US 2775741 A
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Description (OCR text may contain errors)
Dec. 25, 1956 P. l. CORBELL PHASE SHIFTING DEVICE 2 Sheets-Sheei;
Filed Dec. 10, 1952 A I) 5 8 p s 4 m 6 3 WP, .H w w m L Q r J 6 w L 5 Y D INVENTOR. P4041 (o/Pail;
147 r a/im [y Dec. 25, 1956 P. l. CORBELL PHASE SHIFTING DEVICE 2 Sheets-Sheet 2 Filed Dec. 10, 1952 INVENTOR. I240 Canwuzl.
A T ran/v17 PHASE SHIFTING DEVICE Paul I. Corbell, Palo Alto, Calif., assignor, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission Application December 10, 1952, Serial No. 325,155
5 Claims- (Cl. 333-31) This invention relates in general to a phase shifting device, and in particular to means for shifting phase at microwave frequencies.
In transmission line systems, it is oftentimes necessary to change the phase of transmitted energy before it is received at the end of the line. At relatively low frequencies, phase shifting can be accomplished by using lumped reactive elements in shunt with the line. In general so as to obtain the desired ratio of voltage to current at the end of the line, additional 'reactiveelements are required.
' Patented "Dec; 25,-"1956 2 of legs 21 and 22, respectively, and a top frame member 23.
As best shown in Figure 2, the top frame member 23 is formed with an extension 24 which supports a bracket 26 upon which a driving means 27, as for example an electric motor, is supported. v
A jack 28 is attached to the member 23 and supports a longitudinal member 29. A jack screw 31 controls the position of the jack 28 and is connected to the motor 27 by means of gears 32 and 33, universals 34 and 36, and
a slide shaft 37.
Supported from the member 29 are a pair of dielectric probes 38 and 39 which are attached to hangers 41 and 42 connected to the support 29. The hangers 41 and 42 are connected by suitable clamps 43 and 44 to the probes 38 and 39.
The probes 38 and 39 extend within the confines of the wave guide 10 and pass through openings 46 and 47,
respectively, formed in the top wall 11. Guide members 48 and 49 are attached to the top wall 11 in alignment with the openings 46 and 47 and the probes 38 and 39 pass therethrough as shown in detail in Figure 3.
At high radio frequencies (short wave lengths) where a phase shift of many electrical degrees occurs in a relatively short length of transmission line, it is possible to devise means for physically altering the length of the line so as to produce the desired amount of phase delay. Such arrangements are called line stretchers.
In high frequency lines it is also possible to introduce reactance in shunt with the line by using transmission line stubs, and thus obtain phase delay.
At microwave frequencies it becomes difiicult to mechanically build a line stretcher and generally shunt impedances are inserted into the line to obtain the desired phase shift. Such impedances may be in the form of dielectric wedges, such as described in Ragan Microwave Transmission System, volume 9, MIT series, published by McGraw-Hill.
l t is an object of the present invention to provide phase shift at microwave frequencies by inserting into wave guides, dielectric probes causing a resultant capacity and shunt across the line.
Another object of the present invention is to provide a phase shifting device for microwave frequencies which will not cause reflection or continuity.
Yet another object of the present invention is to control the phase shift in a microwave guide.
A feature of the present invention is found in the provision for the insertion of a pair of dielectric rods into the plane of the maximum voltage lines in a wave guide with the probes separated one-quarter wave length so as to cancel reflections.
Further features, objects and advantages of this invention will become apparent from the following description and claims when read in view of the drawings, in which:
Figure 1 is a sectional view of a wave guide with the apparatus of this invention installed therein;
Figure 2 is a side view of the phase shifting apparatus of this invention; and
Figures 3, 4, and 5 are detailed sectional views of various embodiments of the dielectric probe of this invention.
Figure 1 illustrates a wave guide designated generally as 19 which has upper and lower conducting walls 11 and 12 and side walls 13 and 14, respectively. A pair of brackets 16 and 17 which might, for example, be angle irons are attached to the upper surface 11 of the wave guide and support a pair of U-shaped frame members 18 and 19. The members 18 and 19 are formed with a pair With the structure thus shown, the vertical positions of the probes 38 and 39 may be controlled together.
The probes 38 and 39 are made of dielectric material so that energy passing down the wave guide will be rotated in phaseby them. Various materials may be .used for the probes 38 and 39, as for example, ceramic rods, hollow glass rods filled with oil, hollow glass rods filled with water, and glass rods filled with dielectric powder. When rods are filled with dielectric powder as shown in Figure 4, the powder in both rods may be similarly compressed to a multitude of densities to vary the effective dielectric constant. Figure 3 illustrates a solid plastic or ceramic dielectric rod. Figure 4 illustrates a hollow glass tube filled with dielectric powder. Figure 5 illustrates a hollow glass tube filled with a liquid dielectric.
Applicant has also found that the probes shown in Figure 2 work satisfactorily wherein a glass tube has its bottom end closed and its upper end closed by a stopper 51 through which a pair of tubes 52 and 53 extend. The tube 53 extends adjacent the bottom of the probe and tube 52 terminates adjacent the stopper 51. If water or other suitable dielectric liquid is fed into the tube 53, it will emerge adjacent the bottom of the tube and force the other liquid up and out of the tube 52.
It is to be realized, of course, that a certain amount of energy is absorbed by the probes, resulting in heating of the probes. Thus, circulation of liquid keeps the bottom ends of the probes at a safe operating temperature.
A pair of probes 38 and 39 are used and are spaced one-quarter guide-wave length apart so as to cancel reflections, caused by the probes. It is well known that discontinuities encountered by energy passing through a Wave guide cause reflections and if a pair of similar objects are inserted into the guide and spaced one-quarter wave lengths apart, these reflections will cancel.
A particular embodiment constructed by applicant was designed for 202.5 megacycles wherein the air wave length is approximately 60 inches. Wave guide was used with the sides 11 and 12 being 48 inches long and the sides 13 and 14 being 12 inches high. With this wave guide, the wave length is 84 inches and one-quarter wave length is 24 inches. Thus, the probes 38 and 39 were separated 24 inches.
With probes one and a half inches in diameter and using water as the dielectric, phase rotations up to 25 degrees were obtained with the two probes. It is to be realized, of course, that the phase rotation depends upon the length of the probes within the wave guide.
It is seen that this invention provides a novel way for rotating the phase of energy passing down a relatively large wave guide in a manner such that no reflections occur.
Although this invention has been described with respect to a particular embodiment thereof, it is not to be so limited as changes and modifications may be made which are within the full intended scope of the invention, as defined by the appended claims.
1. Means for adjusting the phase of energy traveling down a wave guide comprising, a pair of openings formed in a wide side of said wave guide, a pair of probes extending through said openings and separated longitudinally of said wave guide by substantially one-quarter wave length, and said probes comprising generally hollow cylindrical tubes with their lower ends closed, closure means mounted in the other ends of said tubes, a pair of openings formed in each of said closure means, and a separate pair of smaller tubes extending through the openings of each of said closure means with one of said smaller tubes of each pair extending further into its respective probe than the other.-
2, Means vfor changing the efiective length of a waveguide without causing substantial reflection of energy comprising, a first dielectric probe comprising a hollow dielectric container of a fixed geometrical form containing at least one dielectric material which is incapable of maintaining a fixed geometrical form by itself, said probe being inserted through an opening in said waveguide, a second dielectric probe identical with said first probe inserted through another opening in said waveguide, said probes longitudinally spaced one-quarter wavelength apart, a pair of guide members mounted on the outside of said waveguide in alignment with said openings to guide said probes into alignment with said openings, jack means supported on the outside of said waveguide, a longitudinal member supported by said jack means, and hanger means mounted from said longitudinal member and supporting said probes so that said probes are adjustable together into said waveguide by said jack means.
3. A device as in claim 2 wherein said probes are glass tubes sealed at their bottom ends, a stopper mounted in the upper end of each probe and formed with a pair of openings, a pair of small tubes supported through the openings in each stopper with the portion of one tube Within the probes being substantially longer than the equivalent portion of the other, and a dielectric material other than glass contained within each of said probes.
4. A device as in claim 2 wherein a dielectric powder is contained within each probe.
5 A device as in claim 2 wherein said probes are glass tubes sealed at one end, a stopper mounted in the other end of each probe and formed with a pair of openings, a pair of small tubes supported through the openings in each stopper, with the portion of one tube which is within the probes being substantially longer than the other and a dielectric fluid contained within each of said probes.
References Cited in the file of this patent UNITED STATES PATENTS 2,556,001 Robertson June 5, 1951 2,605,413 Alvarez July 29, 1952 2,705,307 Nyswander Mar. 29, 1955