Shunt multiplex accessory for test and measurement instruments

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 first plurality of inputs and a second multiplexer having a second plurality of inputs, and a first multiplexer having a first plurality of inputs, each input of the first plurality of inputs coupled to a different one of the plurality of test signals from one or more devices under test and having a first output of a selected one of the first plurality of inputs, and a second plurality of inputs having a second output of a selected one of the first plurality of inputs, each input of the second plurality of inputs is coupled to a different one of the plurality of test signals from the one or more devices under test, and has a second output of a selected one of the plurality of inputs. Methods are also described.

Description

Technical Field

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

[0002] Many DUTs include numerous similarly designed signal paths. For example, a Peripheral Component Interconnect Express (PCI Express, PCIe or PCI-e) plug-in card and / or a PCIe motherboard slot typically includes up to sixteen electrical signal "lanes". Electrical signal lanes are typically differential signal lanes, which means that one differential lane requires two electrical measurement ports to fully measure the differential signal of the lane. Thus, to fully measure a sixteen-lane PCIe device, 32 electrical measurement ports would be required. However, test and measurement instruments commonly used to test such DUTs (such as oscilloscopes or bit error rate testers (BERTs)) typically have one, two or four input ports. Although some oscilloscopes include eight input channels or ports, high-performance instruments typically have fewer input channels due to the increased hardware cost associated with each channel. For reasons of heat dissipation and throughput, physical channel density limitations may also keep the total number of channels low. For this reason, typically, a test and measurement instrument configuration will only be connected to a subset of the electrical signal lanes to be tested.

[0003] Since only a subset of the lanes is coupled to the test and measurement instrument, if a user wishes to test all signal lanes, the user must manually move the connection (e.g., test cable or probe) between the test and measurement instrument and the DUT from each lane to the next. Manually moving the cable or probe is an error-prone and very time-consuming process. Alternatively, in a two-channel test and measurement environment, for example, a radio frequency (RF) switch can be built and maintained to enable automated testing of all signal lanes of the DUT. However, at higher frequencies, it is difficult to identify a suitable switch and correctly de-embed the effect of the switch on the signal path (which is performed manually). For these reasons, many users do not trust that the switch can be de-embedded without significant error, especially above 25 GHz. De-embedding or "calibrating" for the effect of a switch or other component on the signal path is the compensation for the negative effect that the switch has on the signal propagating through the signal path. In addition to the need for de-embedding, RF switch matrices are physically large, which makes RF switch matrix solutions particularly unattractive to users with limited physical area for testing.

[0004] An additional problem with electromechanical switch solutions is that they typically leave unselected inputs open (i.e., not typically terminated), which can affect the signal integrity of the DUT.

[0005] Examples of the present disclosure address these and other deficiencies of the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Aspects, features, and advantages of examples of the present disclosure will become apparent from the following description of examples with reference to the accompanying drawings, in which:

[0007] Figure 1 is a block diagram of a test and measurement system according to some embodiments of the present disclosure, the test and measurement system including a shunt selector, wherein lower frequency or DC signals and higher frequencies are selected independently.

[0008] Figure 2 is a block diagram of a test and measurement system according to some examples of the present disclosure, the test and measurement system including a shunt selector, wherein lower frequency or DC signals and higher frequencies are selected independently and can subsequently be amplified independently.

[0009] Figure 3 is a block diagram of a test and measurement system according to some embodiments of the present disclosure, the test and measurement system including a shunt selector, wherein lower frequency or DC signals and higher frequencies are selected independently and are subsequently sent separately to test and measurement equipment for recombination.

[0010] Figure 4 is a block diagram of a test and measurement system according to some embodiments of the present disclosure, the test and measurement system including a shunt selector, wherein lower frequency or DC signals and higher frequencies are selected independently and the lower frequency or DC signals are converted to digital signals by an analog-to-digital converter.

[0011] Figure 5 is a block diagram of a test and measurement system according to an embodiment, the test and measurement system including a shunt selector, wherein lower frequency or DC signals and higher frequencies are selected independently and the test and measurement system further includes a feedforward control system.

[0012] Figure 6 is a block diagram of a test and measurement system according to an embodiment, the test and measurement system including a shunt selector, wherein lower frequency or DC signals and higher frequencies are selected independently and the test and measurement system further includes a feedback control system. DETAILED DESCRIPTION

[0013] Embodiments of the present disclosure utilize a multiplexing component to implement switching between multiple DUT signals and test and measurement instruments. In a multiplexing system, the high-frequency portion and the low-frequency portion of the signal under test are separated, and then these two portions are switched through separate signal paths. Advantageously, the high-frequency path can be switched by a solid-state RF switch, which is much smaller, less expensive, and more reliable than an electromechanical switch. For example, the solid-state switch can be a PIN diode switch. In some embodiments, a duplexer is used to separate frequencies. In some embodiments, a second duplexer is used to recombine the separated frequency divisions before sending the resulting signal to the test and measurement instrument (although there are many variations as described below).

[0014] In embodiments of the present disclosure, a remote or distant location of the multiplexing switching system means that the test and measurement system does not need to occupy significant space on the workbench where the test and measurement system is located in an attempt to position the input of the system as close as possible to the test point of the DUT.

[0015] Figure 1 is a block diagram of a test and measurement system 100 according to some examples of the present disclosure. The test and measurement system 100 includes a multiplexing selector 130 coupled between a plurality of test boards or DUTs 110 available for testing and a test and measurement instrument 160. Although the signal can originate from a test board or from other sources, for convenience, in the present disclosure, the signal for testing is described as originating from the DUT 110. In this example embodiment, there are four DUTs 110, labeled DUT 1, DUT 2, DUT 3, and DUT N, which indicates that the multiplexing selector 130 can select between a large number of different signals for testing and is not limited to four. As described in further detail below, in some embodiments, the multiplexing selector 130 can include 8, 16, or 32 switches.

[0016] In Figure 1 a duplexer 112 is coupled between each DUT 110 and the multiplexing selector 130. In this embodiment, each DUT 110 includes a separate duplexer 112, but this correspondence is not required in all embodiments. The function of the duplexer 112 is to split a signal (such as a signal that can be measured by the test and measurement instrument 160) into its components - a low-frequency and / or direct current (DC) portion (sometimes abbreviated as LF / DC) and a high-frequency portion (HF). Depending on the architecture, the duplexer 112 includes an electrical network composed of any one or all of capacitors, resistors, and inductors and is well known. The duplexer 112 can be selected based on its splitting frequency and other performance characteristics. In other words, the frequency that distinguishes the LF / DC signal from the HF signal can vary depending on the particular duplexer 112 selected. In one example, in Figure 1In the system, the diplexer 112 can split its input signal at approximately 10 kHz, such that frequencies in or below 10 kHz in the original signal are routed to the LF / DC output of the diplexer 112, while frequencies above 10 kHz in the original signal are routed to the HF output of the diplexer. Another diplexer 112 can use 1 MHz as the split or crossover frequency. The split frequency of the diplexer 112 according to an embodiment can be specific to the implementation.

[0017] In Figure 1 In the illustrated embodiment, the HF output of the diplexer 112 is fed to the HF multiplexer 131, while the LF / DC output of the diplexer is fed to the LF / DC multiplexer 132. Each of the multiplexers 131, 132 is part of a splitter selector 130 that has the overall function of selecting which DUT 110 is coupled to the test and measurement instrument 160. More specifically, the splitter selector 130 determines which test signal (which originates from the DUT 110 (and can also be a test board or other signal source)) is selected to be coupled to the test and measurement instrument 160.

[0018] As described above, the HF multiplexer 131 can be formed by solid-state RF switches (such as PIN diode switches), which are very small (especially compared to the full-band RF switch matrix described above). The HF multiplexer 131 can also be formed by microelectromechanical switches (MEMS) that are also very small and have good RF performance. Since it is made of physically small switches and other components, it is much easier to integrate the splitter selector 130 on a test bench or in a test device compared to existing equipment. Additionally, as described below, after the desired signal is selected by the multiplexers 131, 132, the signal can be conditioned (such as amplified) or otherwise modified 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, such that all signals from the DUT that are not selected to be sent to the test and measurement instrument 160 do not cause reflections back to other parts of the corresponding device or test system (which could negatively affect the measurement). However, the solid-state RF switches used to form the HF multiplexer 131 generally do not operate at sufficiently low frequencies, which is one of the reasons for the existence of the diplexer 112 - to remove low frequencies from the measured signal from the selected DUT 110 before routing it to the HF multiplexer 131.

[0019] The LF / DC multiplexer 132 can also include a solid-state switch network, although the switches that make up the LF / DC multiplexer 132 can be different from the switches that make up the HF multiplexer 131. For example, the LF / DC multiplexer 132 can be made of field-effect transistor (FET) switches or MEMS switches.

[0020] Depending on the implementation, the electrical connection that couples the HF output of the diplexer 112 to the HF multiplexer 131 can be in the form of a ribbon or coaxial cable. Generally, due to the difference in the frequencies of the signals, the LF / DC output of the diplexer 112 can be coupled to the LF / DC multiplexer 132 via a simple wire.

[0021] In operation, the LF / DC multiplexer 132 and the HF multiplexer 131 operate in concert to select a single input source to present to the test and measurement instrument 160. For example, when it is desired to select a test signal from the DUTs 1, 110, both the LF / DC multiplexer 132 and the HF multiplexer 131 are controlled to select the DUTs 1, 110. Subsequently, as Figure 1 illustrated, after the signal from the DUTs 1, 110, the signal to be tested is first split by the diplexer 1, 112 into an LF / DC portion and an HF portion, which are routed separately to the multiplexer 132 and the HF multiplexer 131. Subsequently, since the LF / DC multiplexer 132 and the HF multiplexer 131 are operated to select the signals originating from the DUTs 1, 110, these signals are output from the LF / DC multiplexer 132 and the HF multiplexer 131. Next, the selected LF / DC signals from the DUTs 1, 110 can be conditioned or buffered in the signal conditioner 133, the function of which is described below. Next, the conditioned LF / DC signals from the signal conditioner 133 are presented to the LF / DC input of the diplexer 134, and the HF signals output from the HF multiplexer 131 are presented to the HF input of the diplexer 134. A diplexer is bi-directional, i.e., as described above, when connected to a single signal source, the diplexer splits the signal into an LF / DC component and an HF component. Conversely, when the diplexer is connected to two signal sources (one signal source having an LF / DC component and the other signal source having an HF component), the diplexer combines the signals into a unified wideband signal having both an LF / DC component and an HF component. Thus, the output of the diplexer 134 is the signal to be measured by the test and measurement instrument 160. As described below, the output of the diplexer 134 can be modified and / or amplified (such as by the amplifier 135) before being sent to the test port 162 of the test and measurement instrument 160 via an RF connection (such as the cable 152).

[0022] The multiplexer selector 130 can receive power from the measuring instrument 160 via the power line 154 to power the multiplexers 131, 132, the amplifier 135, and possibly other components of the multiplexer selector. In other embodiments, the multiplexer selector 130 can be coupled to a power source separate from the measuring instrument 160, such as a power source directly plugged into a wall outlet. In still other embodiments, the multiplexer selector 130 can be capable of drawing power from the DUT 110 without affecting the integrity of the signals of the DUT used for testing. For example, Universal Serial Bus transmits power as well as data over its lines, and the multiplexer selector 130 can be capable of using a small amount of power from a USB cable. In still other embodiments, the power requirements of the multiplexer selector 130 can be so small that they can be met by rechargeable or replaceable batteries contained within the multiplexer selector 130. This can be possible for some embodiments of the multiplexer selector 130, such as when the multiplexer selector 130 is embodied as an application specific integrated circuit (ASIC) or a microelectromechanical systems (MEMS) switch. In other embodiments, the multiplexer selector 130 can include a plurality of discrete components mounted to a printed circuit (PC) board.

[0023] As described below, control signals between the measuring instrument 160 and the multiplexer selector 130 can be carried on the control line 156. In some embodiments, a user or operator can operate the measuring instrument 160 to select a signal from the DUT 110 for testing. In response, the measuring instrument 160 sends a control signal across the control line 156 to cause the multiplexer 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 duplexer 134 and amplified by the amplifier 135 before being sent to the measuring instrument 160 for testing. The user can make the selection on the user interface of the measuring instrument 160, or can use programming control to instruct the instrument, such as using the PI programming interface available on measuring instruments from Tektronix, Inc. of Beaverton, Oregon. By using programming control, signals from any desired DUT 110 can be scripted to be tested in sequence without the user physically changing any cables between the DUT 110 and the measuring instrument 160. Instead, the switching to connect the desired signal of the DUT 110 to the measuring instrument 160 is performed by controlling the multiplexers 131, 132 of the multiplexer selector 130.

[0024] In Figure 1 the connections to the test port 162, the power line 154, and the control line 156 can be included in a probe interface leading to the measuring instrument 160. Additionally, in some embodiments, the power line 154 and the control line 156 can be embodied in a single connection, i.e., a connection that transmits both power signals and control signals over the same line.

[0025] In some examples, the splitter selector 130 can include a memory 136 and / or a controller or processor 138. The splitter selector 130 can be manufactured or factory tested to measure the effect of including the splitter selector 130 in the test system 100 as compared to directly connecting a particular output of the DUT 110 to the test port 162 of the measurement instrument 160. Compensating for any negative effects of including the splitter selector 130, whose components include multiplexers 131, 132, and amplifier 135, and its associated cables is referred to as de-embedding or calibration. The term "calibration parameter" in the present disclosure refers to any calibration parameter, including the de-embedding parameter of the splitter selector 130, which is used to remove the effect or influence of the presence of the splitter selector 130 and its associated cables in the test system 100 from any signal measurements made by the test and measurement instrument 160. The calibration parameters can be stored in a specific calibration parameter memory 140 or in the general memory 136 and sent to the test and measurement instrument 160 during a test session. In some examples, the calibration parameters can be sent to an analysis device remote from the test and measurement instrument 160. As will be understood by those skilled in the art, the analysis device can collect the calibration parameters as well as data from the test and measurement instrument 160 and provide any required processing of the data. In other examples, the calibration parameters for a particular splitter selector 130 can be stored in a memory 163 located in the test and measurement instrument 160 or retrieved from a remote storage device, such as cloud storage, and sent to the splitter selector 130 for storage in its calibration parameter storage device 140. For example, the specific calibration parameters for de-embedding the effect of the splitter selector 130 can be identified based on the serial number or other identification number of the splitter selector 130.

[0026] The scattering parameters (also known as S-parameters) for each port of the multiplexers 131, 132 can be stored together with the calibration parameters 140 or in a separate memory 136 to assist the test and measurement instrument 160 in de-embedding the splitter selector 130 from the signals of the DUT 110. Through-path and isolation-path S-parameters are stored for each connector of the multiplexers 131, 132 and for the port 162 of the measurement instrument 160. In some examples, such as if the user wishes to change the S-parameters or add stress to the system, the user can upload or otherwise port their own S-parameters.

[0027] Amplifier 135 can be an active amplifier with a low impedance input (such as 50 ohms). For example, the active amplifier can be compatible with testing many serial data DUTs 110, such as PCIe devices, Serial ATA (AT Attachment) buses, Mobile Industry Processor Interface (MIPI) interfaces, Fibre Channel, and High-Definition Multimedia Interface (HDMI) interfaces. In other embodiments, amplifier 135 can include or use a buffer to buffer the signal from DUT 110 for testing. In these embodiments, amplifier 135 typically has a relatively high input impedance, such as a 100 kΩ or 150 kΩ DC input resistance. In another example, amplifier 135 can have a 1 MΩ impedance. For example, the splitter selector 130 with this relatively high input impedance facilitates testing memory circuits as well as high-speed serial buses. In the case of a low impedance input amplifier 135 or a high impedance input amplifier 135, including amplifier 135 in the splitter selector allows the selected signal from the outputs of multiplexers 131, 132 to be amplified as close as possible to the selected source and in a manner that maximizes its signal transmission characteristics to the measurement instrument 160. This placement of amplifier 135 within splitter selector 130 not only reduces noise interference, but also allows the calibration plane to be closer to the desired test plane of DUT 110 by using calibration parameters 140 within splitter selector 130.

[0028] In some examples (such as Figure 1 the illustrated example), splitter selector 130 can include a processor 138. Processor 138 can operate multiplexers 131, 132 to connect the selected DUT 110 to the test and measurement instrument 160. In other examples, the processor 164 of test and measurement instrument 160 can send control signals to multiplexers 131, 132 or the processor 138 of splitter selector 130 to connect the selected DUT 110 to the test and measurement instrument 160.

[0029] As described above, before the output is sent to the diplexer 134 for recombination, the output path of the LF / DC multiplexer 132 can include a signal conditioner 133. The signal conditioner 133 can modify the signal after it leaves the LF / DC multiplexer 132 to compensate for differences in the individual LF / DC and HF signals after being split by the diplexer 112. For example, the signal conditioner 133 can introduce a delay into the LF / DC signal so that it combines with the HF signal from the HF multiplexer 131 to more accurately represent the original signal from the DUT 110 before the split. In some cases, the signal conditioner 133 can be programmable to introduce different compensations based on which signal is output from the LF / DC multiplexer 132. For example, the user may be able to adjust the delay provided by the signal conditioner 133 based on the type of signal from the DUT 110, which can vary based on the particular DUT 110 selected for testing. Additional signal compensation can be introduced by the signal conditioner 133 to compensate for the effects of the diplexer 112 on the different LF / DC and HF signals, and to compensate for different effects from the different multiplexers 131, 132. In some cases, little or no adjustment may be required, but in other cases, significant adjustment can be performed by the signal conditioner 133. In some embodiments, the signal conditioner 133 can modify the amplitude of the LF / DC signal before recombination into the diplexer 134, such as by amplifying or attenuating the LF / DC signal received from the multiplexer 132. In other embodiments, the signal conditioner 133 can modify the LF / DC output of the selected DUT 110 by partially or completely removing the DC signal that is normally present on the output of the DUT 110. For example, if the DUT 110 normally generates an AC signal carried on a 1 volt DC bias voltage, the signal conditioner 133 can be operated to remove any or all of the 1 volt DC carrier voltage before combining the remaining LF portion of the signal with the HF portion of the signal in the diplexer 134. When all of the DC portion of the signal is removed as described above, only the AC signal from the DUT 110 is presented to the test and measurement instrument 160, which is the desired signal for analysis.

[0030] Another function of the signal conditioner 133 is that it can be used to provide a voltage termination for the LF / DC signal from the LF multiplexer 132 to a voltage other than ground. For example, when terminating the LF / DC signal from an HDMI signal, the signal conditioner 133 can terminate the signal to 3.3 volts instead of terminating it to reference ground. The signal conditioner 133 can be operated to provide any necessary termination voltage.

[0031] Figure 2is a block diagram of a test and measurement system 200 according to some examples of the present disclosure. The test and measurement system 200 includes a diplexer 230, where lower frequency or DC signals and higher frequencies are independently selected and can then be independently amplified. In Figure 2 for clarity, the DUT test board 110, the duplexer 112, and the routing circuit have been omitted. It can be assumed that the diplexer 230 can be coupled to those components from Figure 1 or other devices having signals to be measured. Additionally, for brevity, the description of the components with common numbers from Figure 1 has been omitted.

[0032] Unlike Figure 1 , the diplexer 230 includes an LF / DC amplifier 212 coupled between the output of the LF / DC multiplexer 132 and the duplexer 134, and an HF amplifier 211 coupled between the output of the HF multiplexer 131 and the duplexer 134. In this embodiment, each of the HF portion of the signal under test and the LF / DC portion of the signal under test can be independently amplified or modified. Although components 211, 212 are illustrated as amplifiers, they can include additional components for conditioning the signal, such as those described above with reference to Figure 1 the signal conditioner 133.

[0033] Figure 3 is a block diagram of a test and measurement system 300 according to some embodiments of the present disclosure. The test and measurement system 300 includes a diplexer 330, as described above, where lower frequency or DC signals and higher frequencies are independently selected through multiplexers 131, 132 and then separately sent to test and measurement equipment for recombination.

[0034] The diplexer 330 is different from the diplexers of Figure 1 and Figure 2 in that the LF / DC portion of the selected signal from the multiplexer 132 and the HF portion of the selected signal from the multiplexer 131 are not recombined in the selector 330. Instead, these LF / DC component portions and HF component portions are separately sent to test and measurement instruments. In one embodiment, the LF / DC component portion and the HF component portion are sent to a compensation box 360, and the compensation box 360 is coupled to the test and measurement instrument 160. Specifically, the LF / DC portion is coupled to the compensation box 360 through a wire 354, and the wire 354 can be much smaller than the RF cable 352 for carrying the HF portion. The compensation box 360 includes a duplexer (not illustrated) for combining the LF / DC component and the HF component back into a complete signal selected from a specific DUT 110 ( Figure 1 ) for measurement by the test and measurement instrument 160.

[0035] As described above Figure 2 the amplifiers 211, 212 can independently modify the LF / DC part and the HF part of the selected signal.

[0036] Figure 4 is a block diagram of a test and measurement system 400, which includes a splitter selector 430, as described above, where the lower frequency or DC signal and the higher frequency are independently selected by the multiplexers 131, 132. Subsequently, different from the previously described embodiments, the LF / DC part of the signal selected for testing is converted into a digital signal using an analog-to-digital converter (ADC) 414. The output of the ADC 414 is a digital signal representing the LF / DC part of the signal selected for testing. The output of the ADC 414 can be brought to the input port 161 of the test and measurement instrument 160, and the HF part of the signal selected for testing is carried by the RF cable 352. Although not shown, it is possible to convert the analog signal of the selected signal from the DUT 110 (not shown) into a digital signal before it is selected by the LF / DC multiplexer 132. In this embodiment, multiple individual ADCs are used, each ADC being between its corresponding DUT 110( Figure 1 ) and the LF / DC multiplexer 132. Additionally, in this embodiment, the LF / DC multiplexer 132 is a digital multiplexer rather than the analog multiplexer as described above. In operation, the digital LF / DC multiplexer 132 is operated to select the selected signal that is already in digital form. The rest of the splitter selector 430 operates as described above.

[0037] In practice, the test and measurement instrument 160 can digitize the HF part of the signal selected for testing after it is received by the input port 162. Subsequently, the test and measurement instrument 160 can combine the digital signals for testing, i.e., the LF / DC digital signal digitized by the ADC 414 in the splitter selector 430 and the HF digital signal digitized by an ADC (not shown) within the test and measurement instrument 160.

[0038] Figure 5is a block diagram of a test and measurement system 500 that includes a splitter selector 530. Similar to the above embodiments, there are two multiplexers 531, 532. However, different from the above embodiments, the test signal selected from the DUT 110 is not split into two components, but the complete test signal is applied to both multiplexers 531, 532 simultaneously. Multiplexer 531 is an RF multiplexer, and the LF / DC multiplexer 532 can be a simpler multiplexer made of solid-state switches that do not need to have good HF quality. In practice, the LF / DC multiplexer 532 allows low-frequency and / or DC signals to pass through and tends to block high-frequency signals, while the HF multiplexer 531 allows high-frequency signals to pass through and tends to block low-frequency signals. Based on the frequency of the signal selected for measurement, the LF / DC multiplexer 532 can allow more of the selected signal to pass through, the HF multiplexer 531 can allow more of the selected signal to pass through, or both multiplexers 531, 532 can allow their respective portions of the selected signal to pass through equally to some extent.

[0039] Comparator 510 compares the outputs of both multiplexers 531, 532, and this comparison is used to drive the low-frequency operational amplifier 512 to add the LF / DC component back to the HF signal output of multiplexer 531. In some embodiments, a low-pass filter 514 is located between the amplifier 512 and the adder 515. As described above, before the combined signal is presented to the amplifier 135, the adder 515 adds the output from the low-pass filter 514 to the output of the HF multiplexer 531 for further transmission to the test and measurement instrument 160. The low-pass filter 514 can include a resistor-capacitor network that has a single-pole crossover at a frequency (selected to be within both the operating frequency band of the LF / DC multiplexer 532 and the operating frequency band of the HF multiplexer 531). For example, the frequency of the low-pass filter 514 can be selected to be between 1 kHz and 10 MHz, and more preferably between 10 kHz and 1 MHz.

[0040] In operation, depending on the selected signal, the components of the splitter selector 530 tend to measure the difference between the outputs of the LF / DC multiplexer 532 and the HF multiplexer 531, and then add this difference back to the output of the HF multiplexer 531 through the adder 515. In Figure 5 's configuration, the comparator 510 is a component of a feed-forward loop that tends to create a signal for presentation to the amplifier 135 that is a faithful representation of the selected signal for testing (i.e., the signal from the selected DUT 110).

[0041] Figure 6 illustrates a test and measurement system 600 that includes a splitter selector 630, which is related toFigure 5 The shunt selector 530 operates similarly. However, in the shunt selector 630, the inputs of the comparator 510 are coupled to the outputs of the LF / DC multiplexer 532 and the output of the amplifier 135, respectively. As Figure 6 The illustrated architecture creates a feedback loop where the output of the amplifier 135 is compared with the output of the LF / DC multiplexer 532 so that the combination of the amplifier 512 and the low-pass filter 514 adds any low-frequency portions of the selected signal back to the output of the HF multiplexer 532, thereby faithfully re-creating the full bandwidth of the signal from the selected DUT 110.

[0042] Compared with Figure 1 the embodiments of, the shunt selectors 530, 630 do not require any duplexers between the DUT 110 and the multiplexers 531, 532, nor do they require combining the outputs of the multiplexers. The operation of the remainder of the systems 500, 600 is the same as or similar to the embodiments described above.

[0043] Aspects of the present disclosure may operate on specifically created hardware, firmware, a digital signal processor, or on a specially programmed computer including a processor operating according to programmed instructions. As used herein, the term "controller" or "processor" is intended to include a microprocessor, a microcomputer, an application specific integrated circuit (ASIC), and a dedicated hardware controller. One or more aspects of the present disclosure may be embodied in computer-usable data and computer-executable instructions executed by one or more computers, including a monitoring module, or other devices, such as in one or more program modules. 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, an optical disk, a removable storage medium, a solid state memory, a random access memory (RAM), etc. As will be understood by those skilled in the art, the functionality of the program modules may be combined or distributed as desired in various aspects. Additionally, the functionality may be embodied in whole or in part in firmware or hardware equivalents, such as integrated circuits, FPGAs, etc. Specific data structures may be used to more effectively 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.

[0044] In some cases, the disclosed aspects may 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 storage media, which can be read and executed by one or more processors. Such instructions may be referred to as a computer program product. As discussed herein, computer-readable media means any media 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.

[0045] Computer storage media means any media 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 technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD), or other optical disc storage, magnetic 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 signals themselves and transient forms of signal transmission.

[0046] Communication media means any media 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 media suitable for communication of electrical, optical, radio frequency (RF), infrared, acoustic, or other types of signals.

[0047] Example

[0048] Illustrative examples of the technologies disclosed herein are provided below. Configurations of the technologies may include one or more of the examples described below and any combination thereof.

[0049] Example 1 is an input selector for electrically connecting one test signal out of a plurality of test signals from one or more devices under test to a test and measurement instrument. The input selector includes a first multiplexer and a second multiplexer. The first multiplexer has a first set of a plurality of inputs, each input in the first set of a plurality of inputs being coupled to a different one of the plurality of test signals from one or more devices under test, and has a first output of a selected one of the first plurality of inputs. The second multiplexer has a second set of a plurality of inputs, each input in the second set of a plurality of inputs being coupled to a different one of the plurality of test signals from one or more devices under test, and has a second output of a selected one of the plurality of inputs.

[0050] Example 2 is an input selector according to Example 1, further comprising a duplexer having an input coupled to one of the one or more devices under test, a low-frequency output coupled to one of a first set of multiple inputs, and a high-frequency output coupled to one of a second set of multiple inputs.

[0051] Example 3 is an input selector according to Example 2, further comprising a second duplexer having a first input coupled to the first output of a first multiplexer, a second input coupled to the second output of a second multiplexer, and an output.

[0052] Example 4 is an input selector according to Example 3, further comprising an amplifier coupled to the output of the second duplexer, the amplifier amplifying a selected test signal of the device under test before the selected test signal of the device under test is sent as the output of the input selector to a test and measurement instrument.

[0053] Example 5 is an input selector according to Example 4, wherein the output of the input selector is sent to a test and measurement instrument via an RF cable.

[0054] Example 6 is an input selector according to any one of the foregoing examples, wherein the first multiplexer comprises a set of solid-state radio frequency switches, PIN diode switches, or MEMS switches.

[0055] Example 7 is an input selector according to Example 6, wherein the second multiplexer comprises a set of field effect transistor switches or MEMS switches.

[0056] Example 8 is an input selector according to any one of the foregoing examples, further comprising a signal regulator configured to modify the signal on the first output of the first multiplexer.

[0057] Example 9 is an input selector according to Example 8, wherein the signal regulator is configured to modify the signal on the first output of the first multiplexer by performing an amplification, attenuation, delay, or analog-to-digital conversion function.

[0058] Example 10 is an input selector according to any one of the foregoing examples, wherein both the first output of the first multiplexer and the second output of the second multiplexer are output from the input selector.

[0059] Example 11 is an input selector according to any one of the foregoing examples, further comprising a comparator coupled to the first output of the first multiplexer and coupled to the second output of the second multiplexer, and configured to generate a comparison signal between the first output and the second output.

[0060] Example 12 is an input selector according to Example 11, further including an amplifier for amplifying the output of the comparator, and an adder for combining the amplified output of the comparator into the output of the second multiplexer.

[0061] Example 13 is a method for selecting a signal for measurement as the selected signal in a selector, the selector being coupled to a plurality of input signals from which to select, the method including: filtering the selected signal into two separate components, one component having a low frequency and the second component having a high frequency higher than the low frequency, routing the low-frequency component through a first switch, and routing the high-frequency component through a second switch.

[0062] Example 14 is a method according to Example 13, further including combining them after the low-frequency component and the high-frequency component have been routed through the first switch and the second switch, respectively.

[0063] Example 15 is a method according to Example 14, further including passing the combined components to a test and measurement device as the signal to be tested.

[0064] Example 16 is a method according to Example 14, further including modifying the low-frequency component before combining the low-frequency component and the high-frequency component.

[0065] Example 17 is a method according to Example 16, wherein the modification includes amplification, attenuation, or delay.

[0066] Example 18 is a method according to any of the preceding example methods, wherein filtering the selected signal into two separate components includes passing the selected signal through a diplexer.

[0067] Example 19 is a method according to any of the preceding example methods, wherein the first switch has signal characteristics different from those of the second switch.

[0068] Example 20 is a method according to any of the preceding example methods, further including passing the output of the first switch and the output of the second switch to a test and measurement device.

[0069] Example 21 is a method according to Example 20, further including converting the output of the first switch into a digital signal before passing the output of the first switch to a test and measurement device.

[0070] Example 22 is a method according to any of the preceding example methods, further including comparing the output of the first switch with the output of the second switch, and adding the output of the comparison to the output of the second switch.

[0071] Previous described versions of the disclosed subject matter have many advantages, which are either described or will be apparent to those skilled in the art. Even so, these advantages or features are not required in all versions of the disclosed apparatus, system, or method.

[0072] In addition, this written description mentions specific features. It should be understood that all features disclosed in the specification (including the claims, abstract, and drawings) and all steps in any method or process disclosed can be combined in any combination, except for combinations in which at least some of such features and / or steps are mutually exclusive. Each feature disclosed in the specification (including the claims, abstract, and drawings) may be replaced by an alternative feature serving the same, equivalent, or similar purpose, unless expressly stated otherwise.

[0073] Furthermore, when a method having two or more defined steps or operations is recited in this application, the defined steps or operations can be performed in any order or simultaneously, unless the context excludes those possibilities.

[0074] Although specific aspects of the present disclosure have been illustrated and described for purposes of illustration, it will be understood that various modifications can be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.

Claims

1. An input selector for electrically connecting one test signal out 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 first set of a plurality of inputs, each input in the first set of a plurality of inputs being coupled to a different one of the plurality of test signals from the one or more devices under test, and having a first output of a selected one of the first plurality of inputs; And A second multiplexer having a second set of a plurality of inputs, each input in the second set of a plurality of inputs being coupled to a different one of the plurality of test signals from the one or more devices under test, and having a second output of a selected one of the plurality of inputs.

2. The input selector according to claim 1, further comprising a duplexer having an input coupled to one of the one or more devices under test, having a low-frequency output coupled to one of the first set of a plurality of inputs, and having a high-frequency output coupled to one of the second set of a plurality of inputs.

3. The input selector according to claim 2, further comprising a second duplexer having a first input coupled to the first output of the first multiplexer, having a second input coupled to the second output of the second multiplexer, and having an output.

4. The input selector according to claim 3, further comprising an amplifier coupled to the output of the second duplexer, the amplifier amplifying the selected test signal of the device under test before the selected test signal of the device under test is sent as an output of the input selector to the test and measurement instrument.

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

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

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

8. The input selector according to claim 1, further comprising a signal conditioner configured to modify a signal on the first output of the first multiplexer.

9. The input selector according to claim 8, wherein the signal conditioner is configured to modify the signal on the first output of the first multiplexer by performing an amplification, attenuation, delay or analog-to-digital conversion function.

10. The input selector according to claim 1, wherein both the first output of the first multiplexer and the second output of the second multiplexer are output from the input selector.

11. The input selector according to claim 1, further comprising a comparator coupled to the first output of the first multiplexer and to the second output of the second multiplexer, and configured to generate a comparison signal between the first output and the second output.

12. The input selector according to claim 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.

13. A method for selecting a signal for measurement as a selected signal in a selector, the selector coupled to a plurality of input signals from which to select, the method comprising: filtering the selected signal into two separate components, one component having a low frequency and a second component having a high frequency higher than the low frequency; routing the low frequency component through a first switch; and routing the high frequency component through a second switch.

14. The method according to claim 13, further comprising combining the low frequency component and the high frequency component after the low frequency component and the high frequency component have been routed through the first switch and the second switch, respectively.

15. The method according to claim 14, further comprising passing the combined components to a test and measurement device as a signal to be tested.

16. The method according to claim 14, further comprising modifying the low frequency component before combining the low frequency component and the high frequency component.

17. The method according to claim 16, wherein the modification comprises amplification, attenuation, or delay.

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

19. The method according to claim 13, wherein the first switch has signal characteristics different from those of the second switch.

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

21. The method according to 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 device.

22. The method according to claim 13, further comprising: comparing the output of the first switch with the output of the second switch; and adding the output of the comparison to the output of the second switch.

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