Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2002-11-12
2004-11-23
Gibson, Randy W. (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S724000, C361S818000, C439S065000, C439S061000
Reexamination Certificate
active
06822874
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to the packaging of electrical systems and devices into a chassis and, specifically, to an improved modular arrangement of the printed circuit boards therein for enabling simple reconfiguration of input/out (“I/O”) interface types and improved fault tolerance for both electrical and optical I/O signals.
BACKGROUND ART
Electronic devices, especially those used in communications systems such as cable head-ends and satellite uplink sites, are typically housed in chassis that are then mounted in vertical racks. In such systems, there is a need to provide I/O connectivity to various sources and destinations outside the device as well as to provide internal connectivity within the device. Furthermore, in devices that perform the function of switching, multiplexing, de-multiplexing, routing or other such similar functions, there is often the need to support multiple interfaces of the same type or of different types. These I/O types may be of either a conducted electrical signal or of an optically carried signal. In order to support multiple I/O interfaces of a variety of types, it has been the practice to divide a chassis into multiple identical slots, where each slot can be configured to support a variety of functions and interface types simply by changing the electronics module that occupies the slot. Each of the modules that contain active circuitry then typically needs to connect signals both to external I/O cables and also internally to other circuitry in the device.
Furthermore, it is desirable that such electronic devices provide high availability of service through fault tolerance and the ability to replace faulty circuitry without interrupting the operation of the device. These goals have typically been met by a) providing redundant circuitry that automatically takes over for circuitry that fails, and b) providing the capability to hot-swap faulty circuitry (that is to replace modules while the device is operational and without interrupting the processing of signals that connect to the device).
To make hot-swapping and cable management non-error prone, it has become common practice to construct these devices such that the circuit modules, which hold active circuitry, are replaceable from the front of a chassis while external I/O cabling is connected to the rear of the chassis. This makes it possible for cables to stay in place while faulty circuitry is replaced and eliminates the possibility of reconnecting cables incorrectly. It also eliminates the down-time that would be caused by the interruption of the flow of the signals on those cables while they are disconnected. Furthermore, it is desirable to provide some means to prevent a circuit module from being incorrectly installed in a slot where it would be connected to an inappropriate I/O type.
Existing devices may be categorized as follows:
a) I/O connection via mid-plane board to parallel connector PCB module;
b) I/O connection via perpendicular connector PCB module;
c) I/O connection via detachable connector faceplate.
FIG. 1
illustrates a device in which the mid-plane approach is employed. A circuit module
102
plugs in and out from the front of a chassis and has at least one right-angle connector along its back edge which mates with a corresponding connector
104
on a mid-plane printed circuit board
106
. The mid-plane printed circuit board (“PCB”)
106
typically extends across the full height of the chassis. Pairs of connectors
104
,
108
on opposite sides of the mid-plane PCB
106
are mounted in opposition to each other such that they can share pins that pass through the mid-plane PCB
106
to transmit all or some of the signals of the circuit module
102
directly through the mid-plane PCB
106
to a connector module
110
. The connector module
110
then makes the connections to the external world using right angle mounted connectors
112
on its rear edge. There is no direct connection from the circuit module
102
to the connector module
110
in this approach.
The mid-plane approach for providing modular I/O connections has been standardized in IEEE 1101.11, wherein the connector modules are called “Rear Plug-in Units”. U.S. Pat. Nos. 5,010,450, 5,315,488, 5,912,801, and 5,488,541 each describe variations of the mid-plane approach.
A disadvantage of the mid-plane approach is the extreme difficulty of making a blind-mateable fiber-optic I/O connection. If it was even realizable, it would be very complex as a blind-mateable optic I/O connection would require multiple fiber optic connections in the signal path between the active circuit module and the eventual external connector on the rear of the connector module. While U.S. Pat. No. 5,010,450 discloses a fiber-optic connection, the connection is not blind-mateable, but requires the physical removal of the cable from the circuit module before the circuit module can be fully removed.
A further disadvantage is that the thru connections from the active circuitry on the front circuit module to the rear connector module cannot be individually tailored with regard to impedance and other electrical characteristics. Rather, one must “make do” with the characteristics of the mid-plane pass-thru connector which cannot be arbitrarily reconfigured on a slot by slot basis.
A still further disadvantage is that a circuit module may inadvertently be inserted in the wrong slot causing the device to malfunction and possibly even destroying circuitry.
Finally, none of these patents present a solution for redundancy in which an I/O signal from a failed circuit module is automatically routed to a spare (backup) circuit module of the same type. Thus, in the event of a failure on a circuit module, the corresponding I/O will not be processed correctly until the faulty module is replaced.
Perpendicular Connector PCB Module
FIG. 2
illustrates a device in which the perpendicular connector PCB approach is employed. It is characterized by a direct connection between a circuit module
202
, which contains active circuitry, and a connector module
210
, which tailors the external I/O connectors
212
to a particular I/O type. However, the connector modules
210
are not co-planar with the circuit modules
202
. Moreover, each connector module
210
is a fairly complex assembly typically involving at least two PCBs that are perpendicular to the circuit module
202
, inter-board connections
214
and multiple stand-offs and spacers (not shown) (see U.S. Pat. No. 5,430,615 for an example). One PCB
216
directly behind the faceplate
218
holds the external I/O connectors
212
and another PCB
220
holds the connector which makes a direct connection to the circuit module
202
. An additional board-to-board stacking connector
214
is used to transport signals between the two PCBs within the connector module
210
. Two PCBs are typically required because the external I/O connectors
212
are generally thru-hole components and hence their protruding leads prevent another connector from being installed directly opposite on the backside of the PCB. By placing the stacking connector
214
off to the side, connectors can be mounted directly opposite one-another. Occasionally, when the slot density in the chassis is low, this approach can be implemented with one perpendicular PCB. However, the slot-to-slot pitch that can be achieved will thereby be limited, along with the density of the electronics. Furthermore, this approach has a high manufacturing cost.
U.S. Pat. No. 5,430,615 discloses a variation on this approach in that it does not include the inter-circuit module connectivity (i.e. cards in one slot cannot communicate to cards in other slots because there is no interconnect PCB which spans across slots). Furthermore the patent presents no solution for optical fiber signals or redundancy.
U.S. Pat. No. 6,144,561 discloses another variation on this approach in that it employs a full top-to-bottom mid-plane board in the chassis, and it connects each circuit module to its connector module via a dedicated hole in the mid-plane. This hole may p
Bui Hung S.
Gibson Randy W.
Swanson & Bratschun LLC
Wooshcom Corporation
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