Patent Publication Number: US-8975520-B2

Title: Ground loop isolator for a coaxial cable

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     One or more embodiments of the invention are related to the field of electrical cables. More particularly, but not by way of limitation, one or more embodiments of the invention enable a ground loop isolator for a coaxial cable, for example that blocks DC current but which allows a desired band of RF through the ground loop isolator, and which is small enough to fit in the areas where coupling of the desired electronic equipment is to occur. 
     2. Description of the Related Art 
     Standard coaxial cables may be utilized to connect high frequency electronic components together. Such a cable is shown in  FIG. 1 . As shown, coaxial cable  101  includes cable  102  and coaxial connector  103 . When coaxial cable  101  is utilized as shown in  FIG. 2 , grounding problems may occur when an ungrounded television or digital video recorder (DVR) is coupled via the coaxial cable with a set top box (STB) for example. This may cause a “ground loop”, wherein undesired currents occur between two devices that should be, but are not at the same voltage, i.e., should be at the ground potential. In some cases, a voltage different of up to 60 volts or more may exist on the television or DVR since two-plug power cables may be utilized to power the devices, and the devices may have a significant potential with respect to ground potential voltage. When coupling a coaxial cable between the ungrounded television/DVR and the set top box, sparks may occur if the differential is high enough, thereby potentially causing a hazard. 
     Many ground loop isolators exist, but are generally large devices, for example that are not configured to fit in small areas such as are found behind television sets, DVRs and set top boxes. In addition, since many set top boxes are configured to output a radio frequency signal for channel  2 ,  3  or  4 , ground loop isolators that utilize “chokes”, i.e., capacitor and inductor filters may limit the radio frequency signals in this range, which defeats the purpose of a ground loop isolator for coaxial cable scenarios, since the radio frequency at least in the range used between the set top box and the television may be blocked by the choke. 
     For at least the limitations described above there is a need for a ground loop isolator for a coaxial cable, for example that blocks DC current but which allows a desired band of RF through the ground loop isolator, and which is small enough to fit in the areas where coupling of the desired electronic equipment is to occur. 
     BRIEF SUMMARY OF THE INVENTION 
     One or more embodiments described in the specification are related to a ground loop isolator for a coaxial cable. Embodiments of the invention may include a transformer and/or other electrical components such as capacitors for example to form a filter that does not allow direct current to pass from one side of the ground loop isolator to the other side, but which allows a desired band of radio frequency voltage through the ground loop isolator. In addition, embodiments of the invention may be physically configured to be small enough to fit in the areas where coupling of the desired electronic equipment is to occur. Embodiments may include an outer area allowing for easier manual coupling of the coaxial cable connector nut or male connector to electronic devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of the invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein: 
         FIG. 1  illustrates coaxial cable coupled with a coaxial cable connector. 
         FIG. 2  illustrates a system diagram having a coaxial cable that is grounded by a coaxial cable junction box for example and a set top box that is thus grounded and that is connected to an ungrounded television and/or digital video recorder. 
         FIG. 3  illustrates a printed circuit board configured to hold the components that are utilized to isolate one side of the ground loop isolator from direct current from the other side, and which are also configured to allow a band of radio frequency voltage to pass between the two sides. 
         FIG. 4  illustrates an embodiment of the invention having a male and female interface. 
         FIG. 5  illustrates an exploded view of the embodiment of the invention shown in  FIG. 4 . 
         FIG. 6  illustrates an embodiment of the invention having two female interfaces. 
         FIG. 7  illustrates an exploded view of the embodiment of the invention shown in  FIG. 6 . 
         FIG. 8  illustrates an embodiment of the invention having two male interfaces. 
         FIG. 9  illustrates an exploded view of the embodiment of the invention shown in  FIG. 9 . 
         FIG. 10  illustrates embodiments of the outer manual rotation aid, without an outer faceted area for use with a wrench, which is configured to allow for easier manual coupling of the apparatus to electrical components. 
         FIG. 11  illustrates an embodiment of the outer manual rotation aid, with an outer faceted area for use with a wrench, that is configured to allow for easier manual coupling of the apparatus to electrical components, while still allowing for use of a wrench to couple the apparatus to electrical components. 
         FIG. 12  illustrates a cutaway view of the embodiment shown in  FIG. 11 . 
         FIG. 13  illustrates a cutaway view of a variation of an embodiment of the outer manual rotation aid have an inner integrated threaded portion which may be utilized in place of a separate coaxial cable connector nut or male connector. 
         FIG. 14  illustrates an embodiment of the invention showing the components on a printed circuit board without the outer cover or manual rotation aid installed so as to show a physical implementation of the embodiment shown in  FIG. 3 . Coin  1401  shows the relative size of the components on printed circuit board  301 . 
         FIG. 15  illustrates a circuit diagram for the electrical components that install on the printed circuit board of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A ground loop isolator for a coaxial cable will now be described. In the following exemplary description numerous specific details are set forth in order to provide a more thorough understanding of embodiments of the invention. It will be apparent, however, to an artisan of ordinary skill that the present invention may be practiced without incorporating all aspects of the specific details described herein. In other instances, specific features, quantities, or measurements well known to those of ordinary skill in the art have not been described in detail so as not to obscure the invention. Readers should note that although examples of the invention are set forth herein, the claims, and the full scope of any equivalents, are what define the metes and bounds of the invention. 
     Embodiments of the invention may include a transformer and/or other electrical components such as capacitors for example to form a filter that does not allow direct current to pass from one side of the ground loop isolator to the other side, but which allows a desired band of radio frequency voltage through the ground loop isolator. In addition, embodiments of the invention may be physically configured to be small enough to fit in the areas where coupling of the desired electronic equipment is to occur. Embodiments may include an outer area configured to enable easier manual coupling of the coaxial cable connector nut or male connector, whether integrated into the embodiment or not, to electronic devices. 
       FIG. 1  illustrates coaxial cable coupled with a coaxial cable connector. Coaxial cable  101  generally includes a conductor or central wire  110 , that is surrounded by a dielectric  111 , which is further surrounded by braided shielding  112 , which is further surrounded by an outer insulating jacket  120 . The cable is generally prepared for coupling with a coaxial cable connector via a tool that removes portions of the cable as shown in prepared cable  101   a , thereby exposing the conductor, dielectric and shielding. As shown in the blow up of coaxial cable connector  102  below cable  101   b , coaxial cable connector  102  or coaxial connector for short includes a post  140 , situated inside nut  103  that is rotationally coupled with the coaxial cable  101   b , optionally with O-ring  142 , and a collar  141 , which is also known as a body, that forms the main outer cylinder of the coaxial connector and which is held onto cable  101   b  via sleeve  143 , for example via a compression coupling with cable  101   b  as is known in the art. Shown in the bottom two cable depictions, rotation aid  160  (which may form cover  420  as is shown in  FIG. 4 ) is placed on the cable, optionally before coaxial cable connector  102  is crimped onto cable  101   c  and then coupled with nut  103  to form cable  101   d  with rotational aid for coupling nut  103  onto electrical equipment. These components in this configuration are also described in the parent patent application that has been incorporated by reference herein. 
       FIG. 2  illustrates a system diagram having coaxial cable  101  that is for example grounded by coaxial cable junction box  201  having ground line  202 , and set top box  203  that is thus indirectly grounded via ground line  202 . Set top box  203  is further connected to an ungrounded television  204  and/or digital video recorder  205 , both of which also float with respect to ground as per negative terminals of their two-prong electric power cords, wherein the power cords are ungrounded as they do not have a third ground line. When coaxial cable  261  is connected between set top box  203  and ungrounded television  204 , a ground loop may be established wherein a hazardous spark may occur when coaxial cable  261  nears or touches ungrounded television  204  since the chassis of the ungrounded television may be at a different electrical potential with respect to ground as opposed to set top box  203  which is effectively grounded to coaxial cable junction box  201  through the outer shielding layer of the coaxial cable itself. This configuration and many others like it where some video components are grounded and some are not, or where some are grounded to a different ground point or circuit are examples where hazardous sparks may occur. 
     Embodiments of the invention are configured to isolate the potential difference between the grounded and ungrounded electrical components from direct current while allowing radio frequency electrical signals to pass only if the signals are within a desired band of frequencies corresponding to channels  2 ,  3  or  4  for example (or any other desired channels) that are utilized to deliver any number of television channels input to set top box  203  and output from set top box  203  on channels  2 ,  3  or  4  to the older television. In this manner, the set top box is utilized to select a channel while the older television merely is set to receive a given channel that does not change when the set top box channel is changed. Embodiments of the invention may also be configured to attenuate radio frequency signals that are not within this desired band. In addition, embodiments of the invention may be provided in any form factor required to fit within the generally small area behind electrical components. One or more embodiments of the invention may be coupled with an existing coaxial cable connector before coupling an embodiment of the invention with ungrounded television  204  or DVR  205 . 
       FIG. 3  illustrates printed circuit board  301  configured to hold the components that are utilized to isolate one side of the ground loop isolator from direct current from the other side, and which are also configured to allow a band of radio frequency voltage to pass between the two sides. As shown, a pair of contact points at  302   a  (two squares next to each other) allow for mounting a capacitor therebetween. Contact points  303   a  and  304   a  allow for coupling one coil of a transformer onto printed circuit board  301 . Contact points  303   b  and  304   b  allow for coupling a second coil to a transformer that is insulated from the first coil to allow only alternating current to pass between opposing sides of the circuit. Contact points  302   b  (two squares next to each other), allow for mounting a capacitor on the opposing side of the circuit with respect to contact points  302   a . This allows for filtering the frequencies that are passed between one side of the circuit to the other. Any other filter configuration that can be made to fit within a coaxial cable connector with or without a rotation aid is in keeping with the spirit of the invention. The 4 holes in printed circuit board  301  may be utilized to couple shield to the printed circuit board to inhibit interference of external electrical signals. In the perspective view, the two holes on the left side “a” side of the circuit may couple with one shield, while the opposing two holes shown on the right side may couple with a second shield for example. 
       FIG. 4  illustrates an embodiment of the invention having male coaxial cable interface  410  coupled with an embodiment of the ground loop isolator, having cover  420  that is further coupled with female coaxial cable interface  430 . Cover may be made from an insulating material in one or more embodiments of the invention and may be manufactured via extrusion molding, or may be injection molded over the PCB and shields for example. In other embodiments of the invention, cover  420  may extend over nut  410 , which forms a portion of the male connector, and engage the nut so as to rotate the nut, while being rotationally coupled over the remainder of the PCB and female coaxial cable interface  430  for example. In other embodiments of the invention, cover has a threaded area molded into it so that a metallic nut is not required. In this embodiment a metallic coating, or conductive plastic for example may be utilized if desired to provide shielding. See  FIG. 13  for an illustration of this embodiment. 
       FIG. 5  illustrates an exploded view of the embodiment of the invention shown in  FIG. 4 . As shown, nut  410  is configured for rotational coupling with male collar  502 . Together, nut  410  and male collar  502  combine to form a male connector wherein the nut is capable of rotation, with respect to the male collar, about the longitudinal axis of the cable. Male collar  502  is configured to hold male connector dielectric  503  that includes a hole that allows male connector pin  504  to pass through male connector dielectric  503 , male collar  502  and nut  410 . Male connector pin is configured on the opposite side to couple with PCB  301 . The internal components of the ground loop isolator couple with wire (see  FIGS. 14 and 15 ), which is isolated from direct currents that could flow from female connector pin  506 , that is coupled to the opposing side of PCB  301 . The components that allow radio frequency signals to pass from one side of PCB  301  to the other include a transformer for example with a ferrite core in one or more embodiments. First shield  505   a  and second shield  505   b  are configured to attenuate external radio frequency signals that may enter the components on PCB  301 . The shields have small extensions on the bottom of them as shown that couple with the holes previously described with respect to  FIG. 3 , for example with solder. First shield  505   a  and second shield  505   b  are separated by a gap between them as shown, so that the two shields do not form a direct electrical connection and so that direct currents cannot pass between them as they are both in electrical contact with the respect coaxial interfaces on each side of the apparatus. On the female side of apparatus, female connector pin  506  includes a forked section shown on the right, which allows for a wire from a coaxial cable to enter between the forks and make electrical contact. Female connector pin  506  resides in female connector dielectric  507  that couples with female connector  430 . Cover  420  can be made a thick or thin as is required for the specific application. In one or more embodiments of the invention, cover may include a faceted area to allow for easier coupling with an electrical component by providing a facet for a wrench or a human hand to gain a better grip on the apparatus. In one or more embodiments, cover  420  forms an outer manual rotation aid, which is described in further detail in  FIG. 13 . 
       FIG. 6  illustrates an embodiment of the invention having two female interfaces  430 . One or more of the female interfaces may couple in a rotational manner with cover  420 , or may couple with cover  420  in a manner which does not allow for axial rotation with respect to cover  420 . An outer manual rotation aid may couple to one or more of the female interfaces, or alternatively none or one of the female interfaces. See  FIG. 13 . 
       FIG. 7  illustrates an exploded view of the embodiment of the invention shown in  FIG. 6 . This embodiment allows for two male cables to couple with the apparatus. The female components are described with respect to  FIG. 5 , however two sets of female components are utilized instead of one as described in  FIG. 5 . 
       FIG. 8  illustrates an embodiment of the invention having two male interfaces  410 . One or more of the male interfaces may couple in a rotational manner with cover  420 , or may couple with cover  420  in a manner which does not allow for axial rotation with respect to cover  420  and hence forms an outer manual rotation aid. See  FIG. 13 . 
       FIG. 9  illustrates an exploded view of the embodiment of the invention shown in  FIG. 9 . This embodiment allows for two female cables to couple with the apparatus. The male components are described with respect to  FIG. 5 , however two sets of male components are utilized instead of one as described in  FIG. 5 . 
       FIG. 10  illustrates embodiments of the outer manual rotation aid that may also be utilized as cover  420 , without an outer faceted area for use with a wrench, which is configured to allow for easier manual coupling of the apparatus to electrical components. The four embodiments shown have different interior variations to allow for engaging the nut, which may gouge the inner portion of the rotation aid in a manner that allows for removal of the rotation aid and subsequent use of the aid on the other end of the cable. These embodiments may be made of an insulating material, or a material that has a shield embedded inside of the insulating material for example. The first embodiment  420   a  is a straight cylinder, the second embodiment  420   b  has an area of thinner inner diameter  1011  that allows for engaging the nut, while the second diameter provides for more clearance around the collar, body or housing of the apparatus. The third embodiment  420   c  has ramps one or both sides  1021  and  1023  with narrower area  1022  so as to allow for easy engagement of the nut, while allowing for the nut to be placed at the other end of the cable without removing the apparatus from the cable, so that for example children cannot swallow the apparatus for example. This is true of all embodiments. In the fourth embodiment  420   d , a small retaining diameter or “stop”  1031  that enables the rotation aid to engage the apparatus between the nut and the housing for example. 
       FIG. 11  illustrates an embodiment of the outer manual rotation aid, with an outer faceted area for use with a wrench, that is configured to allow for easier manual coupling of the apparatus to electrical components, while still allowing for use of a wrench to couple the apparatus to electrical components. Embodiments of the invention may be constructed out of plastic for example. In this embodiment, a separate nut is not needed since the rotation aid includes a threaded area inside that enables the apparatus to screw onto a coaxial interface via the threaded area. 
       FIG. 12  illustrates a cutaway view of the embodiment shown in  FIG. 11 . This embodiment may utilize a smaller inner diameter portion to engage between the collar and the housing for example, see also  FIG. 10 . 
       FIG. 13  illustrates a cutaway view of a variation of an embodiment of the outer manual rotation aid  420  have an inner integrated threaded portion  1301  which may be utilized in place of a separate coaxial cable connector nut. In this embodiment, facets are not utilized on the outer portion of the rotation aid with respect to the embodiment shown in  FIGS. 11 and 12 . 
       FIG. 14  illustrates an embodiment of the invention showing the components on a printed circuit board without the outer cover or manual rotation aid installed so as to show a physical implementation of the embodiment shown in  FIG. 3 . 
       FIG. 15  illustrates a circuit diagram for the electrical components that install on the printed circuit board of  FIG. 3 . Connector J 1  may be implemented as a male or female connector as desired. When connector J 1  is coupled with electrical equipment that is grounded, a path  2  to ground  0  is formed at the outer portion of connector J 1 . A conductive path  1  couples electrically to an inner portion of connector J 1  and with capacitor C 1 . Capacitor C 1  is mounted on printed circuit board  301  between contacts at  302   a  (between the two adjacent square pads). Capacitor C 1  couples with transformer T 1  inductively, via electrical path  1  having a coiled wire section that coils about the transformer and which continues to electrical path  2  and on to ground  0 . The transformer, for this conductive path may be coupled at  303   a  and  304   a  in  FIG. 3  for example. Path  3  also includes a coiled section about transformer T 1  that couples inductively with transformer T 1  and continues to a common voltage point  4 , generally floating and not conductively coupled with ground  0 . Path  3  also couples electrically with capacitor C 2 . Electrical paths  1  and  3  are insulated from one another to prevent a direct current path from one side of the device to the other. Path  3  couples capacitor C 2  to an inner conductive portion of connector J 2 . The outer portion of connector J 2  is electrically coupled to a common voltage point  4  as is the opposing side of the coil of path  3 , which generally is not grounded as the opposing side of the circuit is. 
     While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.