US2794960A

US2794960A - Variable inductance coupling loop

Info

Publication number: US2794960A
Application number: US568067A
Authority: US
Inventors: Charles R Ellis
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1956-02-27
Filing date: 1956-02-27
Publication date: 1957-06-04
Anticipated expiration: 1974-06-04

Description

June 4, 1957 c. R. ELLIS VARIABLE INDUCTANCE COUPLING LOOP Filed Feb. 27, 1956 FIG.I

IIIIIIIIAEVIIIA "IQVENTOR: CHARLES R. ELLIS,

HIS AGENT.

United States Patentjf) "ice 2,794,960 VARIABLE INDUCTANCE COUPLING LOOP Charles R. Ellis, North Syracuse, N. Y., assignor to General Electric Company, a corporation of New York Application February 27, 1956, Serial No. 568,067 7 Claims. .(Cl. 333-24) This invention relates to the art of electromagnetic coupling arrangements and more particularly to the artv caused the development of cavity-resonator type oscilla tors and amplifiers. A problem associated with the. development of these types of equipments .has been the problem of coupling electromagnetic energy within such oscillators to conductive cabling for transmission to equipments utilizing this electromagnetic energy. One type of apparatus developed by the prior art for such coupling arrangements has been that of a coupling loop inserted into the electromagnetic field within the generator. The variation of magnetic fields within the generator will induce a corresponding electrical signal in said loop for transmission to a transmission line such as coaxial cable. It has always been desirable to'arrange the coupling loop in such manner as to enable adjustment of'the effective area of the loop within the electromagnetic field. In this manner, the delivered power can be varied. The need for adjustment of the loop area within the oscillator while maintaining an electrical seal has involved adjustable devices having many sliding joints which exhibit difficulty in maintenance and operation.

It is an object of my invention to provide a variable inductance coupling loop obviating this difficulty.

It is a further object of my invention to provide the coupling loop having an inductance variableby external adjustment which is both simple and efficient inoperation.

It is a further object of my invention to provide a variable inductance coupling loop having but one sliding joint.

It is a further object of my invention to provide animproved means in and relating to signal coupling arrangements.

In accordance with these objects, I have provided, in one embodiment of my invention, a coupling loop attached immovably to :the center conductor of :a coaxial cable and inserted within a cavity resonator through a cylindrical tube or sleeve. By movementof 'thecylindrical sleeve along the length of the loop, the efiective loop 1 'area inserted within the cavity resonator .is changed and therefore the power output-derived from the cavity resonator can be varied.

In a modification of my invention, I have provided in one embodiment, a multi-turn spiral integrally formed with the loop and surrounding the sleeve in the resonator. At the operating frequency, a change .in the position of the sleeve will give a greater percentage change/of effective coupling than a straight-legged loop.

The features of my invention which I believe to be novel, are set forth with particularity in the appended claims. My invention itself, however, .both astoits a0]?- ganization and method of operation, together withfurther objects and advantages thereof, may best be .understood by reference to the following descriptiontaken in, t

I existing within the cavity resonator.

2,794,950 Patented June 4, 1957 connection with the accompanying drawings in which: Figure .1 is a cross-sectioned plan view of a straightlegged coupling loop according to the present invention;

and

Figure 2 is a cross-sectional plan view of a spiral type coupling loop in accordance with the present invention.

Referring now to Figure 1, there is shown a loop inserted within a source of varying electromagnetic energy such as the cavity of a cavity resonator, the walls of which are shown as 1. A shorting plate 2 electrically con- .tacts the cavity walls by means of spring contacts 3. The spring contacts permit movement of theplate without changing the electrical contact. .In this manner, the shorting plate 2 can be moved and positioned within the cavity resonator to determine the operating resonant frequency of the. cavity resonator in a well known manner. The coupling element or loop comprises a shorter leg and a longer leg integrally formed with and connected by a U- shaped member 4. The loop is inserted through the shorting plate. T he longer leg makes contact with the center conductor 5 of the coaxial line 6 which is rigidly fastened to a support such as a frame member. A sleeve 7 surrounds the longer leg of. the loop making contact with the outer conductor of the coaxial line 6 at its lower ex- 25v tremity. The cylinder is maintained at the .same potential as the shorting plate by wiping contacts. 8 affixed over the bearing 9 which maintains the axial alignment of sleeve 7. The sleeve 7 is movable over the lengthof the coupling loop, and is driven by the coupling loop motor 10 acting through the spur gear 1'1 and rack 12. Since the coaxial line is fixed, contact with the outer conductor 6 is maintained by a sliding contact along the surface 13. Shortingfingers or contacts 14 may be provided at the top of sleeve 7 contacting the shorter leg of the coupling loop. The shorting contacts 14 may be .mounted on a conductive block 15 afiixed to the sleeve 7. An insulating block 16 is provided in the tube to maintain concentricity or axial alignment of the longer leg with the sleeve 7. The material used for the conductive components is preferably silver-plated brass.

In operation, after the shorting plate has'been adjusted for the proper resonant frequency of the cavity resonator, the sleeve 7 can be removed by operation of the coupling loop motor 10 to travel up and down in order to properly adjust' the effective area of loop 4 projected within the resonator cavity. Since the sleeve travels as a unit, it is possible to place tuning impedance sections within the lower half of the sleeve'which are effective throughout the range of sleeve travel since the sleeve length to the tuning section is not varied.

As the sleeve is moved with respect to the loop, the conductive surface of the loop will shield the portion of the loop 4 contained within the tube from the magnetic fields Therefore, movement of the tube will vary the effective area of the loop exposed to these, magnetic fields and v ary the power coupled into the coaxial cable.

The variation in effective areaproduced by movement of the tube 7 occurs with or without the shorting contacts 14. However, in many cases it is preferable to employ the shorting contacts 14 because of the greater efiective percentage change of exposed loop area with a fixed change in motion of the coaxial sleeve. At low frequencies the variable inductance coupling loop shown in Figure lrnay become somewhat cumbersome and the modification shown in Figure 2 may preferably be employed.

In Figure .2 is shown a form of coupling loop suitable for low frequency operation. A loop' such as this was satisfactorily operated at a frequency of approximately .megacyclesper second and lower. In this figure,

,partsj similar to those shown in Figure 1 are identically t a numbered. As in Figure 1, a sleeve 7 passes through the shorting plate 2. The coupling loop has a member which is concentric with the walls of said sleeve and contacts the internal connector of the coaxial cable 6. The

sleeve slidingly contacts the external conductor of the coaxial cable along surface 13. r The coupling loop is formed in' a manner similar to that of Figure 1, but with the member inside the oscillator formed in a helix extending around the outside wall of the tube 7.

The end of the helix is secured to the shorting plate by a screw 24 or other appropriate method. The convolutions of the helix pass through a hole in a tab 25 securely affixed to the wall of sleeve 7.= Rotation of the sleeve a helix allows much greater change in the loop coupling.-

for a given linear movement of the concentric tube 7. At low frequencies, this is particularly important, by greatly decreasing the relative sleeve movement which would be necessary with a coupling of the form shown in Figure 1 for the same change in coupling. Contacts similar to contacts 14, Figure 1, may be employed if the electrical contact provided by tab 25 is not sufficient.

While. particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in the broader aspects: and, therefore, the aim in the appended claims is to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l.In combination, in a cavity resonator having a resonant frequency adjusting plate with an aperture therein, a cylindrical sleeve extending through said aperture, a bearing, said bearing mounted in said aperture and adapted to support said sleeve by slideable contact there with, a first contact means mounted on said plate and slideably contacting said sleeve, a coupling element within said resonator, said element having a longer and shorter leg integrally formed with and joined by a U-shaped section, said element having said longer leg positioned within said sleeve and said shorter leg positioned outside of said sleeve, means for axially aligning said longer leg within said sleeve by sliding contact therewith, means for mounting said shorter leg to said shorting plate, a second contact means mounted within said resonator near the end of said sleeve and slideablycontacting said shorter leg, a coaxial cable having a center and outer conductor, means coupling said longer leg to said center conductor, said outer conductor being surrounded by and in slideable contact with said sleeve outside of said resonator, means for moving said sleeve along said longer leg of said coupling element.

2. In combination, in a cavity resonator having a resonant frequency adjusting plate with an aperture therein, a cylindrical sleeve extending through said aperture, a bearing mounted in said aperture and adapted to support said sleeve by slideable contact therewith, a first contact meanslmounted on said plate and in slideable contact with said sleeve, a coupling element within said resonator, said element having a first and second leg integrally formed with and joined by a U-shaped section, said element having said first leg positioned within said sleeve and said second leg positioned outside of said sleeve, means for axially aligning said first leg Within said sleeve by sliding contact therewith, a coaxial cable having a center and outer conductor, means coupling said first leg to said cen- A. ter conductor, said outer conductor being surrounded by and in slideable contact with the sleeve outside of said resonator, said second leg being formed in a helix surrounding said sleeve, securing means adapted to secure said helix to said frequency adjusting plate, tab means affixed to said sleeve within said resonator and mechanically coupled to said helix in a manner to cause the sleeve to ride the helix when sleeve is rotated, and means for rotating said sleeve.

3. In combination, in a source of varying electromagnetic fields having a frequency adjusting plate with an aperture therein, a sleeve of electrically conducting material extending through said aperture and in electrical contact with said plate, a coupling element, said element having a first and second leg integrally formed with and joined by a U-shaped section, said U-shaped section positioned within said source, said first leg positioned Within said sleeve and extending through said plate, means for axially aligning said first leg within said sleeve by sliding contacting therewith, means for securing said second leg to said plate, means for electrically connecting said second leg with the end of said sleeve within said source by sliding contact therewith, a coaxial cable having a center and outer conductor, means connecting said first leg to said center conductor, said outer conductor being surrounded by and in slidable contact with said sleeve outside of said source, means for moving said 'sleeve along said first leg.

4. In combination, in a source of varying electromagnetic fields having a frequency adjusting plate with an aperture therein, a sleeve of electrically conducting material extending through. said aperture and in electrical contact with said plate, a coupling element, said element having a first and second leg integrally formed with and joined by a U-shaped section, said U-shaped section positioned within said source, said first leg positioned within said sleeve and extending through said plate, means for axially aligning said first leg Within said sleeve by sliding contact therewith, means for securing said second leg to said plate, means for electrically connecting said second leg with the end of said sleeve within said source by sliding contact therewith, a coaxial cable having a center and outer conductor, means connecting said first leg to said center conductor, said outer conductor being surrounded by and in slideable contact with said sleeve outside of said source, means for moving said sleeve to vary the sleeve length within said source.

5. In combination a cavity resonator, a shorting plate associated with said resonator for changing the effective volume of said resonator, a conductive sleeve adjustably protruding through an opening in said plate into said resonator, a cable having an inner and an outer conductor, a coupling loop positioned within said cavity resonator and having one end physically connected to said plate and the remaining end connected through said sleeve to the inner conductor of said cable, and said outer conductor slideably connected to the portion of said sleeve protruding outside said cavity resonator.

6. In combination, in a source of varying electromagnetic fields having an enclosing wall with an aperture therein, a sleeve of electrically conducting material extending through said aperture and in electrical contact. with said Wall, a coupling element, said element having a first and second leg integrally formed with and joined by a U-shaped section, said U-shaped section positioned within said source, said first leg positioned within said sleeve and extending through said plate, means for axially aligning said first leg within said sleeve by sliding con- 'ing contact therewith, a coaxial cable having a center and outer conductor, means connecting said first leg to said center conductor, said outer conductor being surrounded by and in slideable contact with said sleeve out- 5 side of said source, means for moving said sleeve to vary the sleeve length within said source.

7. In combination, in a source of varying electromagnetic fields having an enclosing wall with an aperture therein, a cylindrical sleeve extending through said aperture, a bearing mounted in said aperture and adapted to support said sleeve by slidable contact therewith, a first contact means mounted on said plate and in slideable contact with said sleeve, a coupling element within said source, said element having a first and second leg integrally formed with and joined by a U-shaped section, said element having said first leg positioned within said sleeve and said second leg positioned outside of said sleeve, means for axially aligning said first leg within said sleeve by sliding contact therewith, a coaxial cable having a 15 center and outer conductor, means coupling said first leg to said center conductor, said outer conductor being surrounded by and in slideable contact with the sleeve outside of said resonator, said second leg being formed in a helix surrounding said sleeve, securing means adapted to secure said helix to said enclosing Wall, tab means affixed to said sleeve within said resonator and mechanically coupled to said helix in a manner to cause the sleeve to ride the helix when sleeve is rotated, and means for rotating said sleeve.

Van Beuren June 28, 1949 Sydoriak Jan. 12, 1954