Split Path Multiplexing Accessories for Test and Measurement Equipment

Abstract

An input selector for electrically connecting one of a plurality of test signals from one or more devices under test to a test and measurement instrument, the input selector comprising: a first multiplexer having a set of a plurality of first input terminals, each coupled to a different one of the plurality of test signals from the one or more devices under test, and a first output terminal for a selected one of the first input terminals; and a second multiplexer having a set of a plurality of second input terminals, each coupled to a different one of the plurality of test signals from the one or more devices under test, and a second output terminal for a selected one of the second input terminals. A method is also described.

Description

[Technical Field]

[0001] The present disclosure relates generally to systems and methods relating to test and measurement systems, and more particularly to multiplexing accessories for switching multiple signals from one or more devices under test (DUTs). [Background technology]

[0002] Many DUTs contain multiple similarly designed signal paths. For example, a PCI Express (PCIe or PCI-e) plug-in card or PCIe motherboard slot typically contains up to 16 electrical signal "lanes." The electrical signal lanes are typically differential signal lanes, and a complete measurement of the differential signaling across a lane requires two electrical measurement ports per differential lane. Therefore, a complete measurement of a 16-lane PCIe device requires 32 electrical measurement ports. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 6,532,557 [Patent Document 2] US Patent Application Publication No. 2018 / 0026816 [Patent Document 3] US Patent Application Publication No. 2003 / 0071606 [Patent Document 4] US Patent Application Publication No. 2009 / 0134893 Summary of the Invention [Problem to be solved by the invention]

[0004] However, test and measurement equipment commonly used to test such DUTs, such as oscilloscopes and bit error rate testers (BERTs), typically have one, two, or four input ports. While some oscilloscopes have as many as eight input channels or ports, high-performance instruments typically have fewer input channels due to the increased hardware costs associated with each channel. Physical channel density limitations for thermal and throughput reasons can also dictate a lower channel count. For this reason, test and measurement equipment configurations typically connect to only a portion of the electrical signal lanes under test.

[0005] Because only some of the lanes are coupled to the test and measurement equipment, if a user wants to test all signal lanes, they must manually move connections (e.g., test cables and probes) between the test and measurement equipment and the DUT from each lane to the next. Manually moving cables and probes is an error-prone, time-consuming, and labor-intensive process. Alternatively, in a two-channel test and measurement environment, radio frequency (RF) switches can be built and maintained to automate testing of all signal lanes of the DUT. However, identifying the appropriate switches and properly de-embedding their effects from the signal path (which is done manually) is difficult at higher frequencies. For these reasons, many users do not believe they can de-embed switches without significant error, especially above 25 GHz. De-embedding, or "calibrating," the effects of switches and other components in a signal path means compensating for the adverse effects of the switches on the signals propagating through the signal path. In addition to the need for de-embedding, RF switch matrices are physically large, making RF switch matrix solutions particularly unattractive for users with limited physical test space.

[0006] Electromechanical switch solutions have the additional problem of generally leaving the unselected input open circuit, i.e., typically not terminating, which can affect signal quality at the DUT.

[0007] The disclosed embodiments address these and other deficiencies of the prior art. [Means for solving the problem]

[0008] Embodiments of the disclosed technology utilize split-path multiplexing components to enable switching between multiple DUT signals and a test and measurement instrument. Split-path multiplexing systems accomplish this by separating the high-frequency components of the signal under test from the low-frequency components and then routing these two components through separate signal paths. Advantageously, the high-frequency path can be switched through solid-state RF switches, which are much smaller, less expensive, and more reliable than electromechanical switches. The solid-state switches may be, for example, PIN diode switches. In some embodiments, a diplexer is used to separate the frequencies. In some embodiments, a second diplexer is used to recombine the separated frequency components before transmitting the resulting signal to the test and measurement instrument, although there are many variations, as described below.

[0009] In embodiments of the disclosed technology, the split path switching system being located at a long distance or remote location means that the test measurement system does not require a large amount of space on the benchtop, and the test measurement system can be positioned on the benchtop so that the input of the test measurement system is as close as possible to the test points of the DUT.

[0010] Aspects, features, and advantages of embodiments of the disclosed technology will become apparent from the following description of examples, taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram of a test and measurement system including a split path selector in which low frequency or DC signals and high frequencies are independently selected according to some embodiments of the present disclosure. [Figure 2] FIG. 2 is a block diagram of a test and measurement system including a split path selector in accordance with some embodiments of the present disclosure, in which low frequency or DC signals and high frequencies may be independently selected and then independently amplified. [Figure 3] FIG. 3 is a block diagram of a test and measurement system including a split path selector in accordance with some embodiments of the present disclosure, in which a low frequency or DC signal and a high frequency are independently selected and then sent separately to a test and measurement instrument for recombination. [Figure 4] FIG. 4 is a block diagram of a test and measurement system including a split path selector according to some embodiments of the present disclosure, in which a low frequency or DC signal and a high frequency are independently selected and the low frequency or DC signal is converted to a digital signal by an analog-to-digital converter. [Figure 5] FIG. 5 is a block diagram of a test and measurement system including a split path selector in which a low frequency or DC signal and a high frequency are independently selected, and further including a feed forward control system according to an embodiment. [Figure 6] FIG. 6 is a block diagram of a test and measurement system including a split path selector in which a low frequency or DC signal and a high frequency are independently selected, and further including a feedback control system according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] FIG. 1 is a block diagram of a test and measurement system 100 including a split-path selector 130 coupled between multiple test boards or DUTs 110 available for testing and a test and measurement instrument 160, in accordance with some embodiments of the present disclosure. For convenience, this disclosure describes signals for testing as originating from the DUTs 110, although the signals may originate within the test boards or from other sources. In this exemplary embodiment, there are four DUTs 110, labeled DUT1, DUT2, DUT3, and DUT N, indicating that the split-path selector 130 can select from a wide variety of signals for testing and is not limited to four. In some embodiments, the split-path selector 130 may include 8, 16, or 32 switches, as described in further detail below.

[0013] In FIG. 1 , a diplexer 112 is coupled between each DUT 110 and the split path selector 130. In this embodiment, each DUT 110 has a separate diplexer 112, although such correspondence is not required in all embodiments. The function of the diplexer 112 is to split a signal (e.g., a signal that may be measured by the test and measurement instrument 160) into multiple components: a low frequency or direct current (DC) component (sometimes abbreviated as LF / DC) and a high frequency (HF) component. Depending on the architecture, the diplexer 112 may include an electrical circuit composed of any or all of well-known capacitors, resistors, and inductors. The diplexer 112 may be selected based on its split frequency and other performance characteristics. In other words, the frequency at which the LF / DC signal is split from the HF signal may vary depending on the particular diplexer 112 selected. 1, a diplexer 112 may divide its input signal by approximately 10 kHz, such that frequencies below 10 kHz of the original signal are sent to the LF / DC output terminal of the diplexer 112, while frequencies above 10 kHz of the original signal are sent to the HF output terminal of the diplexer. Another diplexer 112 may use 1 MHz as a division or crossover frequency. The division frequency of a diplexer 112 according to an embodiment may be implementation specific.

[0014] 1, the HF output of diplexer 112 is provided to HF multiplexer 131, while the LF / DC output of the diplexer is provided to LF / DC multiplexer 132. Each of multiplexers 131 and 132 is part of split path selector 130, which has the overall function of selecting which of DUT 110 is coupled to test and measurement instrument 160. More specifically, split path selector 130 determines which test signal originating from DUT 110 (which may also be a test board or other signal source) is selected to be coupled to test and measurement instrument 160.

[0015] As mentioned above, the HF multiplexer 131 can be formed of solid-state RF switches, such as PIN diode switches, which are very small, especially compared to the switches in the full-band RF matrix described above. The HF multiplexer 131 can also be formed of MEMS, which are similarly very small and have good RF performance. Because it is made from physically small switches and other components, integrating the split path selector 130 into a test bench or test setup is much easier than previous devices. Also, as described below, after the desired signals are selected by the multiplexers 131 and 132, the signals may be conditioned, such as amplified or modulated, before being sent to the test and measurement instrument 160. Additionally, the solid-state RF switches that make up the multiplexer 131 can be non-reflective, i.e., properly terminated, so that any signals from the DUT not selected for transmission to the test and measurement instrument 160 do not cause reflections to other locations within the device or test system that could adversely affect the measurement. The solid-state RF switches used to construct the HF multiplexer 131 generally do not operate at sufficiently low frequencies, which is one reason why the diplexer 112 is present: to remove low frequencies from the signal under test from the selected DUT 110 before delivering the signal to the HF multiplexer 131.

[0016] The LF / DC multiplexer 132 may also include solid-state switch circuits, but the switches that make up the LF / DC multiplexer 132 may be different from those that make up the HF multiplexer 131. For example, the LF / DC multiplexer 132 may be made with field effect transistor (FET) switches or MEMS switches.

[0017] The electrical connection connecting the HF output of diplexer 112 to HF multiplexer 131 may be in the form of a ribbon band or a coaxial cable, depending on the implementation. In general, due to the difference in signal frequency, the LF / DC output of diplexer 112 may be coupled to LF / DC multiplexer 132 by a simple wire.

[0018] In operation, the LF / DC multiplexer 132 and the HF multiplexer 131 operate in concert to select a single input source to feed the test and measurement instrument 160. For example, if it is desired to select a test signal from DUT1 (110), both the LF / DC multiplexer 132 and the HF multiplexer 131 are controlled to select DUT1 (110). Then, following the signal from DUT1 (110), the signal under test is first split by diplexer 1 (112) into an LF / DC component and an HF component, which are sent separately to multiplexer 132 and HF multiplexer 131, as shown in FIG. 1. The LF / DC multiplexer 132 and HF multiplexer 131 then operate to select the signal originating from DUT1 (110), so that these signals are output from the LF / DC multiplexer 132 and HF multiplexer 131. The selected LF / DC signal from DUT1 (110) may then be conditioned or buffered by signal conditioning circuitry 133, the function of which is described below. The conditioned LF / DC signal from signal conditioning circuitry 133 is then provided to the LF / DC input terminal of diplexer 134, and the HF signal output from HF multiplexer 131 is provided to the HF input terminal of diplexer 134. The diplexer is bidirectional, so when connected to a single signal source, the diplexer splits the signal into LF / DC and HF components as described above. Alternatively, when connected to two signal sources (one with an LF / DC component and the other with an HF component), the diplexer combines the signals into a unified spread-spectrum signal having both an LF / DC component and an HF component. The output of diplexer 134 is therefore the signal measured by test and measurement instrument 160. As described below, the output of diplexer 134 may be modified or amplified, such as by amplifier 135, and then sent to a test port 162 of test and measurement equipment 160, for example, via an RF connection such as cable 152.

[0019] Split path selector 130 may receive power from test and measurement equipment 160 through power supply line 154 to power multiplexers 131, 132, amplifier 135, and potentially other components of the split path selector. In other embodiments, split path selector 130 may be coupled to a power source separate from test and measurement equipment 160, such as a power source plugged directly into a wall power source. In still other embodiments, split path selector 130 may be able to draw power from DUT 110 without affecting the signal integrity of the DUT for testing. For example, USB (Universal Serial Bus) transmits power in addition to data over its lines, and split path selector 130 may be able to use a small amount of power from the USB cable. In still other embodiments, the power needs of split path selector 130 may be small enough to be met by a rechargeable or replaceable battery housed within split path selector 130. This may be possible in certain embodiments of split path selector 130, such as when split path selector 130 is embodied as an application specific integrated circuit (ASIC) or a microelectromechanical system (MEMS) switch. In other embodiments, split path selector 130 may include multiple discrete components mounted on a printed circuit (PC) board.

[0020] As described below, control signals between the test and measurement instrument 160 and the split path selector 130 may be transmitted over control signal line 156. In some embodiments, a user or operator can operate the test and measurement instrument 160 to select a signal to be tested from the DUT 110. In response, the test and measurement instrument 160 sends a control signal over control signal line 156 to cause the split path selector 130 to operate the HF multiplexer 131 and the LF / DC multiplexer 132 to select the desired signal, which is then combined in the diplexer 134, amplified by the amplifier 135, and sent to the test and measurement instrument 160 for testing. The user may make selections on a user interface of the test and measurement instrument 160 or may instruct the instrument using programmatic control, such as using the PI programming interface available in Tektronix instruments from Beaverton, Oregon, USA. Using programmatic control, signals from any desired DUT 110 can be scripted to be tested in sequence, without the user having to physically change any cables between the DUT 110 and the test and measurement equipment 160. Instead, switching to connect the desired signals of the DUT 110 to the test and measurement equipment 160 is performed by controlling multiplexers 131 and 132 of the split path selector 130.

[0021] 1, connections to test port 162, power supply line 154, and control signal line 156 may be included in the probe interface to test and measurement instrument 160. Also, in some embodiments, power supply line 154 and control signal line 156 may be embodied in a single connection, i.e., a connection that carries both power and control signals over the same line.

[0022] In some examples, the split path selector 130 may include a memory 136 and a controller or processor 138. The split path selector 130 may be tested during manufacturing or at the factory to measure the effect of including the split path selector 130 in the test system 100 compared to directly connecting a particular output of the DUT 110 to a test port 162 of the test and measurement instrument 160. Correcting for the adverse effects of including the split path selector 130 and its components (including multiplexers 131 and 132 and amplifier 135), and its associated cabling, is referred to as de-embedding or calibration. The term calibration parameters in this disclosure refers to any calibration parameters, including de-embedding parameters of the split path selector 130, that are used to remove the effects or influences of the presence of the split path selector 130 and its associated cabling in the test system 100 from any signal measurements made by the test and measurement instrument 160. The calibration parameters may be stored in a specific calibration parameter memory 140 or in a general memory 136 and sent to the test and measurement instrument 160 during a test session. In some examples, the calibration parameters may be transmitted from the test and measurement instrument 160 to a remote analytical device. The analytical device may collect the calibration parameters and data from the test and measurement instrument 160 and provide any necessary processing of the data, as would be understood by one of ordinary skill in the art. In other examples, the calibration parameters for a particular split path selector 130 may be stored in memory 163 located within the test and measurement instrument 160 or retrieved from remote storage, such as cloud storage, and transmitted to the split path selector 130 for storage in its calibration parameter memory 140. The particular calibration parameters used to de-embed the effects of the split path selector 130 may be identified based, for example, on the serial number or other identification (ID) number of the split path selector 130.

[0023] The S-parameters (scattering parameters) for each port of multiplexers 131 and 132 may be stored with calibration parameters 140 or may be stored in a separate memory 136 to assist test and measurement instrument 160 in de-embedding split path selector 130 from the signal of DUT 110. S-parameters for the through and isolation paths are stored for each connector of multiplexers 131 and 132 and port 162 of test and measurement instrument 160. In some examples, users can upload or import their own S-parameters, such as when changing S-parameters or adding stress to the system.

[0024] The amplifier 135 is an active amplifier with a low impedance input, such as 50 ohms, which is compatible with testing many serial data DUTs 110, such as PCIe devices, Serial ATA buses, MIPI (Mobile Industry Processor Interface) interfaces, Fibre Channel, and HDMI® interfaces. In other embodiments, the amplifier 135 may include or use a buffer to buffer the signal under test from the DUT 110. In these embodiments, the amplifier 135 typically has a relatively high input impedance, such as a DC input resistance of 100 kOhms or 150 kOhms. In another example, the amplifier 135 may have an impedance of 1 MOhm. This relatively high input impedance of the split path selector 130 is useful for testing memory circuits, for example, high-speed serial buses. Whether it is a low-impedance input amplifier 135 or a high-impedance input amplifier 135, including amplifier 135 in the split path selector allows the selected signal from the output of multiplexers 131 and 132 to be amplified as close as possible to the selected source in a manner that maximizes its signal transfer characteristics to test and measurement instrument 160. Not only does this placement of amplifier 135 within split path selector 130 reduce noise interference, but the use of calibration parameters 140 within split path selector 130 allows the calibration plane (reference plane - the location where calibration occurs) to be closer to the desired test plane of DUT 110.

[0025] 1 , split path selector 130 may include processor 138. Processor 138 may operate multiplexers 131 and 132 to connect the selected DUT 110 to test and measurement instrument 160. In other examples, processor 164 of test and measurement instrument 160 may send control signals to multiplexers 131 and 132 or processor 138 of split path selector 130 to connect the selected DUT 110 to test and measurement instrument 160.

[0026] As mentioned above, the path out of the LF / DC multiplexer 132 may include signal conditioning circuitry 133 before the output is sent to the diplexer 134 for recombination. The signal conditioning circuitry 133 may modify the signal after leaving the LF / DC multiplexer 132 to compensate for differences between the separate LF / DC and HF signals after they have been split by the diplexer 112. For example, the signal conditioning circuitry 133 may introduce a delay into the LF / DC signal so that it is combined with the HF signal from the HF multiplexer 131 to more accurately represent the original unsplit signal provided by the DUT 110. In some cases, the signal conditioning circuitry 133 may be programmable to introduce various corrections based on the signal output from the LF / DC multiplexer 132. For example, a user may be able to adjust the delay provided by the signal conditioning circuitry 133 based on the type of signal from the DUT 110, which may vary based on the particular DUT 110 selected for test. Further signal correction may be introduced by signal conditioning circuitry 133 to compensate for the effects of diplexer 112 on the various LF / DC and HF signals, and to compensate for the various effects of the various multiplexers 131 and 132. In some cases, little or no conditioning may be required, while in other cases, significant conditioning may be performed by signal conditioning circuitry 133. In some embodiments, signal conditioning circuitry 133 may modify the amplitude of the LF / DC signals received from multiplexer 132 before recombining them in diplexer 134, such as by amplifying or attenuating the LF / DC signals. In other embodiments, signal conditioning circuitry 133 may modify the LF / DC output of selected DUTs 110 by partially or completely removing DC signals normally present at the output of DUTs 110. For example, if DUT 110 generates an AC signal that is typically transmitted with a DC offset voltage of 1 volt, signal conditioning circuit 133 may operate to remove some or all of the 1 volt DC carrier voltage, after which the remaining LF component of the signal is combined with the HF component of the signal in diplexer 134.Once all DC components of the signal have been removed as described above, only the AC signal from DUT 110 is provided to test and measurement instrument 160, which is the desired signal for analysis.

[0027] Another function of signal conditioning circuit 133 is that it can be used to voltage terminate the LF / DC signal from LF multiplexer 132 to a voltage other than ground. For example, when terminating the LF / DC signal from an HDMI® signal, signal conditioning circuit 133 may terminate the signal to 3.3 volts rather than terminating the signal to a ground reference. Signal conditioning circuit 133 may operate to provide any necessary termination voltage.

[0028] 2 is a block diagram of a test and measurement system 200 including a split path selector 230 according to some embodiments of the present disclosure, where a low frequency or DC signal and a high frequency may be independently selected and then independently amplified. In FIG. 2, the DUT test board 110 and diplexer 112, as well as wiring circuitry, are omitted for clarity. It is envisioned that the split path selector 230 may be coupled to elements of FIG. 1 or other devices that handle the signal to be measured. Also, descriptions of elements commonly numbered with FIG. 1 are omitted for clarity.

[0029] 1, split path selector 230 includes LF / DC amplifier 212 coupled between the output of LF / DC multiplexer 132 and diplexer 134, and HF amplifier 211 coupled between the output of HF multiplexer 131 and diplexer 134. In this embodiment, the HF component of the signal under test and the LF / DC component of the signal under test may each be independently amplified or modified. Although components 211 and 212 are illustrated as amplifiers, they may include additional components to perform conditioning on the signals, such as those described above with reference to signal conditioning circuit 133 of FIG. 1.

[0030] FIG. 3 is a block diagram of a test and measurement system 300 including a split path selector 330 according to some embodiments of the present disclosure, in which a low frequency or DC signal and a high frequency are independently selected by multiplexers 131 and 132, as described above, and then sent separately to the test and measurement instrument for recombination.

[0031] 1 and 2 in that the LF / DC components of the selected signal from multiplexer 132 and the HF components of the selected signal from multiplexer 131 are not recombined in selector 330. Instead, these LF / DC and HF components are sent separately to the test and measurement instrument. In one embodiment, the LF / DC and HF components are sent to compensation box 360, which is coupled to test and measurement instrument 160. Specifically, the LF / DC components are coupled to compensation box 360 via wire 354, which may be much smaller than the RF cable 352 used to transmit the HF component. Compensation box 360 includes a diplexer (not shown) that combines the LF / DC and HF components back into a complete signal selected from a particular DUT 110 (FIG. 1) for measurement by test and measurement instrument 160.

[0032] Amplifiers 211 and 212 may independently modify the LF / DC and HF components of the selected signal as described above with reference to FIG.

[0033] FIG. 4 is a block diagram of a test and measurement system 400 including a split path selector 430, in which a low frequency or DC signal and a high frequency are independently selected by multiplexers 131 and 132, as described above. Unlike the previously described embodiment, the LF / DC components of the signal selected for test are then converted to digital signals using an analog-to-digital converter (ADC) 414. The output of ADC 414 is a digital signal representing the LF / DC components of the signal selected for test. The output of ADC 414 is transmitted to input port 161 of test and measurement instrument 160, while the HF components of the signal selected for test are transmitted by RF cable 352. Although not shown, the analog signal of the selected signal from DUT 110 (not shown) can also be converted to digital signals before being selected by LF / DC multiplexer 132. In this embodiment, multiple separate ADCs are used, one between each corresponding DUT 110 (FIG. 1) and LF / DC multiplexer 132. Also, in this embodiment, LF / DC multiplexer 132 is a digital multiplexer rather than the analog multiplexer described above. In operation, digital LF / DC multiplexer 132 is operated to select a selected signal that is already in digital form. The remainder of split path selector 430 operates as described above.

[0034] In practice, the test and measurement instrument 160 may digitize the HF components of the signals selected for test after receiving them at input port 162. The test and measurement instrument 160 may then combine these digital signals for test, i.e., the LF / DC digital signal digitized by ADC 414 in split path selector 430 and the HF digital signal digitized by an ADC (not shown) in the test and measurement instrument 160.

[0035] FIG. 5 is a block diagram of a test and measurement system 500 including a split path selector 530. Similar to the previous embodiment, there are two multiplexers 531 and 532. However, unlike the previous embodiment, the selected test signal from the DUT 110 is not split into two components; rather, the full test signal is applied simultaneously to both multiplexers 531 and 532. Multiplexer 531 is an RF multiplexer, while LF / DC multiplexer 532 may be a simpler multiplexer made from solid-state switches that do not necessarily have good HF quality. In effect, LF / DC multiplexer 532 passes low-frequency or DC signals and blocks high-frequency signals, while HF multiplexer 531 passes high-frequency signals and blocks low-frequency signals. Based on the frequency of the signal selected for measurement, the LF / DC multiplexer 532 may pass more of the selected signal, the HF multiplexer 531 may pass more of the selected signal, or both multiplexers 531 and 532 may pass their respective components of the selected signal approximately equally.

[0036] Comparator 510 compares the outputs of both multiplexers 531 and 532, and the result of this comparison is used to drive low-frequency operational amplifier (op-amp) 512 to return the LF / DC component to the HF signal output of multiplexer 531. In some embodiments, low-pass filter 514 is positioned between op-amp 512 and summer 515. Summer 515 adds the output from low-pass filter 514 to the output of HF multiplexer 531 before the combined signal is provided to amplifier 135 and further transmitted to test and measurement instrument 160, as described above. Low-pass filter 514 may include a resistor-capacitor network with a single-pole crossover at a frequency selected to be within the operating bands of both LF / DC multiplexer 532 and HF multiplexer 531. For example, the frequency of low-pass filter 514 may be selected to be between 1 kHz and 10 MHz, and more preferably between 10 kHz and 1 MHz.

[0037] In operation, in response to the selected signal, the split path selector 530 component measures the difference between the output of the LF / DC multiplexer 532 and the output of the HF multiplexer 531, and then feeds the difference back to the output of the HF multiplexer 531 through the summer 515. In the configuration of Figure 5, the comparator 510 is a component of a feed-forward loop that creates a signal provided to the amplifier 135 that faithfully represents the signal selected for test, i.e., the signal from the selected DUT 110.

[0038] 6 shows a test and measurement system 600 that includes a split path selector 630 that operates similarly to the split path selector 530 of FIG. 5. However, in the split path selector 630, the inputs of the comparator 510 are coupled to the output of the LF / DC multiplexer 532 and the output of the amplifier 135, respectively. This architecture, as shown in FIG. 6, forms a feedback loop in which the output of the amplifier 135 is compared with the output of the LF / DC multiplexer 532, and the combination of the operational amplifier 512 and low-pass filter 514 feeds any low-frequency components of the selected signal back to the output of the HF multiplexer 532, thereby faithfully reproducing the full bandwidth of the selected signal from the DUT 110.

[0039] 1, split path selectors 530 and 630 do not require any diplexers between DUT 110 and multiplexers 531 and 532, or to combine the outputs of these multiplexers. The remainder of systems 500, 600 operate the same or similarly to the embodiments described above.

[0040] Aspects of the disclosed technology may operate on specially created hardware, firmware, digital signal processors, or specially programmed general-purpose computers, including processors that operate according to programmed instructions. The terms "controller" or "processor" herein contemplate microprocessors, microcomputers, ASICs, and dedicated hardware controllers, among others. Aspects of the disclosed technology may be implemented with computer-usable data and computer-executable instructions, such as one or more program modules, executed by one or more computers (including a monitoring module) or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc., which, when executed by a processor in a computer or other device, perform particular tasks or implement particular abstract data types. Computer-executable instructions may be stored in computer-readable storage media, such as hard disks, optical disks, removable storage media, solid-state memory, RAM, etc. Those skilled in the art will appreciate that the functionality of the program modules may be combined or distributed as desired in various embodiments. Furthermore, such functionality may be embodied in whole or in part in firmware or hardware equivalents, such as integrated circuits, field programmable gate arrays (FPGAs), etc. Certain data structures may be used to more effectively implement one or more aspects of the disclosed technology, and such data structures are considered within the scope of the computer-executable instructions and computer-usable data described herein.

[0041] The disclosed aspects may, in some cases, be implemented 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 computer-readable media, which may be read and executed by one or more processors. Such instructions may be referred to as a computer program product. As used 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.

[0042] "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 random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory and other memory technologies, compact disc read-only memory (CD-ROM), digital video disc (DVD) and other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage and other magnetic storage devices, and any other volatile or nonvolatile, removable or non-removable medium implemented in any technology. "Computer storage media" excludes signals themselves and transitory forms of signal transmission.

[0043] A communication medium means any medium usable for communicating computer-readable information. By way of example, and not limitation, communication media may include coaxial cable, fiber optic cable, air, or any other medium suitable for communicating electrical, optical, radio frequency (RF), infrared, acoustic, or other types of signals. Example

[0044] The following examples are provided to aid in understanding the technology disclosed in this application. Embodiments of the technology may include one or more of the examples described below, and any combination thereof.

[0045] Example 1 is an input selector for electrically connecting one of a plurality of test signals from one or more devices under test to a test and measurement instrument, the input selector comprising: a first multiplexer having a set of a plurality of first input terminals each coupled to a different one of the plurality of test signals from the one or more devices under test and a first output terminal for one selected from the plurality of first input terminals; and a second multiplexer having a set of a plurality of second input terminals each coupled to a different one of the plurality of test signals from the one or more devices under test and a second output terminal for one selected from the plurality of second input terminals.

[0046] Example 2 is the input selector according to Example 1, further comprising a diplexer having an input terminal coupled to one of the one or more devices under test, a low-frequency output terminal coupled to one of the set of first input terminals, and a high-frequency output terminal coupled to one of the set of second input terminals.

[0047] Example 3 is an input selector according to Example 2, further comprising a second diplexer having a first input terminal coupled to the first output terminal of the first multiplexer, a second input terminal coupled to the second output terminal of the second multiplexer, and an output terminal.

[0048] Example 4 is the input selector according to Example 3, further comprising an amplifier coupled to the output terminal of the second diplexer, amplifying a selected test signal of the device under test and transmitting the amplified test signal as an output of the input selector to the test and measurement equipment.

[0049] Example 5 is the input selector according to Example 4, wherein an output of the input selector is sent to the test and measurement instrument via an RF cable.

[0050] Example 6 is an input selector according to any of the above-described examples, wherein the first multiplexer includes a set of solid-state radio frequency switches, PIN diode switches, or MEMS switches.

[0051] Example 7 is the input selector according to Example 6, in which the second multiplexer includes a set of field effect transistor switches or MEMS switches.

[0052] Example 8 is an input selector according to any of the above-described examples, further comprising a signal conditioning circuit configured to modify a signal at the first output terminal of the first multiplexer.

[0053] Example 9 is an input selector according to Example 8, wherein the signal conditioning circuit is configured to modify the signal at the first output terminal of the first multiplexer by performing a function of amplification, attenuation, delay, or analog-to-digital conversion.

[0054] A tenth embodiment is an input selector according to any of the above-described embodiments, wherein the first output terminal of the first multiplexer and the second output terminal of the second multiplexer are both output terminals of the input selector.

[0055] Example 11 is an input selector according to any of the above-mentioned examples, further comprising a comparator coupled to the first output terminal of the first multiplexer and to the second output terminal of the second multiplexer, and configured to generate a comparison result of signals between the first output terminal and the second output terminal.

[0056] Example 12 is the input selector according to Example 11, further comprising an amplifier for amplifying the output of the comparator, and an adder for combining the amplified output of the comparator with the output of the second multiplexer.

[0057] Example 13 is a method for selecting a signal to be measured as a selection signal in a selector coupled to a plurality of input signals to be selected, the method comprising: filtering the selection signal into two separate components, a low frequency component having a low frequency and a high frequency component having a frequency higher than the low frequency; delivering the low frequency component to a first switch; and delivering the high frequency component to a second switch.

[0058] Example 14 is the method according to example 13, further comprising combining the low frequency component and the high frequency component after delivering them to the first and second switches, respectively.

[0059] Example 15 is the method according to example 14, further comprising passing the combined components to a test and measurement device as the signal under test.

[0060] Example 16 is the method according to example 14, further comprising modifying the low frequency component before combining the low frequency component with the high frequency component.

[0061] Example 17 is the method according to example 16, wherein the modifying process comprises amplifying, attenuating, or delaying.

[0062] Example 18 is the method according to any of the methods of the previous examples, wherein filtering the selected signal into two separate components includes passing the selected signal through a diplexer.

[0063] Example 19 is the method according to any of the methods of the previous examples, wherein the first switch has a different signal characteristic than the second switch.

[0064] Example 20 is a method according to any of the methods of the previous examples, further comprising passing the output of the first switch and the output of the second switch to a test and measurement instrument.

[0065] Example 21 is the method according to example 20, further comprising converting the output of the first switch to a digital signal before passing the output of the first switch to the test and measurement instrument.

[0066] Example 22 is a method according to any of the methods of the above-mentioned examples, further comprising a process of comparing the output of the first switch with the output of the second switch, and a process of adding the output of the comparison process to the output of the second switch.

[0067] Although the above-described versions of the presently disclosed subject matter have many advantages that have been described or that will be apparent to those skilled in the art, not all of these advantages or features are required in every version of the disclosed devices, systems, or methods.

[0068] Additionally, the description in this application refers to specific features. All features disclosed in this specification, including the claims, abstract, and drawings, and all steps in all disclosed methods or processes, may be combined in any combination, unless they are at least partially mutually exclusive. Each feature disclosed in this specification, including the claims, abstract, and drawings, may be replaced with an alternative feature serving the same, equivalent, or similar purpose, unless otherwise specified.

[0069] Furthermore, when this application refers to a method having two or more defined steps or processes, these defined steps or processes may be performed in any order or simultaneously, unless the circumstances do not preclude this possibility.

[0070] Although specific embodiments of the invention have been illustrated and described for purposes of illustration, it will be appreciated that various modifications can be made therein without departing from the spirit and scope of the invention. Accordingly, the invention should not be limited except as by the appended claims.

Claims

1. an input selector for electrically connecting one of a plurality of test signals from one or more devices under test to a test and measurement instrument, a first multiplexer having a set of a plurality of first input terminals each coupled to a different one of the plurality of test signals from the one or more devices under test, and a first output terminal for a selected one of the plurality of first input terminals; a second multiplexer having a set of second input terminals each coupled to a different one of the plurality of test signals from the one or more devices under test, and a second output terminal for a selected one of the second input terminals; An input selector comprising:

2. 2. The input selector of claim 1, further comprising a diplexer having an input terminal coupled to one of the one or more devices under test, a low frequency output terminal coupled to one of the first set of input terminals, and a high frequency output terminal coupled to one of the second set of input terminals.

3. 3. The input selector of claim 2, further comprising a second diplexer having a first input terminal coupled to said first output terminal of said first multiplexer, a second input terminal coupled to said second output terminal of said second multiplexer, and an output terminal.

4. 4. The input selector of claim 3, further comprising an amplifier coupled to the output terminal of the second diplexer for amplifying the selected test signal of the device under test and transmitting it as an output of the input selector to the test and measurement equipment.

5. 5. The input selector of claim 4, wherein the output of the input selector is sent to the test and measurement instrument via an RF cable.

6. 2. The input selector of claim 1, wherein the first multiplexer comprises a set of solid-state radio frequency switches, PIN diode switches, or MEMS switches.

7. 7. The input selector of claim 6, wherein the second multiplexer comprises a set of field effect transistor switches or MEMS switches.

8. 2. The input selector of claim 1, further comprising a signal conditioning circuit configured to modify the signal at said first output terminal of said first multiplexer.

9. 9. The input selector of claim 8, wherein the signal conditioning circuit is configured to modify the signal at the first output terminal of the first multiplexer by performing the functions of amplification, attenuation, delay, or analog-to-digital conversion.

10. 2. The input selector of claim 1, wherein said first output terminal of said first multiplexer and said second output terminal of said second multiplexer are both output terminals of said input selector.

11. 2. The input selector of claim 1, further comprising a comparator coupled to the first output terminal of the first multiplexer and to the second output terminal of the second multiplexer, the comparator being configured to generate a comparison result of signals between the first output terminal and the second output terminal.

12. an amplifier for amplifying the output of the comparator; an adder for combining the amplified output of said comparator with the output of said second multiplexer; 12. The input selector of claim 11 further comprising:

13. 1. A method for selecting a signal to be measured as a selection signal in a selector coupled to a plurality of input signals to be selected, comprising: filtering the selected signal into two separate components: a low frequency component having a low frequency and a high frequency component having a frequency higher than the low frequency; delivering the low frequency components to a first switch; and routing said high frequency components to a second switch.

14. 14. The method of claim 13, further comprising combining the low frequency components and the high frequency components after delivering them to the first and second switches, respectively.

15. 15. The method of claim 14, further comprising passing the combined components to a test and measurement instrument as the signal under test.

16. 15. The method of claim 14, further comprising modifying the low frequency components before combining the low frequency components with the high frequency components.

17. 17. The method of claim 16, wherein the modifying comprises amplifying, attenuating, or delaying.

18. 14. The method of claim 13, wherein filtering the selected signal into two separate components comprises passing the selected signal through a diplexer.

19. 14. The method of claim 13, wherein the first switch has different signal characteristics than the second switch.

20. 14. The method of claim 13, further comprising passing the output of the first switch and the output of the second switch to a test and measurement instrument.

21. 21. The method of claim 20, further comprising converting the output of the first switch to a digital signal before passing the output of the first switch to the test and measurement instrument.

22. comparing the output of the first switch with the output of the second switch; adding the output of the comparing process to the output of the second switch; 14. The method of claim 13 further comprising:

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