Abstract:
An improved RF termination and a method of providing the RF termination are disclosed. The RF termination for terminating an open RF signal from an open RF signal source, includes a hollow shell, and an axial resistor inserted within the hollow shell, wherein the axial resistor includes a first lead connectable to the open RF signal source and a second lead being grounded by the hollow shell.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to RF (Radio Frequency) terminations and, more particularly, to an improved RF termination which is easy to assemble and cost effective to manufacture.  
         BACKGROUND OF THE INVENTION  
         [0002]    Radio Frequency (RF) terminations are devices used to ground or electrically “terminate” open RF signal sources such as RF ports found in common electronic devices such as cellular base stations and RF test equipment. For example, when certain RF ports of an electronic device are not being used, 50 ohm RF terminations are typically used to ground these ports. The RF termination prevents any unwanted and wasteful dissipation of RF signals from the open RF signal source. Furthermore, the RF termination prevents signal interferences with other RF signals which may occur due to the leakage of RF signals through the open RF signal source.  
           [0003]    [0003]FIG. 1 is a sectional view of a conventional 50 ohm RF termination  10  to be used with a conventional female SMA connector  30 . As shown in FIG. 1, the 50 ohm RF termination  10  is typically screwed onto the female connector  30  which is connected to an open RF signal source (not shown) such as a port of an electronic device. The 50 ohm RF termination  10  includes a metal plug body  11  screwed in a coupling nut  12 . A gasket  20  and a retaining ring  22  are used to securely position the plug body  11  in the coupling nut  12 . A male contact pin  14  and a dielectric member  13  are fixedly provided inside the plug body  11 . A 50 ohm resistor  16  is soldered to one end of the male contact pin  14  and to the inner surface of the plug body  11  by solder paste  18 . The 50 ohm resistor  16  is a ceramic thin film having resistive paste and does not have any leads. All these components are assembled together to produce the conventional 50 ohm RF termination  10 .  
           [0004]    When the RF termination  10  is screwed onto the female connector  30 , the female connector  30  is disposed inside the RF termination  10  and the male contact pin  14  will be disposed in a hole  32  of the connector  30 . Through the hole  32 , the pointing end of the male contact pin  14  will contact electrically the open RF signal source disposed on the other side of the female connector  30 . Since one end of the male contact pin  14  is electrically connected to the open RF signal source and the other end of the male contact pin  14  is grounded through the resistor  16  soldered to the plug body  11 , the open RF signal source is grounded, thereby effectively terminating the open RF signal source.  
           [0005]    Although the conventional RF termination is effective, it does suffer from certain disadvantages. For example, the ceramic-type resistor is expensive, resulting in an expensive RF termination. Furthermore, since the ceramic-type resistor is manufactured without any contact leads, the RF termination  10  requires multiple components that must be assembled together to function as the contact leads and housing for the ceramic-type resistor. This complicates the assembly process and increases the manufacturing cost. Moreover, in lieu of the female SMA connector  30 , if a different type of a connector, such as a BNC or Type-N connecter, were to be used, then many different components of the RF Termination  10  need to be modified to adapt to the new connector. This can restrict the applicability of conventional RF terminations.  
           [0006]    Accordingly, a need exists for an improved RF termination which is easy to assemble, inexpensive to manufacture and easily adaptable for different applications.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention is directed to an improved RF termination which overcomes drawbacks associated with conventional RF terminations. Specifically, rather than a ceramic-type resistor, the present invention uses an axial-type resistor which is a widely-available resistor having a resistive element and two contact leads extending directly from the resistive element in the opposite directions.  
           [0008]    The use of an axial resistor rather than a ceramic-type resistor offers a number of advantages over prior art designs. First, the axial resistor is widely available and significantly less expensive than the ceramic-type resistor used in prior art RF terminations. Consequently, the component costs of the RF termination device of the present invention are significantly less than those of conventional devices. Furthermore, the present invention reduces the number of component parts required by exploiting the lead contacts that extend from either end of the axial resistor. Specifically, rather than incorporating additional components in the RF termination device to effect the electrical connections between the resistor and the RF source and between the resistor and ground as is done in the prior art, the RF termination device of the present invention preferably uses one contact lead of the resistor to connect directly with the RF source and the other contact lead to connect directly to the ground. Aside from the obvious savings in both material and manufacturing costs, a reduction in the number of parts to be assembled also improves the adaptability and applicability of the RF termination in accommodating different connectors as needed by different systems. Additionally, the reduction in parts and complexity generally tends to increase reliability. Thus, overall, the present invention provides an improved RF termination which is easy to assemble, cost effective to manufacture, easily adaptable, reliable and refined in appearance.  
           [0009]    In one embodiment, the RF termination of the present invention includes a metal hollow shell and an axial resistor. One lead of the axial resistor is electrically connected to the hollow shell, and the other lead is exposed and positioned such that, when the RF termination is engaged with a connector of a communication device having an open RF signal source, the exposed lead of the axial resistor electrically connects to the open RF signal source through the connector. Since one lead of the axial resistor is electrically connected to the open RF signal source and the other lead of the axial resistor is electrically connected to the hollow shell which in turn is grounded through known grounding techniques, the open RF signal source is grounded by the operation of the RF termination.  
           [0010]    In another embodiment, the present invention is directed to a method of producing a signal termination device for terminating an open RF signal from a communication component containing an open RF signal source. The method comprises the steps of: providing a hollow shell and an axial resistor having first and second leads; and assembling the axial resistor within the hollow shell, wherein the first lead of the axial resistor is electrically connectable to the open RF signal source and the second lead of the axial resistor is grounded by the hollow shell.  
           [0011]    In yet another embodiment, the present invention is directed to a method of terminating an open RF signal source using an RF termination device. The method comprises the steps of: providing the RF termination device including a hollow shell and an axial resistor inserted within the hollow shell, the axial resistor including a first lead connectable to the open RF signal source and a second lead being grounded by the hollow shell; and engaging a connector of the open RF signal source with the RF termination device to terminate the open RF signal source.  
           [0012]    In still another embodiment, the present invention is directed to a communication component which incorporates an RF termination device. The communication component comprises: an RF signal source; a connector coupled with the RF signal source; and an RF termination device comprising at least: a hollow shell coupled with the connector and being grounded; and an axial resistor inserted within the hollow shell and including a first lead electrically connect to the RF signal source and a second lead electrically connected to the hollow shell. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    In the drawings, the same reference numerals are used to indicate the same elements.  
         [0014]    [0014]FIG. 1 is a sectional view of a conventional 50 ohm RF termination connectable to a conventional female SMA connector.  
         [0015]    FIGS.  2 A- 2 C are different views of the components of a RF termination according to one embodiment of the present invention.  
         [0016]    [0016]FIG. 3 is a sectional view of the RF termination of FIG. 2C connectable to a conventional female SMA connector according to one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    FIGS.  2 A- 2 C are sectional views of the components of a RF termination  70  according to one embodiment of the present invention. Referring to FIGS.  2 A- 2 C, the RF termination  70  of the present invention comprises two main components: a metal shell  50  and an axial resistor  60  contained in the metal shell  50 . The metal shell  50  is a hollow housing made with a conductive material such as aluminum. The metal shell  50  includes a hole  50   a  on one end thereof and an opening  50   b  on the opposite end thereof. The metal shell  50  has a cylindrical configuration with a conically tapering portion and can be formed using any known techniques. For example, a deep drawn process or a molding process well known in the art can be used to form the metal shell  50 .  
         [0018]    Once the metal shell  50  is formed, the metal shell  50  is assembled with the axial resistor  60 . The axial resistor  60 , as shown in FIG. 2B, is a conventional axial resistor that is widely available in the market at a minimum cost. As known, the axial resistor  60  includes a resistive element  61  and first and second contact leads  62   a ,  62   b  extending from the opposite ends of the resistive element  61 . Although the preferred resistance of the resistive element  61  is 50 ohm, any resistance value, e.g., 75 ohm, can be used depending on the application.  
         [0019]    The axial resistor  60  is inserted through the metal shell  50  such that the first lead  62   a  projects from the hole  50   a  of the metal shell  50  and the second lead  62   b  projects from the opening  50   b  of the metal shell  50  as shown in FIG. 2C. Once the axial resistor  60  is fit within the metal shell  50 , the first lead  62   a  is trimmed flush with the outer surface of the one end  51   a  of the metal shell  50  and the remaining first lead  62   a  is fixedly positioned within the hole  50   a , e.g., using solder paste. Similarly, second lead  62   b  is trimmed so that the remaining second lead  62   b  is aligned or flush with the other end  51   b  of the metal shell  50 . This completes the formation of the RF termination  70  according to one embodiment of the present invention.  
         [0020]    Depending on the application, in some cases, the second lead  62   b  of the axial resistor  60  may not necessarily need to be flush with the end  51   b  of the metal shell  50 . In fact, in certain cases, it may be desirable to have the second lead  62   b  extend beyond the end  51   b  of the metal shell  50 , or to have the second lead  62   b  extend short of the end  51   b  of the metal shell  50 . One skilled in the art would readily understand that any configuration is possible for the second lead  62   b  as long as the second lead  62   b  can be electrically connected to the open RF signal source when the RF termination  70  mates with a connector such as the connector  30 .  
         [0021]    Referring to FIG. 3, the use of the RF termination  70  according to one embodiment of the present invention will now be discussed. As shown in FIG. 3, the RF termination  70  is mated with a conventional female connector  30  or any other type of connector to terminate or ground an open RF signal source (not shown) coupled to the connector  30 . The threads  31  of the female connector  30  engage the inner surface of the metal shell  50 , and the second lead  62   b  of the axial resistor  60  is inserted in the hole  32  of the female connector  30 . This allows the second lead  62   b  to be electrically connected to the open RF signal source. Since one lead  62   b  of the axial resistor  60  is connected electrically to the open RF signal source via the connector  30  and the other lead  62   a  of the axial resistor  60  is grounded by being soldered or electrically connected to the metal shell  50  which is grounded by known grounding techniques, the open RF signal source will be grounded by the operation of the RF termination  70 .  
         [0022]    The shape, size, configuration, and material of the metal shell  50  as well as the resistance of the axial resistor  60  can vary depending on the application and/or the type of connector used. For example, threads corresponding with the threads  31  of the female connector  30  can be provided on the inner surface of the metal shell  50 , or any other configuration can be provided thereon to facilitate the insertion and fixture of the connector within the metal shell  50 .  
         [0023]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.