Abstract:
An enhanced loadboard and method for enhanced automated test equipment (ATE) signaling. More specifically, embodiments provide an effective mechanism for reducing signal degradation and error interjection by replacing one or more relays with signal splitters for directing signals between one or more pins of a coupled ATE instrument, where the signal splitters reduce loadboard size and operating cost.

Description:
BACKGROUND OF THE INVENTION 
   Loadboards are often used to calibrate and perform diagnostic tests on instruments used in automated test equipment (ATE). For example, a single loadboard coupled to an instrument may couple pins of the instrument for pin-to-pin calibration and diagnostics, whereas multiple loadboards may be coupled to couple pins of multiple instruments for instrument-to-instrument calibration and diagnostics. Given that modern integrated circuits utilize high speed signaling upwards of many gigahertz, loadboard coupled to instruments testing such high-speed devices under test (DUTs) must be able to conduct the high-speed signals with minimal signal degradation such that accurate and precise calibration and/or diagnostics may be performed. 
     FIG. 1  shows conventional ATE loadboard  100  for coupling to an instrument. As shown in  FIG. 1 , loadboard  100  includes a number of relays  110 - 150  for coupling pins  1  through  16  to the reference pin. The 16 pins couple to a 16 functional pins of an instrument, where each functional pin may be calibrated with respect to one another by adjusting the state of relays  110 - 150 . For example, the state of the relays shown in  FIG. 1  enables pin-to-pin calibration of pin  1  with respect to the reference pin by transmitting signals to and from the coupled pins as represented by communication path  160 . The states of the relays may then be successively adjusted to couple the other 15 pins to the reference pin for calibration thereto. As such, all the pins may be calibrated to one another by calibrating each pin to the reference pin. 
   In addition to pin-to-pin calibration, the state of relay  150  may be adjusted to couple the reference pin of one instrument to that of another instrument using a loadboard similar to loadboard  100  for each coupled instrument. By first calibrating respective functional pins to the reference pin of an instrument, functional pins of coupled instruments may be calibrated with respect to one another by calibrating the reference pins of the coupled instruments with respect to one another. 
   Although loadboards similar to conventional loadboard  100  have been used in the past, the increased signaling speeds used by modern DUTs are beginning to exceed the capabilities of the relays. For example, signal degradation is common when using the relays to gate high-speed signals. Additionally, as the average number of devices tested by ATE increases, the space and power consumption of the relays present fiscal and other logistics issues for ATE manufacturers and users alike. Moreover, as the number of pins of an average DUT increases, the limited loadboard real estate is quickly used up, resulting in component placement which compromises signal integrity and other loadboard functionality. 
   Furthermore, conventional loadboard  100  requires that each functional pin be calibrated with respect to the reference pin given the inability to directly couple any two functional pins. As such, the need to switch relay state prevents parallel calibration, thereby increasing calibration time and cost. Additionally, calibration measurements of functional pins with respect to the reference pin must be compared to derive calibration data of functional pins with respect to other functional pins. In addition to adding an extra step, such comparison is likely to interject error due to hysteresis, tolerance buildup, or the like. 
   Thus, not only do relays affect the accuracy and precision of calibration measurements given the inherent signal degradation associated with the relays, but the need to compare measurements with respect to a functional pin exacerbates the problem by interjecting additional error. Furthermore, the decreased accuracy and precision also bring with them increased operation cost, ATE size and signal degradation given the switched nature, large size and power consumption of the relays. 
   SUMMARY OF THE INVENTION 
   Accordingly, a need exists for an enhanced loadboard which saves cost and more effectively utilizes loadboard real estate. Additionally, a need exists to decrease signal degradation associated with loadboards when transmitting high-speed signals. Further, a need exists for more direct pin-to-pin calibration which minimizes error interjection when calibrating with respect to a common reference pin. Embodiments of the present invention provide novel solutions to these needs and others as described below. 
   Embodiments of the present invention are directed towards an enhanced loadboard and method for enhanced automated test equipment (ATE) signaling. More specifically, embodiments provide an effective mechanism for reducing signal degradation and error interjection by replacing one or more relays with signal splitters for directing signals between one or more pins of a coupled ATE instrument, where the signal splitters reduce loadboard size and operating cost. 
   In one embodiment of the present invention, an enhanced component for conducting an ATE signal includes a first element, and a second and third element coupled to the first element. The first, second and third elements may be pins of the loadboard for coupling to functional pins of an ATE instrument. Alternatively, the elements may be pin electronics of the ATE instrument, or instead other signal splitters or relays of the loadboard. The enhanced component may also include a signal splitter coupled between the first, second and third elements, wherein the signal splitter is operable to conduct the signal from the first element to at least one of the second and third elements. The signal splitter may include a first resistive element coupled to the first element, a second resistive element coupled to the second element, and a third resistive element coupled to the third element. The resistive elements may be resistors, transistors, or the like. Additionally, the first, second and third resistive elements may share a common node. 
   In another embodiment of the present invention, an enhanced loadboard for use with ATE includes a plurality of elements for coupling to functional pins of an ATE instrument. The loadboard may also include a plurality of relays coupled to the plurality of elements. A plurality of signal splitters may be coupled to the plurality of relays, wherein the signal splitters are operable to conduct ATE signals between the plurality of elements. The signal splitter may include a first resistive element, a second resistive element coupled to the first resistive element, and a third resistive element coupled to the second resistive element. The first, second and third resistive elements may share a common node. 
   In yet another embodiment of the present invention, a method for enhanced ATE signaling may include transmitting a first signal from a first element of an ATE loadboard to a first resistive element of a signal splitter. The first signal may be split into a second and third signal using a second and third resistive element of the signal splitter. Thereafter, one of the second and third signals may be received using a second element of the ATE loadboard. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements. 
       FIG. 1  shows a conventional ATE loadboard for coupling to an instrument. 
       FIG. 2  shows an exemplary ATE loadboard in accordance with one embodiment of the present invention. 
       FIG. 3  shows an exemplary signal splitter in accordance with one embodiment of the present invention. 
       FIG. 4  shows an exemplary ATE loadboard with additional signal splitters in accordance with one embodiment of the present invention. 
       FIG. 5  shows a portion of an exemplary ATE loadboard with at least one signal processing component in accordance with one embodiment of the present invention. 
       FIG. 6  shows an exemplary ATE system with multiple instruments in accordance with one embodiment of the present invention. 
       FIG. 7  shows an exemplary process for enhanced ATE signaling in accordance with one embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. While the present invention will be discussed in conjunction with the following embodiments, it will be understood that they are not intended to limit the present invention to these embodiments alone. On the contrary, the present invention is intended to cover alternatives, modifications, and equivalents which may be included with the spirit and scope of the present invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, embodiments of the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present invention. 
     FIG. 2  shows exemplary ATE loadboard  200  in accordance with one embodiment of the present invention. As shown in  FIG. 2 , loadboard  200  comprises a reference pin and pins  1 - 16  for coupling to an ATE instrument. In addition to relays  120 - 150 , signal splitters  210 - 217  may be used to couple two or more pins of the loadboard via resistive elements  205 . For example, signal splitter  212  may couple pins  5  and  6  to each other to enable signaling through communication path  270 , or instead couple pins  5  and/or  6  to the reference pin of loadboard  200  by appropriately adjusting the state of relays  121 ,  130 ,  140  and  150 . Thus, two or more pins of the coupled instrument may be coupled (e.g., for pin-to-pin calibration, diagnostics, etc.) by coupling the corresponding pins of loadboard  200 . 
   Referring now to  FIG. 3 , exemplary signal splitter  300  is depicted in accordance with one embodiment of the present invention. Resistive elements  205 A,  205 B and  205 C are shown coupled by common node  302  to provide symmetry to signal splitter  300 . As such, a signal may be fed to any leg and split accordingly. For example, a signal fed to the splitter through lead  308 A may be split into a second and third signal, where the second signal may exit the splitter through resistive element  205 B and the third signal may exit the splitter through resistive element  205 C. Alternatively, a signal fed to the splitter through lead  308 B may be split into a second and third signal, where the second signal may exit the splitter through resistive element  205 A and the third signal may exit the splitter through resistive element  205 C. And in another embodiment, a signal fed to the splitter through lead  308 C may be split into a second and third signal, where the second signal may exit the splitter through resistive element  205 A and the third signal may exit the splitter through resistive element  205 B. 
   In addition to providing symmetric signal flow, signal splitter  300  may also reduce signal degradation by adjusting transmission line properties, where signal degradation may pertain to qualities of the waveform other than signal amplitude (e.g., slew rate, jitter, etc.). For example, where resistive elements  205 A,  205 B and  205 C are resistors, the values of the resistors may be chosen such that impedance mismatch is reduced when sending signals from any resistive element to any other resistive element of the signal splitter. Alternatively, where the resistive elements provide variable resistance (e.g., by using transistors), the values of the resistive elements may be varied (e.g., using a control system to alter transistor bias, etc.) to improve transmission line properties (e.g., on the fly subsequent to manufacturing, etc.). As such, transmission through the signal path may be improved by, for example, reducing reflections caused by impedance mismatch. 
   Additionally, the configuration of the resistive elements in signal splitter  300  offers a broadband frequency response exceeding that of a relay. As such, signal splitters may pass higher-speed signals with less degradation compared to transmission through a relay. Thus, by removing one or more relays as shown in  FIG. 2  and replacing them with signal splitters similar to signal splitter  300 , the degradation of signals passed through loadboard  200  is reduced. 
   Although  FIGS. 2 and 3  depict only a two-way signal splitter, the signal splitter may split a signal into three or more resulting signals in other embodiments (e.g., by adding additional resistive elements). Additionally, although leads  308 A,  308 B and  308 C are shown without a corresponding connection, it should be appreciated that the leads may be placed in a termination state (e.g., held at an approximate steady-state potential, ground, etc.) by an element of either the loadboard (e.g., another signal splitter, relay, loadboard pin, etc.) or a coupled instrument (e.g., pin electronics, reference pin, functional pin, etc.) in another embodiment. Additionally, although  FIG. 3  shows leads and traces coupling the resistive elements, it should be appreciated that the diagram is merely a block diagram drawn to conveniently depict the connection of the resistive elements. As such, the diagram is not to scale, and in other embodiments the traces and/or leads may be omitted or be alternatively scaled. 
   As shown in  FIG. 3 , the resistance value of the resistance elements of signal splitter  300  may be a function of the desired impedance of the signal splitter and the number of times the signal is split. In one embodiment, the resistance value R of each resistance element may be calculated using the following formula: 
           R   =       Z   ⁡     (     N   -   1     )         (     N   +   1     )             
Accordingly, the resistance value R varies as a function of the desired impedance of the signal splitter Z and the number of times the signal is split N. For example, a signal fed through signal splitter  300  is split into two resulting signals (e.g., N=2). As such, if a 50 Ohm impedance is desired for signal splitter  300 , the resistance value of each resistance element would be approximately 50/3 Ohms in accordance with one embodiment of the present invention.
 
   Referring back to  FIG. 2 , signal splitters  210 - 217  may operate analogously to signal splitter  300  as discussed with respect to  FIG. 3  above. As such, a signal fed to one leg of a signal splitter may be split into two or more signals to be received by elements of the loadboard and/or coupled instrument, where one or more of the resistive elements of signal splitter  210  are put in a termination state. For example, a signal transmitted from the reference pin may be sent to pin  1  as shown by communication path  160 , or instead to pin  2  as represented by communication path  165 . The signal to be split may be directed to signal splitter  210  using relays  150 ,  140 ,  130  and  120 . Once the signal reaches signal splitter  210 , it may be split and fed to pin  1  and/or pin  2 . Thus, the relays and signal splitters of loadboard  200  enable calibration (e.g., of pin  1  or pin  2  to the loadboard reference pin) and/or diagnostics operations to be performed on a coupled instrument, where such operations may require unidirectional or bi-directional signaling between pins of the instrument. 
   Alternatively, signals may be transmitted directly between pins of loadboard  200 , which was not possible with the use of a relay. For example, signal splitter  212  enables signaling between pins  5  and  6  as represented by communication path  270 , where one or more of the resistive elements of signal splitter  212  may be put in a termination state. As such, direct pin-to-pin calibration (e.g., of pin  5  to pin  6  using 4-way deskew calibration) and/or diagnostics operations may be performed on a coupled instrument without unnecessarily interjecting error (e.g., from calibrating to a separate reference pin, etc.). Additionally, since signal splitters provide symmetric signal flow, it should be appreciated that any signals received by pins other than those in direct communication (e.g., the reference pin when utilizing communication path  270  if relay  130  were adjusted to route a signal from relay  121  to relay  140 ) may be ignored (e.g., by pin electronics or other components of a coupled instrument, etc.) instead of measured. 
   In addition to communication between pins of the same instrument, loadboard  200  enables communication between pins of different instruments. For example, if the state of relay  150  is adjusted from the state depicted in  FIG. 2 , the reference pin of loadboard  200  may be coupled to another loadboard, thereby enabling the coupling of multiple instruments (e.g., where one instrument is coupled to the reference pin and pins  1  through  16 , and the other coupled to relay  150 ). As such, instrument-to-instrument calibration and/or diagnostics may be performed. 
   As shown in  FIG. 2 , signal splitters  210 - 217  comprise resistive elements  205 . Since resistive elements (e.g., resistors, transistors, etc.) may be significantly smaller and less expensive than a relay, signal splitters save significant loadboard real estate and cost. Additionally, resistive elements use less power than a relay given the absence of a coil to perform the switching, thereby requiring less energy to power each loadboard. Further, signal splitters offer decreased signal degradation given the ability to remove a switch contact (e.g., within a relay) from the signal path. Moreover, any degradation over time from the switched contact is obviated through the use of a signal splitter since the signal splitter contains no moving parts or mechanical contacts. 
   Given the ability to receive a split signal at multiple places at the same time, the addition of signal splitters reduces operation time and cost by enabling parallel measurements. For example, a signal directed from the reference pin to signal splitter  212  may feed pins  5  and  6  simultaneously such that pins of a coupled instrument corresponding to pins  5  and  6  may be calibrated in parallel with respect to the reference pin without adjusting the state of a relay. Additionally, diagnostics operations with respect to pins  5  and  6  may also be performed in parallel. 
   Although  FIG. 2  depicts loadboard  200  with a specific number of pins (e.g., 16), it should be appreciated that loadboard  200  may have a larger or smaller number of pins in other embodiments. Additionally, the number of signal splitters and/or relays may vary in other embodiments. Further, the signal splitters and/or relays may be replaced with other signal conduction components in alternative embodiments. 
     FIG. 4  shows exemplary ATE loadboard  400  with additional signal splitters in accordance with one embodiment of the present invention. As shown in  FIG. 4 , loadboard  400  comprises signal splitters  210 - 217  similar to loadboard  200  shown in  FIG. 2 . However, relays  120 - 150  of loadboard  200  are replaced with signal splitters  420 - 450  in loadboard  400 . 
   As discussed above with respect to  FIGS. 2 and 3 , signal splitters offer several advantages over relays when used in an ATE loadboard. For example, signal splitters may transmit faster signals with less degradation than relays. Also, a loadboard using signal splitters to replace relays is smaller and costs less to operate than one with more relays. Accordingly, loadboard  400  may reduce the size, operating cost and signal degradation by replacing relays  120 - 150  with signal splitters  420 - 450 . 
   Additionally, by increasing the number of signal splitters, loadboard  400  expands the number of pins for which direct pin-to-pin measurements can be taken. For example, signal splitter  422  (in combination with signal splitters  214  and  215 ) effectively couples pins  9 - 12 , thereby enabling the transmission of signals between any of the coupled pins (e.g., between pins  9  and  12  as represented by communication path  480 ). Signal degradation associated with the transmission may be reduced by using coupled signal splitters (e.g.,  214 ,  215 ,  431 , etc.) to place the resistive elements  205  of signal splitter  422  in an appropriate termination state (e.g., as discussed above with respect to  FIGS. 2  and  3 ). Thus, direct pin-to-pin calibration (e.g., of pin  9  to pin  12 ) and/or diagnostics operations may be performed on a coupled instrument without unnecessarily interjecting error (e.g., from calibrating to a separate reference pin, etc.). Additionally, since signal splitters provide symmetric signal flow, it should be appreciated that any signals received by pins other than those in direct communication (e.g., all pins other than pins  9  and  12  when utilizing communication path  480 ) may be ignored (e.g., by pin electronics or other components of a coupled instrument, etc.) instead of measured. 
   As shown in  FIG. 4 , additional signal splitters enable parallel measurements to be taken with respect to a greater number of pins. For example, a signal transmitted from the reference pin of loadboard  400  may be received simultaneously by pin  2  (e.g., as represented by communication path  165 ) and pin  16  (e.g., as represented by communication path  467 ). As such, measurements may be taken in parallel without adjusting a relay state to effectively perform pin-to-pin calibration (e.g., using 4-way deskew calibration) and/or diagnostics operations on a coupled instrument. Alternatively, parallel instrument-to-instrument calibration and/or diagnostics operations may be performed on multiple instruments by simultaneously transmitting to pins of each instrument using signal splitter  450 . 
   Although  FIG. 4  depicts loadboard  400  with a specific number of pins (e.g., 16), it should be appreciated that loadboard  400  may have a larger or smaller number of pins in other embodiments. Additionally, the number of signal splitters may vary in other embodiments. Further, the signal splitters may be replaced with other signal conduction components in alternative embodiments. 
     FIG. 5  shows a portion of exemplary ATE loadboard  500  with at least one signal processing component in accordance with one embodiment of the present invention. As shown in  FIG. 5 , one or more signal processing components (e.g.,  520 A,  520 B and/or  520 C) may be coupled to signal splitters  510  and  511  to process signals transmitted through the signal splitters. It should be appreciated that only a single transmission path is depicted in  FIG. 5  to simplify the discussion, and that in other embodiments, additional signal splitters and/or signal processing components may be used. 
   While signal splitters reduce signal degradation (e.g., slew rate, jitter, etc.) compared to transmission through a relay, it should be appreciated that the signal amplitude may be reduced as a result of the split. Also, it should be appreciated that the signal may be influenced by noise and other interference in the environment. As such, signal processing components  520 A,  520 B and/or  520 C may be placed in the signal path to amplify, filter and/or otherwise process the signals to enhance reception and measurement (e.g., to maintain a sufficient signal-to-noise ratio such that detection is possible). 
   Although  FIG. 5  depicts three signal processing components, it should be appreciated that a larger or smaller number may be used in other embodiments. Additionally, the signal processing components may be placed more or less sporadically (e.g., one signal processing component for every two signal splitters, one for every three signal splitters, etc.). Moreover, although the signal processing components are depicted as a portion of loadboard  500 , it should be appreciated that one or more signal processing components may be located off the loadboard (e.g., on a separate interface board, within a coupled instrument, etc.). 
     FIG. 6  shows exemplary ATE system  600  with multiple instruments in accordance with one embodiment of the present invention. As shown in  FIG. 6 , instrument  610  is coupled to loadboard  615 , and instrument  620  is coupled to loadboard  625 . As such, instruments  610  and  620  may be coupled using interface  630  to couple loadboards  615  and  625 . 
   Instruments  610  and  620  comprise a plurality of pins (e.g.,  611 - 613  and  621 - 623 ), which may be a combination of reference, functional and/or calibration pins. The pin electronics components  617  and  627  may couple to the pins for transmitting and receiving signals during diagnostic, calibration and/or test operations. For example, a driver and/or comparator of a pin electronics component may place resistive components of coupled signal splitters (e.g., within loadboards  615  and/or  625 ) in an appropriate termination state to enable signal transmission through a path with desired transmission line characteristics. Although a single pin electronics component is shown in  FIG. 6 , it should be appreciated that a single pin electronics component may service more than one pin in other embodiments. 
   Loadboard  615  couples to the pins  611 - 613  and may be implemented as discussed above with respect to  FIGS. 2 ,  4  and  5 . Similarly, loadboard  625  couples to the pins  621 - 623  and may be implemented as discussed above with respect to  FIGS. 2 ,  4  and  5 . As such, loadboards  615  and  625  may be used to couple the pins of each respective instrument for pin-to-pin calibration and diagnostics procedures as discussed above. 
   Alternatively, loadboards  615  and  625  may be coupled using interface  630  to perform instrument-to-instrument calibration and/or diagnostics as discussed above. As such, interface  630  may couple to a signal conduction component of the loadboard which effectively couples one or more pins of each instrument. For example, either relay  150  as shown in  FIG. 2  or signal splitter  450  as shown in  FIG. 4  may couple to interface  630  for coupling instruments  610  and  620 . 
     FIG. 7  shows exemplary process  700  for enhanced ATE signaling in accordance with one embodiment of the present invention. As shown in  FIG. 7 , step  710  involves transmitting a first signal from a first element to a first resistive element of a signal splitter. The first element may be an element of either the loadboard (e.g., a signal splitter, relay, loadboard pin, etc.) or a coupled instrument (e.g., pin electronics, reference pin, functional pin, etc.). Additionally, the first element may place the first resistive element (e.g.,  205 A as shown in  FIG. 3 ) in a termination state (e.g., held at an approximate steady-state potential, ground, etc.) to enable the signal splitter to split the signal with reduced signal degradation as discussed above with respect to  FIGS. 2 through 6 . 
   After the signal is fed to the first resistive element, the signal may be split into a second and third signal using a second and third resistive element in step  720 . The second resistive element (e.g.,  205 B) and the third resistive element (e.g.,  205 C) may couple to the first resistive element (e.g.,  205 A) via a common node (e.g.,  302 ). As such, the resistive elements may effectively split the signal with appropriate impedance matching and other transmission line properties such that the degradation of the resulting second and third signals is reduced. Moreover, it should be appreciated that additional resistive elements may be coupled to further split the first signal, where the resistance value of the resistive elements may then change (e.g., as discussed above with respect to  FIG. 3 ) to adjust the transmission line properties in light of the updated number of split signals. 
   As shown in  FIG. 7 , step  730  involves receiving the second signal from the second resistive element at a second element. As discussed above with respect to the first element in step  710 , the second element may be an element of the loadboard on which the resistive elements are located. Alternatively, the second element may be an element of a coupled instrument. The second element may place the second resistive element in a termination state as discussed above with respect to  FIGS. 2 through 6 . Additionally, the second signal may be processed either before or after its receipt in step  730 , where the processing may be performed using a signal processing component as discussed above with respect to  FIG. 5 . 
   Step  740  involves receiving the third signal from the third resistive element at a third element. As discussed above with respect to the first element in step  710  and the second element in step  730 , the third element may be an element of the loadboard on which the resistive elements are located. Alternatively, the third element may be an element of a coupled instrument. The third element may place the third resistive element in a termination state as discussed above with respect to  FIGS. 2 through 6 . Additionally, the third signal may be processed either before or after its receipt in step  740 , where the processing may be performed using a signal processing component as discussed above with respect to  FIG. 5 . 
   After receiving the second and third signals in steps  730  and  740 , the signals may be either measured and/or ignored in steps  750  and  760 . As such, step  750  involves measuring the second signal and ignoring the third signal if communication between the first and second element is desired. As discussed above with respect to  FIGS. 2 and 4 , the measuring and ignoring may be performed by any component or device coupled to the loadboard (e.g., a pin electronics component of a coupled instrument, some other component of a coupled instrument, etc.), where a separate component or device may perform the measuring and ignoring. Additionally, the second signal may be processed before measurement in step  750 , where the processing may be performed using a signal processing component as discussed above with respect to  FIG. 5 . 
   Alternatively, if it is desired to communicate between the first and third elements, the third signal may be measured and the second signal may be ignored in step  760 . As discussed above with respect to  FIGS. 2 and 4 , the measuring and ignoring may be performed by any component or device coupled to the loadboard (e.g., a pin electronics component of a coupled instrument, some other component of a coupled instrument, etc.), where a separate component or device may perform the measuring and ignoring. Additionally, the third signal may be processed before measurement in step  760 , where the processing may be performed using a signal processing component as discussed above with respect to  FIG. 5 . 
   In the foregoing specification, embodiments of the invention have been described with reference to numerous specific details that may vary from implementation to implementation. Thus, the sole and exclusive indicator of what is, and is intended by the applicant to be, the invention is the set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction. Hence, no limitation, element, property, feature, advantage, or attribute that is not expressly recited in a claim should limit the scope of such claim in any way. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.