Abstract:
Chassis for an automated test system including a housing and at least a first and a second backplane in the housing. The first backplane provides electrical connections for at least one functional module of a first type when engaged with the first backplane, while the second backplane provides electrical connections for at least one functional module of a second type different than the first type when engaged with the second backplane. The first and second backplanes include electrical circuitry to enable signals to be provided for the functional modules when engaged therewith. A bottom of the housing includes ducts to enable cooling of both types of functional modules when engaged with the housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 14/487,851 filed Sep. 16, 2014, which claims priority under 35 U.S.C. §119(e) of U.S. provisional patent application Ser. No. 61/878,112 filed Sep. 16, 2013, and 61/902,475 filed Nov. 11, 2013, all of which are incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to automated test systems that utilize modular instrumentation that is intended to be housed within a standardized chassis. 
     BACKGROUND OF THE INVENTION 
     The evolution of test instrumentation has transitioned over the years from a situation where a single stand-alone box that would typically provide a single dedicated function to one where a multitude of standardized chassis now have the ability to house a plurality of modules, with each module providing a dedicated function so that with a single chassis, multiple functions can be provided. 
     Bulky test stations for testing complex pieces of equipment using a rack-and-stack approach have largely morphed into significantly smaller footprints through the use of the modular instrumentation. Rack-and-stack implementations may still be used where instrumentation dictates a stand-alone unit (i.e., a display) but over time, even units requiring displays have also gone ‘faceless’ to reduce complexity. The benefits of a modular approach are readily apparent, including for example, redundant functions (control, cooling, power) are eliminated which in turn results in a reduction of size and an increase in overall station reliability. 
     Over the past 30 years or more, a number of standardized chassis have been implemented including, but not limited to: MMS, Eurocard, VERSAbus, VMEbus, VXI, VPX, PCI, PXI and AXle to name a few (the full terms of these abbreviations are known to those skilled in the art to which this invention pertains). While the modular approach has many benefits, one drawback is most systems typically have unused chassis space. Some systems intentionally allocate unused space for future expansion while in other systems it is simply the result of how the system was populated. Over time, as existing instrumentation is deemed obsolete by the original equipment manufacturers (OEMs), it is often replaced by a different (or even a newer) modular form factor which might not be currently implemented within a test station. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     An object of at least one embodiment of the present invention is to provide a chassis that is capable of supporting a plurality of instrumentation form factors. 
     A chassis for an automated test system in accordance with the invention includes a housing, and at least a first and a second backplane in the housing. The first backplane provides electrical connections for at least one functional module of a first type when engaged therewith, and the second backplane provides electrical connections for at least one functional module of a second type different than the first type when engaged therewith. The first and second backplanes include electrical circuitry to enable signals to be provided for the functional modules when engaged therewith. Thus, two different backplanes are positioned in the same housing. 
     In other embodiments, each of the first and second backplanes includes a respective controller. The first and second backplanes may each be configured to source all voltages required by the functional modules engaging therewith. As an example of backplanes, the first backplane may be a VXI backplane while the second backplane is a PXI backplane. 
     A respective securing arrangement may be provided to secure each of the first and second types of functional modules to the housing. A common DC power source may be installed in the housing to provide power through the circuitry to both types of functional modules when engaged with the housing. The circuitry may be configured to allow for trigger signals to pass between the first and second types of functional modules when engaged with the housing. Additionally or alternatively, the circuitry may be configured to allow for clock signals to pass between the first and second types of functional modules when engaged with the housing in a user-controllable or user-selectable manner. Additionally or alternatively, the circuitry may be configured to provide signal conditioning or level translation of auxiliary signals passing between the first and second types of functional modules when engaged with the housing in a user-controllable or user-selectable manner. 
     A bottom of the housing may include ducts to enable cooling of both types of functional modules when engaged with the housing. Shielding is optionally installed between the first and second backplanes. Potentially, at least one of the first and second backplanes consists of a single printed circuit board. However, at least one of the first and second backplanes may include a plurality of printed circuit boards. 
     A method for designing a chassis that supports different functional modules in accordance with the invention includes determining parameters of a largest one of the modules to be supported by the chassis, configuring a housing of the chassis with respective backplane for each of a plurality of different types of module to enable the housing to support at least one of each type of module, each backplane including electrical circuitry to enable signals to be provided for the modules when engaged therewith, determining required supply voltages of the modules, and configuring the housing to provide at least one of the required supply voltages for each of the modules through the respective backplane. The method also includes arranging a controller for each type of module on the housing, and coupling the controller for each type of module to electrical connectors on the housing that engage with that type of module. 
     Variations to the method which may be implemented individually or in combinations with one another include providing power to the backplanes from a common source through the circuitry to both types of modules when supported by the housing, sourcing a clock signal for the modules when supported by the housing from a clock source on the backplane for a first type of modules, or a clock source on the backplane for a second type of modules, and interposing shielding between the backplanes to reduce signal interference. 
     Another embodiment of a chassis for an automated test system in accordance with the invention includes a housing, and a plurality of different backplanes in the housing all oriented in a common axis and situated alongside one another. Each backplane includes electrical connectors for a plurality of one distinct type of functional modules when engaged with the connectors. Also, each backplane includes electrical circuitry to enable signals to be provided simultaneously for all of the functional modules when engaged with the connectors. A cooling system may be configured to satisfy cooling requirements of the different types of functional modules when engaged with the connectors. The backplanes also include common signal lines additional to a minimum number of signal lines needed to support all of the functional modules, and each of the backplanes is configured to provide an address bus, a data bus, a trigger bus, an interrupt bus, a local bus, clock and power signals and slot identification signals and to source all voltages required by the functional modules. 
     The invention will be described in detail with reference to some preferred embodiments of the invention illustrated in the figures in the accompanying drawings. However, the invention is not confined to the illustrated and described embodiments alone. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Additional objects of the invention will be apparent from the following description of the preferred embodiment thereof taken in conjunction with the accompanying non-limiting drawings, in which: 
         FIG. 1  shows the physical implementation of a chassis which supports both VXI instrumentation as well as 3U/6U PXI instrumentation within the same structure; 
         FIG. 2  is a perspective view showing the mechanical and backplane layout of the chassis; and 
         FIG. 3  is a schematic showing how signal interaction is configured between the different instrumentation types supported by the chassis in an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In an effort to make the most of unused instrumentation space, a primary intent of this invention is to implement a chassis for test instrumentation which allows a plurality of different module types of dissimilar instrumentation standards to reside within the same chassis housing. To enumerate each and every chassis permutation ad nauseam serves no practical purpose, so for the sake of clarity and convenience, the descriptions herein will be limited to VXI (C-Size) and PXI modules due to their ubiquitous presence throughout the test instrumentation industry. The invention is in no way constrained to using only these instrumentation form factors/standards and those skilled in the art could readily adapt a chassis to other current and future instrumentation standards to house different module types/configurations, in view of the teachings disclosed herein. Moreover, the invention is in no way limited to a chassis for test instrumentation or instruments, although this is a preferred implementation. 
     Preferred embodiments of the invention will be described with reference to  FIGS. 1-3  wherein like reference numerals refer to the same or similar elements. In order to implement a chassis that supports multiple instrumentation standards, one must first look at the physical module sizes that are needed within the system to support. In terms of physical sizes, the larger dimension (height, width, depth) of the desired modules will be the determining factor as to how the chassis is implemented and essentially dictate the overall size of the chassis. In the case of the aforementioned C-Size VXI and PXI modules, both are based on the 6U Eurocard standard, both utilize common power supply voltages and both utilize bottom entry vertical airflow cooling. These similarities result in ideal conditions for a chassis that supports both types of modules. In the case of PXI modules, they are available in both 3U (much more prevalent) and 6U variants—one or more of the embodiments of the proposed invention would be capable of supporting both types. 
     The rendering shown in  FIG. 1  reflects a dual standard chassis  10  having both C-Size VXI slots  12  and 3U/6U PXI slots  14  implemented within the same housing. In the embodiment depicted, five (5) VXI slots  12  are populated with instrumentation and four (4) 3U PXI slots  14  are populated with instrumentation. In order to maximize the number of PXI slots  14  without having to implement a hardware bridge, a preferred 19″ wide rack-mount chassis embodiment would house (10) C-Size VXI slots  12  and four (4) 6U PXI slots  14 . Alternate embodiments may utilize a different number of slots  12 ,  14  for either instrumentation standard or may implement additional or other standards as well. Since both VXI and PXI chassis utilize a number of common power supply voltages (+5 VDC, +12 VDC, −12 VDC), the power supply requirements are reduced. VXI chassis also utilize −5.2 VDC, +24 VDC, −24 VDC and −2 VDC supplies while PXI chassis utilize +3.3 VDC. One or more embodiments of the proposed invention would implement all of these supply voltages in order to support both the requirements of VXI and PXI instrumentation. Other embodiments may implement only a subset of the supply voltages. Each portion of the chassis (VXI or PXI) would generally require its own dedicated controller. Remaining components of the chassis  10  may be the same as those in prior art chassis or readily ascertainable by those skilled in the art to which this invention pertains in view of the disclosure herein, unless otherwise disclosed herein. 
       FIG. 2  reflects the implementation of a multi-standard instrumentation chassis. In the preferred embodiment shown, a VXI backplane  16  and a 6U PXI backplane  20  both occupy the rear of the chassis  10 , although at different depths. Specifically, the PXI backplane  20  is forward of the VXI backplane  16 , i.e., closer to the open end of the chassis  10 . 
     The backplane  20  obtains this smaller depth by means of one or more supports or walls that extend beyond the larger depth backplane, i.e., backplane  16 . The supports or walls might be considered to define a housing for supporting circuitry for the backplane  20  or at least a support structure to position and stably support the connectors of the backplane  20  a distance in front of the backplane  16  in which they can receive the functional modules that engage therewith (see  FIG. 2 ). The specific length of the supports or walls in the direction of insertion of the functional modules, i.e., the direction from right to left in  FIG. 2  through the opening of the chassis  10  into the interior chassis space, that engage with backplane  20  may be dimensioned to provide for insertion of the functional modules a distance to engage with connectors of backplane  20  that results in their front ends being in the same or substantially the same plane as the other functional modules being inserted into the backplane  16  (see  FIG. 1  which shows the functional modules in their inserted condition). 
     Both of the backplanes  16 ,  20  are oriented in a common axis, i.e., they are adapted to receive functional modules when inserted from the right side in the orientation illustrated, and that would be urged toward the left into engagement with the connectors on the backplanes  16 ,  20 . Thus, the backplanes  16 ,  20  each include an engagement side (facing the right in  FIG. 2 ) on which the module-engaging portion of each electrical connector is arranged and the engagement sides of the backplanes  16 ,  20  face the opening into the interior chassis space such that the module-engaging portions of electrical connectors of the backplanes  16 ,  20  are oriented toward the opening and the functional modules are insertable through the opening into engagement with the electrical connectors on the engagement side of each backplane  16 ,  20 . Often, the housing of the chassis  10  would include an opening to allow for insertion of the functional modules into engagement with the connectors on the backplanes  16 ,  20 . It is possible that the shallower backplane, i.e., the PXI backplane  20  in this case, would be attached to the substrate defining the deeper backplane, i.e., the VXI backplane  16  in this case (as shown in  FIG. 2 ). Alternatively, the rear of the shallower backplane may rest against in contact with or just alongside the substrate defining the deeper backplane. 
     Each of the backplanes  16 ,  20  could be implemented as a single printed circuit board or as multiple printed circuit boards. A backplane or “backplane system” generally is considered a group of electrical connectors in parallel with each other, so that each pin of each connector is linked to the same relative pin of all the other connectors forming a computer bus. It is typically used as a backbone to connect several printed circuit boards together to make up a complete computer system. 
     Upper and lower extrusions  18  along with card guides  48  permit a plurality of VXI modules (not shown in  FIG. 2 ) to be secured and retained within the chassis  10  in engagement with the VXI backplane  16 . The extrusions  18  and card guides  48  may be considered an example of a securing arrangement that secures the VXI modules to the chassis  10 . Similarly, upper and lower extrusions  22  along with card guides  50  permit a plurality of PXI modules (not shown in  FIG. 2 ) to be secured and retained within the same chassis  10 , and in engagement with the PXI backplane  20 . The extrusions  18 ,  22  and card guides  48 ,  50  may be considered an example of a securing arrangement that secures the PXI modules to the chassis  10 . The extrusions  18  and card guides  48  may be formed as an integral unit, and the extrusions  22  and card guides  50  may be formed as an integral unit. Also, the extrusions  18 ,  22  and card guides  48 ,  50  may be formed as an integral unit. Extrusions  18 ,  22  and card guides  48 ,  50  may be formed in a conventional manner of metalworking, and readily derivable to those skilled in the art to which this invention pertains from the disclosure herein. 
     In a preferred embodiment, a removable divider  24  can be installed within the PXI segment, or portion thereof, to allow the use of 3U PXI cards and/or 6U PXI within the multi-standard instrumentation chassis  10 . Since airflow cooling for both VXI and PXI modules originates from the bottom of the chassis  10 , ducting the airflow for the difference in module depth between the VXI and PXI standards becomes a rather trivial matter readily achievable by one skilled in the art to which this invention pertains in view of the disclosure herein. 
     In terms of electrical compatibility, a primary intent of the invention is to generally isolate the signals present within one backplane  16 ,  20  from those within the other backplane(s)  16 ,  20  to prevent unnecessary noise, signal crosstalk and commingling of signals. Specifically, address and data buses between instrumentation standards/form factors must ideally remain isolated from one another in order to avoid contention between control functions of each instrumentation standard. A preferred embodiment implements shielding in the area where backplane edges are in close proximity to further reduce interaction or interference between the signals of one backplane  16 ,  20  on one or more of the other backplanes  16 ,  20 . In instances where it might be possible to combine multiple instrumentation standards onto a single backplane, each instrumentation standard shall ideally remain isolated from the other standard(s) and implement shielding wherever necessary. 
     As shown in  FIG. 3 , each chassis standard would generally be populated with its own dedicated controller for controlling the backplane, namely controller  26  as a VXI controller and controller  28  as a PXI controller. This not only allows the use of specific controllers as needs dictate, but also minimizes compatibility issues as controllers known to work with a certain configuration can be maintained. As discussed earlier, the DC power sources system  30  and cooling airflow arrangement  32  would be shared amongst the different instrumentation standards. 
     There are instances where it might prove beneficial to allow limited interaction between the instrumentation standard backplanes  16 ,  20  within the multi-standard instrumentation chassis  10 . In a preferred embodiment, the user would be able to configure/select one or more trigger bus signals (represented at  34 ,  36 ) to pass between the VXI and PXI backplanes  16 ,  20 . These trigger signals may flow in a specific direction (i.e., VXI backplane  16  to PXI backplane  20  or PXI backplane  20  to VXI backplane  16 ) or be bi-directional (flows back and forth between VXI and PXI backplanes  16 ,  20 ) as required by customer application. Some signals or embodiments for other chassis standards/form factors may need to implement active circuitry  42 ,  44  to perform signal conditioning and/or level translation to insure compatibility between the signals of the instrumentation standards to be used. The signal conditioning and/or level translation is effected by circuitry  42 ,  44  on auxiliary signals passing between the VXI backplane  16  and the PXI backplane  20  during operation when they have VXI or PXI modules engaged therewith. 
     This circuitry  42 ,  44  may be user-controllable or user-selectable. As such, there may be limited interaction of auxiliary signals (i.e., trigger and/or clock signals) between the VXI backplane  16  and the PXI backplane  20  via user selectable means. 
     For certain applications, synchronized clock distribution between the different instrumentation standards may be desired. A clock might be sourced from the VXI backplane  16  (represented by VXI clock signals  38 ), PXI backplane  20  (represented by PXI clock signals  40 ) or from an external source  46 . In a preferred embodiment, the user would be able to configure/select the clock source  38 ,  40 ,  46  for the various instrumentation backplane(s) implemented within the multi-standard instrumentation chassis  10 . One preferred embodiment would utilize active clock distribution techniques to insure high isolation/buffering between backplanes  16 ,  20  and may optionally include clock multiplier/divider circuitry to allow clocks of different frequencies to be used while maintaining coherency. Alternative embodiments that do not require high isolation may use simpler passive or active circuits for sourcing these clock signals. 
     With the structure described above, the invention allows for specific advantages to be obtained, including configuring a common chassis that is capable of supporting a plurality of instrumentation form factors. 
     Use of the chassis would involve insertion of one or more of the mating modules into the chassis, and more specifically, into engagement with a respective one of the connectors of one or both of the backplanes. It is possible to use the chassis with only one type of functional modules, i.e., one or more functional modules of one type would be connected to the same backplane, or with two types of functional modules, i.e., at least one of a first type would be connected to a respective connector of the first backplane and at least one other, different type module would be connected to a respective connector of the other backplane. Once connected, the combined chassis and functional module(s) would be used in the usual manner in which a test station with one or more functional modules is used, and a variety of uses are known to those skilled in the art to which the invention pertains. 
     Manufacture of the chassis entails design and fabrication of the metalwork and other components, as well as assembly. Such design and assembly would be readily ascertainable by those skilled in the art to which this invention pertains in view of the disclosure herein. 
     Finally, it must be understood that although the illustrated embodiment shows two different backplanes, it is possible to use more than two backplanes in the same manner, i.e., placed the backplanes alongside one another in a common chassis and orient them in a common axis, i.e., in a position in which they are adapted to receive three or different types of functional modules when inserted from a common side of the chassis. It is possible to provide a chassis with two backplanes of the same type with one backplane of a different type interposed between them. Other configurations, combinations and permutations of different backplanes may be used in the invention without deviating from the scope and spirit thereof. 
     A general concept of one embodiment of the invention is therefore the provision of a common chassis with the capability of receiving two or more different types of functional modules arising from the presence of two or more backplanes. This concept may be embodied in a variety of different ways, as disclosed herein and as would be derivable from the teachings herein to those skilled in the art to which the invention pertains. All such disclosed and derivable embodiments are considered to be encompassed within the scope of the claims, to the extent possible. 
     Having thus described a few particular embodiments of the invention, various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications and improvements as are made obvious by this disclosure are intended to be part of this description though not expressly stated herein, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description is by way of example only, and is not limiting. The invention is limited only as defined in the claims and equivalents thereto.