1. Field of the Invention
The present invention relates generally to terminators and CATV coaxial connectors, and more particularly, to a terminator having an improved construction.
2. Technical Background
Cable transmission systems are in wide use throughout the world for transferring television signals, and other types of signals, between devices. For example, a typical CATV system utilizes coaxial cables to provide signal communication between a head end and distributed receiver sets. A conventional CATV system includes a permanently installed cable extending from the head end throughout the area to be served. Various devices, such as directional taps, are spaced along the cable. Individual subscribers are serviced by a drop cable connected to a selected terminal of an equipment box or other device. The terminals that extend from the equipment box are externally threaded female coaxial ports designed to receive a conventional F-connector provided at the end of the drop cable. A terminator is typically affixed to each of the unused terminals of the equipment to maintain proper impedance along the signal transmission path.
In some cases, the equipment to which the drop cables are connected must be located in public areas, and the terminals may be readily accessible to the public. Such circumstances might permit unauthorized persons to move a drop cable from one port to another port, diverting service from a paying subscriber to a non-paying user. In an effort to prevent unauthorized access to the system, suppliers to the CATV industry have provided a type of terminator referred to as tamper-resistant or theft-proof. Typical examples of such tamper resistant terminators are shown and described in U.S. Pat. No. 3,845,454 (Hayward, et al.); U.S. Pat. No. 3,519,979 (Bodenstein); U.S. Pat. No. 4,469,386 (Ackerman); U.S. Pat. No. 5,055,060 (Down); U.S. Pat. No. 5,106,312 (Yeh); U.S. Pat. No. 6,491,546 (Perry); and U.S. Pat. No. 7,144,271 (Burris, et al). A special tool, not generally available to the public, is required for installation and removal of such tamper resistant terminators from the equipment ports to which they are attached.
In other cases, the equipment to which the drop cables are connected are located in relatively secure areas and do not required a tamper-proof termination system. Terminators applied in said application are typically more simplified in their design and, as a result, are of lower cost.
In either case, the current state of the art has been to employ a cylindrical carbon type resistive element that is axially in-line with the components comprising the terminator assembly. The overall length of the resistive element and the cylindrical nature of the design of the resistive element necessitate the use of correspondingly long related components resulting in a relatively long assembly. Electrical tuning of this type of arrangement is somewhat limited by the structural aspect of the arrangement of components and is further limited by the nature of the resistive element itself. Additionally, it is typical to mount the resistive element within a separate component, or holder, often attached to the resistive element by means of a solder joint and is then in turn assembled within the final assembly by means of a press fit. In such configurations, the diameter of the electrical lead of the resistive element is typically required to be less than the diameter of the cable center conductor it is intended to emulate.
One aspect of the invention includes a coaxial terminator for securing and terminating a coaxial equipment port of an equipment box. The coaxial equipment port is of the type having a female center conductor adapted to receive a center conductor of a coaxial connector. The coaxial equipment port is also of the type including an externally threaded outer conductor surrounding the female center conductor and spaced apart therefrom by a dielectric. The coaxial terminator includes a housing having first and second opposing ends, the first end of the housing having a central bore, and the first end of the housing including an internally threaded region to threadedly engage the outer conductor of the coaxial equipment port through rotation of the housing relative to the coaxial equipment port. The coaxial terminator further includes an impedance match element mounted within the housing. The impedance match element includes a central conductive pin having first and second opposing ends, a supportive element, and a resistor having first and second opposing ends, wherein the resistor is in electrical communication with the central conductive pin and wherein the resistor longitudinally extends in a direction that is not coaxial with the longitudinal axis of the central conductive pin.
In a preferred embodiment, the housing includes an internal body and an outer body surrounding the internal body and rotatably secured thereover. The internal body has first and second opposing ends and the first end of the internal body includes the internally threaded region to threadedly engage the outer conductor of the coaxial equipment. The outer body has first and second opposing ends and the second end of the outer body can have a bore formed therein for allowing the insertion of a tool to rotate the internal body, wherein the impedance match element is mounted within the internal body.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description present embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operations of the invention.
Reference will now be made in detail to the present preferred embodiment(s) of the invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.
As used herein, the terms “longitudinal” and “longitudinally” refer to the longest dimension of a three-dimensional object or component.
In preferred embodiments, the present invention can provide an RF terminator having a reduced number of components and a reduced length (thereby reducing the overall amount of material required and, hence, cost). In addition, reduced length can reduce cantilever forces that may be applied to an equipment port, which can provide a more robust, or less prone to breakage system. In preferred embodiments, the present invention may also provide an RF terminator that is highly tunable and contains a center conductor that emulates related cable while still providing at least one positive feature or benefit of prior product offerings, such as use with standardized security tooling and/or weather sealing where required.
RF port member 141 is typically press-fit into inner body 111. Inner body 111 has slotted surfaces 151, for receiving a special tool used to rotate inner body 111. In addition, inner body 111 includes a bowed, thinned region which has an outwardly-extending external circular rib 121 within an annular recess 116 of outer shield 106.
Outer shield 106 surrounds inner body 111 and is rotatably secured over inner body 111 and includes an inner surface defining a smaller diameter central bore 156, formed therein for allowing insertion of a working end of an installation tool to rotate inner body 111. As further shown in
Alternatively, pin 301 may be constructed from copper clad steel and plated with a conductive material such as tin. Impedance match element 300 further comprises a supportive element 306, such as a printed circuit board (“PC board”), which is a copper clad epoxy-glass material known to the industry. Impedance match element 300 further comprises a resistor 311, such as a thick-film chip resistor commercially available from any number of sources including Dale Electronics of Norfolk, Nebr. or Amitron of North Andover, Mass. Resistor 311, in a preferred embodiment, includes a coated ceramic block.
Inner body 211 is preferably forced into outer body 206 during factory assembly. Segments or fingers formed by a plurality of slots 246 form radially inwardly to allow an annular shoulder 231 to pass into annular groove 236. Once positioned, segments or fingers formed by a plurality of slots 246 are formed radially outwardly in a factory assembly process thereby rotatably capturing inner body 211 within outer body 206. Axial movement between inner body 211 and outer body 206 is limited by the axial relationship of annular shoulder 231 and annular groove 236. Internal threaded area 221 provides mechanical coupling with corresponding mating components. (See also
Cavity 226 may be dimensionally altered or tuned by design to provide improved return loss (electrical) response characteristics. In a preferred embodiment, cavity 226 is cylindrical in shape and has a diameter of from 0.200 inches to 0.350 inches and a length or depth of from 0.050 inches to 0.200 inches, such as a diameter of from 0.250 inches to 0.300 inches and a length or depth of from 0.050 inches to 0.150 inches, including a diameter of from 0.265 inches to 0.285 inches and a length or depth of from 0.050 inches to 0.100 inches, including, for example, a diameter of 0.281 inches and a length or depth of 0.050 inches. In a preferred embodiment, cavity 226 is cylindrical in shape and the ratio of the diameter of the cylindrical cavity to the length or depth of the cylindrical cavity ranges from 6:1 to 1:1, such as from 4.5:1 to 1.5:1, and further such as from 3:1 to 1.7:1, and even further such as from 2.5:1 to 1.8:1, and yet even further such as from 2:1 to 1.9:1. Terminator performance in terms of return loss can be modified by adjusting the dimensions of cavity 226. In a preferred embodiment, the terminator provides for a return loss having an absolute value of at least 25 dB, such as at least 30 dB, and further such as at least 35 dB, and even further such as at least 40 dB, and yet even further such as at least 45 dB, including at least 50 dB.
For example, in a preferred embodiment, a terminator providing for a return loss having an absolute value of at least 25 dB includes a cylindrical cavity, wherein the ratio of the diameter of the cylindrical cavity to the length or depth of the cylindrical cavity ranges from 6:1 to 1:1. In a further preferred embodiment, a terminator providing for a return loss having an absolute value of at least 30 dB includes a cylindrical cavity, wherein the ratio of the diameter of the cylindrical cavity to the length or depth of the cylindrical cavity ranges from 4.5:1 to 1.5:1. In yet a further preferred embodiment, a terminator providing for a return loss having an absolute value of at least 35 dB includes a cylindrical cavity, wherein the ratio of the diameter of the cylindrical cavity to the length or depth of the cylindrical cavity ranges from 3:1 to 1.7:1. In still a further preferred embodiment, a terminator providing for a return loss having an absolute value of at least 40 dB includes a cylindrical cavity, wherein the ratio of the diameter of the cylindrical cavity to the length or depth of the cylindrical cavity ranges from 2.5:1 to 1.8:1. In an even further preferred embodiment, a terminator providing for a return loss having an absolute value of at least 45 dB includes a cylindrical cavity, wherein the ratio of the diameter of the cylindrical cavity to the length or depth of the cylindrical cavity ranges from 2:1 to 1.9:1.
In a preferred embodiment, the terminator shown in
Supportive element 306, in a preferred embodiment is a PC board, which is a copper clad epoxy-glass material known to the industry. Supportive element 306 preferably comprises a copper clad trace elements 316 and 326 on the distal side as illustrated in
Trace element 326 contacts related body member to provide an electrical path to ground. Alternatively, another trace element can be utilized on the proximal side of supportive element 306 and joined with trace element 326 by means of through-board via holes or the like creating an alternate ground plane or planes. Use of a secondary or alternate ground plane allows the possibility that internal body 211 to be made from plastic or other non-conductive material further reducing component costs.
Supportive element 306 may be round, hexagonal, square, or virtually any geometric shape. Preferably, resistor 311 longitudinally extends radially along at least a portion of supportive element 306, as shown in
Turning to
Cavity 421 may be dimensionally altered or tuned by design to provide improved return loss (electrical) response characteristics. In a preferred embodiment, cavity 421 is cylindrical in shape and has a diameter of from 0.200 inches to 0.350 inches and a length or depth of from 0.050 inches to 0.200 inches, such as a diameter of from 0.250 inches to 0.300 inches and a length or depth of from 0.100 inches to 0.200 inches, including a diameter of from 0.265 inches to 0.285 inches and a length or depth of from 0.150 inches to 0.200 inches, including, for example, a diameter of 0.281 inches and a length or depth of 0.145 inches. In a preferred embodiment, cavity 421 is cylindrical in shape and the ratio of the diameter of the cylindrical cavity to the length or depth of the cylindrical cavity ranges from 6:1 to 1:1, such as from 4.5:1 to 1.5:1, and further such as from 3:1 to 1.7:1, and even further such as from 2.5:1 to 1.8:1, and yet even further such as from 2:1 to 1.9:1. Terminator performance in terms of return loss can be modified by adjusting the dimensions of cavity 421. In a preferred embodiment, the terminator provides for a return loss having an absolute value of at least 25 dB, such as at least 30 dB, and further such as at least 35 dB, and even further such as at least 40 dB, and yet even further such as at least 45 dB, including at least 50 dB.
For example, in a preferred embodiment, a terminator providing for a return loss having an absolute value of at least 25 dB includes a cylindrical cavity, wherein the ratio of the diameter of the cylindrical cavity to the length or depth of the cylindrical cavity ranges from 6:1 to 1:1. In a further preferred embodiment, a terminator providing for a return loss having an absolute value of at least 30 dB includes a cylindrical cavity, wherein the ratio of the diameter of the cylindrical cavity to the length or depth of the cylindrical cavity ranges from 4.5:1 to 1.5:1. In yet a further preferred embodiment, a terminator providing for a return loss having an absolute value of at least 35 dB includes a cylindrical cavity, wherein the ratio of the diameter of the cylindrical cavity to the length or depth of the cylindrical cavity ranges from 3:1 to 1.7:1. In still a further preferred embodiment, a terminator providing for a return loss having an absolute value of at least 40 dB includes a cylindrical cavity, wherein the ratio of the diameter of the cylindrical cavity to the length or depth of the cylindrical cavity ranges from 2.5:1 to 1.8:1. In an even further preferred embodiment, a terminator providing for a return loss having an absolute value of at least 45 dB includes a cylindrical cavity, wherein the ratio of the diameter of the cylindrical cavity to the length or depth of the cylindrical cavity ranges from 2:1 to 1.9:1.
In a preferred embodiment, the terminator shown in
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
Number | Name | Date | Kind |
---|---|---|---|
3486221 | Robinson | Dec 1969 | A |
3519979 | Bodenstein | Jul 1970 | A |
3573702 | O'Keefe | Apr 1971 | A |
3768063 | Coffman | Oct 1973 | A |
3845454 | Hayward et al. | Oct 1974 | A |
3890028 | Blanchenot | Jun 1975 | A |
4469386 | Ackerman | Sep 1984 | A |
4897008 | Parks | Jan 1990 | A |
5011422 | Yeh | Apr 1991 | A |
5055060 | Down et al. | Oct 1991 | A |
5106312 | Yeh | Apr 1992 | A |
5179877 | Down et al. | Jan 1993 | A |
5273444 | Down et al. | Dec 1993 | A |
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5887452 | Smith et al. | Mar 1999 | A |
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