Tuned coaxial device

[57] ABSTRACT

The disclosure relates to a tuner device in a coaxial connector to readily adjust VSWR of an RF system by a structure which is of improved sensitivity and is practical and usable in the field.

Claims, 9 Drawing Figures

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ΡΑΤΕΝΤΕΟΜΑΪ161972 3,663,901

SHEET 1 OF 3

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PATENTED «η 61972 3,663,901

SHEET 2 OF 3

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PATENTED hat 16 wz

SHEET 3 OF 3

3,663,901

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3,663,901

TUNED COAXIAL DEVICE

This invention relates to a tuner means for a coaxial line connector element for improving the VSWR in coaxial cable systems in which it is connected.

Radio frequency systems frequently contain numerous devices, such as connectors, amplifiers and other components which become sources of signal reflection, due to impedance) mismatch or physical discontinuities introduced in manufacture, handling or during installation of the system. After assembly and installation of the system, it is desirable to reduce signal reflections to thereby minimize the voltage standing wave ratio of the system by creating a source of reflection which balances out intrinsic reflection of the assembled system at the frequency of operation. This may be accomplished by incorporating in the connector and for cooperation therewith, a device which is tunable to provide the desired balancing reflection. The tuner means to be described may also be incorporated in such other radio frequency devices as amplifiers, oscillators, impedance transformers, etc.

A feature of the invention is that the connector which is disposed between a pair of coaxial lines for joining them, itself forms a section of line which is provided with a coaxial line tuning stub connected in shunt therewith and tunable to provide the proper impedance in order to minimize reflections on the line. The device may be considered as a tuned connector element, referred to hereinafter as the connector, and is provided at its ends with means for securing it to mating terminals of coaxial lines or components which are to be joined, which terminals may be secured thereon at the location where the tuner is to be installed. The center contactor of the connector, ’ before being disposed therein, may first be connected to the center conductor of one of the coaxial lines to be joined. The center conductor of the coaxial tuning stub formed, as part of the connector, extends thereinto and is provided with a stirrup through which the contactor of the section can slide when attaching the connector to the line. The stirrup, which is of a dimension to provide good electrical contact with several portions of the surface of the center contactor can be utilized for contactors of different diameters within a range.

It is therefore an object of this invention to provide tuner means in a coaxial connector which may be easily installed in a coaxial line.

It is a further object of the invention to provide tuner means which may be used with coaxial transmission lines having dif- ₄c ferent sized conductors within a range.

It is an additional object of the invention to provide a connector structure for a tuner means which cooperates with terminals on a transmission line which are so formed as to mate with the connector.

The specific nature of the invention as well as other objects and advantages provided thereby, will be made clear from a description of a preferred embodiment as shown in the accompanying drawings in which:

FIG. 1 is an exploded view in perspective of the connector 55 including tuner means and termination means of a coaxial line;

FIG. 2 is a cross-sectional view of a coaxial cable connector assembled to one end of a coaxial line;

FIG. 3 is a partial perspective of the stirrup of the tuner 60 means;

FIG. 4 is a cross-sectional view along line 4—4 of FIG. 2; and

FIGS. 5-9 are views showing in sequence the various stages of cable preparation and installation with respect to one end 65 of the tunable connector.

Referring to FIG. 1 of the drawings, the connector element C includes a hollow cylindrical shell 2 of brass or bronze open at its ends. The interior of the shell is provided with a bore 5 at its forward end, a threaded bore 24 at its opposite end and an 70 shown in HG. 5, an end portion of the outer conductor of intermediate bore 15 of lesser diameter than and a opening -----' ' --into the adjacent bores. Because of the reduced diameter of bore 15, a wall 5' is formed at the bottom of bore 5 and a wall 24' at the bottom of bore 24. The forward end portion ofthe thickness and a forwardly facing wall 9. A hollow cylindrical ferrule 6 has one end provided with longitudinally extending slots 6' around its periphery and its other end enlarged in cross-section to substantially form a circumferential bead 7. A centrally apertured dielectric spacer 8 having the combined length of the bore 5 and ferrule 6 is located within the bore with its rear end wall against wall 5'. The diameter of the portion of the spacer 8 within the bore is substantially that ofthe bore and its forward end extending outwardly thereof is of somewhat reduced diameter and is the same as the inner diameter of the ferrule 6. With the ferrule 6 surrounding the spacer and the end wall at which the bead 7 is located being disposed against the wall 9, the rim 4 is rolled over the bead to secure the spacer and ferrule to the shell 2. The free end ofthe spacer 8 is recessed as at 8', the recess being tapered and outwardly diverging to mate with a complementary dielectric spacer of a complementary line terminal in a housing or connector element (not shown). A hollow dielectric spacer 10 is disposed within the intermediate bore 15 and has a pair of diametrically opposed slots 11 through its peripheral wall. These slots extend parallel to the longitudinal axis of the spacer from the left end thereof to a point beyond the center of the spacer, as shown.

The cylindrical shell member 2 is provided with an opening 28 through its wall, the axis of which is alined with the center of the bore 15; i.e. at the midpoint of its longitudinal axis. The opening 28 is enlarged at its outer end to accommodate a conductive hollow tubular member 16 which is conductively 30 secured to the shell 2. The inner diameter of the tubular member 16 is the same as the smaller diameter of opening 28. The interior wall of the tubular member 16 is threaded and provides a passageway 17 for an externally threaded short-circuiting member 20 which cooperates with the threads on the i inner wall of tubular member 16 to move along the wall when rotated by a tool inserted from the open end of the passageway. Member 20 has a central aperture therethrough to receive a center rod 18 which extends substantially the full length of member 16. A hollow tubular extension 20' is pro¹ vided at the inner end of member 20 and is longitudinally slotted, as shown at 21 in FIG. 4, to form a plurality of spring fingers which engage and contact the center rod 18. Secured to the bottom of the rod 18, as by welding or soldering, is a loop or stirrup member 14, provided by a flat strip 12 of conductive resilient material, which is first bent into the form of a U, the free end portions of the U then being bent into abutting relation as shown at 12' and soldered or otherwise secured together, either before or at the time the stirrup member 14 is being secured to the end wall of the rod 18. As is evident, the end edges 13 of the flat strip 12 effectively form a flat wall which provides a sufficiently large surface capable of being attached to the end of the rod, or the latter may be grooved to accept the end edge portions of the strip before soldering or welding. With the rod 18 positioned in the passageway 17 as shown in FIG. 2, the stirrup extends through and below the upper slot 11 in the dielectric spacer 10 and thus into the hollow space at the interior of the spacer. In assembly of the device, stirrup 14 is located within bore 15 and then spacer 10 is inserted in the bore 15; the narrowed neck 12' ofthe stirrup will be received in the upper slot 11 as the spacer is fitted into the bore. This serves to orient or key the spacer 10 in its proper position. The end of the shell 2, to which is secured the slotted ferrule 6, may be circumferentially threaded if desired, as at 29, to receive a threaded sleeve on a complementary terminal connector element of a second coaxial line, not shown.

The end of the coaxial line which is to enter the connector through the bore 24 and is to be secured therein, is provided with terminal members in a manner shown in FIGS. 5-8. As __________a coaxial cable 30 is cut away to expose a short length S of the solid dielectric D between the conductors. A collet 32 having a longitudinally slitted cylindrical body and a radial flange 34 at one end, is provided with an axial opening therethrough to ----------------------- is bore 5 is enlarged to leave a rim portion 4 of reduced wall 75 closely fit tiieoiiter surface“d“the cS iableTZilX f

3,603,901 provided with an opening therethrough to snugly receive the body of the collet when mounted on the outer conductor of; the coaxial line, and is of a diameter to be received within an opening in an exteriorly threaded nut 38. The diameter of the threaded portion of the nut is such that it can be threaded into the bore 24 of the connector member. With the collet, ferrule and nut disposed about the outer conductor of the cable, the ferrule 36 is slipped over the collet and both the collet and ferrule are crimped, soldered or otherwise secured to the outer conductor of the cable with the outermost surface of the flange 34 of the collet being in radial alinement with the transverse edge at the end of the outer conductor. The parts so assembled are shown in FIG. 7.

The exposed portion of the inner dielectric D is then removed to expose the length of the inner conductor 40 which extends outwardly from the end of the outer conductor. A cylindrical conductive pin contact 22 is provided at one end 23 with a central recess to slidably receive the exposed portion 40 of the inner conductor. The end portion of contact pin 22 in which the portion 40 of the inner conductor is entirely disposed, is then crimped, as by a crimping tool T, to mechanically secure the portion 40 to the contact pin and to obtain good electrical contact. The contact pin 22 is of smaller diameter than the outer conductor 30 and does not contact the flange 34 when crimped onto the center conductor. The contact pin is tapered to converge inwardly at its opposite end 42 for enabling it to easily enter between the straight walls of the stirrup 14 and the central opening in dielectric spacer 8. The length of the contact pin 22 is such that when located within the body of the connector C with the flange 34 of the collet against the bottom wall 24' of the bore 24, the tapered end 42 thereof will be located within the opening 8' of the spacer 8 for engagement with a complementary terminal contact member, not shown. The nut 38 when threaded into the bore 24 and against the wall of the flange 34 secures the cable to the connector with the center contact within the stirrup.

As can be seen in FIG. 3, the resilient normally straight walls of the stirrup member 14 are bowed out by the contact pin 22 to maintain good electrical engagement therewith as shown in FIG. 4. The shorting member 20 within which the center rod 18 is frictionally supported by means of the aforementioned spring fingers, may have its outer end portion slotted to receive a spanner wrench or shaped to receive a socket wrench for turning it to move toward or away from the center contact pin 22. The rod 18 is held in the selected position against any substantial axial movement (i.e. along the length of the tubular member 16) due to the fact that stirrup 14 is disposed within dielectric spacer 10, with only the narrowed neck 12' thereof able to move within the slot 11. Any slight axial movement of the rod 18, while the stirrup is in engagement with the contact 22, has little or no effect on the electrical results obtained and poses no problem. However, it is obvious that the free end of the rod 18 could be secured against such axial movement relative to the outer tube 16 by any other desired mechanical means. If so desired, a dielectric washer may be disposed within the shell 2 in the space surrounding the flange 34 for centering purposes. The connector having the tuner means constructed as a part thereof as described above, is particularly useful for connecting together a pair of coaxial lines but may also be used for directly connecting the tuner means as a component of a circuit for tuning an oscillator or amplifier or as a tuned filter.

Although this invention has been disclosed for use with specific terminal structures of the coaxial lines to be connected, it is obvious that other forms of terminals may be utilized and the connector element modified for use with different terminals without departing from the spirit and scope of this invention.