US2602893A - Wave guide antenna - Google Patents

Description

July 8, 1952 w. H. RATLIFF, JR 2,602,893

WAVE GUIDE ANTENNA Original Filed March 31, 1942 \vAmAaLE FR: uENcy `fioufzcr: Q pity if 53 INVENTOR ATTORNEY Patented July 8, 1952 UNITED s WAVE conm ANTENNA William Hardy Ratliif, Jr., Hempstead, N, Y., as-

signor to The Sperry Corporation, acorporation of Delaware Original application March 31, 1942, Serial No. v 437,004, now Patent No. 2,433,368, dated December 30, 1947. Divided and this application July 17, 1943, Serial No. 495,101

17 claims. (ci. 25a-33.63)

This invention relates generally to ultra high frequency energy radiating or receiving devices and, more particularly, to an improved type ultra high frequency substantially end-lire wave guide radiator or antenna having an adjustable or periodically variable directivity pattern. The present invention constitutes a division of prior copending application Serial No. 437,004, filed March 31, 1942, now Patent No. 2,433,369, issued December 30, 1947.

In the above application Serial No. 437,004, a wave guide antenna is disclosed and claimed, which is adapted to produce a substantially end- `fire radiation pattern. The present invention is directed toward the provision of scanning means for periodically varying the directivity pattern of antennas of the type shown in said prior application. The present invention is also directed toward the utilization of such antenna in instrument landing systems for aircraft and in pulse or other systems. v

One object of the present invention is to provide an improved antenna device Whose directivity may be adjusted or periodically varied.

Another object of the present invention is to provide an improved wave guide antenna having an adjustable or variable directivity pattern.

Still anotherobject of the present invention is to provide simple mechanical or electrical means for varying the eifective directivity axis of a wave guide antenna.

Another object of the present invention is to provide improved high frequency apparatus having a pair of overlapping directivity characteristics suitable for use in instrument landing or automatic landing of aircraft.

Other obj ects and advantages of the present invention will become apparent from the specification, taken in connection with the accompanying drawings wherein the invention is embodied in concrete form.

In the drawings,

Fig. 1 is a perspective view, partly in section, o a Wave guide antenna of the type disclosed in said prior application;

Fig. 2 illustrates one 'type of directivity pattern obtainable by use of the wave guide antenna of Fig. 1;

Fig. 3 illustrates a pair of overlapping directivity patterns obtainable by proper excitation of the antenna of Fig. 1 andv useful in instrument landing systems;

Fig. 4 shows a transversev cross-sectional view of a wave guide antenna similar to that of Fig. 1, incorporating means for adjusting or varying the directivity Pattern thereof; and

Figs. 5, 6, and 7 are similar crossfsectional view of modifications of the device of Fig. 4.

As is described more in detail in the aboveidentified application, the directional radiation pattern or receptivity characteristic of a wave guide antenna of the type shown in Fig. 1,'cmprising a substantially rectangular Wave guide I'l having a lslot l2 formed in the upper face thereof and with side ground plates or launching I4 in the plane of slot l2, Will be of the4 type shown in Fig. 2, namely, a cone having an faxis- I6A extending along the length of the wave'guideantenna Il and produced by rotation of a narrow lobe llrabout the axis I6. The semi-angle'cof this conical radiation pattern will have a value given by where lo is the Wavelength of the high frequency energy in free space and ko is the free space propagation constant, or f 7 o A and 7c are correspondingly the wavelength and propagation constant kfor energy vtraveling Within the Wave guide l l along the length'thereof.

By properly selecting the relationship between the wavelengths of the energy in free space and in the wave guide, any angle 0 may be produced as desired. For example, the theoretically perfect end-nre condition is obtained for 0=0 when the propagation constantis the same within the wave guide as in free space.

As is seen from the above equation, the angle 0 is a function of the exciting wavelength lo in the guide. Thus the angle 0 may be selected by suitably selecting the Wavelength of the exciting energy in relation to the dimensions of the Wave guide. For this purpose, high frequency source 8 is coupled in any conventional manner, as by coupling line 9, to the Wave guide section -i Uffee'ding the slotted guide I l. By varying the exciting frequency of source 8 in any suitable manner, such as by frequency modulation thereof, the radiation pattern of beamof radiant energy may be caused to scan between two limits,` the amount of swing being determined by the frequency swing of the frequency modulated Wave.A Forinstrument landing purposes, the beammaybe swung between two extreme positions indicated bythe directivity patterns I8 and I9 of Fig. 3, having respective anglesi and 02 and providing an equisignal surface which mayV be used to define an instrument landing .path for aircraft if desired.

The present invention may also be utilized to provide pulses of high frequency energy with a highly directive characteristic. Thus, as is well known, wave guides yhave a sharp cut-off frequency below which vthey will pass no energy. It is at this cut-off frequency that the true broad- Side condition takes place. Thus, by frequency modulating the exciting energy derived from source 8 (which may then be a frequency-modulated oscillator) about a mean frequency substantially or exactly equal to the cut-off frequency of the wave guide radiator Il or section Il), the radiating energy may be periodically cut off, so that pulses of radiant energy/Will betransmitted with a highly directive characteristic perpendicular to the length of the wave guide antenna. The character and duration of the pulses may be varied by corresponding variation of the mean frequency of the frequency modulated wave or of the frequency swing or vrof the modulating frequency ofgthis Wave.

As Y another Way of utilizing the invention for instrument landingor similar purposes, two separate frequencies maybe fed to or received by .the ,antenna of Fig. l.v Such separate frequen- -ciesvmay-be fed to-antenna I l by substituting two vseriesc ;1nr le,cted sources for vthe source 8'shown in Fig. 1. Ifthese `frequencies are selected so as to provide the respective directional characteristics I 8'and i9 shown in Fig. 3, their overlapping will -again provide va -sharply defined path for instrument landing purposes or any similar function.

As has been discussed above and is discussed more in detail in the above-mentioned application Serial No. 437,004, the angle of Fig. 2 depends upon the phase velocity of the energy within the Wave guide antenna. This is merely another way of stating that'this angle 0 depends upon the lwavelength of the energy within the wave guide of the antenna or upon the propagation constant of this high frequency energy. By periodically varying this phase velocity, the lobe l1 may be periodically scanned between two limits in a manner similar to that produced by frequency modulating .the .produced energy.

Figs. 4, 5, 6.and 7 show various devices for varying the physical geometry of the wave guide as a desired function of time to produce a corresponding variation of the wave phase velocity and to thereby scan the directivity pattern.

Fig. 4 shows a wave guide 2l of the low slot impedance type described in the above-mentioned application Serial No. 437,004, which may be partially filled with dielectric material in the form of a slab of dielectric material 22 extending along the bottom of this wave guide 2l. Guide 2! may have ground plates or launching plates such as 2D, 20' adjacent the slot 25 therein. If desired, plates 20 may be inclined or curved to modify the directivity of the device. Running through the length of wave guide 2| is a rotatable rectangular rod 23 of dielectric or conducting material, which may be uniformly or otherwise rotated to correspondingly vary the phase velocity of the energy within the guide and thereby vary the directivity characteristic of the radiated energy or received energy. If desired, the rectangular rod 23 vmay merely lbe positioned to adjust the directivity characteristic as desired, for example, to provide lthat shown in Fig. 2 or to approach the end-fire condition. Y

Fig. 5 shows a modification ofthe device of Fig. 4 in which the wave guide 2| may have a slab of dielectric material 22' lining one side thereof,

and also a slab of dielectric material 22" lining the slot walls. The side wall of wave guide 2 I is extended to form a semi-cylindrical portion 24 in which is ylocated a .rotatable semi-cylindrical member Y26 of dielectrioor conducting material. Rotation of member 26 to vary its position within wave guide 2 l will correspondingly vary the Wave phase velocity in a manner similar to that of Fig.

v 4,and will produce the same results as in Fig. 4.

,-Fig. 6 shows still another form of the invention applied'fto .aslightly different form of wave guide 27. Inthis instance one Wall, such as 28, of the Wave guide 2 may be made movable as by means vof a suitablerodg29 or in any other manner. By

Avarying the ,dimensions of the wave guide in this manner, the phase Velocity of the energy in the guide Will be correspondingly varied to either periodically vary or to adjust the directivity characteristic thereof. If desired, a slab of dielectric material 3| may bermoved with the wall 23, and Willmodify the 'wave guide as discussed in application Serial N o. 437,004.

In place of moving 'the entire wall 28, resort may be had-to thefdevjce of Fig. "7, in which the Wall 28 is iixed,`but the slab '3| is shown as movable under the raction of `rod'2r9, actuated, for example, from a Scotch yoke Vmechanism 32 driven from a wheel 33. In'Fig. 7 .themovable slab 3i may be made of dielectric material or conducting material, as desired.

in this manner I have provided an adjustable or variable directivity pattern by use of' a wave guide antenna adapted to radiate or receive ultra high frequency energy. Itis to be understood that the dielectric filling or lining used in Figs. 4, 5, and 6 may be dispensed with where its added effect is not desired. It will be clear that the adjustable antenna or -scanner of the present invention may be utilized equally -well for receiving or transmitting, its directivity characteristic being determined by the considerations mentioned above for either use. The term antenna is intended .as generic both to a receiving antenna. and to a radiating antenna.

As many changes could bemade in the above n construction and many apparently widely differ# vent embodiments of this Vinvention could be made Without departing from the scope thereof, it is intended that all matter contained in the above description `or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A substantially end re directive radiator comprising a rectangular conducting wave guide partially lled with solid dielectric material and excited by electromagnetic waves of substantially linear polarization, and a dielectric `rod within and extending along said guide, said rod being turnable about its longitudinal axis for altering the phase velocity of said waves Within said guide.

2. A substantially end re directive radiator comprising a rectangular conducting Wave guide partially filled with solid dielectric material and excited by electromagnetic waves of substantially linear polarization, a dielectric rod Within and extending along said guide, said rod being turn able about its 'longitudinalaxis for altering the phase velocity of said waves within said guide, said guide having distributed radiating means extending along `the length of the same at right angles to the electric vector of said waves for propagating said `waves into space, the direction of said propagation being shifted as the phase velocity of said waves within said guides is altered by said turnable rod.

3. A substantially end fire directive radiator comprising a rectangular conducting wave guide partially filled with solid dielectric material and excited by electromagnetic waves of substantially linear polarization, and an adjustable dielectric member for varying the phase Velocity of said waves therein, said guide being apertured to enable the radiation of said waves into space, the adjustment of said member changing the radiation pattern of the guide.

4. An end fire directive radiator as defined in claim 3 wherein said member constitutes a portion of the wall of the guide, whereby the adjustment of the member varies the cross-sectional area of the guide.

5. A substantially end fire directive radiator comprising a rectangular conducting Wave guide partially filled with solid dielectric material and excited by electromagnetic waves of substantially linear polarization, an adjustable member for varying the phase velocity of said waves therein, said guide being apertured to enable the radiation of said waves into space, the adjustment of said member changing the radiation pattern of the guide, and means for continuously adjusting said member to thereby continuously Vary the radiation pattern to eiect a scanning operation.

6. A high frequency antenna comprising an elongated hollow-pipe wave guide apertured along the major dimensions thereof, and means for periodically Varying the phase velocity of energy within said hollow-pipe wave guide to thereby periodically vary the directivity pattern produced by said antenna, said last-named means comprising a member extending longitudinally within said Wave guide, and means for periodically varying the position of said member relative to said guide.

7. A high frequency antenna comprising an elongated hollow-pipe wave guide apertured along the major dimensions thereof, and means for periodically Varying the phase velocity of energy within said hollow-pipe Wave guide to thereby periodically vary the directivity pattern produced by said antenna, said last-named means comprising a non-circular rod of dielectric material extending along the length of said wave guide, and means for rotating said rod about an axis parallel to said Wave guide.

8. A high frequency antenna comprising an elongated hollow-pipe wave guide apertured along the major dimension thereof, and means for periodically varying the phase velocity of energy within said hollow-pipe wave guide to thereby periodically vary the directivity pattern produced by said antenna, said last-named means comprising a member of dielectric material extending along the length of said wave guide, and means for periodically and linearly varying the position of said member relative to a wall of said wave guide.

9. A high frequency antenna comprising an elongated wave guide apertured along the length thereof, and means for periodically varying the cross-section of said Wave guide to Vary the directivity pattern of said antenna.

10. A high frequency antenna having a pulsed directivity characteristic comprising an elongated hollow-pipe Wave guide apertured along one dmension thereof to have a directive characteristic and adapted to contain high frequency energy,

and means for periodically varying the frequency of said energy above and below the cut-off value thereof, whereby said antenna is periodically swung below cut-01T and a pulsed directivity characteristic is produced.

11. A high frequency pulse transmitter for transmitting high frequency energy having a predetermined frequency, comprising a hollow-pipe wave guide radiator adapted to be excited by said energy and having a cut-off frequency only slightly different from said predetermined frequency, and means for periodically varying said predetermined frequency above and below said cut-off frequency, whereby only pulses of said energy are radiated by said radiator.

12. In a radio system, a dielectric channel having a uniform cross-sectional area, and means for cyclically anduniformly varying said area.

13. In a radio system, a dielectric channel connected to a translation device and having a uniform phase velocity characteristic, and means for varying said phase velocity characteristic cyclicallying and equally along the length of said channel.

14. A high frequency antenna comprising an elongated wave guide apertured along the major dimension thereof, and means for periodically varying the phase velocity of energy within said Wave guide to thereby periodically vary the directivity pattern produced by said antenna, said phase velocity Varying means comprising means physically Varying the propagation characteristics of said wave guide for energy of a given frequency.

15. A high frequency antenna comprising an elongated Wave guide apertured for distributed radiation along the major dimension thereof, and means including a movable element in said wave guide for periodically varying the phase velocity 40 of energy of a predetermined frequency within said wave guide to thereby periodically vary the directivity pattern produced by said antenna.

16. A high frequency antenna as defined in claim 15, wherein said movable element comprises one wall of said wave guide.

17. A high frequency antenna as defined in claim 15, wherein said Wave guide comprises fixed conductive boundaries, and said movable element comprises a longitudinally extensive element 1nside the walls of said wave guide.

WILLIAM HARDY RA'I'LJFF, JR.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,301,644 Buckley Apr. 22, 1919 1,562,961 Heising Nov. 24, 1925 2,129,669 Bowen Sept. 13, 1938 2,197,123 King Apr. 16, 1940 2,206,683 Wolfi' July 2, 1940 y 2,263,248 Roberts Nov. 18, 1941 60 2,408,435 Mason Oct. 1, 1946 2,422,691 Mason June 24, 1947 2,461,005 Southworth Feb. 8, 1949 FOREIGN PATENTS Number Country Date 802,756 France June 13. 1936 23,15% Australia June 22, 1936

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