Patent Application
20080283379
The present disclosure is directed generally to coaxial switches.
Coaxial switches are employed in modem electronic test equipment. These coaxial switches include insulated or dielectric contact carriers that are actuated to direct incoming signals to different receiving and transmitting paths with an extremely high degree of signal fidelity. As the coaxial switch is actuated multiple times, however, the insulated contact carriers frictionally engage metallic electrically conductive components or elements of the coaxial switch body. The insulated contact carrier acts as a dielectric and static charge, known as tribo-electric charge, accumulates and stores on the dielectric until a discharge level is reached. The tribo-electric discharge usually occurs in the signal path. A tribo-electric discharge through the signal path is undesirable because it may cause false triggering in digital circuits and may jeopardize the signal fidelity.
As the coaxial switch 100 is actuated, the contact carrier 102 moves in direction A and B. The coaxial switch 100 may be employed in modem electronic test equipment. The coaxial switch 100 may be actuated multiple times to direct incoming signals coupled to the metal RF body 108 to different receiving paths coupled by the conductive reed 110 with an extremely high degree of signal fidelity. As the coaxial switch 100 is actuated, however, the bearing surface 106 of the contact carrier 102 frictionally engages the inner metallic surface 124 of the electrically conductive metal RF body 108. Tribo-electric charge is created by the friction between the inner surface 124 of the metal RF body 108 and the bearing surface 106 dielectric 104 material of the insulated contact carrier 102. The tribo-electric charge accumulates and is stored in the dielectric 104 material until a discharge level is reached. As previously discussed, a tribo-electric discharge through signal path C is undesirable because it causes false triggering in digital circuits and also greatly jeopardizes the signal fidelity.
Accordingly, there is a need for a coaxial switch that eliminates or minimizes tribo-electric charge accumulation in the contact carrier. Furthermore, there is a need for a high frequency coaxial switch that eliminates or minimizes tribo-electric discharge in the signal path.
In one embodiment, a contact carrier comprises a body formed of an electrically insulative material. The body comprises a longitudinally extending shaft portion and a stem portion. At least one conductive layer is formed on the body.
In one general respect, the embodiments described herein are directed to a coaxial switch that eliminates or minimizes tribo-electric charge accumulation in the contact carrier and/or eliminates or minimizes tribo-electric discharge in the signal path. In other general respects, the embodiments described herein are directed to a high frequency coaxial switch that eliminates or minimizes tribo-electric charge accumulation in the contact carrier and/or eliminates or minimizes tribo-electric discharge in the signal path. In one embodiment, a coaxial switch reduces the generation of charge on a component bearing surface during switch actuation. In another embodiment, the coaxial switch provides an instantaneous ground discharge path. In one embodiment, a conductive layer may be formed over the bearing surface of a dielectric carrier for a conductive reed, generally referred to a contact carrier or a dielectric contact carrier. The conductive layer formed over the dielectric material reduces and minimizes tribo-electric charge accumulation in the dielectric and therefore, eliminates or minimizes tribo-electric discharge. Although a relatively small tribo-electric charge may be created from metal to metal surface friction, the amount of charge is much less than the tribo-electric charge created by dielectric to metal surface friction. In addition, the conductive property of the conductive layer formed over the dielectric contact carrier allows tribe-electric charges to dissipate to ground at each actuation of the switch. Thus, further minimizing the accumulation of tribo-electric charge due to repeated and multiple actuations of the contact carrier.
Accordingly, in one embodiment, a coaxial switch comprises a dielectric contact carrier comprising a conductive layer that is selectively metallized in a first region to reduce charge generation and provide a ground dissipation path. The unmetallized region of the dielectric contact carrier performs the conventional contact carrier function with minimal disturbance in mechanical functionality and electrical performance. Any suitable metallization process may be employed to form the conductive layer on the friction bearing surface of the contact carrier body. For example, the conductive layer may be formed by one or more processes including plating, electro-plating, vacuum depositing, evaporating, sputtering, other generally well-known metallization techniques.
With reference now to both
In one embodiment, the dielectric 104 may be formed of any suitable dielectric material such as, for example, Polychloro Trifluoro Ethylene. In one embodiment, the first metallic layer may be formed of a micro-inch layer of metal, for example. The first metallic layer may comprise a 50-100 micro-inch layer of the first metal. The first metal may be Nickel, for example. In one embodiment, second metallic layer may be formed of a micro-inch layer of the second metal, for example. The second metallic layer may comprise 100-150 micro-inch layer of the second metal. The second metal may be Gold, for example. In one embodiment, the second metal may be hard Gold. The metallization of the first and second conductive layers 220, 222 may be formed by employing any suitable metallization process to form the first conductive layer 220 over the friction bearing surface of the contact carrier body 202 and forming the second layer 222 over the first layer 220, and so on. For example, the first and second conductive layers 220, 222 may be formed by one or more processes including plating, electro-plating, vacuum depositing, evaporating, sputtering, other generally well-known metallization techniques.
Multiple stationary probes 340a, 304b, and so forth, are engage RF signals. In the illustrated embodiment, the multiple stationary probes 304a, b and the respective conductive reeds 110a, b direct incoming and outgoing RF signals from an input signal path 308a or an output signal path 308b. The RF signals are switched with an extremely high degree of signal fidelity by actuating the plated dielectric contact carriers 200a, b of the coaxial switch 300. The stationary probes 304a, b comprise respective electrical conductive surfaces 306a, and 306b to electrically engage respective surfaces 120c and 120d of the respective conductive reeds 110a, b.
The conductive reeds 110a, b electrically engage and disengage the upper RF body 108 and the respective stationary probes 304a, b by actuating the contact carrier bodies 202a, b. As shown in the illustrated embodiment, the carrier contact body 202a is in the “OFF” position and is maintained in there by the force of the spring 112a in direction B. The first surface 120a of the conductive reed 110a is in electrical contact with the second surface 118b of the upper RF body 108. The second surface 120c of the conductive reed 110a is not in electrical contact with the electrical conductive surface 306a of the stationary probe 304a. Accordingly, the RF OUT signal in the signal path 208b is not coupled by the coaxial switch 300 to external devices.
In the illustrated embodiment, the carrier-contact body 202b is in the “ON” position. The carrier body 202b is actuated applying a force in direction A and compressing the spring 112b. The carrier body 202b remains in the “ON” position until it is actuated once again and it returns to the “OFF” position by the spring 112b acting in direction B. The first surface 120b of the conductive reed 110b is not in electrical contact with the second surface 118b of the upper RF body 108. The second surface 120d of the conductive reed 110b is in electrical contact with the electrical conductive surface 306b of the stationary probe 304b. Accordingly, the RF IN signal in the signal path 208a from external devices is coupled by the coaxial switch 300 through the conductive reed 110b.
Each of the carrier contact bodies 202a, b of the dielectric contact carriers 200a, 200b comprise the metallized layer 204. Accordingly, as the bearing surfaces 208a, b of the respective contact carrier bodies 202a, b are repeatedly actuated, the charge accumulated in the dielectric 104 material is minimized because of the metal to metal friction between the metallized conductive layer 204 and the upper RF body 108. Thus, any tribo-electric charge created by metal to metal surface friction by the metallized conductive layer 204 and the upper RF body 108 is much less than the tribo-electric charge created by dielectric to metal surface friction in conventional coaxial switches (e.g., coaxial switch 100 illustrated in
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Numerous specific details have been set forth herein to provide a thorough understanding of the embodiments. It will be understood by those skilled in the art, however, that the embodiments may be practiced without these specific details. In other instances, well-known operations, components and circuits have not been described in detail so as not to obscure the embodiments. It can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments.
It is also worthy to note that any reference to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.
Some embodiments may be described using the expression “coupled” and “connected” along with their derivatives. It should be understood that these terms are not intended as synonyms for each other. For example, some embodiments may be described using the term “connected” to indicate that two or more elements are in direct physical or electrical contact with each other. In another example, some embodiments may be described using the term “coupled” to indicate that two or more elements are in direct physical or electrical contact. The term “coupled,” however, may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. The embodiments are not limited in this context.
While certain features of the embodiments have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the embodiments.
