Electrical connectors – Preformed panel circuit arrangement – e.g. – pcb – icm – dip,... – For receiving coaxial connector
Reexamination Certificate
2002-08-12
2004-02-17
Paumen, Gary (Department: 2833)
Electrical connectors
Preformed panel circuit arrangement, e.g., pcb, icm, dip,...
For receiving coaxial connector
C439S581000
Reexamination Certificate
active
06692262
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a connector assembly for coupling a plurality of coaxial cables to a substrate, such as a circuit board, and in particular a connector assembly that provides high RF signal throughput with reduced losses and allows the center contacts of the assembly to be easily serviced or replaced.
BACKGROUND OF THE INVENTION
The use of RF signals to transfer data among various electronic components has grown in necessity as the complexity of such electronic components has increased. For example, test equipment that is used to analyze semiconductor chips requires very sophisticated data transmission techniques that operate at very high frequencies.
In order to ensure that the high frequency signals are delivered from one piece of equipment to another (e.g., from a test head for a semiconductor chip to a sophisticated piece of analysis equipment), it is common to use flexible or semi-rigid coaxial cable consisting of a center conductor, a dielectric insulator, and an outer shielding conductor. These types of cable are widely available, and can carry signals exceeding 40 GHz.
Since the coaxial cables are repeatedly mated and demated with the associated equipment, it is necessary to use coaxial cable connectors to terminate the ends of the cables, and the connectors must be able to pass the high frequency signals with minimal loss. One example of such a coaxial cable connector is an SSMA type connector, which can easily pass a signal up to 40 GHz.
While the coaxial cable and connectors can transmit high frequency signals, significant losses occur at the juncture between the cable connector and the printed circuit board that forms part of the functional piece of equipment. For example, one type of cable connector includes a connector body that transmits the RF signal in a direction 90 degrees offset from the transmission direction within the coaxial cable. This type of connector is designed to mate with a port that is hard soldered to the circuit board, and the conductor pin in the port also mates with conductive traces on the circuit board at yet another right-angle transition. Accordingly, when using this type of connector, the RF signal must propagate through two right-angle transition points, which results in significant loss to the point where the signal actually delivered to the conductive trace on the circuit board usually cannot exceed 10 GHz.
Another typical cable conductor used in these applications is mounted on the edge of the circuit board, as shown in
FIG. 12
, in an attempt to avoid the right-angle transitions discussed above (this type of multiple channel connector also allows a plurality of connections with a single coupling operation). This type of “edge-launch” connector requires the use of relatively long conductive traces on the circuit board itself to carry the signal to the functional device mounted on the circuit board at some remote location. It is well known, however, that it is very difficult to maintain high RF signals in circuit board conductive traces without experiencing significant losses. RF transmission lines require a delicate balance between the structure and position of the individual copper traces on the circuit board, the spacing therebetween, the ground planes used in the circuit board, and the dielectric materials used to make up the circuit board itself. Standard dielectric materials such as fiber glass materials usually are incapable of maintaining high RF signals within the transmission lines formed on the circuit board. While the dielectric material of the circuit board could be replaced with a higher quality material, this solution unacceptably increases the overall expense of the circuit board.
In order to overcome the inherent shortcomings of transmission lines formed on standard printed circuit boards, it has been a practice to terminate the coaxial cable at a position as close as possible to the intended functional device mounted on the circuit board. This minimizes the length of the conductive trace that must actually be formed on the circuit board. Coaxial connectors that are used for this type of termination are designed to mate with a port extending upwardly from the circuit board. Again, however, there is usually at least one angled transition involved, which, as explained above, results in significant signal loss.
Another problem with attaching the coaxial cable to a position closely adjacent to the intended functional device arises from the fact that the coaxial cable will be subjected to hundreds of mating/demating cycles with the port on the circuit board. Consequently, there is the possibility that the technician performing the connection may damage sensitive electronic components that are positioned adjacent to the port. Still further, when the coaxial cable is semi-rigid, torquing forces imposed on the port by the relatively long coaxial cable can damage the port, the underlying connection to the circuit board, or the circuit board itself, all of which could result in significant repair cost.
Yet another problem with locating the port immediately adjacent to the end device occurs when multiple cables are necessary for communicating with multiple devices on a single circuit board. That is, since each port will be located at a different location on the circuit board, it is impossible to use any type of multiple channel connector (such as shown in FIG.
12
), since such a connector would require the ports to be arranged adjacent to one another on the circuit board. Accordingly, whenever a technician has to perform a connection, each of the plurality of coaxial cables has to be handled individually.
Having a plurality of semi-rigid cables connected at a variety of locations on a circuit board gives rise to several additional problems. For example, the more cables a technician has to handle, the more likely it is that there will be a mistake in matching up the correct cable with the correct port. Further, the presence of numerous cables extending in a variety of directions from the circuit board makes it more difficult to access and house the circuit board, especially in test head type applications.
U.S. Pat. No. 4,995,815 attempts to address the problem of remote cable termination at a variety of locations on a circuit board, by providing a coupler that can be mounted directly on the circuit board for electrical connection to a conductive trace formed at some remote location on the circuit board. The coupler disclosed in U.S. '815 (shown in
FIG. 13
) also orients the coaxial cable termination end in line with a shorter length of coaxial cable in an attempt to provide a smooth transition onto the circuit board. The above-discussed problems still exist, however, in that the coupler must be positioned at a variety of different locations on the circuit board.
U.S. Pat. No. 6,007,347 also attempts to provide an improved connector assembly for a circuit board.
FIG. 14
shows a plurality of coaxial cables
240
extending from a connector frame
140
mounted to the edge of a circuit board
120
. The terminal end of each coaxial cable
240
is electrically connected within a complicated “slot-and-pad connection element”
320
formed at specific locations on the circuit board. While this arrangement may be intended to reduce signal loss between the connector at the end of the exterior coaxial cable and the beginning of the conductive trace on the circuit board, it still does not address the inherent problem of signal losses occurring in the conductive traces on the circuit board itself. Specifically, the '347 patent shows the slot-and-pad connection elements all arranged near the edge of the circuit board, and, consequently, significant signal losses will be encountered within the conductive traces that actually supply the signals to the functional devices that are located at interior, relatively remote portions of the circuit board. In addition, due to the complicated nature of the slot-and-pad connection elements
320
, the cost of manufacturing the circuit board is somewhat p
Burr & Brown
Huber & Suhner, Inc.
Paumen Gary
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