Controlled impedance cable termination for cables with conductive foil shields

Abstract

A cable termination that allows an SMA connector to be attached to a controlled impedance cable with a conductive foil-wrapped shield. In a separate ferrule embodiment, the sheath is stripped on the cable to expose the foil shield surrounding the dielectric. The ferrule is slid or clamped over the foil shield to mate. The ferrule face is finished so that the foil shield and dielectric are flush with the ferrule face, and the signal conductors protrude from this face. This cable subassembly is assembled into a boss in the housing to prevent movement of the ferrules relative to each other, so that each ferrule face aligns with the boss opening through which the SMA connector barrel is attached to the ferrule. A cover secures the cable subassembly to the housing.

Description

[Technical field]

[0001] This invention relates to electrical cable terminations, and more particularly to terminations for controlled impedance cables made with a conductive metal foil shield or a composite metal foil and plastic as a ground path, which are less expensive to manufacture, more flexible, and are commonly used to transmit high frequencies in electronic equipment. [Background technology]

[0002] The purpose of a cable termination is to provide an interconnection from a cable to an electrical device and to provide a separable electrical interconnection between the cable and its operating environment. The separable feature means that the cables are not interconnected by permanent mechanical means such as soldering or bonding, but rather by temporary mechanical means.

[0003] A typical controlled impedance cable has one or more signal conductors, each surrounded by a dielectric. The dielectric is surrounded by a ground shield, which is optionally covered by a sheath. A cable can have one signal conductor (coax), two signal conductors (twinax), three signal conductors (triax), or more, each with its own dielectric. Each conductor / dielectric can have its own ground shield, or a single ground shield surrounds all conductors / dielectrics. A variety of ground shield constructions are available, including woven wire mesh, metal jacketing, and foil wrap, all of which are conductive. Of these various ground shield constructions, foil wrap is less expensive to manufacture, more flexible, and is commonly used to transmit high frequencies in electronic equipment.

[0004] In an attempt to minimize the deleterious electrical effects of the terminations, SMA (Subminiature Version A) connectors and variations thereof are commonly connected to controlled impedance cables to maintain good electrical contact. Controlled impedance cables have a ground shield that has some structural integrity, such as the metal braid of a standard flexible cable or a thin metal jacket, as used for semi-rigid coaxial cables. These cables can be easily soldered and the connector will not fail at the junction of the ground shield and the connector, because the shield has its own structural integrity.

[0005] Foil-wrapped cables are smaller and denser, but lack the structural integrity to fit into an SMA connector because the foil is designed to be very thin and flexible, with a small volume. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention is a cable termination that allows for the attachment of an SMA connector to a controlled impedance cable with a conductive foil wrapped shield, providing stiffness and strain relief to the cable, as well as a means to control signal integrity and phase length. [Means for solving the problem]

[0007] The present invention has two embodiments: a separate ferrule embodiment and an integrated ferrule embodiment.

[0008] In a split ferrule embodiment, the sheath is stripped at the cable to expose the foil shield surrounding the dielectric to form the shield line. Alternatively, the dielectric is also stripped and replaced with a dielectric sleeve. If the cable is a single foil shield surrounding all the dielectric, the foil shield is split and rewrapped around each dielectric.

[0009] A rigid ferrule is slid or clamped over the foil shield and optionally bonded to the shield line, giving the cable the structural integrity required to mount the SMA connector barrel. The face of the ferrule is finished to be flush with the face of the foil shield and dielectric, from which the signal conductors protrude. A precision finish is used to set the electrical length of the cable. In the case of twinax cables, the shield line can be matched as precisely as desired.

[0010] The cable subassembly fits into a boss on the housing and is secured by a cover that fits over the boss. The boss has features to capture the ferrules and prevent movement of the ferrules relative to one another. These features position the cable subassembly so that each ferrule face aligns with a corresponding connector opening in the boss. Once the cable subassembly is positioned in the boss, each SMA connector barrel is fitted over a ferrule through the opening.

[0011] After the SMA connector barrel is installed, the cover is placed and attached to the boss, and the cable is sandwiched between the boss and the cover to provide strain relief.

[0012] In an integrated ferrule embodiment, the sheath is stripped and the foil shield is stripped a small amount. If the cable has separate dielectrics, the dielectric is not stripped, leaving each line to form the cable subassembly. If the cable has a single dielectric, the dielectric is stripped along with the foil shield and a dielectric sleeve is slid over the signal conductors, thereby forming the cable subassembly. The signal conductors are bent away from each other at an angle.

[0013] The cable subassembly is fitted into a boss of the housing and secured by a cover, the boss having a number of recesses for receiving the cable subassembly, each of which has a corresponding recess in the cover, the combination of which forms a space in the housing through which the cable subassembly extends.

[0014] The cable fits into a strain relief at one end of the housing. The strain relief opens into a junction space that receives the cable junction where the signal conductors separate. The neck presses the foil shield to provide an electrical connection between the foil shield and the housing. The signal conductor / dielectric fits into a signal path that extends away from the junction space at the same angle that the signal conductors are bent away from each other. The signal path runs through a protrusion that extends from the edge of the housing to an opening in the protrusion face. The signal conductors protrude from the protrusion face.

[0015] After preparing and / or finishing the projection surfaces, the SMA connector barrel is attached to the projections by suitable means.

[0016] The objectives of the present invention will become apparent upon consideration of the following drawings and detailed description of the invention.

[0017] For a more complete understanding of the nature and objects of the present invention, reference is made to the accompanying drawings. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is a front perspective view of a fully assembled termination assembly of a split ferrule embodiment of the present invention for a twin-ax cable. [Diagram 2] FIG. 2 is a front perspective view of a fully assembled termination assembly of the present invention for a coax cable. [Diagram 3] FIG. 2 is a rear perspective view of the termination assembly of the present invention; [Figure 4] FIG. 2 is a front view of the termination assembly of FIG. 1. [Diagram 5] FIG. 2 is a right side view of the termination assembly of FIG. 1. [Figure 6] FIG. 2 is a rear view of the termination assembly of FIG. 1. [Figure 7] FIG. 2 is a top view of the termination assembly of FIG. 1. [Figure 8] FIG. 2 is a perspective view of a twinax cable end with a separate dielectric and separate ground shield. [Figure 9] FIG. 2 is a perspective view of a twinax cable end with a separate dielectric and single ground shield. [Figure 10] FIG. 1 is a perspective view of a twinax cable end with a single dielectric and single ground shield. [Figure 11] FIG. 1 shows a twin-ax cable with a split dielectric and single foil shield in a first step in preparation for assembling a termination to the cable. [Figure 12] FIG. 12 is a detailed view of 12-12 in FIG. [Figure 13] FIG. 1 shows a twin-ax cable with a split dielectric and single foil shield, showing the cable in a second step in preparation for assembling a termination. [Figure 14] FIG. 14 is a detailed view of 14-14 in FIG. [Figure 15] FIG. 2 is a top view of a single-piece ferrule. [Figure 16] FIG. 16 is a partial side perspective view of the single-piece ferrule of FIG. 15. [Figure 17] FIG. 16 shows the ferrule face end of the single-piece ferrule of FIG. 15. [Figure 18] FIG. 2 is an exploded perspective view of a two-piece ferrule. [Figure 19] FIG. 19 is an exploded cross-sectional view of the two-piece ferrule of FIG. 18. [Figure 20] FIG. 13 is an exploded perspective view of another two-piece ferrule. [Figure 21] FIG. 21 is an exploded cross-sectional view of the two-piece ferrule of FIG. 20. [Figure 22] FIG. 13 is an exploded perspective view of another two-piece ferrule. [Diagram 23] FIG. 23 is an exploded cross-sectional view of the two-piece ferrule of FIG. 22. [Figure 24] FIG. 2 is a perspective view of a single-piece ferrule to be assembled into a shielded line. [Diagram 25] FIG. 1 is a perspective view of a two-piece ferrule that is assembled into a shielded line. [Figure 26] FIG. 2 is a perspective view of a ferrule incorporated in a shielded line. [Figure 27] FIG. 27 is a detailed view of a ferrule incorporated into the shielded line of FIG. 26. [Figure 28] FIG. 2 is a perspective view of a ferrule assembled to a shielded line and a ferrule face finished to receive a connector. [Figure 29] FIG. 29 is a detailed view of a ferrule incorporated into the shielded line of FIG. 28. [Diagram 30] FIG. 2 is a cross-sectional view of a ferrule for a cable having multiple signal conductors and a single dielectric. [Diagram 31] FIG. 13 is a cross-sectional view of another ferrule for a cable having multiple signal conductors and a single dielectric. [Diagram 32] FIG. 13 is a cross-sectional view of another ferrule for a cable having multiple signal conductors and a single dielectric. [Diagram 33] FIG. 1 shows the cable after preparation for assembling the termination into a twin-ax cable with a single dielectric. [Diagram 34] FIG. 2 is a perspective view of a single-piece ferrule for assembly with a signal conductor. [Diagram 35] FIG. 1 is a perspective view of a two-piece ferrule that fits over a signal conductor. [Diagram 36] FIG. 2 is a perspective view of a ferrule assembled to a signal conductor. [Figure 37] FIG. 2 is a perspective view of a completed cable subassembly. [Figure 38]FIG. [Figure 39] FIG. 13 is a perspective view of a boss with an assembled cable subassembly. [Diagram 40] FIG. 13 is a front view of the boss with the cable subassembly installed. [Diagram 41] FIG. 2 is an exploded view of the termination assembly. [Diagram 42] FIG. 7 is a cross-sectional view of the termination assembly taken at 42-42 in FIG. 6. [Diagram 43] FIG. 2 is a rear perspective view of a fully assembled termination assembly of an integrated ferrule embodiment of the present invention for a twin-ax cable. [Diagram 44] FIG. 2 shows a split dielectric twin-ax cable after preparation as a cable subassembly. [Diagram 45] FIG. 2 shows a single dielectric twin-ax cable after preparation for assembling the cable subassembly. [Diagram 46] FIG. 2 is an exploded view of the termination assembly. [Figure 47] FIG. [Figure 48] FIG. [Figure 49] FIG. 13 is a perspective view of a boss with an assembled cable subassembly. [Figure 50] FIG. 13 is a cross-sectional view of the assembled housing with the cable. [Figure 51] 51 is a detailed cross-sectional view taken along line 51-51 in FIG. [Figure 52] 52 is a cross-sectional view of the configuration of the protrusion portion at 52-52 in FIG. 50. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] As mentioned above, a typical controlled impedance cable 20 has one or more signal conductors 22, each surrounded by a dielectric 24. The dielectric 24 is surrounded by a ground shield 26, which is optionally covered by one or more sheaths 28a, 28b (collectively 28). The cable 20 may have one (coax), two (twinax), three (triax), or more signal conductors (22). In some cable constructions, each signal conductor 22 has its own dielectric 24 and ground shield 26, as in FIG. 8. In other cable constructions, each signal conductor 22 has its own dielectric 24 and a single ground shield 26 that surrounds all of the dielectrics 24, as in FIG. 9. In yet another cable construction, a single dielectric 24 surrounds all of the signal conductors 22, and a single ground shield 26 surrounds the dielectric 24, as in FIG. 10. This specification uses several terms to identify different combinations of cable elements. The line 30 is a combination of the signal conductor 22 and the dielectric 24. The shielded line 32 is a combination of the signal conductor 22, the dielectric 24, and the shield 26.

[0020] The present invention is intended for use with cables 20 in which only the ground shield 26 is comprised of a conductive foil wrap, which may be metal foil or a composite of metal foil and plastic. The term foil shield is used herein to refer to a conductive foil wrapped ground shield 26. The present invention is not intended for use with cables having a ground path that incorporates something other than a foil shield.

[0021] The present invention is a cable termination 10 that allows for the attachment of an SMA connector to a controlled impedance cable 20 with a foil shield 26. As will be described in detail below, the cable termination 10 of the present invention provides stiffness to the cable 20 and provides strain relief, as well as a means for controlling signal integrity and phase length.

[0022] The present invention has two embodiments, a separate ferrule embodiment shown in FIGS. 1-42 and a unitary ferrule embodiment shown in FIGS.

[0023] Briefly, in a split ferrule embodiment, the sheath 28 is stripped away from the cable 20 and the foil shield 26 remains surrounding the dielectric 24 to form the shield line 32. A rigid ferrule 40 is slid or bonded over the foil shield 26 and bonded to the shield line 32 to give the cable 20 the structural integrity required to fit the SMA connector barrel 12. This cable subassembly 14 is assembled into a boss 60 of the housing 16 and secured in place by a cover 62 which is attached to the boss 60 by screws 64 or other mechanical means.

[0024] The housing 16 provides a platform upon which the SMA connector barrel 12 can be mechanically attached to the ferrule 40 and prevents bowing at the mated interface between the ferrule 40 and the shielded line 32 .

[0025] 1-7 show a cable termination assembly 10 in a split ferrule embodiment of the present invention with an SMA connector barrel 12. FIGS. 1 and 3-7 show the termination assembly 10 with a twinax cable 20, and FIG. 2 shows the termination assembly 10 with a coax cable 20. This specification describes the termination of the present invention as used with a twinax cable 20. However, the present invention can be used with any controlled impedance cable 20 having one or more signal conductors 22.

[0026] The cable subassembly 14 is assembled by assembling a ferrule 40 onto each shielded line 32 of the cable 20, as shown in Figures 11-34. The sheath 28 is stripped to expose the foil shield 26 wrapped around the line 30. The length of the sheath 28 that is stripped, and thus the length of the foil shield 26 that is exposed, will depend on the particular application and parameters of the housing 16, as described below.

[0027] For a cable 20 with two or more signal conductors 22, with each signal conductor 22 having a dielectric 24 and a foil shield 26, the shielded line 32 are simply separated.

[0028] For a cable 20 with two or more signal conductors 22 with a dielectric 24 for each signal conductor 22 and a single foil shield 26 surrounding all of the dielectric 24, the foil shield 26 is split into sections 36 for each of the lines 30, as in Figures 11 and 12. The split foil shield 26 is then rewrapped around each dielectric 24 to form shield lines 32, as in Figures 13-14. Note that each cut foil shield 26 section 36 is not wide enough to extend around the entire circumference of the dielectric 24, thus leaving an air gap 34 in the foil shield 26 for each shield line 32, as in Figure 14. Either condition, whether the foil shield 26 completely surrounds the dielectric 24 or whether the foil shield 26 does not completely surround the dielectric 24, is considered to surround the dielectric 24 in this application.

[0029] The present invention also contemplates that the dielectric 24 can be stripped away and replaced with a dielectric sleeve. This can be convenient, for example, when the impedance of the cable needs to be changed.

[0030] Several configurations of ferrules 40 to be assembled into each shield line 32 in a cable 20 with a separate dielectric 24 are shown in Figures 15-23. The ferrule 40 is a cylinder constructed of a rigid material. In one form, the ferrule 40 is made of a conductive material such as brass or copper. In another form, the ferrule 40 is made of an insulating material.

[0031] The ferrule 40 has an axial through bore 42 which is line 14. The ferrule 40 has a capture section 80 adjacent the line opening 44 and an SMA mounting section adjacent the ferrule face 50. The through bore 42 has a diameter such that it can receive the shield line 32 as shown in FIG. 14. The ferrule 40 has a capture section 80 adjacent the line opening 44 and an SMA mounting section adjacent the ferrule face 50.

[0032] Optionally, the ferrule 40, as in Figures 18-23, consists of two longitudinal parts 40a, 40b, which together make up the complete ferrule 40. In the configuration of Figures 18 and 19, the two parts 40a, 40b are identical, i.e., each part 40a, 40b extends 180° around the ferrule 40.

[0033] 20 and 21, the larger piece 40a extends more than 180° of the ferrule 40, leaving a wedge-shaped cut 102 that is less than 180°, and the smaller piece 40b extends above the angle of the cut 102. In the example of Figures 20 and 21, the larger piece 40a extends approximately 270°, leaving a 90° cut 102. This particular shape aids in alignment when mating the two pieces 40a, 40b.

[0034] In the configuration of Figures 22 and 23, the parts 40a, 40b are stepped to facilitate alignment when fitting them together. Each of the two parts 40a, 40b extends approximately 180° in the ferrule 40. The first part 40a has one or two longitudinal grooves 106 adjacent the bore 42, and the second part 40b has a longitudinal mating ridge 108 adjacent the bore 42. The parts 40a, 40b can also be viewed in an alternative manner, with the first part 40a having a longitudinal ridge 110 adjacent the outer surface 114, and the second part 40b having a longitudinal mating groove 112 adjacent the outer surface 114. Alternatively, the grooves and ridges are between the hole 42 and the outer surface 114, but spaced apart from the bore 42 and the outer surface 114. This stepped configuration aids in alignment and helps block signal leakage when mating the two parts 40a, 40b.

[0035] For the single-piece ferrule 40 of Figures 15-17, the shielding line 32 is inserted into the line opening 44 and slid over the shielding line 32 as in Figure 24 until the end of the shielding line 32 extends from the face opening 46 as in Figures 26 and 27. For the two-piece ferrule 40 of Figures 18 and 19, as well as Figures 22 and 23, and the two-piece ferrule 40 of Figures 20 and 21, when the wedge angle is close to 180°, the two parts 40a, 40b are placed on the shielding line 32 with their longitudinal faces 54 abutting each other as in Figure 25, and the end of the shielding line 32 extends from the face opening 46 as in Figures 26 and 27. For the two-part ferrule 40 of Figures 20 and 21, where the wedge angle is significantly less than 180°, the shielding line 32 is inserted into the line opening 44 in the first part 40a, and the first part 40a is slid over the shielding line 32 until the end of the shielding line 32 extends from the face opening 46, as in Figures 26 and 27. The second part 40b is then placed over the shielding line with two longitudinal faces 54 abutting each other.

[0036] The amount of shield line 32 that extends from face opening 46 depends on the length of shield line 32 desired in cable subassembly 14. Optionally, foil shield 26 can be trimmed, but must still make electrical contact with ferrule 40 if ferrule 40 is conductive.

[0037] If the ferrule is non-conductive, it can be plated with a conductive surface, in which case the foil shield 26 must be in electrical contact with the ferrule 40. In cases where the shielded line 32 is in a sufficient impedance environment, the ferrule 40 does not need to be conductive.

[0038] In one form, the bonding agent secures the ferrule 40 to the shield line 32, thereby creating a rigid structure at the end of the shield line 32. The bonding agent can be introduced into the bore 42 through a bonding agent hole 52 that intersects the bore 42, which helps provide a clean supply of bonding agent. Alternatively, the bonding agent is injected into one or both bore openings 44, 46 of the ferrule 40. Alternatively, when a two-piece ferrule 40 is used, the bonding agent is applied to both halves of the bore 42 prior to installation of the ferrule 40 on the shield line 32.

[0039] The bonding agent can be any type of adhesive suitable for a particular application. The bonding agent may or may not be conductive. The present invention contemplates that the bonding agent can be metallic or non-metallic and can be thermal, chemical, or radiation bonded.

[0040] For a two-piece ferrule 40, a bonding agent may also be used to attach the two parts 40a, 40b together to form the complete ferrule 40. Alternatively, the ferrule parts 40a, 40b may be attached together using any other means appropriate for the application. Examples include soldering, welding, adhesive bonding, clamping, and boss features as described below.

[0041] Once the adhesive has set, the ferrule face 50, dielectric 24, and foil seal 26 are finished with precision trim (if not trimmed prior to insertion into the line opening 44) so ​​that the dielectric 24 and foil shield 26 are flush with the ferrule face 50, thereby creating a flat mating surface with the signal conductor 22 slightly protruding and undamaged, as at 56 in FIGS. 28 and 29. This precision trimming, along with the distance the ferrule 40 slides over the shield lines 32, is also used to set the electrical length or phase of the cable. Trimming the surface 50 electrically shortens the shield lines 32. In the case of a twin-ax cable 20, the shield lines 32 can be precisely matched so that they have the same or specific different electrical or phase lengths as desired.

[0042] As mentioned above, the ferrule 40 can be constructed of a conductive or insulating material. If a conductive material, the ferrule 40 operates electrically as part of the foil shield 26, so that the foil shield 26 does not need to be exposed at the ferrule face 50 after finishing.

[0043] If the ferrule 40 were constructed of an insulating material, it would not act as part of the foil shield 26, and so the foil shield 26 would have to extend to the ferrule face 50 in some manner. Any suitable method may be utilized by the present invention and is considered part of the finishing process. In one form, the ferrule face 50 has a conductive coating that is electrically connected to the foil shield 26. In another form, the bonding agent is conductive and extends to the ferrule face 50.

[0044] Several configurations of ferrules 40 for incorporation into each signal conductor 22 of cable 20 with a single dielectric 24 are shown in Figures 30-32. Ferrule 40 is a cylinder constructed of a rigid conductive material, such as brass or copper, and has an axial through bore 120. As further noted above, ferrule 40 can be constructed from a single piece, or from two longitudinal pieces.

[0045] 30, the ferrule 40 has an integral rigid dielectric 122 that resides within and extends the entire length of the bore 120. The dielectric 122 has an axial through hole 124 for the signal conductor 22. The dielectric 122 may be either separate from the ferrule 40 or may be press-fit or otherwise secured to the bore 120. If the ferrule 40 is a two-piece ferrule 40, the dielectric may be a single piece or two pieces.

[0046] The configuration of FIG. 31 is the same as FIG. 30, but adds a slight indentation 128 in the dielectric 122 at the line end 48. The indentation 128 provides an anchor for the shielded line 32. As noted above, the dielectric 122 can either be separate from the ferrule 40 or can be press-fit or otherwise secured in the bore 120. As noted above, if the ferrule 40 is a two-piece ferrule 40, the dielectric can be a single piece or two pieces.

[0047] 32, the ferrule has an air dielectric 130. A number of dielectric spacers 132 provide axial through holes 124 for the signal conductors 22.

[0048] For cables 20 with two or more signal conductors 22 having a single dielectric 24 and a single foil shield 26 surrounding the dielectric 24, the foil shield 26 and dielectric 24 are split and stripped prior to installation of the ferrule 40, leaving only the single bare conductor 22 as shown in FIG. 33.

[0049] When the dielectric is separated from the ferrule 40, the dielectric 122 is slid over the signal conductor 22 until it abuts the trimmed dielectric 24 and foil shield 26. The one-piece ferrule 40 is assembled to the dielectric 122 by inserting the signal conductor 22 / dielectric 122 into the line opening 44, and the dielectric 122 is removed. 2 The ferrule 40 is slid over the signal conductor 22 / dielectric 122 as in Fig. 34 until the ferrule face 50 is reached and the end of the signal conductor 22 extends from the face opening 46 as in Fig. 36. The two-piece ferrule 40 is assembled as in Fig. 35 and described above by placing the two parts into the dielectric 122 with their longitudinal faces abutting each other, thereby properly positioning the end of the dielectric 120 in the bore 120 so that the signal conductor extends from the face opening 46 as in Fig. 36.

[0050] Once the dielectric is secured in the bore 120, the single piece ferrule 40 secures the signal conductor 22 to the Axial through hole 124 36, and the ferrule 40 is slid over the signal conductor 22 until the end of the signal conductor 22 extends from the face opening 46, as in FIG. 36. The two-piece ferrule 40 is assembled as described above onto the signal conductor 22 with the two parts abutting each other with their longitudinal faces facing each other, so that the signal conductor extends from the face opening 46, as in FIG.

[0051] Optionally, a bonding agent secures the ferrule 40 to the signal conductor 22. As described above, the bonding agent may be Axial penetration The bonding agent can be introduced into the bore 120 through a bonding agent hole that intersects with the hole 124. Alternatively, the bonding agent can be Axial penetration Alternatively, when using a two-piece ferrule 40, the bonding agent may be injected into one or both ends of the bore 124 before the ferrule 40 is placed on the signal conductor 22. Axial penetration Apply to both halves of hole 124.

[0052] As noted above, the bonding agent can be any type of adhesive suitable for a particular application. As noted above, for a two-piece ferrule 40, a bonding agent can also be used to attach the two parts 40a, 40b together to form the complete ferrule 40. Alternatively, the ferrule parts 40a, 40b can be attached together using any other means suitable for the application. Examples include soldering, welding, adhesives, clamping, and boss features as described below.

[0053] Once the adhesive has set, the ferrule face 50 is optionally finished by precision trimming to set the electrical length or phase of the cable. Trimming the face 50 electrically shortens the shield lines 32. The two shield lines 32 of a twin-ax cable 20 can be precisely matched so that the shield lines 32 are the same or have specific different electrical lengths or phase lengths, as desired.

[0054] Once face 50 is finished, signal conductor 22 is trimmed to protrude at 56 by a length determined by the specifications of the desired SMA connector type, typically in the range of 25-75 mils.

[0055] After the ferrules 40 have been assembled onto each shielded line 32 and finished, the cable subassembly 14 is ready to be assembled into the housing 16, as shown in FIG.

[0056] The housing 16 includes a boss 60 and a cover 62, both of which are made of a rigid material. The boss 60 and the cover 62 can be made of an insulating material or a conductive material. A conductive material helps with better EMI shielding.

[0057] 39-42, the cable subassembly 14 is positioned in the boss 60 by resting the capture section 80 of the ferrule 40 on separate features 66 in the boss 60 and by resting the cable 20 in a cable opening 90. The features 66 position the cable subassembly 14 so that each ferrule face 50 aligns with a corresponding connector opening 68 in the side of the boss 60. Optionally, the features 66 include elements that cooperate with the ferrule 40 to prevent back and forth movement and rotation of the ferrule 40 within the boss 60.

[0058] 38, the feature 66 in this design includes a recess 72 in the boss 60 with a wider portion 74 at one end adjacent to an elongated portion 76. The wider portion 74 can be circular or rectangular in cross section. The elongated portion 76 is rectangular in cross section with opposing parallel walls 78.

[0059] 15-17, the capture section 80 of the ferrule 40 has a complementary configuration with a larger diameter than the cylindrical SMA barrel mounting section 82. The capture section 80 has a pair of opposed, parallel flat walls 86 that extend along a portion of the capture section 80 adjacent the SMA barrel mounting section 82, leaving a cylindrical foot 84 adjacent the line end 48. The foot 84 fits within the wide portion 74 of the recess 72, and the flat walls 86 extend along the recess 72 against the opposed walls 78. 2 The foot 84 of the wide portion 74 fits within the elongated portion 76 of the ferrule 40. 2 The flat wall 86 abutting the opposing wall 78 prevents the ferrule 40 from moving back and forth within the recess 78. 2 Prevents rotation inside.

[0060] Optionally, the boss 60 includes features for clamping the two parts 40a, 40b of the two-part ferrule 40 together.

[0061] Once the cable subassembly 14 is positioned in the boss 60, each SMA connector barrel 12 is mounted by suitable means through the opening 68 onto the SMA barrel mounting section 82 of the ferrule 40. The SMA barrel mounting section 82 is configured for the particular type of SMA connector barrel 12 to be mounted. The mounting can be permanent, but is preferably removable. In one configuration, the SMA barrel mounting section 82 is threaded such that the SMA connector barrel 12 screws onto the ferrule 40. In another configuration, the SMA connector barrel 12 is press-fit onto the SMA barrel mounting section 82. In another configuration, the SMA connector barrel 12 has external threads that screw into the connector opening 68 and slide onto the SMA barrel mounting section 82.

[0062] The ferrule 40 is connected to the boss of the subassembly 14. 60 The trim face 50 of the ferrule 40 provides a flat and predictable interface profile so that mating SMA connectors can mate.

[0063] After the SMA connector barrel 12 is mated with the ferrule 40 in the boss 60, the cover 62 is placed on the boss 60 and attached with screws 64 through holes 70 in the cover 62, as shown in FIG. 41, or by other mechanical means, to form the complete termination assembly 10 shown in FIGS. 1-7. To minimize stress on the cable 20, the cable 20 is sandwiched between the cable opening 90 of the boss and the cover 62. Optionally, the cable 20 is wrapped with additional material, such as a sheath material, at the point of pinching to add stiffness and prevent large bends where the cable 20 exits the housing 16.

[0064] The boss 60 grips and holds the cable subassembly 14 by the ferrule 40, thereby minimizing stress at the interface between the ferrule 40 and the shielded line 32. That is, there are no pulling, pushing, or bending forces on the shielded line 32 where it enters the ferrule 40. These forces would detrimentally change the electrical characteristics, such as impedance, at the interface. This results in a stable electrical interface between the foil shielded cable 20 and the SMA connector barrel 12, which allows multiple mating and unmating without changing the electrical characteristics of the transmission line.

[0065] The integrated ferrule embodiment 210 shown in Figures 43-52 can be used with any cable construction, including cable constructions with a separate foil shield 26 or a single foil shield and a separate dielectric 24 or a single dielectric 24.

[0066] Briefly, the sheath 28 is stripped and the foil shield 26 is stripped a small amount. If the cable 20 has a separate dielectric 24, the dielectric 24 is not stripped, leaving each line 30 to form the cable subassembly 214. If the cable 20 has a single dielectric 24, the dielectric 24 is stripped along with the foil shield 26 and the dielectric sleeve 220 is slid over the signal conductors 22 to form the lines 30, thereby forming the cable subassembly 214. The cable subassembly 214 is assembled into the boss 224 of the housing 216 and secured by a cover 226 that is attached to the boss 224 by screws 228 or other mechanical means. The SMA connector barrel 212 is attached to a projection 232 from the boss 224 from which the signal conductors 22 extend.

[0067] The housing 216 provides a platform onto which the SMA connector barrel 212 can be electrically attached to the cable 20 without placing stress on the cable 20 .

[0068] 43 shows a fully assembled cable termination assembly of an integrated ferrule embodiment 210 of the present invention with an SMA connector barrel 212. This specification describes the termination of the present invention using a twin-ax cable 20, but it may also be adapted for use with a cable 20 having one or more signal conductors 22.

[0069] The cable subassembly 214 is assembled by first stripping the sheath 28 to expose the foil shield 26 wrapped around the dielectric 24. The next step depends on the cable construction. In a cable 20 with a separate dielectric 24, the foil shield 26 is stripped somewhat less than the sheath 28 to expose the dielectric 24 as in FIG. 44. As above, each signal conductor 22 / dielectric 24 combination is shown with a line 30. The length that the sheath 28 and foil shield 26 are stripped will depend on the particular application and parameters of the housing 216, as described below. The lines 30 are bent away from each other at 234 by an angle described below to form the cable subassembly 214. The section of the cable 20 where the foil shield 26 is stripped and the lines 30 are bent away is referred to as the splice 236.

[0070] In a cable with a single dielectric 24, the foil shield 26 and dielectric 24 are stripped somewhat less than the sheath 28, as in FIG. 45, to expose the signal conductors 22. The length to which the sheath 28, foil shield 24, and dielectric 24 are stripped will depend on the particular application and parameters of the housing 216, as described below. The signal conductors 22 are bent away from each other at 234 at an angle, as described below. As mentioned above, the section of the cable 20 where the foil shield 26 and dielectric 24 are stripped and the signal conductors 22 are bent away is referred to as the junction 236.

[0071] A single dielectric cable subassembly 214 is assembled by sliding a dielectric sleeve 220 over each signal conductor 22. The dielectric sleeve 220 is cylindrical with axial through holes 222 for the signal conductors 22. The dielectric sleeve 220 is long enough to cover most of the signal conductors 22, as described below. The cable subassembly 214 is ready to be assembled into a housing 216.

[0072] Housing 216 includes boss 224 and cover 226, both of which are made of a rigid material. Boss 224 is made of a conductive material and acts as a ground. Cover 226 can be made of either an insulating material or a conductive material. A conductive material serves as a better EMI shield and as a continuation of the ground. Boss 224 and cover 226 can be made of an insulating material if they are coated with a conductive material, such as a metal plating.

[0073] As shown in Fig. 47, the boss 224 has several recesses for receiving the cable subassembly 214. Each of the recesses in the boss has a corresponding recess in the cover 226, shown in Fig. 48, which in combination form a space in the housing 216 through which the cable subassembly 214 extends. The sheathed cable 20 fits into a strain relief 240 formed by a recess 240a in the boss 224 and a recess 240b in the cover 226 at one end of the housing 216. The strain relief 240 opens into a splice space 242 formed by a recess 242a in the boss 224 and a recess 242b in the cover 226, which receives the cable splice 236. The signal path 244 formed by the recess 244a in the boss 224 and the recess 244b in the cover 226 extend away from the interface space 242 at an angle relative to one another depending on the particular application. In the present design, the angle is approximately 60°. This is the same angle at which the lines 30 / signal conductors 22 are bent away from one another when assembling the cable subassembly 214. The signal path 244 extends through the protrusion 232 formed by the fingers 232a extending from the boss 224 and the fingers 232b extending from the cover 226, which extends from the edge of the boss 224 to an opening 252 in the protrusion surface 238.

[0074] 50 and 51 , the cable 20 is captured in the strain relief 240 when the cover 226 is attached to the boss 224. Optionally, the cable 20 is wrapped with additional material 254, such as a sheath material, at the strain relief 240 to add stiffness and prevent large bends at the point where the cable 20 exits the housing 216.

[0075] The cable 20 extends into the mating space 242 to a neck 246 that receives the foil shield 26. The foil shield 26 / dielectric 24 is forced between the boss neck 246a and the cover neck 246b, providing a good electrical connection between the foil shield 26 and the housing 216.

[0076] The bend 234 of the line / signal conductor is The recess 248a of the boss 224 and the recess 248b of the cover 226 are included.It is received by throat 248 which is slightly narrower than neck 246 to compensate for the air dielectric and to control impedance in the neck region.

[0077] The signal path 244 is cylindrical with a complementary diameter to the dielectric 24 / dielectric sleeve 220. With a separate dielectric cable 20, the line 30 extends somewhat past the protruding surface 238, as at 256 in FIG. 49. With a single dielectric cable 20, the dielectric sleeve 220 extends the full length of the signal path 244 until it is flush with the protruding surface 238, and the signal conductor 22 extends somewhat past the protruding surface 238, as at 256 in FIG.

[0078] As mentioned above, if the signal conductors 22 of a cable 20 with a single dielectric 24 are separated, the single dielectric 24 must be split between the two signal conductors 22. When that happens, the dielectric 24 is no longer whole, i.e., no longer provides the correct impedance. To alleviate this problem, the dielectric 24 is stripped along with the foil shield to the joint 236, and the dielectric sleeve 220 is slid over the exposed signal conductors 22. The outer diameter of the dielectric sleeve 220 and the inner diameter of the signal path 244 are designed to provide the proper impedance and to operate similarly to a cable 20 with a split dielectric 24.

[0079] Once the cable subassembly 214 is positioned in the boss 224, the cover 226 is installed on the boss 224 and attached with screws 228 through holes 230 in the cover 226, as shown in FIG. 46, or by other mechanical means, thereby enclosing the strain relief 240, the joint space 242, the neck 246, the neck 248, and the signal path 244.

[0080] As can be seen in FIG. 46, the projection 232 comprises a finger 232a extending from the boss 224 and a finger 232b extending from the cover 226. In the same way that the two parts 40a, 40b of the two-part ferrule 40 together form the complete ferrule 40, the two fingers 232a, 232b together form the complete projection 232 when the cover 226 is attached to the boss 224. Like each part 40a, 40b of the two-part ferrule 40, the fingers 232a, 232b have complementary abutment surfaces 258a, 258b. The present invention contemplates that any suitable shape of the complementary abutment surfaces 258a, 258b may be used, including the shapes described above with reference to the two-part ferrule 40. Another example of the complementary abutment surfaces 258a, 258b is shown in FIG. 52. The boss 224 has 180° of the signal path 244 and extends a parallel tangential wall 260. The cover 226 has another 180° of the signal path 244 and a flat parallel wall 262. The fingers 232b of the cover slide into the fingers 232a of the boss to complete the projection 232.

[0081] After the cover 226 is installed, for the separate dielectric 24, the dielectric 24 is finished to be flush with the protruding surface 238. Optionally, for all cables 20, the protruding surface 238 is finished by precision trimming to set the electrical length or phase of the cable 20. Trimming the surface 238 electrically shortens the shield 26. The two lines 30 of the twinax cable 20 can be precisely matched to have the same or specific different electrical lengths or phase lengths, as desired.

[0082] After trimming and / or finishing the prong surface 238, the SMA connector barrel 212 is attached to the prong 232 by suitable means, as in FIG. 43. The prong 232 functions similarly to the ferrule 40 in the previous embodiment 10. The prong 232 is configured for the particular type of SMA connector barrel 212 to which it is to be attached. The attachment can be permanent, but is preferably removable. Typically, the prong 232 is threaded such that the SMA connector barrel 12 screws onto the ferrule 232. Alternatively, the SMA connector barrel 12 is press-fit onto the prong 32.

[0083] The boss 224 allows the cable subassembly 214 to be properly positioned and held securely so that the mating of the cable 20 and SMA connector barrel 212 consistently provides the best signal integrity. The raised surface 238 provides a flat and predictable interface profile so that mating SMA connectors can mate.

[0084] Thus, a controlled impedance cable termination having a conductive foil shield has been shown and described. All matter set forth in the foregoing specification and shown in the accompanying drawings is intended to be illustrative and not limiting, since certain changes may be made to the disclosure without departing from the scope of the invention.

Claims

1. 1. A method for terminating a controlled impedance cable having a ground path consisting solely of one or more signal conductors, a dielectric surrounding said signal conductors, and a foil shield surrounding said dielectric, comprising: (a) providing a ferrule for each signal conductor, each ferrule constructed from a rigid material, cylindrical with opposite ends and having an axial through bore extending from a line opening at one end to a face opening at a ferrule face at the other end, said ferrule providing a receiving section adjacent said line opening, and an SMA barrel mounting section adjacent said ferrule face; (b) assembling a cable subassembly by: (1) forming each signal conductor, a dielectric surrounding the signal conductor, and a foil shield surrounding the dielectric in a shield line; (2) assembling the ferrule into the shield line such that the signal conductors protrude from the face opening; (3) securing the ferrule to the shield line; and (4) finishing the ferrule face such that the foil shield and the dielectric form a flat mating surface flush with the ferrule face and the signal conductors protrude from the ferrule face. (c) providing a housing comprising a boss and a cover constructed from a rigid material, the boss providing a cable opening, a connector opening for each shielded line, and a recess complementary to the receiving section of the ferrule for receiving each ferrule such that the ferrule face is aligned with a corresponding connector opening in the boss; (d) assembling the cable subassembly into the boss by assembling each ferrule into a corresponding one of the recesses and attaching a controlled impedance cable into the cable opening; (e) attaching the cover to the boss; A method comprising:

2. 2. The method of claim 1, further comprising the step of installing an SMA connector barrel through the connector opening onto each ferrule after the cable subassembly is assembled into the boss.

3. 2. The method of claim 1, wherein the ferrule is constructed from a single piece, and wherein assembling the ferrule to the shielded line includes sliding an end of the shielded line into the line opening of the ferrule until the end of the shielded line extends from the face opening.

4. 2. The method of claim 1, wherein the ferrule is constructed from two longitudinal parts, and the step of assembling the ferrule to the shielded line includes the step of installing the two longitudinal parts to the shielded line.

5. The method of claim 1 , wherein the ferrule is secured to the shielded line by a bonding agent.

6. The method of claim 5 , wherein the bonding agent is introduced into the ferrule by a hole in a side of the ferrule that intersects the bore.

7. The method of claim 1, wherein the receiving section of the ferrule has opposing parallel walls and a wide foot near the line opening to prevent back and forth movement and rotation of the ferrule within the boss, and the recess has opposing parallel walls and a wide section for the foot.

8. 2. The method of claim 1, wherein finishing the ferrule face comprises trimming the ferrule face to a desired length of the shield line.

9. 10. The method of claim 1, wherein the controlled impedance cable has two or more signal conductors and a single foil shield surrounding all of the dielectric, and further comprising the steps of: dividing the foil shield into portions for each signal conductor and wrapping each portion around the dielectric of a corresponding signal conductor to form the shielded line prior to sliding a ferrule over the shielded line.

10. 2. The method of claim 1, wherein the controlled impedance cable has two signal conductors forming two shielded lines, the lengths or phases of the two shielded lines being matched by finishing the ferrule faces.

11. The method of claim 1 , wherein assembling the cable subassembly comprises stripping a dielectric and sliding a dielectric sleeve over the signal conductors.

12. The method of claim 1 , wherein the step of attaching the cover comprises sandwiching the controlled impedance cable between the boss and the cover.

13. 10. The method of claim 1, wherein the controlled impedance cable further comprises a sheath, and the sheath is prepared prior to sliding the ferrule over the shielded line.

14. The method of claim 1 , wherein the boss is constructed from an insulating material.

15. The method of claim 1 , wherein the boss is constructed from a conductive material.

16. 1. A termination assembly comprising: (a) a controlled impedance cable having one or more signal conductors, a dielectric surrounding the signal conductors, and a ground consisting only of a foil shield surrounding the dielectric, each signal conductor forming a shield line, the shield line being composed of a dielectric surrounding the signal conductor and a foil shield surrounding the dielectric; (b) a ferrule for each signal conductor, each ferrule constructed of a rigid material, cylindrical with opposite ends, having an axial through bore extending from a line opening at one end to a face opening in a ferrule face at the other end, the bore receiving and securing the shield line, the foil shield and dielectric forming a flat mating surface flush with the ferrule face, the signal conductor protruding from the ferrule face, the ferrule having a receiving section adjacent the line opening and a mounting section for an SMA barrel adjacent the ferrule face; (c) a housing comprising a boss and a cover constructed from a rigid material, the boss having a cable opening for receiving a controlled impedance cable, a connector opening for each shield line, and a recess for receiving each ferrule complementary to the receiving section of the ferrule, the recess aligning the ferrule face with a corresponding connector opening in the boss; (d) the cover attached to the boss; A termination assembly comprising:

17. 17. The termination assembly of claim 16, further comprising an SMA connector barrel attached to the ferrule through the connector opening.

18. The termination assembly of claim 16 , wherein the ferrule is comprised of a single piece.

19. The termination assembly of claim 16 , wherein the ferrule is made of two longitudinal parts.

20. 17. The termination assembly of claim 16, wherein the ferrule is secured to the signal conductor with the dielectric and foil shield by a bonding agent.

21. The termination assembly of claim 20 , wherein the ferrule includes a hole in the ferrule intersecting a bore through which the bonding agent is introduced.

22. A termination assembly as described in claim 16, wherein the receiving section of the ferrule has opposing parallel walls and a wide foot near the line opening to prevent back and forth movement and rotation of the ferrule within the boss, and the recess has opposing parallel walls and a wide section for the foot.

23. The termination assembly of claim 16 , wherein the boss and cover comprise elements that sandwich the controlled impedance cable therebetween.

24. The termination assembly of claim 16 , wherein the boss is constructed from a dielectric material.

25. The termination assembly of claim 16 , wherein the boss is constructed from a conductive material.

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