Patent Publication Number: US-2021172977-A1

Title: Triaxial power and control systems and methods

Description:
PRIORITY 
     This disclosure claims benefit of U.S. Provisional Application No. 62/945,035, titled “TRIAXIAL POWER AND CONTROL METHOD,” filed on Dec. 6, 2019, which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This disclosure is directed to systems and methods related to test and measurement systems, and in particular, to test and measurement systems that employ triaxial connectors and cables. 
     BACKGROUND 
     For a number of reasons, when setting up a test for a device under test (DUT), it can often be required or beneficial to place a remote device between the test and measurement instrument and the device under test. Such remote modules may include, for example, preamplifiers for low current measurements, devices to modify or protect the test and measurement instrument behavior, remote bias tees (RBTs) to allow for direct current and alternating current testing, and matrices for general switching of instruments to different devices under test. 
     However, many of these remote devices have no means to control different modes of operation. Further, it is often not practical to add connections, such as wires, to these modules to allow digital communication to change the modes, due to spacing and size concerns, as well as cost to develop the control hardware and drivers. 
     Embodiments of the disclosure address these and other deficiencies of the prior art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects, features and advantages of embodiments of the present disclosure will become apparent from the following description of embodiments in reference to the appended drawings in which: 
         FIG. 1  is a block diagram of a test and measurement system including a remote device. 
         FIG. 2  is a block diagram of a test and measurement system including a remote device according to some embodiments of the disclosure. 
         FIG. 3  is an example of a signal that may be received at the remote device of  FIG. 2 . 
         FIG. 4  is another example of a remote device according to other embodiments of the disclosure. 
     
    
    
     DESCRIPTION 
     Embodiments of the disclosure are directed to remote modules and circuitry which are connected between a test and measurement instrument and a device under test, and that are capable of changing modes based on an output from the test and measurement instrument. 
       FIG. 1  illustrates a block diagram of an example test system according to embodiments of the disclosure. A test and measurement instrument  100 , such as a source measure unit (SMU), can connect to a device under test  104  through a remote device  102 . The test and measurement instrument  100  may also directly connect to the device under test  104 . The test and measurement instrument  100  connects to the remote device  102  and/or the device under test  104  through one or more triaxial cables. A triaxial cable generally includes a center conductor, often known as the force. The center conductor and an inner insulative layer are surrounded by an intermediary conductor, often known as the guard. The guard and another insulative layer are then surrounded by a third outer conductor or shield, which often serves as a ground. Finally, the outer shield is typically surrounded by an outer insulative protective layer, 
     The remote device  102  receives a voltage across two conductors  106  and  108  of the triaxial cable connected to the test and measurement instrument  100 . The test and measurement instrument  100  can connect to the device under test  104  through the third conductor  110  of a triaxial cable or can connect directly to the device under test  104  through another triaxial cable. Through the two conductors  106  and  108 , the test and measurement instrument  100  can instruct the remote device  102  to change modes for testing the device under test  104 . The remote device  102  can modify the signal pathway from the test and measurement instrument  100  for an appropriate test of the device under test  104 . In some embodiments, the conductor  106  may be a conductor of a first triaxial cable, and the conductor  108  may be a conductor of a second triaxial cable. 
     Presently, there is a problem in semiconductor parametric test systems, for example, wherein low current direct current, capacitance-voltage (C/V), and pulse measurements must all be switched and connected to a device under test  104  with the same triaxial cabling. The guard of the triaxial cable is needed for direct current testing, but is often undesirable for C/V and pulse testing. The remote device  102  of the disclosure can allow for the remote device  102  to be closer to the device under test  104 , while being able to change modes as needed for testing. 
       FIG. 2  illustrates a remote device according to some embodiments of the disclosure. In this system, the test and measurement instrument  100  can energize a remote device  102  that detects and executes an encoded command to change the mode of the remote device. The system includes a test and measurement instrument  100 , a remote device  102 , and a device under test  104 . The test and measurement instrument  100  can be connected to the remote device  102  through one or more triaxial cables. 
     The remote device  102  can include a power supply  206 , a signal decoder  208 , a device control circuit  210  and device or measurement circuitry  212 . The remote device is connected to at least two conductors  214  and  216  of a triaxial cable connecting the remote device  102  to the test and measurement instrument  100 . The third conductor  218  of the triaxial cable can be directly connected to the device under test  104 . 
     The test and measurement instrument  100  can output a first voltage on a first conductor  214  and a second voltage on a second conductor  216  to change the mode of the remote device  102 . In the illustration in  FIG. 2 , the first conductor  214  is a guard and the second conductor  216  carries a LO signal, while a HI signal is sent to the device under test  202  through the third conductor  218 . However, the conductors be configured to can carry a variety of signals, such as HI to guard, guard to LO, HI to LO, or a first guard to a second guard. As long as different voltage signal are sent on each conductor, the conductors  214 ,  216  can be used to power and communicate with the remote device  102 . 
     The test and measurement instrument  100  can send an initial power signal to the remote device  102  through the first conductor  214  and the second conductor  216 , which are received by the power supply  206 . The power supply  206  receives the variable voltage from the first conductor  214  and the second conductor  216  and generates a constant voltage supply based on the variable voltage. The constant voltage supply can be used to power the signal decoder  208  and the device control circuit  210 . 
     Once powered, the signal decoder  208  monitors the voltage on the first conductor  214  relative to the second conductor  216  to determine what command the test and measurement instrument  100  is sending to the remote device  102 . Using an established communication protocol, the signal decoder  208  can decode a command signal sent from the test and measurement instrument  100  based on the voltages of the first conductor  214  and the second conductor  216 . 
     The device control circuit  210  receives the command from the signal decoder  208  and the device control circuit  210  can take an action to change the operating mode of the remote device  102  in the device circuitry  212 . During normal testing, a signal  220  may be output through the remote device  104  to the device under test  104 . 
     In some embodiments, the power supply  206 , signal decoder  208 , and device control circuit  210  are only active or “on” when voltage is received between the first conductor  214  and the second conductor  216  and otherwise can be powered down or placed in sleep mode. 
     For example, in some embodiments, the power supply  206  can be a capacitor that is charged from the voltage between the first conductor  214  and the second conductor  216 . The capacitor would be large enough to power the signal decoder  208  and the device control circuit  210  to receive and execute the command from the test and measurement instrument  100 . When the capacitor has discharged, the power supply  206 , signal decoder  208 , and device control circuit  210  power off. 
     As will be understood by one skilled in the art, more complex circuits may be provided to power the signal decoder  208  and the device control circuit  210  down when not in use, such as a switch which disconnects the power supply  206  from the first conductor  214  and the second conductor  216 . The switch may be activated based on the voltage between the first conductor  214  and the second conductor  216 . 
       FIG. 3  illustrates an example of a signal  300  that may be sent from the test and measurement instrument  100  to the remote device  102  through the first conductor  214  and the second conductor  216 . The signal  300  may include a power-on portion  302 , a command portion  304 , a command execute portion  306 , before turning off and normal testing  308  can begin. 
     The power on portion  302  of the signal  300  is received first to provide a variable voltage to the power supply  206  to generate the constant voltage for the signal decoder  208  and the device control circuit  210 . The power on portion  302  of the signal  300  is configured to guarantee that enough charge is delivered to the power supply  206  to power the signal decoder  208  and the device control circuit  210  until the command execute portion  306  of the signal  300  is received and executed. 
     The command portion  304  is a unique signal that can be decoded by the signal decoder  208 . The command portion  304  can be unique so that it is unlikely a test sequence accidentally triggers the device control circuit  210  and causes the remote device  102  to change modes if the power supply  206  is not powered down during the normal testing. In such embodiments, the remote device  102  may include modulating a frequency or pulse amplitude to ensure that the command signal is unique and cannot be triggered by a test sequence. 
     The signal  300  also includes a command execute portion  306  which informs the remote device  102  that the entirety of the command signal  304  has been received and the device control circuit  210  can change the mode of the remote device  102  based on the decoded command signal from the signal decoder  208 , for example, by changing the configuration of device circuitry  212 . Once the command has been executed, normal testing of the device under test  104  through the remote device  102  can proceed. 
     When not powered, the power supply  206 , signal decoder  208 , and device control circuit  210  float with the guard signal, so that these components do not induce any extra leakage during testing of the device under test. 
     In some embodiments, the remote device  102  may send a communication signal back to the test and measurement instrument  100 , such as to confirm the state or operating mode of the remote device  102 . For example, in some embodiments, when the device control circuit  210  has completed executing the command, the device control circuit  210  may initiate a communication back to the test and measurement instrument  100  to confirm that the mode of the remote device  102  has changed. The device control circuit  210  may also confirm which mode the remote device  102  changed to in some embodiments, rather than just confirming the change occurred, so that the test and measurement instrument  100  can confirm that the correct signal was received and decoded by the remote device  102 . 
     The remote device  102  may send the communication signal back to the test and measurement instrument  100  through a separate connection, or may use the first and second conductors  114  and  116 . In some embodiments, a third conductor of the triaxial cable may be used to send the signal back to the test and measurement instrument  100 . In other embodiments, the remote device  102  may include a transmitter or transceiver that can send the communication back to the test and measurement instrument  100 . 
       FIG. 4  is another example of a remote device  102  which may be connected between the device under test  104  and the test and measurement instrument  100  (not shown in  FIG. 4 ).  FIG. 4  illustrates three Kelvin triaxial connections connected to a three terminal device under test  104 . Each Kelvin connection includes two cables  400  and  402 , a relay coil  404 , and a switch  406 . 
     An intermediary conductor  408  of each cable  400  and  402  is connected to the relay coil  404 . The center conductor  410  is connected to one of the terminals of the device under test  104 . The switch  406  connects the center conductors  408 , the terminal of the device under test  104 , and the outer conductor  412  to each other when engaged. The outer conductors  412  of each of the cables  400  and  402  are connected to each other. 
     In the embodiments of  FIG. 4 , the test and measurement instrument  100  can instruct the remote device  102  to activate or release the switch  406  based on the type of measurement being performed. For example, the switch  406  may be activated to perform high frequency measurements that require the use of the outer conductor  412 . 
     During operation, the test and measurement instrument  100  may open and close each switch  406  by energizing or de-energizing the associated relay coil  404 . To energize or de-energize the relay coil  404 , the test and measurement instrument  100  can send a differential voltage across the intermediary conductors  408  of the Kelvin pair of cables  400  and  402 . When the switch  406  is open, and relay coil  404  is not activated, the relay coil  404  is at the guard signal, which reduces leakage to the terminal of the device under test  104 . 
     In the embodiment illustrated in  FIG. 4 , the coil relays  404  can be placed physically close to the device under test  104 , which can provide advantages for fast pulse measurements, radio frequency measurements, and high frequency measurements, for example. That is, the remote device as illustrated in  FIG. 4  can provide benefits for high frequency measurements, but without giving up accurate measurements for direct current. 
     Aspects of the disclosure may operate on particularly created hardware, firmware, digital signal processors, or on a specially programmed computer including a processor operating according to programmed instructions. The terms controller or processor as used herein are intended to include microprocessors, microcomputers, Application Specific Integrated Circuits (ASICs), and dedicated hardware controllers. One or more aspects of the disclosure may be embodied in computer-usable data and computer-executable instructions, such as in one or more program modules, executed by one or more computers (including monitoring modules), or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types when executed by a processor in a computer or other device. The computer executable instructions may be stored on a computer readable storage medium such as a hard disk, optical disk, removable storage media, solid state memory, Random Access Memory (RAM), etc. As will be appreciated by one of skill in the art, the functionality of the program modules may be combined or distributed as desired in various aspects. In addition, the functionality may be embodied in whole or in part in firmware or hardware equivalents such as integrated circuits, FPGA, and the like. Particular data structures may be used to more effectively implement one or more aspects of the disclosure, and such data structures are contemplated within the scope of computer executable instructions and computer-usable data described herein. 
     The disclosed aspects may be implemented, in some cases, in hardware, firmware, software, or any combination thereof. The disclosed aspects may also be implemented as instructions carried by or stored on one or more or computer-readable storage media, which may be read and executed by one or more processors. Such instructions may be referred to as a computer program product. Computer-readable media, as discussed herein, means any media that can be accessed by a computing device. By way of example, and not limitation, computer-readable media may comprise computer storage media and communication media. 
     Computer storage media means any medium that can be used to store computer-readable information. By way of example, and not limitation, computer storage media may include RAM, ROM, Electrically Erasable Programmable Read-Only Memory (EEPROM), flash memory or other memory technology, Compact Disc Read Only Memory (CD-ROM), Digital Video Disc (DVD), or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, and any other volatile or nonvolatile, removable or non-removable media implemented in any technology. Computer storage media excludes signals per se and transitory forms of signal transmission. 
     Communication media means any media that can be used for the communication of computer-readable information. By way of example, and not limitation, communication media may include coaxial cables, fiber-optic cables, air, or any other media suitable for the communication of electrical, optical, Radio Frequency (RF), infrared, acoustic or other types of signals. 
     EXAMPLES 
     Illustrative examples of the technologies disclosed herein are provided below. An embodiment of the technologies may include any one or more, and any combination of, the examples described below. 
     Example 1 a test and measurement device, comprising a first input structured to receive a first voltage from a first conductor of a first triaxial cable; a second input structured to receive a second voltage from a second conductor of the first triaxial cable or a second triaxial cable; circuitry configured to change modes based on the first voltage and the second voltage; and an output structured to output a signal. 
     Example 2 is the test and measurement device of example 1, further comprising a power supply configured to receive the first voltage and the second voltage and generate a constant voltage supply based on a voltage differential between the first voltage and the second voltage; and a signal decoder configured to receive the constant voltage supply and monitor the first voltage relative to the second voltage to determine a command code for changing modes. 
     Example 3 is the test and measurement device of example 2, wherein the power supply is a capacitor. 
     Example 4 is the test and measurement device of example 2 or 3, further comprising device control circuitry configured to receive the command code from the signal decoder and cause measurement circuitry to change modes based on the command code. 
     Example 5 is the test and measurement device of example 4, wherein the first conductor is configured to conduct a low signal of the first triaxial cable and the second conductor is a guard of the first triaxial cable. 
     Example 6 is the test and measurement device of any one of examples 1-5, wherein first voltage and the second voltage are received from a test and measurement instrument. 
     Example 7 is the test and measurement device of example 1, wherein the second voltage is received from the second conductor of the second cable, the output includes a third conductor of the first triaxial cable and a fourth conductor of the second triaxial cable that are coupled to the device under test, and the circuitry further includes a relay coil connected to the first input and the second input, the relay coil structured to activate based on a voltage differential between the first voltage and the second voltage, and a switch connected to a fifth conductor of the first triaxial cable, wherein the switch changes states when the relay coil is activated. 
     Example 8 is the test and measurement device of any one of examples 1-7, wherein the output is a first output coupled to a device under test, and the device further comprises a second output configured to send information to a test and measurement instrument. 
     Example 9 is a system for measuring a device under test, comprising a test and measurement instrument coupled to at least one triaxial cable, the test and measurement instrument configured to output a first voltage on a first conductor of the at least one triaxial cable and to output a second voltage on a second conductor of the at least one triaxial cable; and a module coupled to the test and measurement instrument by the at least one triaxial cable, the module configured to change a mode based on the first voltage and the second voltage. 
     Example 10 is the system of example 9, wherein the module further includes a power supply configured to receive the first voltage and the second voltage and generate a constant voltage supply based on a voltage differential between the first voltage and the second voltage; and a signal decoder configured to receive the constant voltage supply and monitor the first voltage relative to the second voltage to determine a command code for changing modes. 
     Example 11 is the system of example 10, wherein the power supply is a capacitor. 
     Example 12 is the system of either one of examples 10 or 11, wherein the module further includes mode control circuitry configured to receive the command code from the signal decoder and cause a measurement circuit to change modes based on the command code. 
     Example 13 is the system of any one of examples 9-12, wherein the first conductor is configured to conduct a low signal of a first triaxial cable and the second conductor is a guard of the first triaxial cable. 
     Example 14 is the system of any one of examples 9, wherein the first conductor is a conductor of a first triaxial cable and the second conductor is a conductor of a second triaxial cable. 
     Example 15 is the system of example 14, wherein the module includes a relay coil connected to the first input and the second input, the relay coil structured to activate based on a voltage differential between the first voltage and the second voltage, and a switch connected to a third conductor of the first triaxial cable, wherein the switch changes states when the relay coil is activated. 
     Example 16 is the system of any one of examples 9-15, wherein the module is further configured to send a communication signal to the test and measurement instrument. 
     Example 17 is a method for operating a remote device, comprising receiving at the remote device a voltage differential between two conductors of one or more triaxial cables from a test and measurement instrument; activating mode circuitry on the remote device to change an operating mode based on the voltage differential; and outputting a signal to a device under test based on the operating mode of the remote device. 
     Example 18 is the method of example 17, further comprising powering a power supply based on the voltage differential; and decoding a command signal based on the voltage differential to determine the operating mode. 
     Example 19 is the method of example 17, wherein activating mode circuitry includes activating a relay coil to cause a switch to open or close. 
     Example 20 is the method of any one of examples 17-19, further comprising transmitting a signal from the remote device to the test and measurement instrument to confirm a mode change. 
     The previously described versions of the disclosed subject matter have many advantages that were either described or would be apparent to a person of ordinary skill. Even so, these advantages or features are not required in all versions of the disclosed apparatus, systems, or methods. 
     Additionally, this written description makes reference to particular features. It is to be understood that the disclosure in this specification includes all possible combinations of those particular features. Where a particular feature is disclosed in the context of a particular aspect or example, that feature can also be used, to the extent possible, in the context of other aspects and examples. 
     Also, when reference is made in this application to a method having two or more defined steps or operations, the defined steps or operations can be carried out in any order or simultaneously, unless the context excludes those possibilities. 
     Although specific examples of the invention have been illustrated and described for purposes of illustration, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, the invention should not be limited except as by the appended claims.