupled out energy beam. In this particular type of waveguide antenna, coupling out of the energy is accomplished by means of a series of small holes or groups of holes longitudinally distributed along a side wall of the antenna, the dimensioning of the holes themselves being below cut-off so as to be non-resonant. Although by certain theory the coupling out of the energy would normally be inefficient, it is found that a high degree of efficiency can be realized by proper hole size, distribution, and provision of a thinned wall portion through which the hole pass, and by suitable impedance coupling media cooperating with the holes.

The type of beam produced by the waveguide above described in my co-pending application is that of a fan shape, the plane of the fan being normal to the longitudinal direction of the waveguide. The fan itself may be sweep back and forth through a given angle by means of the reciprocating ridge member introduced into the interior of the waveguide.

In waveguide scanning antennas of the foregoing type, the sweeping of the beam is back and forth taking place at a speed which varies sinusoidally. As a consequence, the beam is moving slower at the limits of its angular movement than is the case when it scans through the central portion of the overall angle of scan. The sinusoidal characteristic of the scan is a direct consequence of the sinusoidal movement of the ridge member in carrying out the scanning. While the scanning beam is linear with respect to movement of the ridge in my above described ridge antenna, most scanning systems provide a non-linear scan as a function of linear displacement of the scanning element, such as a change in the width of the waveguide.

It would be highly desirable if a waveguide type scanning antenna could be devised wherein the scan was essentially linear in time as well as linear with the mechanical position of the scanning element rather than varying non-linearly. Further, it would help in some instances if the scan was consistent in one direction so that the whole area of the reproduced picture on a radar screen would be consistent and of equal intensity or strength. In otherwords, there would not be involved dwell times of the scanning beam over certain portions of the ground or other areas the beam scanned. Finally, it would be desirable if a mechanical system could be devised to effect a continuous scanning in a linear manner which avoided reciprocating elements. The elimination of reciprocating elements enormously simplifies any type of mechanical configuration and will considerably lengthen the life of operation of such configuration as well as permit the speed of scanning to be greatly increased.

BRIEF DESCRIPTION OF THE PRESENT INVENTION Bearing in mind the foregoing, the present invention contemplates an improved waveguide scanning antenna functioning similarly to the ridge scan antenna described in my co-pending applicationbut wherein a repetitive linear scan is effected by continuous motion of the scanning means. The scan will start at one angular limit and sweep essentially linearly through a given angle to its other limit. The antenna does not effectively radiate beyond the limit to result in a stop band. In a first embodiment, the scan after the stop band period will scan from the other angular limit back to the one angular limit and immediately a next back and forth sweep takes place. In a second embodiment, the scan takes place in one direction only, each sweep being separated by a stop band.

In both embodiments, the repetitive scanning can take place at an extremely high rate. Further, the invention accomplishes such scanning in a manner avoiding reciprocating mechanical movement all to the end that a desired high scanning rate can be achieved with minimum mechanical wear.

Briefly, the continuous scanning antenna of the invention comprises a waveguide for receiving electromagnetic energy in one end and having a series of holes in one longitudinal side wall dimensioned below cut-off so as to be non-resonant, the holes coupling energy out from the waveguide in a manner to define a given beam pattern. In this respect, the antenna is similar to that described in my co-pending application.

Rather than a ridge member reciprocating into and out of one wall of the antenna to effect scanning, in accord with the present invention there is provided at least one ring member and preferably a plurality of ring members including alternate segments of conductive and dielectric material. Means are provided for supporting the rings for rotation about an axis generally parallel to and spaced from the longitudinal axis of the waveguide such that the rings pass into one wall of the waveguide and out an opposite wall.

With the foregoing arrangement, the alternate segments traverse the interior of the waveguide in a direction substantially normal to and intersecting the waveguide axis thereby varying the phase velocity of energy propagated along the waveguide in a manner to effect a repeated scanning of the given beam pattern at a very rapid rate. If the continuous direction of rotation of the various rings is reversed, the scan will take place in an opposite sense in a repetitive manner and each scan itself will be linear. l

Since the scanning is accomplished by a continuous rotation of the rings, reciprocating parts are avoided and very high scanning rates for the scanning can be achieved with minimum mechanical wear.

BRIEF DESCRIPTION OF THE DRAWINGS A better understanding of the invention will be had by now referring to one example thereof as illustrated in the accompanying drawings in which:

FIG. 1 is a perspective fragmentary view of basic components making up the continuous scanning waveguide antenna of the invention;

FIG. 2 is a cross section of the antenna taken in the direction of the arrows 2-2 of FIG. 1;

FIG. 3 is an enlarged fragmentary cross section transversely through the waveguide of FIG. 2;

FIG. 4 is a fragmentary plan view on a reduced scale of the waveguide of FIG. 2;

FIG. 5 graphically illustrates the repetitive scanning pattern as a function of time of the antenna;

FIG. 6 is a cutaway perspective view of a modified embodiment; and,

FIG. 7 depicts the scanning pattern for the embodiment of FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION Referring first to FIG. 1 there is illustrated in fragmentary form an elongated waveguide 10 having a longitudinal axis A-A. The waveguide 10 may be similar to that shown in certain embodiments of my RIDGE SCAN ANTENNA set forth in my heretofore referred to co-pending application except that instead of a ridge member entering and leaving the waveguide, there are provided at least one and preferably a plurality of rings 11.

As shown in FIG. 1, means are provided for supporting the rings 11 in coaxial relationship with their axis, designated B-B spaced from and parallel to the waveguide axis A-A. This supporting means may take the form of at least three rollers shown at l2, l3, and 14. The arrangement is such that one side of the rings pass in rolling tangential engagement with two of the spaced rollers such as 13 and 14 the other side, which in the embodiment illustrated constitutes the inside of the rings, tangentially engages the third roller 12 at a point between the other two rollers. Means for rotating one of the rollers such as 12 is schematically indicated by the motor M.

In the embodiment illustrated in FIG. 1, the waveguide includes serially spaced groups of

holes

15 and 16 along the top and bottom longitudinal edges of the top and

bottom walls

17 and 18 respectively. These holes are dimensioned below cutoff so as to be nonresonant and serve to couple energy out from the waveguide in a manner to define a given beam pattern. The means in the form of the rollers support the various rings in such a manner that the rings pass into one wall of the waveguide, preferably the top wall 17 as shown and out an opposite wall such as the wall 18. In FIG. 1, the separation distance between the rings is greatly exaggerated for purposes of clarity. Actually, this separation distance is made substantially less than one half wave length so as to be well below cut-off.

With reference to FIG. 2, each of the rings 11 is made up of alternate segments of conductive material 19 and dielectric material 20. In the case of the particular rings illustrated in FIGS. 1 and 2, the cross section of the ring is rectangular and thus the segments of conductive material 20 are in the form of parallelepiped shaped slugs with their leading and trailing surfaces slightly out of parallelism in order to follow the contour of the ring. Each of these conductive slugs has six surfaces which are all highly conductive. The cross section and waveguide wall openings for the rings could be circular in which event the slugs would be of cylindrical shape.

The alternately disposed segments 20 of dielectric material may constitute a plastic foam or equivalent non-conductive dielectric.

As will be clear from FIG. 2, when the rings 11 are rotated as by the rollers, the alternate segments will traverse the interior of the waveguide in a direction substantially normal to and intersecting the waveguide axis A. The presence of the conductive slugs entering the waveguide serves to vary the phase velocity of electro' magnetic energy propagated along the waveguide in a manner to effect a repeated scanning of the given beam pattern in a back and forth direction, the slugs passing into and leaving the guide in a symmetrical manner.

With the use of a plurality of rings, the conductive slugs will be entering the waveguide over a substantial longitudinal axial distance of the guide. It is very important that a synchronous relationship exists between the rings in order that all of the slugs will enter simultaneously. Towards this end, the driving roller 12 may be provided with a longitudinal bead 21 or slight projection coextensive with its length. This head is arranged to index in grooves such as indicated at 22 formed on the inside surface of the various rings, the circumference of the roller 12 equalling the arcuate distance between the grooves. With this arrangement, consistent indexing of the rings is assured so that they will rotate at precisely the same speeds and in exact synchronism.

In FIG. 2, it will be noted that the waveguide 10 includes entrance and exit channels in the form of

walls

23 and 24 running longitudinally along the top wall of the waveguide and

walls

25 and 26 running longitudinally along the bottom wall 18. These walls define parallel conductive surfaces between which the rings pass in entering and leaving the waveguide.

Referring now to FIG. 3, further details of the

openings

15 and 16 for coupling energy out from the guide will be evident. As shown, the top and

bottom walls

17 and 18 include reduced thickness portions 17' and 18 in which the series of

holes

15 and 16 are formed. Between this reduced thickness portion and the top wall portion 27 of the guide there is defined a thin slot 28 from which radiation takes place.

Similarly, between the lower reduced thickness wall portion 18' and the bottom edge surface 29 of the waveguide there is defined a slot opening 30 from which radiation is coupled out from the guide. Entrance and exit of the ring segments takes place through windows 31 and 32 in the top and

bottom walls

17 and 18 respectively. Preferably,

metallic portions

33 and 34 provide extended conductive surfaces adjacent to the slots for coupling out energy. These coupling surfaces together with a dielectric member 35 match the energy from the slots into a common forward area for radiation to the left as viewed in FIG. 3.

The group of small holes in the upper and lower edge portions of the longitudinal walls of the guide are staggered as shown in FIG. 1 in a manner to provide scanning through broadside.

The foregoing will be more evident by referring to the plan view of FIG. 4 of the waveguide wherein the radiated beam is indicated by the letter P which beam sweeps from a minus 0 angle to a plus 0 angle through broadside.

Referring to FIG. 5, the repetitive scans efi'ected as the metallic slugs of the rings pass through the guide are graphically indicated by the

lines

36, 37, 38, and 39. It will be noted that the scan is linear from one limit of the angle of scan to the other limit of the angle of scan and that the scanning is back and forth with stop bands" 40 and 41 between the reversal of scan direction at the plus 0 limit.

When the metallic slug is centrally positioned in the waveguide there will be little if any useful radiation from the

slots

28 and 30 of FIG. 3. The

stop bands

40 and 41 indicate this lack of radiation on the time scale shown in FIG. 5.

From the foregoing, it will'be appreciated that the scanning beam when used as a radar beam will sweep over a given area in a uniform manner, there being no dwell time at the ends of the limits of scan as characterizes conventional back and forth sinusoidal scanmng.

In addition to the foregoing featues of linearity and equally distributed scanning energy, the use of rings continuously rotating in one direction provides for a very simply and neat mechanical arrangement. In other words, there is avoided the use of any reciprocating type of mechanical elements for effecting the scan. As a consequence, very high scanning rates can be achieved since the rings can be rotated at a very high speed without any appreciable vibration.

Referring now to FIG. 6, there is shown a modified embodiment of the invention wherein the pattern scans from one end limit up to broadside but not through broadside and wherein the scanning takes place consistently in one direction between these limits. As shown, a waveguide 42 is provided with a series of small holes 43 in closely spaced side by side relationship between one edge and the longitudinal center line of the top wall. These holes are dimensioned below cut-off and preferably are covered with dielectric strips 44 to increase the coupling out efficiency of energy.

Upper wall members

45 and 46 define an entrance channel for the various rings, these walls being closed by a top wall 47 provided with a series of windows 48 for receiving the rings. As in the case of the showing of FIG. I, the separation distance between the rings and windows 48 is greatly exaggerated for purposes of clarity. Actually, such separation distance is substantially less than one half wave length.

The bottom wall of the waveguide includes

exit channel walls

49 and 50 extending from windows 51 in the bottom wall of the waveguide itself. In this respect, the lower porition of the waveguide is similar to the lower structure shown in FIG. 3.

The short vertical wall of the waveguide 42 adjacent to the series of holes 43 includes an extended flange structure 52 to define a metallic conducting surface together with the outer surface of the wall 46 for coupling energy from the holes in an upward direction.

Because of the assymetrical relationship between the entrance and exit channels as shown in FIG. 6 wherein there is provided a continuous channel opening in the top wall of the waveguide and the windows receiving the rings are formed in the top portion of the

entrance channel walls

45 and 46, the scanning of the beam takes place essentially in only one direction between broadside and one end of the waveguide. This scanning pattern is depicted in FIG. 7 wherein repetitive scans are indicated at 53, 54, 55, and 56. When the metallic slug portion of the ring is fully centered in the guide, there results the heretofore described situation of no useful radiation resulting in stop bands" such as indicated at 57 in FIG. 7. It will be noted in FIG. 7 that the sweep angle extends between broadside or zero degrees and one end of the guide.

From the foregoing, it will be evident that the present invention has provided a vastly improved scanning system for waveguide type antennas particularly useful in radar and in applications involving perspective radar such as referred to in my previously mentioned copending patent application.

What is claimed:

1. A continuous scanning antenna comprising, in combination:

a. a waveguide for receiving electromagnetic energy in one end and having a series of holes in one longitudinal side wall dimensioned below cut-off so as to be non-resonant, said holes coupling energy out from the waveguide in a manner to define a given beam pattern;

b. at least one ring member including alternate segments of conductive and dielectric material making up the ring; and,

c. means supporting said ring for rotation about an axis generally parallel to and spaced from the longitudinal axis of the waveguide such that the ring passes into one wall of the waveguide and out an opposite wall, the alternate segments traversing ,the interior of the waveguide in a direction substantially normal to and intersecting the waveguide axis to thereby vary the phase velocity of energy propagated along the waveguide in a manner to effect a scanning of said given beam pattern which is essentially linear in time.

2. An antenna according to claim 1, including a plurality of rings constructed similarly to and coaxial with said one ring, said rings being uniformly spaced along the axis of the one ring to define a generally cylindrical shape, said means for supporting the one ring for rotation also supporting the remaining rings for simultaneous rotation in synchronism so that an elongated axial portion of the interior of said waveguide is subject to the alternate passing normally therethrough of the conductive and dielectric segments of the rings.

3. An antenna according to claim 2 in which the exterior portions of said one and opposite walls through which the rings pass include conductive walls defining entrance and exit channels for the rings on opposite sides of the waveguide so that the waveguide appears generally cruciform in cross section, the cruciform cross section comprising an extrusion.

4. An antenna according to claim 2, in which said means supporting the rings for simultaneous rotation in synchronism includes at least three rollers in the form of elongated cylindrical bodies all parallel to each other and to the axis of the rings and positioned so that one side of the rings pass in rolling tangential engagement with two of the spaced rollers and the other side of the rings tangentially engage the third roller between the other two rollers; and means for rotating one of the rollers to thereby rotate the rings simultaneously, a side of each ring and one of the rollers including cooperating groove and bead structures arranged to index together at their tangential engagement points during rotation to assure synchronous rotation of all of the rings.

5. An antenna according to claim 3, in which said one and opposite wall of the waveguide include windows through which the rings pass, said series of holes being formed in groups staggered adjacent to the upper and lower edges of said walls, the walls including edge slots communicating with the holes; cooperating conductive surfaces projecting beyond the edges; and a dielectric between the surfaces to provide for a beam pattern which is scanned through broadside upon rotation of the rings.

6. An antenna according to claim 3, in which said entrance channel includes a top wall having a series of window openings through which said rings enter the channel to pass into the waveguide, the opposite wall of the waveguide having a series of windows through which the rings exit from the waveguide into the exit channel, said series of openings extending along said one wall between the longitudinal center line of the wall and one edge; dielectric material overlying said series of holes; and an upwardly extending metal flange at said one edge defining with an exterior wall of said entrance channel guiding conductive surfaces to provide for a beam pattern which is scanned between broadside and one end of the waveguide upon rotation of the rings.

Claims

1. A continuous scanning antenna comprising, in combination: a. a waveguide for receiving electromagnetic energy in one end and having a series of holes in one longitudinal side wall dimensioned below cut-off so as to be non-resonant, said holes coupling energy out from the waveguide in a manner to define a given beam pattern; b. at least one ring member including alternate segments of conductive and dielectric material making up the ring; and, c. means supporting said ring for rotation about an axis generally parallel to and spaced from the longitudinal axis of the waveguide such that the ring passes into one wall of the waveguide and out an opposite wall, the alternate segments traversing the interior of the waveguide in a direction substantially normal to and intersecting the waveguide axis to thereby vary the phase velocity of energy propagaTed along the waveguide in a manner to effect a scanning of said given beam pattern which is essentially linear in time.