Self-calibrating deskew device

Abstract

A deskew device (100) includes: first and second deskew detection points (110 and 120) for contacting first and second probes (115 and 125), respectively, during deskew calibration; a signal generation circuit (130) for generating a calibration signal provided to the first and second deskew detection points (110 and 120); and a feedback loop for automatically self-calibrating the deskew device (100).

Description

Background Art

[0001] A deskew device is a circuit that can be connected to signal probes (such as current and voltage probes) to eliminate timing differences (skew) between the signals provided by each signal probe. For example, skew can be a timing delay between the rising edge of the actual signal and the acquired signal. Due to the internal circuitry of the signal probes, this timing delay can cause distortion and measurement inaccuracies. Skew can also be caused by manufacturing, design, and / or architectural differences between signaling probes.

[0002] In order to obtain accurate measurements (such as power measurements), the probes (e.g., current probes and voltage probes) must be de-skewed using a deskew device during calibration. Conventional deskew devices (such as the U1880A power measurement deskew device available from Keysight Technologies) enable the user to perform dual probes on the same signal in close physical proximity to the voltage and current probes in order to measure and eliminate any skew between the two probe channels and / or between the two test instrument channels or inputs (e.g., oscilloscope channels) to which the probes are connected. However, it is preferred to measure voltage and current simultaneously using simultaneously connected voltage and current probes. In this case, the deskew device does not use the same probe point location (electrical length) for both the voltage and current probes and does not provide a way to calibrate the inherent skew between the probe points. Therefore, deskewing the probes is very important for timing-sensitive applications (such as power measurements). The accuracy of the power measurement depends largely on the accuracy of the deskew between the voltage probe and the current probe.

[0003] Typically, conventional deskew devices use an electrical signal that can be detected by two probes. When the signal is generated on the deskew device, the signal generation is limited and is generally not adequately adapted to probes with different bandwidths and input levels. Furthermore, there is no control over the parameters of the signal, such as waveform and amplitude. For example, with the U1880A power measurement deskew device, the signal is generated by a 555 clock IC that produces one type of square wave (frequency and amplitude). It can be difficult to use one waveform type to deskew probes that inherently have different bandwidths. In contrast, when the signal is generated externally to the deskew device, the user may not be aware of the type of signal being generated and may not have the equipment to generate the appropriate signal. For example, an external signal generator may have sufficient bandwidth but may not output insufficient current.

[0004] Additionally, conventional deskew devices cannot generate sufficient current levels, so multiple windings may be included to increase the effective current. The windings introduce inductance, which can cause unwanted phase shift, making it more difficult for the output driver to maintain linearity. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The exemplary embodiments are best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be emphasized that the various features are not necessarily drawn to scale. In fact, for clarity of discussion, dimensions may be arbitrarily increased or decreased. Where applicable and practicable, like reference numerals refer to like elements.

[0006] Figure 1 is a simplified block diagram of a deskew device with self-calibration capabilities, according to a representative embodiment.

[0007] Figure 2 is a simplified block diagram of a deskew device with self-calibration capabilities, according to a representative embodiment.

[0008] Figure 3 is a simplified flow chart of a deskewing method for a deskewing device with self-calibration capability according to a representative embodiment. DETAILED DESCRIPTION

[0009] The present invention includes the following embodiments:

[0010] 1. A deskew apparatus for improving the accuracy of deskew calibration performed on a first probe and a second probe by a test instrument for measuring electrical parameters of a device under test (DUT), the deskew apparatus comprising:

[0011] a first deskew detection point configured to receive a first calibration signal when in contact with the first probe;

[0012] a second deskew detection point configured to receive a second calibration signal when in contact with the second probe; and

[0013] A feedback loop for automatically self-calibrating the deskew device, the feedback loop comprising:

[0014] a first analog-to-digital converter (ADC) configured to digitize the first calibration signal at the first deskew detection point to provide a first digitized calibration signal;

[0015] a second ADC configured to digitize the second calibration signal at the second deskew detection point to provide a second digitized calibration signal; and

[0016] a processing unit programmed to use the first and second digitized calibration signals to determine an inherent skew of the deskew device between the first and second deskew detection points, and to adjust timing of at least one of the first or second calibration signals.

[0017] 2. The deskewing device according to item 1, further comprising:

[0018] At least one signal generating circuit is configured to generate the first and second calibration signals received by the first deskew detection point and the second deskew detection point.

[0019] 3. The deskew device according to item 1, wherein the processing unit is further programmed to provide the determined intrinsic skew to the test instrument for the deskew calibration of the first probe and the second probe.

[0020] 4. The deskewing device according to item 1, further comprising:

[0021] A signal conditioning circuit is connected to at least one of the first or second deskew detection points and is configured to adjust the timing of the at least one of the first calibration signal or the second calibration signal in response to a control signal from the processing unit.

[0022] 5. The de-skewing device according to item 2, wherein the at least one signal generating circuit includes a first signal generating circuit and a second signal generating circuit, and wherein the first calibration signal is generated by the first signal generating circuit and the second calibration signal is generated by the second signal generating circuit.

[0023] 6. The deskewing device according to item 2, further comprising:

[0024] At least one variable gain amplifier (VGA) is connected between the at least one signal generation circuit and the first deskew detection point and is configured to amplify at least one of the first calibration signal or the second calibration signal.

[0025] 7. The deskew device of item 4, wherein the signal conditioning circuit comprises at least one delay circuit configured to delay at least one of the first calibration signal or the second calibration signal to adjust the timing of the at least one of the first calibration signal or the second calibration signal in response to a control signal from the processing unit.

[0026] 8. The deskew device of clause 4, wherein the signal conditioning circuit comprises one or more of:

[0027] at least one filter configured to adjust a bandwidth of at least one of the first calibration signal or the second calibration signal to correspond to a first bandwidth of the first probe or to adjust a second bandwidth of the second calibration signal to correspond to a second bandwidth of the second probe, respectively; and

[0028] At least one rise-time converter configured to adjust a bandwidth of at least one of the first calibration signal or the second calibration signal.

[0029] 9. The deskewing device according to item 5, further comprising:

[0030] A switch is configured to selectively connect one of the first signal generating circuit and the second signal generating circuit to the second deskew detection point while the first signal generating circuit remains connected to the first deskew detection point.

[0031] 10. The deskew device of item 2, wherein the at least one signal generating circuit comprises at least one arbitrary waveform generator (AWG).

[0032] 11. The deskewing device according to item 2, further comprising:

[0033] A synchronization clock is configured to provide synchronization between the at least one signal generating circuit and each of the first and second ADCs.

[0034] 12. The deskew device of item 1, wherein each of the first deskew detection point and the second deskew detection point is modular, so that the first deskew detection point and the second deskew detection point can be removed and replaced according to the type and bandwidth of the first probe and the second probe, respectively.

[0035] 13. The deskew device of item 12, wherein the processing unit is further programmed to identify the modular first and second deskew detection points and automatically configure the identified modular first and second deskew detection points accordingly.

[0036] 14. A deskew apparatus for improving the accuracy of deskew calibration performed on a first probe and a second probe by a test instrument for measuring electrical parameters of a device under test (DUT), the deskew apparatus comprising:

[0037] base;

[0038] a first modular deskew probing point removably connected to the base and configured to contact the first probe during the deskew calibration, the first modular deskew probing point customized to the geometry and radio frequency (RF) characteristics of the first probe;

[0039] a second modular deskew probing point removably connected to the base and configured to contact the second probe during the deskew calibration, the second modular deskew probing point customized to the geometry and RF characteristics of the second probe;

[0040] at least one signal generating circuit on the base, the signal generating circuit being configured to generate at least one calibration signal, the calibration signal being provided to the first modular deskew detection point and the second modular deskew detection point respectively;

[0041] a first analog-to-digital converter (ADC) configured to digitize the at least one calibration signal at the first modular deskew probe point when the first probe is in contact with the first modular deskew probe point to provide a first digitized calibration signal;

[0042] a second ADC configured to digitize the at least one calibration signal at the second modular deskew probe point when the second probe is in contact with the second modular deskew probe point to provide a second digitized calibration signal; and

[0043] A processing unit programmed to determine a skew between the first modular deskew detection point and the second modular deskew detection point using the first digitized calibration signal and the second digitized calibration signal.

[0044] 15. The deskew device of item 14, wherein the at least one signal generation circuit generates the at least one calibration signal in response to signal generation and signal conditioning inputs from the test instrument.

[0045] 16. The deskew apparatus of item 14, wherein the processing unit is further programmed to provide the determined skew to the test instrument for the deskew calibration performed by the test instrument on the first probe and the second probe.

[0046] 17. The deskewing device according to item 14, further comprising:

[0047] a signal conditioning circuit connected between the at least one signal generation circuit and at least one of the first and second modular deskew detection points and configured to adjust the timing of the at least one calibration signal,

[0048] Wherein the processing unit is further programmed to control the signal conditioning circuit to adjust the timing of the at least one calibration signal based on the determined skew.

[0049] 18. A deskew apparatus for improving the accuracy of deskew calibration performed on a first probe and a second probe by a test instrument for measuring electrical parameters of a device under test (DUT), the deskew apparatus comprising:

[0050] a first deskew detection point configured to receive a first calibration signal when in contact with the first probe;

[0051] a second deskew detection point configured to receive a second calibration signal when in contact with the second probe;

[0052] a first analog-to-digital converter (ADC) configured to digitize the first calibration signal at the first deskew detection point to provide a first digitized calibration signal; and

[0053] a second ADC configured to digitize the second calibration signal at the second deskew detection point to provide a second digitized calibration signal,

[0054] The deskew device provides deskew information to the test instrument for the deskew calibration of the first probe and the second probe, wherein the test instrument uses the deskew information to adjust the deskew calibration to compensate for an inherent deskew of the deskew device.

[0055] 19. The deskewing device according to item 18, further comprising:

[0056] a processing unit programmed to determine the intrinsic skew of the deskew device using the first and second digitized calibration signals, and to provide the deskew information including the determined intrinsic skew to the test instrument for deskew calibration of the first and second probes.

[0057] 20. The deskew device of item 18, wherein the deskew information comprises the first and second digitized calibration signals, and the test instrument determines the inherent skew of the deskew device based on the deskew information using the first and second digitized calibration signals.

[0058] In the detailed description that follows, example embodiments disclosing specific details are set forth for purposes of explanation, not limitation, to provide a more complete understanding of the embodiments according to the present teachings. However, it will be apparent to those skilled in the art having the benefit of this disclosure that other embodiments according to the present teachings that depart from the specific details disclosed herein are still within the scope of the appended claims. Furthermore, known devices and methods are not described here in detail so as not to obscure the description of the exemplary embodiments. Such methods and apparatus are expressly intended to be within the scope of the present teachings.

[0059] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. The defined terms are to be given the technical and scientific meanings of the defined terms as commonly understood and accepted in the art of the present teachings.

[0060] Unless otherwise specified, when a first element is referred to as being connected to a second element, this includes situations where one or more intermediate elements may be used to connect the two elements to each other. However, when a first element is referred to as being directly connected to a second element, this only includes situations where the two elements are connected to each other without any intermediaries or intermediate devices. Similarly, when a signal is referred to as being coupled to an element, this includes situations where one or more intermediate elements may be used to couple the signal to the element. However, when a signal is referred to as being directly coupled to an element, this only includes situations where the signal is directly coupled to the element without any intermediaries or intermediate devices.

[0061] As used in this specification and the appended claims, the terms "a," "an," and "the" include singular and plural referents unless the context clearly indicates otherwise. Thus, for example, "a device" includes both one device and a plurality of devices. As used in the specification and the appended claims, in addition to their ordinary meaning, the terms "substantially" or "approximately" mean within acceptable limits or degrees. As used in the specification and the appended claims and in addition to their ordinary meaning, the term "approximately" means within acceptable limits or amounts to a person skilled in the art. For example, "approximately the same" means that a person of ordinary skill in the art would consider the items to be the same after comparison.

[0062] Relational terms such as "above," "below," "top," and "bottom" may be used to describe the relationship between different elements as shown in the accompanying drawings. These relational terms are intended to encompass different orientations of their elements in addition to the orientation depicted in the accompanying drawings. For example, if an apparatus (e.g., a signal measuring device) depicted in a drawing is inverted relative to the view in the drawing, an element described as being "above" another element would now be below the element. Similarly, if the apparatus is rotated 90° relative to the view in the drawing, an element described as being "above" or "below" another element would now be "adjacent" to the other element; where "adjacent" means adjacent to the other element or having one or more layers, one or more materials, structures, etc. between the elements.

[0063] Typically, a test instrument (e.g., an oscilloscope) can be used to measure time-varying characteristics of a device under test (DUT), such as voltage, current, and / or power, using two or more probes connected to channels of the test instrument. First, the test instrument performs a deskew calibration on the probes before using the probes to measure the DUT. Deskew calibration resolves the timing differences (skews) between the signals respectively provided by the probes so that subsequent measurements of the DUT by the probes are aligned in time (deskewed). For deskew calibration, according to various embodiments, the test instrument is connected to a deskew device while the probes are placed in contact with corresponding deskew detection points on the deskew device. A calibration signal generated by an integrated signal generating circuit of the deskew device is applied to the detection points. The test instrument receives the signals from the probes and the timing information from the deskew device, which enables the test instrument to determine the skew between the probes and calculate a deskew function to eliminate the skew. According to various embodiments, the timing information from the deskew device includes deskew information, which resolves the skew introduced by the deskew device itself during the deskew calibration of the probes. Thus, the test instrument is able to perform a more accurate deskew calibration compared to conventional deskew calibration techniques that do not account for the skew introduced by conventional deskew equipment.

[0064] Figure 1 is a simplified block diagram of a deskew device with self-calibration capabilities, according to a representative embodiment.

[0065] refer to Figure 1The deskew device 100 includes a first deskew probe point 110 and a second deskew probe point 120 configured to contact a first probe 115 and a second probe 125, respectively. The first probe 115 can be connected to a first channel of a test instrument 160, and the second probe 125 can be connected to a second channel of the test instrument 160. The test instrument 160 can be implemented as any type of test instrument compatible with the first probe 115 and the second probe 125, such as, for example, an oscilloscope, a network analyzer, or a power analyzer. The deskew device 100 also includes an integrated signal generation circuit 130, a signal conditioning circuit 140, and a processing unit 150.

[0066] The test instrument 160 is configured to perform a deskew calibration on the first probe 115 and the second probe 125, which includes accounting for the skew introduced by the deskew device 100. This deskew calibration enables the test instrument 160 to accurately deskew the signals passing through the first probe 115 and the second probe 125 during subsequent testing of the DUT (not shown). For illustrative purposes, although the first probe 115 may be a voltage probe and the second probe 125 may be a current probe, the deskew device 100 can accommodate other types and combinations of probes without departing from the scope of the present teachings. For example, both the first probe 115 and the second probe 125 may be voltage probes, or both the first probe 115 and the second probe 125 may be current probes.

[0067] The first deskew detection point 110 is connected to a first analog-to-digital converter (ADC) 118, while the second deskew detection point 120 is connected to a second ADC 128 of the deskew device 100. The first ADC 118 digitizes the calibration signal sampled at the first deskew detection point 110 to provide a first digitized calibration signal, while the second ADC 128 digitizes the calibration signal sampled at the second deskew detection point 120 to provide a second digitized calibration signal. The first ADC 118 and the second ADC 128 are shown collocated with the first deskew detection point 110 and the second deskew detection point 120, respectively, so that the timing of the calibration signal arriving at the first ADC 118 is substantially the same as the timing of the calibration signal arriving at the first deskew detection point 110, and the timing of the calibration signal arriving at the second ADC 128 is substantially the same as the timing of the calibration signal arriving at the second deskew detection point 120. Although the first ADC 118 and the second ADC 128 do not need to be collocated with the corresponding first and second deskew detection points 110 and 120, the closer they are to the first and second deskew detection points 110 and 120, respectively, the more accurate the deskew will be. The deskew device 100 may also include a synchronization clock (not shown) configured to provide synchronization between the signal generation circuit 130 and each of the first and second ADCs 118 and 128.

[0068] First ADC 118 and second ADC 128 provide the timing for digitizing the calibration signal, thereby enabling deskew device 100 to automatically self-calibrate, as discussed below with reference to processing unit 150. Generally, self-calibration eliminates the inherent skew between the two physical locations of first deskew probe point 110 and second deskew probe point 120, thereby making the final deskew calibration performed by test instrument 160 more accurate. Furthermore, self-calibration allows for a wide range of variations in the physical locations of first deskew probe point 110 and second deskew probe point 120, thereby eliminating the requirement in conventional deskew devices that the deskew probe points must be in close proximity. Thus, self-calibration provides deskew device 100 with the ability to know when the calibration signal arrives at first deskew probe point 110 and second deskew probe point 120 and automatically eliminate inherent skew errors in deskew device 100.

[0069] In one embodiment, one or both of the first deskew probe point 110 and the second deskew probe point 120 are modular in that they are removably connected to the base of the deskew device 100, as indicated by the first probe point module 101 and the second probe point module 102. The first probe point module 101, the second probe point module 102, and the base are indicated by dashed lines to the extent that they are optional. The first probe point module 101 and the second probe point module 102 are removably connected to the base using a first connector and a second connector (not shown), respectively. For example, particularly suitable for probes that require adequate deskewing of large amplitude signals, the first and second connectors can be high-quality RF connectors, such as, for example, a Subminiature Version A (SMA) connector, a Micro Coaxial (MCX) connector, or a Miniature Coaxial (MMCX) connector.

[0070] In one embodiment, in addition to the RF connector, the first probe point module 101 and the second probe point 102 may also include a digital connector so that an auxiliary digital signal can be sent to the processing unit 150, thereby enabling automatic detection and configuration of the first probe point module 101 and the second probe point module 102. In addition, the processing unit 150 can be programmed to identify the type of module and can pass this information to the test instrument 160. The identification of the module type can be performed, for example, by using resistor values and a lookup table and / or using the auxiliary digital signal.

[0071] First probe point module 101 and second probe point module 102 can have different physical dimensions and / or can include first deskew probe points 110 and second deskew probe points 120 having different physical dimensions and form factors to accommodate probes of different types, bandwidths, and / or sizes that can be connected to test instrument 160. That is, one or both of first probe point module 101 and second probe point 102 can be customized based on the geometry and RF characteristics of first probe 115 and second probe 125, respectively. Deskew device 100 supports arbitrary probe geometries, allowing first probe 115 and second probe 125 to be precisely and more conveniently assembled, resulting in more accurate and repeatable deskew measurements. Furthermore, this architecture allows the physical location of first deskew probe point 110 and second deskew probe point 120 to be decoupled from the circuitry. The self-calibration discussed above enables the use of first and second probe point modules 101, 102 of different sizes, since without self-calibration, first and second probe point modules 101, 102 would introduce excessive, uncorrectable errors due to skew. Furthermore, unlike conventional deskew devices, deskew device 100 can be used to measure high-frequency (e.g., frequencies greater than 100 MHz) current probes using corresponding first and second deskew probe points 110, 120. In this case, signal generation circuit 130 would be configured to generate a high-frequency calibration signal, and signal conditioning circuit 140 would be configured to support the additional bandwidth of the high-frequency calibration signal.

[0072] Furthermore, in the depicted embodiment, the first ADC 118 and the first deskew probe point 110 are located on the first probe point module 101, while the second ADC 128 and the second deskew probe point 120 are located on the second probe point module 102. This configuration places the first ADC 118 and the second ADC 128 in close proximity to the first deskew probe point 110 and the second deskew probe point 120, respectively, which in turn reduces or prevents the effects of additive skew based on the relative positions of the first ADC 118 and the second ADC 128. Furthermore, the first ADC 118 and the second ADC 128 can have various characteristics (e.g., sampling rates) that are specific to the complementary characteristics of the first deskew probe point 110 and the second deskew probe point 120. In alternative embodiments, the first ADC 118 and the second ADC 128 can be included in the base of the deskew device 100, rather than being modular.

[0073] Signal generation circuit 130 may be, for example, a signal generator, an arbitrary waveform generator (AWG), or other RF signal source whose output is controllable by a user and / or processing unit 150. Signal generation circuit 130 generates an electrical calibration signal that is applied to first deskew probe point 110 and second deskew probe point 120 via signal conditioning circuit 140. In one embodiment, the characteristics of the calibration signal generated by signal generation circuit 130 may be controlled by signal generation and / or signal conditioning inputs from test instrument 160.

[0074] When implemented as a signal generator, the signal generating circuit 130 generates, for example, a sine wave as a calibration signal. The user can control the basic characteristics of the sine wave, such as amplitude and frequency. When implemented as an AWG, the signal generating circuit 130 can generate a variety of calibration signals, thereby enabling the calibration signal characteristics (e.g., including amplitude, frequency, shape, bandwidth, and rise time) to be fully customized. This in turn enables very accurate deskew calibration for different probe types and different applications. For example, the signal generating circuit 130 can be controlled to generate a calibration signal with a low repetition rate, which is useful for rough deskew adjustment. In addition, the signal generating circuit 130 can be controlled to generate a square wave for a broadband signal, and to generate a sine wave with frequency variation across the entire bandwidth for improving overall accuracy. The AWG can also be controlled to generate a custom calibration signal that is similar or identical to the expected signal on the DUT. In general, the ability to adapt the calibration signal to different probes and / or different applications can optimize deskew performance.

[0075] The signal conditioning circuit 140 is configured to condition the calibration signal output by the signal generating circuit 130, for example, to provide a stronger or more ideal calibration signal to the first deskew detection point 110 and the second deskew detection point 120. For example, the signal conditioning circuit 140 may amplify the calibration signal, thereby eliminating the need for an inductor winding, and / or may pre-reduce the skew between the first deskew detection point 110 and the second deskew detection point 120, thereby minimizing the deskew required by the test instrument 160. The signal conditioning circuit 140 may include the following references: Figure 2One or more of the amplifier, low-pass filter, band-pass filter, delay line, and rise time converter discussed herein. The amplifier may be, for example, a variable gain amplifier (VGA) configured to increase the power of the calibration signal under the control of the processing unit 150 before applying the calibration signal to the first deskew detection point 110 and the second deskew detection point 120. The low-pass and band-pass filters are configured to pass only certain frequencies of the calibration signal. The delay line is connected between the signal generation circuit 130 and one of the first deskew detection point 110 and the second deskew detection point 120 to delay the calibration signal from reaching the one of the first deskew detection point 110 and the second deskew detection point 120. Thus, most of the time delay (skew) between the first deskew detection point 110 and the second deskew detection point 120 can be removed before being processed by the processing unit 150, as discussed below. The rise time converter is configured to adjust the pulse edge rise time of the calibration signal according to the bandwidth of the first probe 115 and / or the second probe 125. It is worth noting that to the extent that the first deskew probe point 110 and the second deskew probe point 120 are modular, the signal generation circuit 130 and / or the signal conditioning circuit 140 can be adjusted to account for form factor variations of the first probe point module 101 and the second probe point module 102.

[0076] The processing unit 150 may include one or more processor devices, such as a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a digital signal processor (DSP), a microprocessor, a computer processor, or a combination thereof, using any combination of hardware, software, firmware, hard-wired logic circuits, or combinations thereof. The processing unit 150 may include its own memory (e.g., volatile and / or non-volatile memory) for storing software instructions and / or computer-readable code that enables the various functions described herein to be performed. For example, the memory may store software instructions / computer-readable code that can be executed by the processing unit (e.g., a computer processor) to perform some or all aspects of the functions and methods described herein.

[0077] The memory may be implemented by, for example, any number, type, and combination of random access memory (RAM) and read-only memory (ROM), and may store various types of information, such as software algorithms and computer programs executable by the processing unit 150. The various types of ROM and RAM may include any number, type, and combination of computer-readable storage media, such as disk drives, electrically programmable read-only memories (EPROMs), electrically erasable programmable read-only memories (EEPROMs), registers, hard disks, removable disks, magnetic tape, compact disk read-only memories (CD-ROMs), digital versatile disks (DVDs), floppy disks, Blu-ray disks, universal serial bus (USB) drives, or other forms of storage media known in the art, which are tangible, non-transitory storage media (e.g., as compared to transient propagating signals).

[0078] The processing unit 150 may also include a user interface for providing information and data to a user and / or for receiving information and data from a user. That is, the user interface enables a user to input data and control or manipulate various aspects of the deskew device 100 (e.g., the signal generation circuit 130, the signal conditioning circuit 140, and / or the processing unit 150), and also enables one or more processor devices to indicate the effects of the user's control or manipulation. The user interface may provide information and data to the user via a display, which may include a graphical user interface. The user interface may receive information and data from the user, for example, via one or more of a keyboard, a mouse, a trackball, a joystick, a touchpad, and a touch screen.

[0079] Processing unit 150 is programmed to determine the inherent skew of deskew device 100 between first deskew probe point 110 and second deskew probe point 120 caused by the physical separation. Processing unit 150 provides deskew information regarding the skew determination to test instrument 160. Test instrument 160 then de-skews first probe 115 and second probe 125 using one of well-known deskew algorithms and uses the deskew information provided by deskew device 100 to adjust the deskew calibration to compensate for the inherent skew between first deskew probe point 110 and second deskew probe point 120. For example, assuming that second deskew probe point 120 is determined to lag behind first deskew probe point 110 by 1 nanosecond (ns), processing unit 150 communicates this determination to test instrument 160 as deskew information. When performing deskew calibration on first probe 115 and second probe 125 , test instrument 160 refers to the deskew information and, based on the deskew information, adds another 1 ns to the overall skew of first probe 115 , thereby accounting for inherent skew in deskew apparatus 100 .

[0080] Processing unit 150 can also be programmed to adjust parameters of signal generation circuit 130 and / or signal conditioning circuit 140 in response to the determined inherent skew of deskew device 100 to reduce or eliminate skew between first deskew detection point 110 and second deskew detection point 120. In this case, processing unit 150, first ADC 118, and second ADC 128 effectively form a feedback loop for reducing or eliminating inherent skew. That is, processing unit 150 receives first and second digital calibration signals and corresponding timing information from first ADC 118 and second ADC 128, and determines the skew between the first and second digital calibration signals by comparing the timing between first deskew detection point 110 and second deskew detection point 120. In response to this feedback, processing unit 150 can send control signals to signal generation circuit 130 and / or signal conditioning circuit 140 to adjust the corresponding parameters to reduce or eliminate skew.

[0081] For example, assuming again that second deskew detection point 120 is determined to lag first deskew detection point 110 by 1 ns, processing unit 150 may adjust signal generation circuit 130 to generate the second calibration signal to be applied to second deskew detection point 120 1 ns before it generates the first calibration signal to be applied to first deskew detection point 110 (e.g., assuming signal generation circuit 130 includes two AWGs or signal generators). Consequently, the first and second calibration signals will arrive at first deskew detection point 110 and second deskew detection point 120 simultaneously. Alternatively, processing unit 150 may adjust a delay in one of the signal paths of signal conditioning circuit 140 to reduce the skew between first deskew detection point 110 and second deskew detection point 120. That is, processing unit 150 may adjust the delay line to first deskew detection point 110 to add a 1 ns delay, thereby causing the first and second calibration signals to arrive at first deskew detection point 110 and second deskew detection point 120 simultaneously.

[0082] To the extent that adjustments made by signal generation circuitry 130 and / or signal conditioning circuitry 140 can remove inherent skew from deskew device 100, deskew calibration need not be performed by test instrument 160. Thus, in this case, test instrument 160 does not require deskew information from processing unit 150 regarding deskew device 100 and can therefore use a conventional deskew algorithm (which does not inherently account for the inherent skew of deskew device 100) to deskew first probe 115 and second probe 125. This is useful when test instrument 160 does not support data communication with the deskew device. In one embodiment, both a feedback loop and test instrument 160 can be used to compensate for inherent skew, wherein the feedback loop substantially reduces the inherent skew and information about any remaining skew is provided to test instrument 160, which accounts for any remaining inherent skew when calibrating first probe 115 and second probe 125.

[0083] Although shown within deskew device 100, it should be understood that processing unit 150 and all or part of the processing performed by processing unit 150 can be included in test instrument 160 rather than deskew device 100 without departing from the scope of the present teachings. That is, processing unit 150 can be implemented by a processing unit within test instrument 160 itself, or one or more functions that processing unit 150 is programmed to perform can be performed by a processing unit within test instrument 160. In this case, deskew information provided to test instrument 160 by deskew device 100 via a digital connection includes first and second digital calibration signals provided by first ADC 118 and second ADC 128. Test instrument 160 then uses the first and second digitized calibration signals retrieved from the deskew information to determine the inherent skew of deskew device 100.

[0084] In various embodiments, in addition to or in lieu of the first deskew probe point 110 and the second deskew probe point 120 discussed above, one or more of the signal generation circuit 130, the signal conditioning circuit 140, and the processing unit 150 can be modular. For example, the modular signal generation circuit 130 can be modified to provide different types of calibration signals for different probes, such as calibration signals with higher speeds and / or frequencies. Furthermore, for example, all or a portion of the modular signal conditioning circuit 140 can be modified to provide higher amplitudes through different amplifiers.

[0085] Figure 2 is a simplified block diagram of a deskew device including self-calibration according to a representative embodiment, wherein the test equipment includes or otherwise has access to a plurality of signal generation circuits. Figure 2 The deskew device also includes a signal conditioning circuit, which can be provided in various combinations.

[0086] refer to Figure 2 , deskew device 200 includes a first deskew probe point 110 connected to a first ADC 118 and a second deskew probe point 120 connected to a second ADC 128. Optionally, as discussed above, first deskew probe point 110 and first ADC 118 may be included in first probe point module 101, while second deskew probe point 120 and second ADC 128 may be included in second probe point module 102. A first probe to be calibrated (e.g., first probe 115) contacts first deskew probe point 110, while a second probe to be calibrated (e.g., second probe 125) contacts second deskew probe point 110, wherein the first probe is connected to a first channel of a test instrument 160, while the second probe is connected to a second channel of the test instrument 160.

[0087] Deskew device 200 includes two integrated signal generating circuits, depicted as a first AWG 230 and a second AWG 232, which can be controlled by processing unit 150 to generate a first calibration signal and a second calibration signal, respectively. Each of first AWG 230 and second AWG 232 is capable of generating multiple types of calibration signals, thereby enabling full customization of calibration signal characteristics (e.g., including amplitude, frequency, shape, bandwidth, and rise time) as discussed above. Additionally, deskew device 200 includes a first signal input 233 and a second signal input 234, which can be used to connect deskew device 200 to external signal generating circuitry (not shown), such as a signal generator and / or additional AWGs. Switch 271 selectively connects one of first AWG 230 and first signal input 233, and switch 272 selectively connects one of second AWG 232 and second signal input 234. The positions of switches 271 and 272 can be controlled by processing unit 150, for example, automatically or by a user through interfacing with processing unit 150. In alternative embodiments, deskew device 200 can include only one of first AWG 230 and second AWG 232, or can include an additional integrated AWG or other type of signal generating circuit without departing from the scope of the present teachings. Furthermore, one or both of first AWG 230 and second AWG 232 can be replaced by a signal generator or other type of signal generating circuit. Additionally, in alternative embodiments, one or both of first signal input 233 and second signal input 234 can be eliminated, in which case the corresponding switches 271 and 272, respectively, are also eliminated.

[0088] The deskew device 200 also includes two sets of signal conditioning circuits, each of which can be implemented as the signal conditioning circuit 140 discussed above. The first signal conditioning circuit 240 includes any combination of a first VGA 241, a first delay line 242, a first filter 243, and a first rise time converter 244, while the second signal conditioning circuit 245 includes any combination of a second VGA 246, a second delay line 247, a second filter 248, and a second rise time converter 249. The first signal conditioning circuit can be selectively connected to the first AWG 230 (or the first signal input 233) via a switch 271 located between the first AWG 230 and the first VGA 241. Moreover, in the depicted embodiment, the second signal conditioning circuit can be selectively connected to the second AWG 232 (or the second signal input 234) via switches 272 and 273 located between the second AWG 232 and the second VGA 246, and can be further connected to the first AWG 230 (or the first signal input 233) via switches 271 and 273 between the first AWG 230 and the first VGA 241. That is, the inclusion of the additional switch 273 enables both the first signal conditioning circuit 240 and the second signal conditioning circuit 245 to be connected to the first AWG 230 (or the first signal input 233), so that one RF signal source can be used to provide the first calibration signal to both the first deskew detection point 110 and the second deskew detection point 120.

[0089] Deskew device 200 also includes a switch 274 that selectively connects second delay line 247, filter 248, and second rise time converter 249 to the output of first VGA 241, thereby bypassing second VGA 246. Switch 274 enables both first signal conditioning circuit 240 and a portion of second signal conditioning circuit 245 to be connected to first AWG 230 (or first signal input 233) and first VGA 241 after being connected to second VGA 246, enabling a single RF signal source and a single amplifier to provide a first calibration signal to first deskew detection point 110 and second deskew detection point 120. In alternative embodiments, deskew device 200 may not include switch 273 and / or switch 274 without departing from the scope of the present teachings. In this case, first AWG 230 (or first signal input 233) is dedicated to first signal conditioning circuit 240, while second AWG 232 (or second signal input 234) is dedicated to second signal conditioning circuit 245.

[0090] The first VGA 241 and the second VGA 246 can be individually controlled by the processing unit 150 to vary the amplification of the respective first and second calibration signals. As mentioned above, for example, the first VGA 241 and the second VGA 246 can amplify the current of the calibration signal, thereby eliminating the need for additional windings in the deskew device 200, which would otherwise be necessary to increase the current to a level sufficient to perform deskew measurement and calibration. The reduction in windings avoids unnecessary inductance that would otherwise interfere with the performance of the deskew device 200. Moreover, depending on the characteristics of the first probe 115 and the second probe 125, the first VGA 241 and the second VGA 246 can have different amplification requirements. For example, when the first probe 115 is a voltage probe and the second probe 125 is a current probe with high attenuation, the second VGA 246 is configured to provide a higher output current than the first VGA 241, thereby making the second VGA 246 more suitable for high attenuation. In an alternative embodiment, the first VGA 241 and the second VGA 246 may be implemented as amplifiers without variable gain, in which case the first and second calibration signals are amplified by a fixed amount.

[0091] The first delay line 242 and the second delay line 247 are configured to delay one or both of the first calibration signal and the second calibration signal applied to the first deskew detection point 110 and the second deskew detection point 120, respectively. The delays implemented by the first delay line 242 and the second delay line 247 can be fixed or can be controlled, for example, by the processing unit 150. Delaying one or both of the first and second calibration signals substantially aligns the first and second calibration signals in the time domain, which can reduce skew at the first deskew detection point 110 and the second deskew detection point 120, in addition to skew correction that can be performed through a feedback loop implemented using the processing unit 150.

[0092] The first filter 243 and the second filter 248 can be any type of filter that limits the frequency and / or bandwidth of the first and second calibration signals, respectively. When a single AWG (e.g., the first AWG 230) is used to generate both the first and second calibration signals, the first filter 243 and the second filter 248 are typically incorporated. For example, the first filter 243 and the second filter 248 can be low-pass filters that adjust the first and second calibration signals to within the bandwidth of the first probe 115 and the second probe 125, respectively. Alternatively, the first filter 243 and the second filter 248 can be band-pass filters that remove DC components and otherwise ensure that the first and second calibration signals are within the bandwidth of the first probe 115 and the second probe 125. The first filter 243 and the second filter 248 can be adjustable filters that can be controlled by the processing unit 150. For example, the cutoff frequency of the band-pass filter or low-pass filter can be adjusted in response to the type of probe used (e.g., the first probe 115 and the second probe 125).

[0093] The first rise time converter 244 and the second rise time converter 249 are configured to adjust the pulse edge rise time of the first and second calibration signals for the different bandwidths of the first probe 115 and the second probe 125. The first rise time converter 244 and the second rise time converter 249 are essentially low-pass filters with different frequency responses (as discussed above), which will be apparent to those skilled in the art. The first rise time converter 244 and the second rise time converter 249 can be controlled by the processing unit 150.

[0094] The conditioned first and second calibration signals are provided to the first deskew detection point 110 and the second deskew detection point 120, respectively, while the first probe 115 and the second probe 125 are in contact with the first deskew detection point 110 and the second deskew detection point 120. The first ADC 118 samples and digitizes the first calibration signal at the first deskew detection point 110 and provides the digitized first calibration signal to the processing unit 150, thereby forming a first feedback loop 251, for example, to control the first AWG 230 and the first signal conditioning circuit 240. The second ADC 128 samples and digitizes the second calibration signal at the second deskew detection point 120 and also provides the digitized second calibration signal to the processing unit 150, thereby forming a second feedback loop 252, for example, to control the second AWG 232 and the second signal conditioning circuit 245.

[0095] Figure 3FIG2 is a simplified flowchart of a deskew method for a deskew device with self-calibration functionality according to a representative embodiment. As discussed above, the deskew device includes at least two deskew detection points (e.g., first deskew detection point 110 and second deskew detection point 120) with corresponding ADCs (e.g., first ADC 118 and second ADC 128) for digitizing calibration signals received at the deskew detection points. The deskew device also includes a processing unit (e.g., processing unit 150) that performs the signal processing steps of the flowchart.

[0096] refer to Figure 3 In block S311, calibration signals are received at the deskew detection points when the probes to be calibrated are in contact with the deskew detection points. As discussed above, the deskew detection points can receive the same calibration signal from a single signal generating circuit or different calibration signals from separate signal generating circuits, at least one of which is integrated with the deskew device. In block S312, the calibration signals at the deskew detection points are sampled and digitized using ADCs.

[0097] In block S313, the processing unit receives the digitized calibration signal and timing information, and in block S314, determines the inherent skew of the deskew device. For example, the processing unit can receive the digitized calibration signal (samples) from the ADC and resolve the two digitized calibration signals in time. For example, assuming the calibration signal is a pulse, and a pulse at the second deskew detection point occurs 1 nanosecond after a corresponding pulse at the first deskew detection point, the processing unit can determine the skew between the first deskew point and the second deskew point by comparing the time difference between the pulses of the two digitized calibration signals. The timing difference may be due to, for example, physical separation of the deskew detection points from each other, from one or more signal generation circuits, and from the processing unit.

[0098] At block S315, one of more adjustments to be made to one or more components of the deskew device is determined to reduce or eliminate the determined inherent skew. The adjustment is implemented at block S316 in response to one or more control signals provided by the processing unit. For example, when a delay line of the signal conditioning circuit is included in one of the signal paths leading to the deskew detection point, the processing unit may determine that a certain amount of delay adjustment is required to compensate for the detected inherent skew. The delay adjustment may result in the calibration signal being received at the deskew detection point at substantially the same time, or, to the extent that skew is introduced after the deskew detection point, the delay adjustment may result in the calibration signal being received at the deskew detection point at a different time.

[0099] At the same time, in block S317, the determined inherent skew is provided to a test instrument (e.g., test instrument 160). The test instrument is configured to execute a known de-skew algorithm during calibration to de-skew the probe for subsequent testing. The test instrument can use the determined skew provided by the processing unit to compensate for any inherent skew of the de-skew device. In various embodiments, the method may include executing blocks S315, S316, and / or S317.

[0100] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

[0101] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude the inclusion of other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0102] Although representative embodiments are disclosed herein, those skilled in the art will appreciate that many variations are possible in light of the present teachings and still fall within the scope of the appended claims. Accordingly, the present invention is intended to be limited only by the scope of the appended claims.

Claims

1. A deskew apparatus for improving the accuracy of deskew calibration performed on a first probe and a second probe by a test instrument for measuring electrical parameters of a device under test (DUT), the deskew apparatus comprising: a first deskew detection point configured to receive a first calibration signal when in contact with the first probe; a second deskew detection point configured to receive a second calibration signal when in contact with the second probe; as well as A feedback loop for automatically self-calibrating the deskew device, the feedback loop comprising: a first analog-to-digital converter (ADC) configured to digitize the first calibration signal at the first deskew detection point to provide a first digitized calibration signal; a second ADC configured to digitize the second calibration signal at the second deskew detection point to provide a second digitized calibration signal; and a processing unit programmed to use the first and second digitized calibration signals to determine an inherent skew of the deskew device between the first and second deskew detection points, and to adjust timing of at least one of the first or second calibration signals.

2. The de-skew device according to claim 1, further comprising: At least one signal generating circuit is configured to generate the first and second calibration signals received by the first deskew detection point and the second deskew detection point. 3 . The deskew device of claim 1 , wherein the processing unit is further programmed to provide the determined intrinsic skew to the test instrument for deskew calibration of the first probe and the second probe.

4. The de-skew device according to claim 1 , further comprising: A signal conditioning circuit is connected to at least one of the first deskew detection point or the second deskew detection point and is configured to adjust the timing of at least one of the first calibration signal or the second calibration signal in response to a control signal from the processing unit.

5. The deskew device of claim 2 , wherein the at least one signal generating circuit comprises a first signal generating circuit and a second signal generating circuit, and wherein the first calibration signal is generated by the first signal generating circuit and the second calibration signal is generated by the second signal generating circuit.

6. The de-skew device according to claim 2, further comprising: At least one variable gain amplifier (VGA) is connected between the at least one signal generation circuit and the first deskew detection point and is configured to amplify at least one of the first calibration signal or the second calibration signal.

7. The deskew device of claim 4 , wherein the signal conditioning circuit comprises at least one delay circuit configured to delay at least one of the first calibration signal or the second calibration signal to adjust the timing of at least one of the first calibration signal or the second calibration signal in response to a control signal from the processing unit.

8. The deskew device of claim 4 , wherein the signal conditioning circuit comprises one or more of: at least one filter configured to adjust a bandwidth of at least one of the first calibration signal or the second calibration signal to correspond to a first bandwidth of the first probe or to adjust a second bandwidth of the second calibration signal to correspond to a second bandwidth of the second probe, respectively; and At least one rise-time converter configured to adjust a bandwidth of at least one of the first calibration signal or the second calibration signal.

9. The de-skew device according to claim 5, further comprising: A switch is configured to selectively connect one of the first signal generating circuit and the second signal generating circuit to the second deskew detection point while the first signal generating circuit remains connected to the first deskew detection point.

10. The deskew device of claim 2, wherein the at least one signal generating circuit comprises at least one arbitrary waveform generator (AWG).

11. The de-skew device according to claim 2, further comprising: A synchronization clock is configured to provide synchronization between the at least one signal generating circuit and each of the first and second ADCs.

12. The deskew apparatus of claim 1 , wherein each of the first deskew detection point and the second deskew detection point is modular such that the first deskew detection point and the second deskew detection point can be removed and replaced depending on the type and bandwidth of the first probe and the second probe, respectively.

13. The deskew device of claim 12, wherein the processing unit is further programmed to identify the modular first and second deskew detection points and automatically configure the identified modular first and second deskew detection points accordingly.

14. A deskew apparatus for improving the accuracy of deskew calibration performed on a first probe and a second probe by a test instrument for measuring electrical parameters of a device under test (DUT), the deskew apparatus comprising: base; a first modular deskew probing point removably connected to the base and configured to contact the first probe during the deskew calibration, the first modular deskew probing point customized to the geometry and radio frequency (RF) characteristics of the first probe; a second modular deskew probing point removably connected to the base and configured to contact the second probe during the deskew calibration, the second modular deskew probing point customized to the geometry and RF characteristics of the second probe; at least one signal generating circuit on the base, the signal generating circuit being configured to generate at least one calibration signal, the calibration signal being provided to the first modular deskew detection point and the second modular deskew detection point, respectively; a first analog-to-digital converter (ADC) configured to digitize the at least one calibration signal at the first modular deskew probe point when the first probe is in contact with the first modular deskew probe point to provide a first digitized calibration signal; a second ADC configured to digitize the at least one calibration signal at the second modular deskew probe point when the second probe is in contact with the second modular deskew probe point to provide a second digitized calibration signal; as well as A processing unit programmed to determine a skew between the first modular deskew detection point and the second modular deskew detection point using the first digitized calibration signal and the second digitized calibration signal.

15. The deskew device of claim 14, wherein the at least one signal generation circuit generates the at least one calibration signal in response to signal generation and signal conditioning inputs from the test instrument.

16. The deskew apparatus of claim 14, wherein the processing unit is further programmed to provide the determined skew to the test instrument for the deskew calibration performed by the test instrument on the first probe and the second probe.

17. The de-skewing device according to claim 14, further comprising: a signal conditioning circuit connected between the at least one signal generating circuit and at least one of the first modular deskew detection point and the second modular deskew detection point and configured to adjust the timing of the at least one calibration signal, Wherein the processing unit is further programmed to control the signal conditioning circuit to adjust the timing of the at least one calibration signal based on the determined skew.

18. A deskew apparatus for improving the accuracy of deskew calibration performed on a first probe and a second probe by a test instrument for measuring electrical parameters of a device under test (DUT), the deskew apparatus comprising: a first deskew detection point configured to receive a first calibration signal when in contact with the first probe; a second deskew detection point configured to receive a second calibration signal when in contact with the second probe; a first analog-to-digital converter (ADC) configured to digitize the first calibration signal at the first deskew detection point to provide a first digitized calibration signal; as well as a second ADC configured to digitize the second calibration signal at the second deskew detection point to provide a second digitized calibration signal, The deskew device provides deskew information to the test instrument for the deskew calibration of the first probe and the second probe, wherein the test instrument uses the deskew information to adjust the deskew calibration to compensate for an inherent deskew of the deskew device.

19. The de-skewing device according to claim 18, further comprising: a processing unit programmed to determine the intrinsic skew of the deskew device using the first and second digitized calibration signals, and to provide the deskew information including the determined intrinsic skew to the test instrument for deskew calibration of the first and second probes.

20. The deskew device of claim 18, wherein the deskew information comprises the first digitized calibration signal and the second digitized calibration signal, and the test instrument determines the inherent skew of the deskew device based on the deskew information using the first and second digitized calibration signals.

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