Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – With rotor
Reexamination Certificate
2000-10-20
2002-09-17
Nguyen, Vinh P. (Department: 2829)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
With rotor
C324S095000
Reexamination Certificate
active
06452379
ABSTRACT:
BACKGROUND OF THE INVENTION
In general, a thorough test of a high-speed digital system includes a procedure for sampling signals from hardware components of the system (e.g., circuit boards, interconnects, silicon devices, etc.) in order to determine how these components affect signal integrity. To access these signals, an engineer or technician typically connects specialized measurement equipment to the system hardware. In some configurations, such equipment includes a measuring device (e.g., a Time Domain Reflectometer or TDR) that connects to a circuit board which is either (i) part of the high-speed digital system under test, or (ii) a specialized assembly (e.g., a daughter card) that closely integrates with the system under test (e.g., through high-density connectors). Typically, the engineer permanently mounts a coaxial radio frequency (RF) connector to a specialized feature of the circuit board called a signal launch. The engineer can then attach a coaxial cable (e.g., a 50 ohm cable) from the measuring device to the soldered RF connector in order to access signals of the system under test.
One type of permanent mount RF connector, which is hereinafter referred to as an edge mount connector, has soldering posts that attach to an edge mount signal launch along an edge of a special type of circuit board called a microstrip, or microstrip line, which has an exposed signal conductor on one side of a dielectric substrate and an exposed ground conductor on the other side. Both the signal and ground conductors typically run to the edge of the circuit board to form the edge mount signal launch. An engineer typically solders an inner soldering post of the edge mount connector to the signal conductor and solders outer soldering posts to the ground conductor. The engineer can then access signals of the system under test by attaching a coaxial cable from a measuring device to the edge mount connector.
Another type of permanent mount RF connector, which is hereinafter referred to as a posted surface mount connector, has soldering posts that attach to a surface mount signal launch residing on the surface of a circuit board (rather than along an edge) in order to mount to the circuit board perpendicularly relative to the circuit board surface. The soldering posts of the posted surface mount connector are used in a manner similar to the soldering posts of the above-described edge mount connector. That is, an engineer typically solders an inner soldering post of the connector to a signal conductor of the surface mount signal launch and solders outer soldering posts to a ground conductor. The engineer can then access signals of the system under test by attaching a coaxial cable from a measuring device to the posted surface mount connector.
Another type of permanent mount RF connector, which is hereinafter referred to as a flat-faced surface mount connector, has a flat-faced base portion that sits flush on a surface mount signal launch. The flat-faced base portion does not include any protrusions (e.g., soldering posts, tabs, etc.). Rather, the base portion includes (i) a recessed, cylindrically-shaped signal conductor that receives a signal pin of the surface mount signal launch, and (ii) a ground conductor that defines mounting holes. To mount the flat-faced surface mount connector to the signal launch, an engineer typically inserts the signal pin of the signal launch into the signal conductor of the connector base portion, and aligns the mounting holes defined by the ground conductor with matching ground vias of the signal launch. The engineer then inserts screws through (i) the mounting holes of the connector and (ii) the matching ground vias of the signal launch, and fastens nuts on the ends of the screws to hold the connector firmly against the signal launch. The engineer can then attach a coaxial cable from the flat-faced surface mount connector to the measuring device in order to access signals of the system under test using the measuring device.
Most circuit boards, which are configured with a permanently mounted RF connector for external high-speed signal access, have multiple permanently mounted RE connectors to enable an engineers to access many different signals. When the engineers wants to sample a particular signal, the engineers attaches a cable from the measuring equipment to one of the permanently mounted RF connectors. If the engineer wishes to sample a different signal the engineers can detach the cable from that permanently mounted RF connector and attach the cable to another permanently mounted RF connector.
Some measurement equipment does not connect to circuit boards through permanent mount RF connectors. Such equipment typically includes a measuring device, an RF probe and a cable that connects the RF probe to the measuring device. The RF probe alleviates the need for an engineer to permanently mount RF connectors to signal launches of a circuit board. Rather, the engineer simply can temporarily attach the RF probe directly to the signal launch in order to access signals from the circuit board.
One type of RF probe has an elongated shape with a cable connecting portion at one end, and a pointed signal pin at the other end. Near the pointed signal pin is a cylindrical ground conductor. Typically, an engineer attaches a metallic ground extension to the cylindrical ground conductor, and moves the RF probe (i.e., manually manipulates the RF probe) such that (i) the signal pin of the RF probe contacts the signal conductor (e.g., a signal via) of the signal launch, and (ii) the metallic ground extension contacts the ground conductor (e.g., a ground via) of the signal launch. An example of a similar type of RF probe is that manufactured by Tektronix of Beaverton, Oregon.
One type of metallic ground extension has a cuff that fits over the cylindrical ground conductor of the RF probe, and a ground pin that extends from the cuff in the same direction as the signal pin. Another type of metallic ground extension includes a multi-pronged cuff that fits over the cylindrical ground conductor of the RF probe such that multiple prongs of that cuff extend in the same direction as the signal pin. Yet another type of metallic ground extension includes a spring that fits around the cylindrical ground conductor of the RF probe such that a wire end of the spring extends in the same direction as the signal pin. Accordingly, a portion of each type of metallic ground extension can engage a ground via of the signal launch (e.g., the ground via that normally receives a screw to permanently mount an RF connector) as the signal pin engages a signal via of the signal launch.
SUMMARY OF THE INVENTION
Unfortunately, there are deficiencies to the above-described conventional approaches to connecting to signal launches of circuit boards. For example, in connection with conventional permanent mount RF connectors, such connectors are typically expensive. Although an engineer typically connects a measuring device to only one or two permanent mount RF connectors on a circuit board at any given time, a circuit board with signal launches typically includes many permanent mount RF connectors for convenience. As such, in order to sample a different signal of the circuit board, the engineer can simply unscrew a coaxial cable from one connector and screw it onto another connector. Moreover, since such connectors are permanently mounted (e.g., soldered or screwed onto the circuit board), it would be a significant burden to require the engineer to unfasten (e.g., unsolder or unscrew) a conventional permanently mounted RF connector from one signal launch of the circuit board and refasten (e.g., solder or screw) that connector to another signal launch each time the engineer samples a different circuit board signal. Accordingly, the use of many expensive RF connectors results in a high cost for sampling signals.
Additionally, some conventional permanent mount RF connectors are not very well impedance-matched with signal launches. For example, in connection with posted surface mount connectors, there are typicall
Chapin & Huang , L.L.C.
Huang David E.
Nguyen Vinh P.
Teradyne, Inc.
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