Connector For Flexible Transmission Line

Abstract

An electrical connector for flexible transmission lines of the coaxial type including an elongated probe of conductive metal having an end portion protruding insulatingly into the open end of a tubular center conductor of the coaxial line for a distance equal to an effective quarter wavelength of the energy to be transmitted by the line whereby an open circuit occurs at the engaged end of the probe and a low impedance junction is established between the circular end of the center conductor and the adjacent portion of the probe; and a coaxial, cylindrical shell of conductive metal having an internal shoulder clamped in direct metallic contact with a flanged end of the outer coaxial conductor.

Description

K

BACKGROUND OF THE INVENTION

The invention herein described was made in the course of and under a contract or subcontract thereunder, with the Department of the Army.

This invention is related generally to electrical connectors and is concerned more particularly with high frequency connectors for flexible transmission lines.

When microwave energy flows through a coaxial transmission line, the resulting electromagnetic fields impress an alternating voltage across the annular space between the coaxial conductors and induce alternating currents in the adjacent layers of the concentric conductors. The induced currents generate heat in the coaxial conductors and, therefore, represent power losses in the transmitted waves. These heat losses are proportional to the ohmic resistance of the conductor material and the impedance of the interface connections in the transmission line. Consequently, the conductors are made of low resistivity material, such as copper for example, and the impedance of each coupling connection is minimized as much as possible. The center conductor of a coaxial line stabilizes at a higher temperature than the outer conductor due to the higher current density in its reduced cross section. Therefore, the problem of minimizing resistance between contacting surfaces is more acute in the center conductor connections than between contacting surfaces in the outer conductor. A problem of equal importance in coaxial lines is the concentration of electric field intensity around the smaller surface of the center conductor, thereby establishing high voltage gradients near the surface of the center conductor. When poor contacting surfaces occur in the center conductor line, these high intensity electric fields build up a voltage potential between the contacting surfaces. At sufficiently high voltage, air or other gaseous medium between the poor contacting surfaces ionizes and arcing occurs across the intervening film of ionized gas. This burning process deteriorates the contacting surfaces and opens the gap wide enough to constitute an impedance discontinuity in the line. As a result, reflected waves are formed at the boundary of the discontinuity which travel back toward the input end of the line and, in doing so, pass through increasingly stronger electric fields of the transmitted waves. When the reflected waves are in phase with the transmitted waves, the voltage maxima of both waves combine and produce a corona discharge between the concentric conductors of the coaxial line. As a consequence of this short circuit in the transmission line, the associated transmitting equipment may be seriously damaged. Therefore, low resistance contacting surfaces in centerline connections are not only important to avoid heat losses but also to avoid corona discharge between the concentric conductors of the coaxial line.

Long transmission runs with many twists and bends are produced easily and efficiently with the use of flexible or semirigid transmission lines. However, the center conductor in a flexible or semirigid coaxial line operates at a higher temperature than the center conductor in a rigid coaxial line, because the former requires dielectric supporting means at frequent intervals along the line in order to maintain concentricity during flexing. Electromagnetic energy losses in the dielectric material of the supporting means produces heat which is transferred to the center conductor by means of conduction and convection. This additional heat energy in the center conductor of a flexible or semirigid coaxial line contributes to the development of poor contacting surfaces in coupling connectors of the prior art. Usually, the center conductor junction in prior art connectors is formed by plugging the slotted "bullet" of a male connector into the open end of a center tube or jack in the female connector, thus providing a direct metal-to-metal contact. The slotted bullet comprises a tapered cylinder of resilient fingers which are compressed radially inward when the bullet is inserted into the tubular portion of the female connector. This connection between mating parts is made as tight as possible in order to minimize the impedance of the connection and to reduce the possiblity of field discontinuity. However, tolerances must be allowed on the dimensions of the mating parts because of the sliding engagement required by this type of connection.

It has been found that heat generated in the center conductor during pulse transmission of microwave energy and subsequent cooling causes the mating members of the connector to expand and contract. After a period of time, the constant expansion and contraction causes the spring fingers of the bullet to lose some resiliency and a small gap develops between one or more fingers and the rigid wall of the female tube. Flexing of the coaxial line also puts an additional stress on the resilient fingers of the bullet and contributes to the development of the gap between mating parts of the connector. As described above, the ohmic resistance of the gap causes greater heat losses in the transmitted waves and the high intensity electric fields surrounding the center conductor produce voltage breakdown across the gap. The subsequent arcing burns and pits the surfaces on each side of the gap, thereby widening the gap to form an impedance discontinuity in the line. The reflected waves produced at the boundary of this discontinuity lead to corona discharge and short circuiting of the transmission line.

SUMMARY OF THE INVENTION

Accordingly, this invention provides a low impedance coupling connector which does not depend upon direct metallic contact in the centerline connection. A dielectric bushing is fixedly mounted in the opening at one end of a tubular center conductor. The bushing has an annular flange which abuts the circular end of the center conductor and a longitudinal cavity having an open end centrally located in the flanged end of the bushing. An end portion of an elongated probe is inserted into the cavity and slidingly engages the inner diameter of the bushing. The engaged length of the probe reaches a maximum when an annular shoulder on the probe butts against the annular flange of the dielectric bushing, thus preventing metallic contact between the shoulder of the probe and the circular end of the center conductor. The engaged length of the probe equals an effective quarter-wavelength in the waveband to be transmitted by the coaxial line. Thus, an open circuit occurs at the engaged end of the probe and a low impedance junction is established between the circular end of the center conductor and the adjacent portion of the probe. Since the junction presents a low impedance to the transmitted waves, there is very little heat loss or voltage buildup across the junction.

BRIEF DESCRIPTION OF THE DRAWING

For a better understanding of this invention, reference is made to the accompanying drawing wherein:

FIG. 1 is a fragmentary longitudinal view, partly in axial section, of a preferred embodiment of this invention; and

FIG. 2 is a fragmentary longitudinal view, partly in axial section, of another preferred embodiment of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawing wherein like characters of reference designate like parts throughout the several views, there is shown in FIG. 1 one end of a flexible transmission line 10 connected to a similar transmission line 12 by means of an intervening connector assembly 14. Transmission line 10 comprises two coaxial conductors, a center conductor 16 and an outer surrounding conductor 18. Similarly, transmission 12 comprises a center conductor 20 and an outer surrounding conductor 22. The respective conductors 16, 18, 20 and 22 are flexible tubes of helically corrugated metal, such as copper for example. Each of the respective center conductors, 16 and 20, is centrally located and insulatingly supported within the respective outer conductors, 18 and 22, by means of a helical membrane 24 of dielectric material, such as polyethylene for example. One longitudinal edge of the respective membranes 24 fits tightly against the adjacent surface of the respective center conductors 16 and 20. The other longitudinal edge of the respective membranes 24 is provided with transverse slots 26 which interlock with the adjacent corrugated walls of the respective outer conductors 18 and 22.

Connector assembly 14 comprises a male connector 32 mated to a female connector 34. Connector 32 includes an outer shell 36 which is clamped to outer conductor 18, a dielectric bushing 38 which is mounted in an open end of center conductor 16 and a cylindrical probe 40 which has an end portion disposed in dielectric bushing 38. Outer shell 36 comprises a metallic nut 42 having internal threads 44 adjacent one end and a restricted neck portion 46 at the opposite end which slides over the major diameter of outer conductor 18. An internal shoulder 48 is formed in nut 42 where the neck portion 46 joins the larger diameter portion of nut 42. A cast collet 50 of light weight metal, such as aluminum for example, is provided with a helically corrugated inner surface which threads loosely onto the corrugated outer surface of conductor 18. An enlarged end 52 of collet 50 provides an annular bearing surface for the internal shoulder 48 of nut 42. The circular end of outer conductor 18 is flared radially outward to form an annular flange 54 which abuts the adjacent end 56 of collet 50. A cylinder housing 60 of conductive metal, such as bronze for example, is provided with a restricted portion 62 which forms an internal shoulder 64. The larger diameter portion of housing 60 slides over the outer surface of collet 50 until internal shoulder 64 butts against the flange 54 of conductor 18. External threads 66 adjacent the larger diameter end of housing 60 are engaged by the internal threads 44 of nut 42. When nut 42 is rotated, internal shoulder 48 bears against the adjacent end 52 of collet 50 and presses the opposite end 56 against flange 54. Since collet 50 is threaded loosely onto conductor 18, there is sufficient play between the helical corrugations of collet 50 and those of conductor 18 to allow slight axial movement of collet 50. As a result, flange 54 is forced against the internal shoulder 64 of housing 60, thus effecting a direct metal-to-metal contact between conductor 18 and outer shell 36. The opposite end of housing 60 terminates in an annular coupling flange 68.

Connector 32 also includes a bushing 38 of dielectric material, such as polytetrafluoroethylene for example, which is fixedly mounted in an open end of center conductor 16, as by journaling for example. Bushing 38 is provided with an annular flange 72 which abuts the circular end of center conductor 16 and a longitudinal cavity 74 having a circular opening disposed in the flanged end of bushing 38. Connector 32 also includes a cylindrical probe 40 of conductive metal, such as copper for example. A reduced diameter portion 78 at one end of probe 40 forms an annular shoulder 80 where it joins a larger diameter portion 82 of probe 40. The reduced diameter 78 of probe 40 slidingly engages the inner diameter of bushing 38 when inserted into cavity 74. The maximum engaged length of the reduced portion 78 is reached when the shoulder 80 of probe 40 butts against the flange 72 of bushing 38. Thus, the shoulder 80 prevents the engaged end 84 of probe 40 from touching the bottom of cavity 74 and the flange 72 prevents the shoulder 80 from contacting the circular end of the center conductor 16. Usually, shoulder 80 is spaced slightly away from flange 72 to allow for thermal expansion during transmission and a possible buildup of manufacturing tolerances. When transmitted energy flows through line 10, the annular space between the center conductor 16 and the engaged end 84 of probe 40 represents an infinite impedance to the transmitted waves. Therefore, the electric field and the resulting voltage potential reach a maximum value in this region of the center conductor line. However, an effective quarter-wavelength back, the annular space between the circular end of the center conductor 16 and the adjacent surface of the probe 40 represent a low impedance to the transmitted waves. Therefore, the magnetic field and resulting current density reach a maximum value in this low impedance region of the center conductor line. Because of the low impedance, heat losses will be low also. Since the electric field intensity reaches a minimum value at the low impedance junction, voltage breakdown and arcing will not occur between the circular end of center conductor 16 and the adjacent portion of probe 40. Thus, the connector 34 shown in FIG. 1 avoids the problems encountered when using the direct metallic pressure connections of the prior art.

The dielectric material of bushing 38 and the capacitance between probe end 84 and the bottom of cavity 74 both have the electrical effect of increasing the engaged length of probe 40. In order to offset this electrical effect, the engaged length of probe 40 is made physically shorter than would be required if it were surrounded by free space. Thus, the engaged length of probe 40 is referred to as an "effective quarter-wavelength," because it has the same electrical effect as a free space quarter-wavelength. Transverse motion of center conductor 16 during flexing of the line 10 does not distort the concentricity because the engaged length of probe 40 is surrounded by the dielectric bushing 38. However, flexing of line 10 may cause slight longitudinal movement of the center conductor 16 whereby the flange 72 of bushing 38 moves away from the shoulder 80 and the engaged length of probe 40 decreases. In this case, the resultant engaged length of probe 40 equals an effective quarter-wavelength for another frequency in the transmitted waveband. The resultant junction between the circular end of center conductor 16 and the then adjacent portion of probe 40 will still represent a low impedance path to the entire band of transmitted waves.

The opposite end portion of probe 40 may be terminated in any manner required for mating with a connecting device. For connecting two transmission lines, as shown in FIG. 1, the opposite end portion 90 of probe 40 is provided with a reduced diameter similar to end portion 78 and forms an annular shoulder 92 where it meets the larger diameter portion 82 of probe 40. Female connector 34 includes a dielectric bushing 94 which is fixedly mounted in an open end of center conductor 20. Bushing 94 is provided with an annular flange 96 which abuts the circular end of center conductor 20 and a longitudinal cavity 98 having an open end disposed in the flanged end of bushing 94. The inner diameter of bushing 94 slidingly engages the reduced diameter portion 90 of probe 40 when the latter is inserted into cavity 98. The maximum engaged length of the reduced portion 90 is reached when flange 96 of bushing 94 butts against the shoulder 92 of probe 40. Thus, shoulder 92 prevents the end 100 of reduced diameter portion 90 from touching the bottom of cavity 98 and the flange 96 prevents the shoulder 92 from contacting the circular end of center conductor 20. However, in practice, shoulder 92 is spaced slightly away from flange 96 to allow for thermal expansion during transmission and a possible buildup of manufacturing tolerances. When transmitted energy flows through line 10 and connector assembly 14, the annular space between the end 100 of probe 40 and the center conductor 20 represents an infinite impedance to the transmitted waves. An effective quarter-wavelength back, the annular space between the circular end of center conductor 18 and the adjacent surface of the probe 40 represents a low impedance path to the transmitted waves. Thus, a low impedance connection is achieved between the probe 40 and the center conductor 20 which results in low heat loss and avoids the buildup of high voltages across the junction thus formed. Female connector 34 also includes an outer shell 102 having a metallic nut 104 with a restricted neck portion 106 and an internal shoulder 108. Threads 110 are disposed on the inner surface of nut 104 adjacent the larger diameter end thereof. A metallic collet 112 is provided with a helically corrugated inner surface which threads loosely onto the outer surface of conductor 4 22. An enlarged end 114 of collet 112 provides an annular bearing surface for the internal shoulder 108 of nut 104. The circular end of conductor 22 is flared radially outward to form an annular flange 116 which abuts an adjacent end 118 of collet 112. A cylindrical housing 120 is provided with a restricted portion 126 which forms an internal shoulder 124. The enlarged diameter portion of housing 120 slides over the outer surface of collet 112 until the internal shoulder 124 butts against flange 116 of conductor 22. External threads 128 are provided adjacent the larger diameter end of housing 120, which threads are engaged by the internal threads 110 of nut 104. When nut 104 is rotated, the internal shoulder 108 bears against the adjacent end of collet 112 and presses the opposite end 118 against flange 116 of conductor 22. Thus, flange 116 is forced against the internal shoulder 124 of housing 120 and a direct metal-to-metal contact is achieved between outer conductor 22 and the shell 102. The restricted portion 126 terminates at one end of housing 120 in a coupling flange 130 which interfaces with the coupling flange 68 of connector 32. An annular projection 132 on the interfacing surface of flange 68 engages an annular recess 134 in the interfacing surface of flange 130, thus providing alignment during coupling. An O-ring 136 is disposed in cooperating grooves 138 and 140 in the adjacent surfaces of the respective flanges 68 and 130 to provide a pressure-tight joint between the respective housings 60 and 120. Flanges 68 and 130 are coupled with a V-band clamping ring 142 of the conventional type which compresses O-ring 136 and brings the interfacing surface of flange 68 into direct metallic contact with the interfacing surface of flange 130. Thus, shells 36 and 102 form an outer metallic casing which has a portion in metallic contact with outer conductor 18 and another portion in metallic contact with outer conductor 22. Consequently, a direct current path is produced between outer conductor 18 of transmission line 10 and outer conductor 22 of transmission line 12.

FIG. 2 illustrates how the male connector 32 connects flexible transmission line 10 to an electrical component 150. The component 150 is provided with an outer rigid tube 152 having a flange 154 which is secured to component 150 by conventional means, as by bolts 156 for example. The opposite end of tube 152 terminates in a coupling flange 158 which interfaces with coupling flange 68 of outer shell 36. The annular recess 160 in the interfacing surface of flange 158 receives the annular projection 132 of flange 68 for alignment purposes during coupling. An O-ring 136 is disposed in cooperating grooves 162 and 138 in the adjacent surfaces of respective flanges 68 and 158 whereby a pressure-tight joint is achieved during coupling. Flange 68 is coupled to flange 158 by means of a conventional V-band clamping ring 142 which compresses O-ring 136 and brings the interfacing surface of flange 68 into direct metallic contact with the interfacing surface of flange 158. A rigid center conductor 170 projects out of electrical component 150 and is insulatingly supported within rigid tube 152 by means of dielectric bead 172. Center conductor 170 comprises a hollow tube of conductive material, such as copper for example, and a bushing 174 of dielectric material, such as polytetrafluoroethylene for example, is fixedly mounted in the open end thereof. Bushing 174 is provided with an annular flange 176 which abuts the circular end of center tube 170 and a longitudinal cavity which is similar to cavity 74 in bushing 38 of connector 32. The reduced diameter end portion 90 of probe 40 slidingly engages the inner diameter of bushing 174 when it is inserted into the longitudinal cavity of bushing 174. The maximum engaged length of the reduced diameter portion 90 is reached when shoulder 92 abuts the flange 176 of bushing 174. Thus, shoulder 92 prevents the end of reduced diameter portion 90 from touching the bottom of the longitudinal cavity in bushing 174, and the flange 176 of bushing 174 prevents the shoulder 92 from contacting the circular end of center tube 170. Preferably, shoulder 92 is spaced slightly away from flange 176 to allow for thermal expansion during transmission and a possible buildup of manufacturing tolerances. When transmitted energy flows through line 10 and connector 32, the annular space between the end of reduced diameter portion 90 and the surrounding portion of center tube 170 represents an infinite impedance to the transmitted waves. An effective quarter-wavelength back, the annular space between the circular end of center tube 170 and the adjacent surface of reduced diameter portion 90 represents a low impedance to the transmitted waves. Thus, a low impedance connection is achieved between the probe 40 and the center tube 170 which results in low heat loss and avoids the buildup of high voltages across the junction thus formed. The annular space between center conductor 16 and outer conductor 18 does not have the same physical dimensions as the annular space in a rigid coaxial line because of the corrugated walls and the dielectric membrane 24. However, transmission line 10 is designed and fabricated to provide the same characteristic impedance as an equivalent rigid coaxial line, 50 ohms for example. The annular space between the larger diameter portion 82 of probe 40 and the inner diameter of restricted portion 62 is equal dimensionally to the equivalent annular space in the rigid coaxial line and provides the same characteristic impedance, such as 50 ohms for example. Therefore, transmission line 10 and connector 32 are impedance matched to connect directly to a standard rigid coaxial line, as shown in FIG. 2.

Thus, there has been disclosed herein a novel connector for flexible transmission lines having an outer shell which is clamped in direct metallic contact with one conductor of the transmission line and an inner probe having a portion thereof disposed in spaced, parallel relationship with a portion of the other conductor of the transmission line for a distance equal to an effective quarter-wavelength of the energy to be transmitted by the flexible line. Thus, an open circuit occurs between the end of the probe and the opposing surface of the flexible center conductor; and a low impedance junction occurs between the end of the flexible center conductor and the opposing surface of the probe. Although a corrugated type of flexible transmission line has been illustrated herein, the connector of this invention is applicable to other flexible types of transmission lines, such as a bellows type for example. Furthermore, the center conductor of the flexible transmission line need not be hollow but may be filled with a flexible dielectric material and have hollow end portions, for example. Also, the dielectric bushing fixedly mounted in the open end of the center conductor could be replaced by a dielectric sleeve having a longitudinal bore open at both ends. These and other modifications of this type are within the spirit and scope of this invention and, as such, are intended to be included in the claims appended hereto.

Claims

We claim:

1. In combination, a male connector and a flexible coaxial transmission line comprising:

a first flexible conductor having a hollow end portion;

a second flexible conductor surrounding said first conductor and disposed in spaced, parallel relationship therewith;

a dielectric cylinder fixedly mounted in said hollow end portion of the first conductor and having a longitudinal bore disposed therein, said bore having an opening in the end of said cylinder adjacent the end of the first conductor:

an elongated conductive probe having an end portion slidably engaged in said bore, being mounted for slidable movement within said bore in response to flexing of said line, and extended in parallel relationship with said end portion of the first conductor for a distance equal to a quarter-wavelength of one frequency to be transmitted by the line;

a tubular housing insulatingly surrounding a portion of said probe and having a portion disposed in abutting relationship with an end portion of said second conductor; and

means for clamping said abutting portions of the housing and the second conductor into direct metallic contact with one another.

2. In combination, a male connector and a flexible coaxial transmission line as set forth in claim 1 wherein said dielectric cylinder is a bushing and said longitudinal bore is a cavity closed at the end of the bushing remote from the end of the first conductor.

3. In combination, a male connector and a flexible coaxial transmission line comprising:

a first, tubular, flexible conductor having an open end;

a second, tubular, flexible conductor surrounding said first conductor and disposed in spaced concentric relationship therewith;

a dielectric bushing fixedly mounted in the open end of the first conductor, and having a longitudinal cavity therein, said cavity having an open end in the end of the bushing disposed adjacent the end of the center conductor;

an elongated probe having an end portion slidably engaged in said cavity, being mounted for slidable movement within said cavity in response to flexing of said line, and a portion of said end portion extended in parallel relationship with an end portion of the first conductor for a distance predetermined to be equal to a quarter-wavelength of one frequency to be transmitted through the coaxial transmission line;

a tubular shell insulatingly surrounding a portion of said probe and having a portion thereof clamped to an abutting end portion of said outer conductor; and

means for clamping said portion of the shell into direct metallic contact with said abutting end portion of the outer conductor.

4. In combination, a male connector and a flexible coaxial transmission line comprising:

a first, tubular, flexible conductor having an open end;

a second, tubular, flexible conductor disposed in spaced concentric relationship with said first conductor and terminating at one end in a radially extending flange;

a dielectric bushing fixedly mounted in the open end of the first conductor, said bushing including an annular flange disposed in abutting relationship with the end of the first conductor and a longitudinal cavity having an open end in the flanged end of the bushing;

an elongated probe having an end portion slidably engaged in said cavity, being mounted for slidable movement within said cavity in response to flexing of said line, the length of said end portion being substantially equal to the thickness of the flange of the bushing plus a quarter-wavelength of one frequency in the waveband to be transmitted through said line, said probe further having an oppositely directed end portion;

a tubular shell disposed in surrounding, spaced relationship with a portion of said probe and having an internal shoulder disposed in abutting relationship with said flanged end of said outer conductor and an opposite end having a flange disposed in abutting relationship with a similar flange on a connecting device; and

means for clamping said flanged end of the outer conductor into direct metallic contact with said internal shoulder of the shell.

5. In combination, a connector assembly and two, flexible, coaxial transmission lines comprising:

a first, flexible, center conductor insulatingly disposed within a first flexible concentric conductor, said first center and concentric conductors having adjacent hollow end portions;

a second, flexible, center conductor insulating disposed within a second, flexible, concentric conductor, said second center and concentric conductors having adjacent hollow end portions;

said first center and concentric hollow end portions disposed adjacent said second center and concentric hollow end portions;

a first dielectric cylinder interfitted in the hollow end portion of the first center conductor and having a longitudinal bore, said bore having an opening in the end of said cylinder adjacent the end of the first conductor;

a second dielectric cylinder interfitted in the hollow end portion of the second center conductor and having a longitudinal bore, said bore having an opening in the end of said cylinder adjacent the end of the second conductor;

an elongated probe having one end portion slidably engaged in said bore of the first dielectric cylinder, being mounted for slidable movement within said bore in response to flexing of said first center conductor, and supported in spaced, parallel relationship with an end portion of the first center conductor and an opposite end portion slidably engaged in said bore of the second dielectric cylinder, being mounted for slidable within said bore in response to flexing of said second center conductor, and supported in spaced, parallel relationship with an end portion of the second center conductor, the end portions of the probe and center conductors being equal to an effective quarter-wavelength of one frequency to be transmitted through said transmission lines;

a tubular casing disposed in surrounding spaced relationship with said probe and having a portion disposed in abutting relationship with an adjacent end portion of the first concentric conductor and an opposite end portion disposed in abutting relationship with an adjacent end portion of the second concentric conductor; and

means for clamping said abutting portions of the casing into direct metallic contact with said end portion of the respective first and second concentric conductors of the respective transmission lines.

6. In combination, a connector assembly and two flexible coaxial transmission lines comprising:

a first, tubular, center conductor made of flexible material and insulatingly disposed within a first, tubular concentric conductor also made of flexible material;

a second, tubular, center conductor made of flexible material and insulatingly disposed within a second tubular conductor also made of flexible material;

said first center and concentric conductors having respective end portions axially aligned with respective end portions of said second center and concentric conductors;

a first dielectric bushing fixedly mounted in said end portion of the first center conductor and having a longitudinal cavity disposed therein, said cavity having an open end located in the exposed end of the bushing;

a second dielectric bushing fixedly mounted in said end portion of the second center conductor, and having a longitudinal cavity disposed therein, said cavity having an open end in the exposed end of said second dielectric bushing;

an elongated probe having an end portion slidably disposed in said cavity of the first dielectric bushing, being mounted for slidable movement within said cavity in response to flexing of said first center conductor, and surrounded by said end portion of the first center conductor, and an opposite end portion slidably disposed in said cavity of the second dielectric bushing, being mounted for slidable movement within said cavity in response to flexing of said second center conductor, and surrounded by said end portion of the second center conductor, said respective end portions of the probe and center conductors each being equal to a quarter-wavelength of one of the frequencies to be transmitted by the respective transmission lines;

a first tubular shell disposed in surrounding spaced relationship with a portion of said probe and having an end portion surrounding an adjacent end portion of the first concentric conductor and an opposite end portion;

a second tubular shell disposed in surrounding spaced relationship with another portion of the probe and having an end portion surrounding an adjacent end portion of the second concentric conductor in said other transmission line and an opposite end portion interlocked with said opposite end portion of the first shell; and

means for clamping said respective end portions of the first and second shells into direct metallic contact with the respective end portions of the respective first and second concentric conductors in the respective transmission lines.

7. In combination, a connector assembly and two flexible coaxial transmission lines comprising:

a first, tubular, center conductor made of flexible material and insulatingly disposed within a first, tubular concentric conductor made of flexible material and having a radial flange on one end thereof;

a second, tubular, center conductor made of flexible material and insulatingly disposed within a second tubular concentric conductor made of flexible material, and having a radial flange on one end thereof;

said first center and concentric conductors having respective end portions axially aligned with respective end portions of said second center and concentric conductors;

a first dielectric bushing interfitted in said end portion of the first center conductor and having an annular flange disposed in abutting relationship with the circular end of said first center conductor and a longitudinal cavity disposed therein having an open end in the flanged end of said first bushing;

a second dielectric bushing interfitted in said end portion of the second center conductor and having an annular flange disposed in abutting relationship with the circular end of second center conductor and a longitudinal cavity disposed therein having an open end in the flange end of said second bushing;

an elongated probe having an end portion slidably disposed in said cavity of the first bushing, being mounted for slidable movement within said cavity in response to flexing of said first center conductor, and surrounded by said end portion of the first center conductor in said one line, and an opposite end portion slidably disposed in said cavity of the second bushing, being mounted for slidable movement within said cavity in response to flexing of said second center conductor, and surrounded by said end portion of the second center conductor, said respective end portions of the probe and center conductors each being equal to a quarter-wavelength of one of the frequencies to be transmitted through the respective transmission lines;

a first tubular shell disposed in surrounding spaced relationship with a portion of said probe and having a portion thereof abutting said flanged end of the first concentric conductor and an oppositely disposed end having an annular coupling flange;

a second tubular shell disposed in surrounding spaced relationship with a portion of said probe and having a portion thereof abutting said flanged end of the second concentric conductor and an oppositely disposed end having an annular coupling flange clamped into direct metallic contact with said coupling flange of the first shell; and

means for clamping said respective abutting portions of the respective shells into direct metallic contact with said respective flanged ends of the first and second concentric conductors in the respective transmission lines.