Interconnect system with high current and low leakage capabilities

Abstract

The present invention relates to an interconnection system with high current and low leakage capability. The present disclosure relates to systems and methods related to test and measurement systems, and in particular to an interconnection system between a test and measurement instrument such as a source measurement unit (SMU) and a device under test (DUT). The test and measurement instrument switch matrix includes: a first cable including a center conductor and a shield connected to a first output of the test and measurement instrument; a second cable including a center conductor and a shield connected to a second output of the test and measurement instrument; a third cable including a center conductor and a shield connected to the device under test; and a fourth cable including a center conductor connected to the device under test and a shield connected to the device under test.

Description

[0001] priority

[0002] This disclosure claims the benefit of U.S. Provisional Application No. 62 / 858,291, filed on June 6, 2019, entitled “INTERCONNECT SYSTEM WITH HIGHCURRENT AND LOW LEAKAGE CAPABILITY,” which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to systems and methods related to test and measurement systems, and in particular to interconnection systems between test and measurement instruments, such as source measure units (SMUs), and devices under test (DUTs). Background Art

[0004] Test and measurement systems are designed to receive and test signals from the DUT. In some test and measurement systems, such as those that include an SMU, the test and measurement system also sends signals to the DUT to test the DUT's response. In some systems, switching devices are used to switch between different inputs and outputs of the test and measurement system and the DUT.

[0005] Typically, triaxial cable is used in such systems. However, triaxial cables often suffer from relatively high center conductor resistance, especially in high voltage applications. In high voltage applications, the result is that the maximum current through the switching device is very limited.

[0006] Embodiments of the present disclosure address these and other deficiencies of the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Aspects, features and advantages of embodiments of the present disclosure will become apparent from the following description of embodiments with reference to the accompanying drawings, in which:

[0008] Figure 1 is a block diagram of an example test system according to some embodiments of the present disclosure;

[0009] Figure 2 According to some embodiments of the present disclosure Figure 1 A diagram of an example switch matrix;

[0010] Figure 3 According to some embodiments of the present disclosure Figure 1 A diagram of another example switch matrix;

[0011] Figure 4 According to some embodiments of the present disclosure Figure 1 Schematic diagram of another example switch matrix. DETAILED DESCRIPTION

[0012] Conventional switch matrices in test and measurement systems use multiple cables, typically triaxial cables, to connect the DUT to the test and measurement instruments. For example, to connect an SMU to a DUT, the switch matrix may include at least one HI force cable and one LO force cable, and at least one HI sense cable and one LO sense cable. The force cables send signals to the DUT, while the sense cables transmit measurements from the DUT to the test and measurement instruments.

[0013] The triaxial cable includes a center conductor and an inner conductive sheath or shielding layer coaxial with and surrounding the center conductor. The inner conductive shielding layer may be referred to as a shielding layer. The protection signal is routed through the shielding layer, along with the applied and sensed signals, through the center conductor to minimize the error currents in the wiring and any switches present in the system. The triaxial cable also includes an outer conductive shielding layer, housing or casing coaxial with and surrounding both the center conductor and the shielding layer. However, the triaxial cable is often affected by the relatively high center conductor resistance, especially if the triaxial cable is used for high voltage applications. In these cases, the maximum current passing through the triaxial cable is very limited, and such a switching device cannot be effectively used in high current applications.

[0014] Figure 1 An example block diagram of an example test system 100 is illustrated, which includes a switch matrix 102 connected to a DUT 104 and a test and measurement instrument 106. The switch matrix 102 is configured to switch test signals between the test and measurement instrument 106 and the DUT 104. The switch matrix 102 may include one or more drivers 108 to control switches in the switch matrix 102. The one or more drivers 108 may include one or more controllers or processors. The switch matrix 102 may also include a memory 110 for storing instructions to be executed by the one or more drivers and / or processors 108. In some embodiments, the instructions for the one or more drivers 108 are transmitted from the test and measurement instrument 106.

[0015] As will be appreciated by those skilled in the art, although the switch matrix 102 is shown as being separate from the test and measurement instrument 106 , in some embodiments, the switch matrix 102 may be included as a component of the test and measurement instrument 106 .

[0016] Figure 2 1 illustrates an example switch matrix according to some embodiments of the present disclosure, which may be used as the switch matrix 102. Figure 2 2 is shown connected to a test and measurement instrument 200 (such as an SMU) and a DUT 202. For ease of illustration, Figure 2The switch matrix of FIG. 1 does not depict various other components of the switch matrix, such as one or more processors, drivers, memory, etc.

[0017] As will be appreciated by those skilled in the art, the switch matrix may include paths for HI and LO signals, as well as force and sense paths. The switch matrix includes a plurality of force cables 204, 206, 208, 210 and a plurality of sense cables 212, 214, 216, and 218. Each of the cables includes a center conductor 220 and a shield 222, which may also be referred to as an inner shield. Voltage and / or current are sent from the test and measurement instrument 200 to the DUT 202 via the force cables 204, 206, 208, 210, and voltage and / or current from the DUT 202 are sent to the test and measurement instrument 200 for measurement via the sense cables 212, 214, 216, and 218.

[0018] The HI signal from the test and measurement instrument 200 may be routed to the DUT through the center conductor 220 of the apply cables 204 and 206. A switch 224 may be provided between the cables 204 and 206. The center conductor 220 of the apply cable 206 is connected to the DUT 202. The center conductor 220 of the apply cable 204 is connected to the test and measurement instrument 200.

[0019] The HI signal from the DUT 202 may be routed to the test and measurement instrument 200 through the center conductor 220 of the sense cables 212 and 214. A switch 226 may be provided between the sense cables 212 and 214. The center conductor 220 of the sense cable 214 is connected to the DUT 202. The center conductor 220 of the sense cable 212 is connected to the test and measurement instrument 200.

[0020] The LO signal from the test and measurement instrument 200 may be routed to the DUT 202 through the center conductor 220 of the apply cables 208 and 210. A switch 228 may be provided between the apply cables 208 and 210. The center conductor 220 of the apply cable 210 is connected to the DUT 202. The center conductor 220 of the apply cable 208 is connected to the test and measurement instrument 200.

[0021] The LO signal from the DUT 202 may be routed to the test and measurement instrument 200 through the center conductor 220 of the sense cables 216 and 218. A switch 230 may be provided between the sense cables 216 and 218. The center conductor 220 of the sense cable 218 is connected to the DUT 202. The center conductor 220 of the sense cable 216 is connected to the test and measurement instrument 200.

[0022] Switches 232, 234, 236, and 238 may also be provided between the HI application cable pair 204 and 206, the HI sensing cable pair 212 and 214, the LO sensing cable pair 216 and 218, and the LO application cable pair 208 and 210, respectively, to connect the shielding layer 222 of each of these cable pairs. The shielding layers 222 of the cables 204 and 212 are connected to each other, and the shielding layers 222 of the cables 206 and 214 are connected to each other. The shielding layers 222 of the cables 216 and 208 are connected to each other, and the shielding layers 222 of the cables 208 and 210 are connected to each other.

[0023] However, unlike conventional switch matrices, separate guard signals are not sent to the guard layers 222 of the individual force and sense cables 204, 206, 208, 210, 212, 214, 216, and 218. Instead, the guard layer 222 of each of the force cable 204 and the sense cable 212 is shorted or electrically connected to the center conductor 220 of the force cable 204, so that the HI force signal is sent to the DUT through the guard layer 222 of the cables 204 and 212. The guard layer 222 of each of the force cable 208 and the sense cable 216 is shorted to the center conductor 220 of the force cable 208, so that the LO force signal is sent to the DUT through the guard layer 222 of the cables 208 and 216. The guard layers 222 of the cables 206, 210, 214, and 218 are each connected to the corresponding center conductor 220 of the cables 206, 210, 214, and 218, and connected to the DUT 202.

[0024] In addition, if Figure 2 , the outer shield 240 of each of the cables 204, 206, 208, 210, 212, 214, 216, and 218 are connected together at the LO output of the test and measurement instrument 200, and are also connected together in close proximity to the DUT 202. Connecting the outer shield 240 of each of the cables 204, 206, 208, 210, 212, 214, 216, and 218 in this manner may allow the overall connection inductance to be kept low and enable high speed, high current pulses to be achieved.

[0025] Compared to conventional switch matrices with separate guard signals, Figure 2 The switch matrix provides a much lower path resistance through the shield layer 222, and therefore provides a greater current carrying capacity. Further, although Figure 2 Not shown, but additional cables could be provided in the system that do not have the shield 222 shorted to the center conductor 220 and these paths could still provide full low leakage capability.

[0026] Figure 3Another example of a switch matrix according to some embodiments of the present disclosure is illustrated, which can be used as Figure 1 Again, for ease of discussion, no Figure 3 Depicted in Figure 3 Various other components of the switch matrix (such as Figure 1 Further, the above Figure 2 Included in the discussion Figure 3 The components in the switch matrix are given the same reference numerals and are not related to Figure 3 Further detailed discussion.

[0027] exist Figure 3 In the switch matrix of the test and measurement instrument 200, a switch 300 may be provided for the HI guard signal, which may be cut into the shield 222 of the force cable 204 and the sense cable 212. Further, another switch 302 may be provided between the HI signal of the test and measurement instrument 200 and the shield 222 of the force cable 204 and the sense cable 212. Similarly, a switch 304 may be provided for the LO guard signal, which may be cut into the shield 222 of the force cable 208 and the sense cable 216. Further, a switch 306 may be provided between the LO signal of the test and measurement instrument 200 and the shield 222 of the force cable 208 and the sense cable 216.

[0028] The shields 222 of cables 206 and 214 are connected to each other, and the shields 222 of cables 210 and 218 are connected to each other. A switch 308 may be provided to connect the shields 222 of cables 206 and 214 to DUT 202, and a switch 310 may be provided to connect the shields 222 of cables 214 and 218 to DUT 202.

[0029] Switches 312 and 314 may also be provided on the test and measurement instrument 200 side of the switch matrix to switch in the sense signals from the sense cables 212 and 216 .

[0030] Using these switches, Figure 3 The switch matrix can provide both high current with remote sensing and low current with guard path capability. When higher current is being used, the guard signal can be cut off and the applied signal from the test and measurement instrument 202 can be cut into the guard layer 222.

[0031] Figure 4 Another example of a switch matrix according to some embodiments of the present disclosure is shown, which can be used as Figure 1 Again, for ease of discussion, no Figure 4 Depicted in Figure 4 Various other components of the switch matrix (such as Figure 1 Further, the above Figure 2 and 3 Included in the discussion Figure 4 The components in the switch matrix are given the same reference numerals and are not related to Figure 4 Further detailed discussion.

[0032] exist Figure 4 In the switch matrix of , cables 204, 206, 208 and 210 can be used as both force cables and sense cables. Additional switches 400 and 402 can be added to switch the HI and LO signals from the test and measurement instrument 200 into the center conductor 220 of the cables 204 and 208.

[0033] use Figure 4 The switch matrix can perform both high current measurement, remote sensing measurement, and low leakage capability through the same path while maintaining compatibility with existing infrastructure. Eliminating the dedicated sensing path reduces the system cost of the switch matrix while also reducing size and improving reliability due to fewer components in the switch matrix.

[0034] exist Figure 2-Figure 4 Connecting the shield directly to the HI or LO output of the test and measurement instrument 200 in each of the switch matrices of the present invention allows higher current to pass through the switch matrix and perform telemetry measurements of the DUT 202, which is not possible with conventional switch matrices using triaxial cables (assuming that the triaxial cables have a small high resistance center conductor). One or more drivers 108 of the switch matrix can operate Figure 2-Figure 4 The memory 110 may be used to control various switches of the switch matrix to allow force and sense signals to be sent between the test and measurement instrument 200 and the DUT 202. In some embodiments, the memory 110 stores instructions for one or more drivers 108, while in other embodiments, the instructions may be sent from the test and measurement instrument 200.

[0035] For example, in Figure 3 and 4 In the switch matrix of the test and measurement instrument 200, the test and measurement instrument 200 may include instructions for driving one or more drivers 108, as discussed above. When the current exceeds the threshold, the test and measurement instrument 200 may instruct the switch to connect the shield 222 of the cable 204, 208, 212, and / or 216 to the HI or LO applied signal from the test and measurement instrument.

[0036] Further, although switches 300, 302, 304, 306, 312, 314, 400, and 402 are shown as Figure 3 and 4The switches may be part of a switch matrix of the test and measurement instrument 200 , but in some embodiments, the switches may be included directly in the test and measurement instrument 200 and driven by one or more processors and / or drivers in the test and measurement instrument 200 .

[0037] In some embodiments, the outer shield 240 of each of the cables 204, 206, 208, 210, 212, 214, 216, and 218 is connected together at the LO output of the test and measurement instrument 200 through a switch, as will be appreciated by those skilled in the art. For example, when only DC high current is required, the outer shield 240 may not be connected to the LO output of the test and measurement instrument 200.

[0038] Aspects of the present disclosure may operate on specially created hardware, firmware, digital signal processors, or on specially programmed computers including processors operating according to programming 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 present disclosure may be embodied in computer-usable data and computer-executable instructions, such as embodied in one or more program modules executed by one or more computers (including monitoring modules) or other devices. In general, program modules include routines, programs, objects, components, data structures, etc., which perform specific tasks or implement specific abstract data types when executed by a processor in a computer or other device. Computer executable instructions may be stored on a computer-readable storage medium, such as a hard disk, an optical disk, a removable storage medium, a solid-state memory, a random access memory (RAM), etc. As will be appreciated by those skilled in the art, the functions of the program modules may be combined or distributed as desired in various aspects. In addition, the functions may be embodied in firmware or hardware equivalents such as integrated circuits and FPGAs in whole or in part. Certain data structures may be used to more efficiently implement one or more aspects of the present disclosure, and such data structures are contemplated within the scope of the computer-executable instructions and computer-usable data described herein.

[0039] In some cases, the disclosed aspects may be implemented with hardware, firmware, software, or any combination thereof. The disclosed aspects may also be implemented as instructions carried by or stored on one or more computer-readable storage media, which may be read and executed by one or more processors. Such instructions may be referred to as computer program products. As discussed herein, computer-readable media refers to any medium that can be accessed by a computing device. By way of example and not limitation, computer-readable media may include computer storage media and communication media.

[0040] Computer storage media refers to 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, cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, and any other volatile or non-volatile, removable or non-removable media implemented in any technology. Computer storage media excludes the signals themselves and the temporary form of signal transmission.

[0041] Communication media refers to any medium that can be used for 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 medium suitable for communication of electrical, optical, radio frequency (RF), infrared, acoustic or other types of signals.

[0042] Example

[0043] Illustrative examples of the techniques disclosed herein are provided below. Implementations of the techniques may include any one or more of the examples described below and any combination of these examples.

[0044] Example 1 is a test and measurement instrument switch matrix, comprising: a first cable, including a center conductor and a shield connected to a first output of the test and measurement instrument; a second cable, including a center conductor and a shield connected to a second output of the test and measurement instrument; a third cable, including a center conductor and a shield connected to a device under test; and a fourth cable, including a center conductor connected to the device under test and a shield connected to the device under test.

[0045] Example 2 is the test and measurement instrument switch matrix of Example 1, wherein an outer shield of each of the first cable, the second cable, the third cable, and the fourth cable is connected to each other and to a second output of the test and measurement instrument.

[0046] Example 3 is the test and measurement instrument switch matrix of any one of Examples 1 and 3, further comprising: a fifth cable comprising a shielding layer and a center conductor connected to a first input of the test and measurement instrument; a sixth cable comprising a shielding layer and a center conductor connected to a second input of the test and measurement instrument; a seventh cable comprising a center conductor and a shielding layer connected to a device under test; and an eighth cable comprising a center conductor connected to the device under test and a shielding layer connected to the device under test and the shielding layer of the fourth cable.

[0047] Example 4 is the test and measurement instrument switch matrix of Example 3, wherein the guard layer of the fifth cable is connected to the first output of the test and measurement instrument.

[0048] Example 5 is the test and measurement instrument switch matrix of Example 4, further comprising a first switch connecting a shield of a fifth cable to a first output of the test and measurement instrument.

[0049] Example 6 is the test and measurement instrument switch matrix of Example 5, further comprising a second switch to connect the guard layer of the first cable and the guard layer of the fifth cable to the first guard signal.

[0050] Example 7 is the test and measurement instrument switch matrix of Example 6, further comprising a third switch to connect the guard layer of the second cable and the guard layer of the sixth cable to the second guard signal.

[0051] Example 8 is a test and measurement instrument switch matrix of any one of Examples 1 to 7, further comprising a first switch for connecting the shield layer of the first cable to the first output; a second switch for connecting the shield layer of the first cable to the first protection signal; a third switch for connecting the shield layer of the second cable to the second output; and a fourth switch for connecting the shield layer of the second cable to the second protection signal.

[0052] Example 9 is the test and measurement instrument switch matrix of any one of Examples 1 to 8, further comprising a first switch for connecting the center conductor of the first cable to the first output of the test and measurement instrument; and a second switch for connecting the center conductor of the second cable to the second output of the test and measurement instrument.

[0053] Example 10 is the test and measurement instrument switch matrix of Example 9, further comprising a third switch for connecting the center conductor of the first cable to the first input of the test and measurement instrument; and a fourth switch for connecting the center conductor of the second cable to the second input of the test and measurement instrument.

[0054] Example 11 is the test and measurement instrument switch matrix of any one of Examples 1 to 10, further comprising a first switch for connecting the shield of the third cable to the device under test; and a second switch for connecting the shield of the fourth cable to the device under test.

[0055] Example 12 is the test and measurement instrument switch matrix of any of Examples 1 to 11, wherein each of the first cable, the second cable, the third cable, and the fourth cable is a triaxial cable.

[0056] Example 13 is a test and measurement system, comprising: the test and measurement switch matrix of Example 1; and a test and measurement instrument connected to the test and measurement switch matrix, the test and measurement instrument comprising a first switch for connecting the shielding layer of a first cable to a first output; a second switch for connecting the shielding layer of the first cable to a first protection signal; a third switch for connecting the shielding layer of a second cable to a second output; and a fourth switch for connecting the shielding layer of the second cable to a second protection signal.

[0057] Example 14 is the test and measurement system of Example 13, wherein the test and measurement instrument further includes: a fourth switch for connecting the center conductor of the first cable to the first output of the test and measurement instrument; and a fifth switch for connecting the center conductor of the second cable to the second output of the test and measurement instrument.

[0058] Example 15 is the test and measurement system of Example 14, wherein the test and measurement instrument further includes: a sixth switch for connecting the center conductor of the first cable to the first input of the test and measurement instrument; and a seventh switch for connecting the center conductor of the second cable to the second input of the test and measurement instrument.

[0059] Example 16 is the test and measurement system of any one of Examples 13 to 15, wherein the test and measurement instrument further includes one or more processors, and the one or more processors are configured to: when the current of the first output or the second output exceeds a threshold, connect the shielding layer of the first cable to the first output through the first switch, and connect the shielding layer of the second cable to the second output through the third switch.

[0060] Example 17 is a method for operating a switch matrix connected to a test and measurement instrument and a device under test, the method comprising transmitting a first output of the test and measurement instrument to the device under test through a center conductor and a shielding layer of a first cable; and transmitting a second output of the test and measurement instrument to the device under test through a center conductor and a shielding layer of a second cable.

[0061] Example 18 is the method of Example 17, further comprising switching a guard layer of the first cable to transmit a first guard signal.

[0062] Example 19 is the method of Example 18, wherein switching the shielding layer of the first cable to transmit the first shielding signal comprises: switching the shielding layer of the first cable to transmit the first shielding signal when the current of the first output is lower than a threshold.

[0063] Example 20 is the method of any of Examples 17 to 19, further comprising switching a center conductor of the first cable to a first input of the test and measurement instrument; and switching a center conductor of the second cable to a second input of the test and measurement instrument.

[0064] The previously described versions of the disclosed subject matter have many advantages that are described or apparent to those of ordinary skill. Even so, not all versions of the disclosed apparatus, system or method require these advantages or features.

[0065] Additionally, this written description mentions specific features. It should be understood that the disclosure in this specification includes all possible combinations of those specific features. Where specific features are disclosed in the context of a particular aspect or example, the features may also be used in the context of other aspects and examples to the extent possible.

[0066] Furthermore, when a method having two or more defined steps or operations is referred to in the present application, the defined steps or operations may be performed in any order or simultaneously, unless the context excludes those possibilities.

[0067] Although specific examples of the present invention have been illustrated and described for purposes of illustration, it will be appreciated that various modifications may be made without departing from the spirit and scope of the present invention. Accordingly, the present invention should not be limited except by the appended claims.

Claims

1. A test and measurement instrument switch matrix comprising: a first cable including a center conductor and a shield connected to a first output of a test and measurement instrument; a second cable including a center conductor and a shield connected to a second output of the test and measurement instrument; a third cable including a center conductor and a shield connected to the device under test; a fourth cable, comprising a center conductor connected to the device under test and a shield connected to the device under test; a first switch for connecting a shield of a first cable to a first output; a second switch for connecting the shield of the first cable to the first shield signal; a third switch for connecting the shield of the second cable to the second output; as well as A fourth switch is used to connect the shielding layer of the second cable to the second shielding signal.

2. The test and measurement instrument switch matrix of claim 1, wherein: The outer shield of each of the first cable, the second cable, the third cable, and the fourth cable is connected to each other and to a second output of the test and measurement instrument.

3. The test and measurement instrument switch matrix of claim 1 , further comprising: a fifth cable including a shield and a center conductor connected to a first input of a test and measurement instrument; a sixth cable comprising a shield and a center conductor connected to a second input of the test and measurement instrument; a seventh cable, comprising a center conductor and a shield connected to the device under test; as well as An eighth cable includes a center conductor connected to the device under test and a shielding layer connected to the device under test and the shielding layer of the fourth cable. 4 . The test and measurement instrument switch matrix of claim 3 , wherein the shield of the fifth cable is connected to the first output of the test and measurement instrument.

5. The test and measurement instrument switch matrix of claim 4, further comprising: A fifth switch is configured to connect a shield of a fifth cable to the first output of the test and measurement instrument.

6. The test and measurement instrument switch matrix of claim 5, further comprising: A sixth switch is configured to connect the shielding layer of the first cable and the shielding layer of the fifth cable to the first shielding signal.

7. The test and measurement instrument switch matrix of claim 6, further comprising: A seventh switch is configured to connect the shielding layer of the second cable and the shielding layer of the sixth cable to the second protection signal.

8. The test and measurement instrument switch matrix of claim 1 , further comprising: a ninth switch for connecting the center conductor of the first cable to the first output of the test and measurement instrument; as well as A tenth switch is used to connect the center conductor of the second cable to the second output of the test and measurement instrument.

9. The test and measurement instrument switch matrix of claim 8, further comprising: an eleventh switch to connect the center conductor of the first cable to the first input of the test and measurement instrument; as well as A twelfth switch is used to connect the center conductor of the second cable to a second input of the test and measurement instrument.

10. The test and measurement instrument switch matrix of claim 1, further comprising: a fifth switch for connecting a shield of a third cable to the device under test; as well as A sixth switch is used to connect the shielding layer of the fourth cable to the device under test.

11. The test and measurement instrument switch matrix of claim 1 , wherein: Each of the first cable, the second cable, the third cable, and the fourth cable is a triaxial cable.

12. A test and measurement system comprising: The test and measurement instrument switch matrix of claim 1; as well as Test and measurement instruments connected to the test and measurement switch matrix.

13. The test and measurement system of claim 12, wherein the test and measurement instrument further comprises: a fifth switch to connect the center conductor of the first cable to the first output of the test and measurement instrument; as well as A sixth switch is provided to connect the center conductor of the second cable to a second output of the test and measurement instrument.

14. The test and measurement system of claim 13, wherein the test and measurement instrument further comprises: a seventh switch to connect the center conductor of the first cable to the first input of the test and measurement instrument; as well as An eighth switch to connect the center conductor of the second cable to a second input of the test and measurement instrument.

15. The test and measurement system of claim 12, wherein: The test and measurement instrument further includes one or more processors configured to: connect the shield of the first cable to the first output through the first switch, and connect the shield of the second cable to the second output through the third switch when the current of the first output or the second output exceeds a threshold.

16. A method for operating a test and measurement instrument switch matrix according to any one of claims 1 to 11 connected to a test and measurement instrument and a device under test, the method comprising: transmitting a first output of the test and measurement instrument to the device under test via the center conductor and the shield of the first cable; as well as A second output of the test and measurement instrument is transmitted to the device under test via the center conductor and the shield of the second cable.

17. The method of claim 16, further comprising switching a guard layer of the first cable to transmit the first guard signal.

18. The method according to claim 17, wherein: Switching the shielding layer of the first cable to transmit the first protection signal includes: when the current of the first output is lower than a threshold, switching the shielding layer of the first cable to transmit the first protection signal.

19. The method according to claim 16, further comprising: switching a center conductor of the first cable to a first input of the test and measurement instrument; as well as Switch the center conductor of the second cable to the second input of the test and measurement instrument.

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