Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2002-01-04
2004-03-23
Le, N. (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C439S426000
Reexamination Certificate
active
06710604
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device and method for directly injecting a test signal into a cable, so that the isolating characteristics of the system immunity response can be evaluated.
2. Background Information
Computer systems typically include a number of electrical components, such as printed circuit boards, that are electrically coupled together. One way to accomplish this is to use electrical cables to electrically join the respective electrical components. For example, the electrical cables allow electrical signals, via signal wires, to be transmitted from one printed circuit board to another printed circuit board, so that various electronic devices on the one printed circuit board can communicate with electronic devices on the other printed circuit board. Cables are also used to supply power to and from the various electrical components.
However, many electrical devices, both inside of the computer system and external to the computer system, when operated, generate emissions that include electromagnetic radiation. This electromagnetic radiation may travel through the air, and be received by the signal wires of the cable. The received electromagnetic radiation may then adversely affect the operation of the electronic devices to which the cable is connected, causing the computer system to malfunction. When this electromagnetic radiation influences the proper functioning of the electronic devices, the result is known as electromagnetic interference (also known as EMI). Thus, in order to ensure reliable operation, the signal wires within the cables must be shielded against outside interference. For example, it is known to wrap or encircle all of the wires in a cable by a conducting shield, usually foil or braided wire, which is connected to an external jacket, such as a metal housing shield of a plug, at each end of the cable. The metal housing shield is then coupled to a ground potential, so that any electromagnetic radiation is conducted to the ground potential, thereby preventing the radiation from adversely affecting the electronic devices coupled to the cable.
Certain regulations have been established which provide a frequency range that a shield must be capable of isolating the cable's signal wires from, to ensure that the conducting shield of the cable provides adequate protection against electromagnetic interference. For example, the International Electrotechnical Commission (IEC) has established and published various standards that stipulate the frequency ranges that the shields must provide isolation for. One published standard (IEC Standard 61000-4-6, entitled
Immunity to Conducted Disturbances Induced by Radio Frequency Fields
) provides that a shield must isolate the internal cable wires from electromagnetic interference radiation in the frequency range between 150 kilohertz to 80 megahertz. Moreover, this standard provides criteria that must be in place when the testing is performed. For example, this standard dictates that in testing a system's immunity response, a test signal (which simulates electromagnetic interference radiation in the noted frequency range) must be directly injected into the shield of the cable, via a 100-Ohm resister, while the cable is disposed 30 mm from the floor, in order to test the system immunity response. If the system is not isolated from the test signal, for example if the shield does not isolate the internal cable wires from the test signal, then the system will be deemed as being unsatisfactory for use in certain environments. For example, all systems marketed in Europe must meet the requirements of the standard.
However, although the above standard provides guidelines for testing the system, the standard is silent on how to actually perform the test. Thus, it is up to the end user of the system, to provide a mechanism and procedure that will allow the system to be tested to ensure that they meet the shielding requirements of this and other various standards.
Moreover, it is known to test a system for susceptibility to electromagnetic radiation interference by injecting the test signal using antennas. However, a test signal injected using an antenna is not directly injected, but instead is remotely injected, and thus would not meet the requirements of a standard that requires a direct injection of a test signal. Thus, there is a need for a device that allows a test signal to be directly injected into a shield of a cable. Moreover, there is a need for a procedure for implementing the direct injecting of a test signal into a shield of a cable.
Further, it is desirable to perform the direct injecting of the test signal into the shield without damaging the cable. That is, typically the shield is covered with an outer insulating sheathing (cover). Obviously, to access the shield for the direct injection, the cover must be penetrated in some manner. However, it would be desirable if this penetration did not damage the cable to an extent that the cable could no longer be used. Thus, there is a need for a device that allows for the direct injecting of a test signal into a shield of a cable, that does not damage the cable.
Furthermore, as previously discussed, the shield surrounds the wires of the cable. However, for the testing to be accurately performed, it is important that the device used for injecting the test signal does not contact the underlying wires. If the device should contact one or more of the wires, then the wires will conduct the test signal, skewing the results of any test. Thus, there is a need for a device that allows for the direct injecting of a test signal into a shield of a cable, while ensuring that the wires within the cable are not contacted by the device.
SUMMARY OF THE INVENTION
It is, therefore, a principal object of this invention to provide a device and method for directly injecting a test signal into a cable.
It is another object of the invention to provide a device and method for directly injecting a test signal into a cable that solves the above-mentioned problems.
These and other objects of the present invention are accomplished by the device and method for directly injecting a test signal into a cable disclosed herein.
According to one aspect of the invention, a device for directly injecting a test signal into a cable is provided. The device includes a lower clamp member, and an upper clamp member superposed over the lower clamp member. Both the lower clamp member and the upper clamp member are preferably formed from an insulating material, such as plastic. Forming these features of an insulating material ensures that these components will not form a conductive path for the injected test signal.
In an exemplary aspect of the invention, the device has a conductive piercing member, such as a metal pin, disposed on the lower clamp member to project toward the upper clamp member. In use, the conductive piercing member will pierce an outer sheathing (which is typically an insulator) of the cable, and engage an inner conductive shield of the cable, in a manner that will be subsequently described. Moreover, the conductive piercing member preferably has a sharp, pointed tip that can easily pierce the outer sheathing of the cable.
The device further has a conductive coupling member disposed on an upper surface of the lower clamp member. The conductive coupling member is electrically coupled to the conductive piercing member.
In the exemplary embodiment, the conductive piercing member is integral to the conductive coupling member. For example, the conductive piercing member can be a pin that is welded or soldered, or otherwise permanently fastened to the conductive coupling member. Alternatively, the conductive piercing member can be stamped from the conductive coupling member. With this arrangement, the conductive piercing member would have an inverted V-shaped configuration to facilitate the stamping of a suitably sharp piercing member.
The device may further include a coaxial connector that is electrically coupled, via a resistor for
Christopherson Scott Lee
Gillard Edward Charles
Gilliland Don Alan
Monsen Kenneth E.
Dole Timothy J.
International Business Machines - Corporation
Le N.
Rabin & Berdo P.C.
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