Patent Publication Number: US-6213801-B1

Title: Electrical coupling and switching device with flexible microstrip

Description:
FIELD OF THE INVENTION 
     The present invention relates to electrical connectors, and more particularly to electrical coupling and switching devices for use in high frequency transmission rate applications. 
     BACKGROUND OF THE INVENTION 
     Electrical connectors and switching devices have been used for many years in various industries, such as the broadcast industry. The devices are used in electrical equipment systems to provide a transfer of electrical signal to different components of the particular system. The devices typically employ a mechanical-type action, such as a biasing action, in order to connect or disconnect various components of the system. 
     For example, a common type of connector and switching device or jack employs spring arms that are normally biased to provide electrical communication between two equipment plugs, such as standard BNC plugs, that are engaged in the device, typically on the same end of the device. The spring arms are individually moveable away from the normally biased position such that the equipment plugs can be terminated separately. In particular, a patch plug is often provided for urging a respective spring arm away from the normally biased position such that the patch plug is in electrical communication with one of the equipment plugs, while the remaining equipment plug is terminated through a resistor via the remaining spring arm. 
     Typically, these conventional jacks perform satisfactorily for standard television signals or for serial digital signals having a maximum bandwidth of about 750 megahertz. More specifically, the signal loss and discontinuity associated with these conventional jacks are not deleterious for most applications because most applications in the broadcast field for which they were designed do not require a high level of performance. However, with the advent of high definition television and other formats where the operating bandwidth is now beyond 2.4 gigahertz, conventional jacks do not provide effective signal carrying capacity as required for these applications. In particular, conventional jacks have excessive return losses at these high bandwidths. Thus, there is a need for an electrical switching jack that provides low discontinuity while minimizing return loss at bandwidths of about 1.5 GHz and higher. The jack, however, must be durable and capable of withstanding the repetitious cycling of the equipment and patch plugs. 
     SUMMARY OF THE INVENTION 
     These and other needs are provided by the present invention, which, in one embodiment, comprises an electrical coupling and switching device having a low-discontinuity, impedance-controlled electrical flowpath between two equipment plugs along a flexible microstrip. Advantageously, the flexible microstrip can be moved by insertion of a patch plug into the device in order to break the connection between the equipment plugs and establish electrical communication between the patch plug and the corresponding equipment plug. 
     In particular, the electrical coupling and switching device or jack in one embodiment comprises a housing defining first and second equipment ports, wherein each port includes a conductor pin. The conductor pins are adapted for connecting to the center conductor of a equipment plug, such as a coaxial or BNC plug, which is inserted into the respective equipment port. The housing further defines first and second patch ports for receiving first and second patch plugs, such as video-style plugs. 
     The jack also includes first and second insulative actuators positioned within the housing. Each actuator includes a conducting member that is positioned to be engaged by a patch plug when the patch plug is inserted into the respective patch port. The conducting member is also positioned such that as the patch plug is fully inserted into the respective patch port, the conducting member contacts the conductor pin of the respective equipment port so as to establish electrical communication or connection between the patch plug and the equipment port. 
     Advantageously, the flexible microstrip has first and second portions that, in a normal mode, are biased into contact with the conductor pins of the first and second equipment ports, respectively. In this regard, a connection is made between the first and second equipment ports when no patch plugs are inserted into the patch ports. More specifically, an impedance-controlled electrical flowpath is established along the flexible microstrip between the first and second equipment plugs in the normal mode, i.e., when no patch plugs are inserted into the patch ports. 
     When a patch plug, such as a video plug, is inserted into one of the patch ports, the patch plug engages the respective insulative actuator. As the patch plug engages the patch port, the actuator is urged toward the respective equipment port. This action causes the actuator to engage and urge the respective portion of the flexible microstrip away from and out of contact with the conductor pin on the respective equipment port, thus creating a patched circuit between the patch plug and the respective equipment port and an unpatched circuit to the remaining equipment port. Preferably, the actuator includes a ramped or angled surface for gradually engaging the respective portion of the flexible microstrip. 
     In one embodiment, the jack of the present invention also includes a resistive termination device, such as a resistor, that is positioned inside the housing so as to be contacted by the flexible microstrip when one of the insulative actuators urges the respective portion of the microstrip out of contact with the conductor pin of the respective equipment port. As the flexible microstrip contacts the termination device, the remaining unpatched equipment port is thereby terminated. In addition, the termination device preferably has the same impedance as the unpatched circuit, thereby substantially eliminating return loss. In order to facilitate contact between the termination device and the flexible microstrip, a conductive tab portion is attached to the flexible microstrip at each of its respective ends. 
     Thus, the jack of the present invention overcomes the problems mentioned above. In particular, the coaxial-to-flexible microstrip transition provides a more constant impedance in the normal mode than conventional jacks which employ spring arms to carry the signal between the equipment ports. In addition, the jack provides a low discontinuity flowpath between the equipment ports in the normal mode, which results in better signal integrity, particularly at bandwidths of 1.5 GHz and greater. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     While some of the objects and advantages of the present invention have been stated, others will appear as the description proceeds when taken in conjunction with the accompanying drawings, which are not necessarily drawn to scale, wherein: 
     FIG. 1 is a perspective view of a portion of an electrical coupling and switching device according to one embodiment of the present invention; 
     FIG. 2 is a perspective view of a portion of an electrical coupling and switching device according to the present invention showing a pair of insulative actuators; 
     FIG. 3 is a cross-sectional view of a flexible microstrip according to the present invention; and 
     FIG. 4 shows several views of an insulative actuator according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     Turning to FIGS. 1-4, an electrical coupling and switching device or jack according to the present invention is generally designated by the numeral  10 . The jack  10  may be used in many different applications, but is particularly advantageous for use in high bandwidth applications, such as high definition television or other applications with bandwidths of 1.5 GHz or greater. In particular, the jack  10  comprises a housing  12  made from a die cast conductive material, such as nickel plated zinc, including a front wall  14 , a back wall  16 , and side walls  18 . The walls,  14 ,  16 ,  18  cooperate with a bottom wall  20  and a cover (not shown) to define a housing interior  22 . In one embodiment, the housing has a length of about 34 inches, a width of about 1.5-2.5 inches, and a thickness of about 0.5-1.0 inches. 
     The front wall  14  defines two equipment ports  30 ,  32  to receive coaxial plugs, such as standard BNC-style plugs E (only one shown) having a center conductor surrounded by an outer sleeve. The equipment ports  30 ,  32  include conductor pins  34 ,  36 , respectively, that extend into the housing interior  22 . The conductor pins  34 ,  36  are positioned such that the center conductors of respective coaxial equipment plugs E engage the conductors pins and establish electrical communication therewith. Although the conductor pins  34 ,  36  are shown as having a generally circular cross section, the conductor pins can have other shapes and dimensions. The equipment ports  30 ,  32  also engage the outer sleeves of the coaxial plugs in order to connect the outer sleeves to an electrical ground. 
     The jack  10  also includes a flexible microstrip  50  having first and second portions  52 ,  54  that is positioned within the housing interior  22  proximate the front wall  14 . As shown in FIG. 3, the flexible microstrip  50  comprises a ground element  56 , a dielectric layer  58 , and a conducting track  60  extending along an upper surface of the dielectric layer. Desired impedance of the microstrip  50  can be controlled by the thickness of the dielectric layer  58 , the dielectric constant of the dielectric layer, and the width of the conducting track  60 . More specifically, the microstrip  50  can be formed via flexible printed circuit board technology or by interposing a highly flexible, homogenous, isotropic polymeric sheet, such as polytetrafluoroethylene (PTFE), between two metal sheets, which can be formed from brass, copper, or other conductive metal. In one advantageous embodiment, the ground element  56  comprises a resiliently flexible conductive material, such as beryllium copper. The dielectric layer  58  is also highly flexible. As such, the microstrip  50  is resiliently flexible, and can withstand a minimum of 30,000 flexure cycles, as discussed more fully below. 
     In a normal mode, an electrical circuit is established from one equipment port to the other equipment port via the flexible microstrip. In particular, the electrical circuit, which in one embodiment has a characteristic impedance of 75 Ohms, is established by directing an electrical signal from one equipment plug, through the respective equipment port  30  and conductor pin  34  to the flexible microstrip  50 . The signal is further directed along the conducting track  60  of the microstrip to the conductor pin  36  of the other equipment port  32 , which is in electrical communication with the other equipment plug. In order to maintain a continuous ground plane, the microstrip  50  should make sufficient contact with the equipment ports  30 ,  32 . To facilitate this contact, a grounding device (not shown) is provided between the ground element of the microstrip and the housing  12  proximate the wall  14 . 
     A conductive tab portion  62  is secured to each end of the microstrip  50  for facilitating positive contact between the microstrip and the conductor pins  34 ,  36 . In addition, each conductive tab portion  62  is wrapped around the respective end of the microstrip  50  so that the signal along the conducting track  60  is carried to the opposite surface of the microstrip for engagement with a resistive termination device  64 , as discussed more fully below. Advantageously, the conductive tab portion  62  in conjunction with the flexible microstrip  50  substantially eliminates discontinuity between the equipment ports  30 ,  32 . 
     The back wall  16  defines two patch ports  40 ,  42  adapted to receive patch plugs P (only one shown). In one embodiment, the patch ports  40 ,  42  are adapted to receive coaxial video-style patch plugs, although other types of patch plugs may also be used. The patch ports  40 ,  42  are formed in a conventional manner for releasably securing the patch plugs to the jack  10 , and define openings so that the patch plugs can extend therethrough into the housing interior  22 . 
     As shown in FIGS. 2 and 4, the jack  10  also includes a pair of insulative actuators or shuttles  44  that are movably disposed in the housing interior  22 . In particular, the shuttles  44  have a body portion  45  formed of a lubricious, insulative material, such as acetal resin. Suitable acetal resins are available from DuPont under the Delrin® trademark. Other materials may also be used, such as PTFE. In addition, the shuttles  44  include a conducting portion or member  46  extending therethrough. In should be noted, however, that the conducting member  46  does not have to extend through the body portion  45 , but instead could extend around the body portion in the shape of a full or partial band without parting from the spirit and scope of the present invention. The conducting member  46  includes a patch plug contact  47  for engaging the respective patch plug and a socket  48  or the like for engaging the conducting pins  34 ,  36  of the respective equipment ports. In one embodiment, the shuttles  44  may include a bias member (not shown), such as a spring, in order to hold the shuttles in a position proximate the back wall  16  unless acted upon by a sufficient external force. The bias member should also be capable of returning the shuttle to a fully disengaged position proximate the back wall. The body portion  45  of the shuttle  44  generally has an “H” shape that facilitates movement along the housing interior  22 , although other shapes may also be used. More specifically, the shape of the shuttle  44  allows suitable cooperation with the bottom wall  20  and the cover of the housing to form a “track and rail” system along the housing interior  22  of the jack  10 . This design ensures minimal wear on the jack components and maintains proper alignment between the shuttles  44  and the equipment ports  30 ,  32 . 
     In a patched mode, a video-style patch plug P is inserted into a particular patch port, such as the patch port designated by the numeral  40 . This may be desirable if there is a need to patch around a particular piece of equipment connected to the jack  10  at one of the equipment ports, such as the equipment port designated by the numeral  32 . As the patch plug is fully seated into the patch port  40 , the patch plug urges or pushes the shuttle  44  towards the respective equipment port  30 , which preferably is located across the interior portion  22  of the housing  12  along a common longitudinal axis with the patch port  40 . As the shuttle  44  is urged toward the equipment port  30 , the shuttle  44  engages the flexible microstrip  50 . In one embodiment, the body portion  45  of the shuttle  44  includes an angled or ramped bottom surface  49  substantially corresponding to the angle of the flexible microstrip  50  when the microstrip is in the normal mode in order to facilitate gradual engagement therebetween. As such, as the shuttle  44  moves towards the respective equipment port  30 , the shuttle progressively engages the first portion  52  of the flexible microstrip  50  and urges the first portion of the microstrip away from the respective conductor pin  34 . When the patch plug is fully seated in the patch port  40 , the socket  48  extending from the shuttle  44  engages and mates with the conductor pin  34  extending from the corresponding equipment port  30 . As a result, an electrical patch circuit is established between the patch plug and the equipment port  30  via the shuttle  44 , cover, and conductor pin  34 . Advantageously, the patch circuit provides a constant impedance for the patched signal. 
     According to one embodiment of the present invention, the unpatched equipment port  32  is terminated in its characteristic impedance while the shuttle  44  moves toward the corresponding equipment port  30  and urges the first portion  52  of the flexible microstrip  50  away from the conductor pin  34 . More specifically, as the patch plug is fully seated in the patch port  40  and the socket  48  has engaged the conductor pin  34 , the tab portion  62  connected to the flexible microstrip  50  proximate the first portion  52  thereof is urged away from the conductor pin  34  and contacts the resistive termination device  64 . 
     As shown in FIGS. 1 and 2, the resistive termination device  64  comprises a resistor of the same value as the characteristic impedance of the system, such as 75 Ohms. There is a contact for the termination device  64  beneath each portion  52  and  54  of the microstrip. Preferably, a high frequency or microwave resistor is used and the contacts are nickel-passivated or otherwise treated to ensure reliable contact. To minimize return loss, the circuit on the flexible microstrip  50  should make suitable contact with the resistor, which in turn makes contact with the ground. Preferably, the grounding should occur in close proximity to the resistor. In this regard, the conductive tab portion  62  extends around the end of the flexible microstrip  50  such that in the patched mode the tab portion contacts the resistor and thus terminates the unpatched equipment port, which in the present example is the port  32 . In addition, the ground element  56  of the microstrip  50  comprises a resilient material, which is capable of returning the flexible microstrip  50  back into contact with the conductor pin  34  when the shuttle  44  is moved away from the microstrip, thereby transferring from the patched mode to the normal mode. 
     Although the foregoing only describes a patch mode using a single patch plug in conjunction with one of the equipment ports, it is also within the scope of the present invention to patch both equipment ports  30 ,  32  to corresponding patch plugs that are inserted into the patch ports  40 ,  42  of the jack. When both equipment ports  30 ,  32  are in the patched mode, both shuttles  44  are fully engaged so that the flexible microstrip  50  has moved away from both conductor pins  34 ,  36  of the equipment ports  30 ,  32 , respectively. To return one of the equipment ports to the normal mode, for example the equipment port designated by numeral  30 , the patch plug is removed from the corresponding patch port  40 , which causes the corresponding shuttle  44  to move away from the equipment port and return to its retracted position proximate the back wall  16 . As the shuttle  44  moves away from the equipment port  30 , the first portion  52  of the flexible microstrip  50  moves away from the termination device  64  and contacts the equipment port. Because the second portion  54  of the microstrip is still in contact with the termination device  64 , the equipment port  30  is terminated as described above while the other equipment port  32  remains in the patched mode. To return to the normal mode for both equipment ports  30 ,  32 , both patch plugs must be removed from the respective patch ports  40 ,  42  so that both portions  52 ,  54  of the flexible microstrip  50  return to the normal position, as described above. Advantageously, the patch circuits can be repetitively opened and closed while maintaining the impedance of the circuit between the equipment ports  30 ,  32 . 
     Thus, the present invention provides an electrical coupling and switching device or jack  10  for coaxial applications having a low-loss, low-discontinuity, constant-impedance electrical flowpath for coaxial signals and, when in the patched mode, terminating the unpatched equipment port in a low return loss impedance that is substantially equivalent to the system impedance while the patched equipment port maintains a low-loss and low-discontinuity patched signal. Advantageously, the jack of the present invention has minimal return loss and discontinuity at bandwidths of 1.5 GHz and higher, yet is durable enough to withstand repetitious cycling of the flexible microstrip  50  and associated components from the normal mode to the patch mode and vice versa. As such, the present invention provides a jack and a method of patching a circuit that overcomes the problems mentioned above. 
     Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. For example, the jack  10  may be designed such that the equipment parts  30 ,  32  are positioned at an angle, such as 90° or other angle, relative to the patch ports  40 ,  42 , instead of each equipment port having a common longitudinal axis with the respective patch port as illustrated in the drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.