阅读说明：本技术 自校准去扭斜设备 (Self-calibrating deskew device ) 是由 E·V·布鲁什 于 2020-08-27 设计创作，主要内容包括：一种去扭斜设备(100)包括：第一和第二去扭斜探测点(110和120),所述去扭斜探测点用于在去扭斜校准期间分别接触第一和第二探针(115和125)；信号发生电路(130),所述信号发生电路用于生成被提供给所述第一和第二去扭斜探测点(110和120)的校准信号；和反馈回路,所述反馈回路用于自动地自校准所述去扭斜设备(100)。(A deskewing apparatus (100) comprising: first and second deskew probe 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 which is provided to the first and second deskew detection points (110 and 120); and a feedback loop for automatically self-calibrating the deskewing apparatus (100).)

1. A deskewing apparatus (100) for improving the accuracy of deskewing calibrations performed on a first probe (115) and a second probe (125) by a test instrument (160) for measuring electrical parameters of a Device Under Test (DUT), the deskewing apparatus (100) comprising:

a first deskew detection point (110) configured to receive a first calibration signal upon contact with the first probe (115);

a second deskew detection point (110) configured to receive a second calibration signal upon contact with the second probe (125); and

a feedback loop for automatically self-calibrating the deskewing apparatus (100), the feedback loop comprising:

a first analog-to-digital converter (ADC) configured to digitize the first calibration signal at the first deskew detection point (110) to provide a first digitized calibration signal;

a second ADC (128) configured to digitize the second calibration signal at the second deskew detection point (110) to provide a second digitized calibration signal; and

a processing unit (150) programmed to determine an intrinsic skew of the deskew device (100) between the first deskew detection point and the second deskew detection point using the first and second digitized calibration signals and to adjust a timing of at least one of the first calibration signal or the second calibration signal.

2. The deskewing apparatus (100) of claim 1, further comprising:

at least one signal generation circuit (130) for generating the first and second calibration signals received by the first deskew detection point (110) and the second deskew detection point (110).

3. The deskewing apparatus (100) of claim 1, wherein the processing unit (150) is further programmed to provide the determined intrinsic skew to the test instrument (160) for the deskew calibration of the first probe (115) and the second probe (125).

4. The deskewing apparatus (100) of claim 1, further comprising:

a signal conditioning circuit (140) connected to at least one of the first or second deskew detection points (120) and 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 (150).

5. The deskewing apparatus (100) of claim 2, wherein the at least one signal generation circuit (130) comprises a first signal generation circuit (130) and a second signal generation circuit (130), and wherein the first calibration signal is generated by the first signal generation circuit (130) and the second calibration signal is generated by the second signal generation circuit (130).

6. The deskewing apparatus (100) of claim 2, further comprising:

at least one Variable Gain Amplifier (VGA) connected between the at least one signal generation circuit (130) and the first deskew detection point (110) and configured to amplify at least one of the first calibration signal or the second calibration signal.

7. The deskewing apparatus (100) of claim 4, wherein the signal conditioning circuit (140) 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 (150).

8. The deskewing apparatus (100) of claim 4, wherein the signal conditioning circuitry (140) comprises one or more of:

at least one filter (248) 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 (115) or adjust a second bandwidth of the second calibration signal to correspond to a second bandwidth of the second probe (125), 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 deskewing apparatus (100) of claim 5, further comprising:

a switch (271) configured to selectively connect one of the first signal generating circuit (130) and the second signal generating circuit (130) to the second deskew detection point (110), while the first signal generating circuit (130) remains connected to the first deskew detection point (110).

10. The deskewing apparatus (100) of claim 2, wherein the at least one signal generation circuit (130) comprises at least one Arbitrary Waveform Generator (AWG).

Background

A deskewing apparatus is a circuit that is connectable to signal probes, such as current and voltage probes, to cancel timing differences (skew) between signals provided by the signal probes, respectively. For example, skew may be a timing delay of a rising edge between an actual signal and an acquired signal, which may cause distortion and measurement inaccuracies due to internal circuitry of the signal probe. Skew may be caused by manufacturing, design, and/or architectural differences between signaling probes.

To obtain accurate measurements (such as power measurements), the probes (e.g., current probes and voltage probes) must be deskewed using deskewing equipment during calibration. Conventional deskewing equipment, such as the U1880A power measurement deskewing equipment available from Keysight Technologies, enables a user to double probe 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 the voltage and current simultaneously using simultaneously connected voltage and current probes. In this case, the deskewing apparatus does not use the same probe location (electrical length) for both the voltage and current probes, and does not provide a way to calibrate the inherent skew between the probe locations. Deskewing the probe is therefore important for timing sensitive applications such as power measurement. The accuracy of the power measurement depends to a large extent on the accuracy of the deskew between the voltage probe and the current probe.

Typically, conventional deskewing apparatus uses an electrical signal that can be detected by two probes. When generating signals on a deskewing apparatus, signal generation is limited and probes with different bandwidths and input levels are generally not adequately accommodated. Also, there are no parameters of the control signal, such as waveform and amplitude. For example, for a U1880A power measurement deskew device, the signal is generated by a 555 clock IC that produces a type of square wave (frequency and amplitude). It may be difficult to deskew probes that inherently have different bandwidths using one waveform type. In contrast, when the signal is generated outside of the deskewing device, the user may not know the type of signal produced and may not have the device to generate the appropriate signal. For example, the external signal generator may have sufficient bandwidth, but may output insufficient current.

In addition, conventional deskewing apparatus cannot generate sufficient current levels, and thus may include multiple windings to increase the effective current. The windings introduce inductance which may cause unnecessary phase shifts, making it more difficult for the output driver to maintain linearity.

Drawings

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

Fig. 1 is a simplified block diagram of a deskewing apparatus with self-calibration functionality in accordance with a representative embodiment.

Fig. 2 is a simplified block diagram of a deskewing apparatus with self-calibration functionality in accordance with a representative embodiment.

Fig. 3 is a simplified flow diagram of a deskewing method of a deskewing apparatus with self-calibration functionality according to a representative embodiment.

Detailed Description

The present invention includes the following embodiments:

1. a deskewing apparatus for improving the accuracy of deskew calibrations performed on a first probe and a second probe by a test instrument for measuring electrical parameters of a Device Under Test (DUT), the deskewing apparatus comprising:

a first deskew probe point configured to receive a first calibration signal upon contact with the first probe;

a second deskew probe point configured to receive a second calibration signal upon contact with the second probe; and

a feedback loop for automatically self-calibrating the deskewing apparatus, 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 probe point to provide a second digitized calibration signal; and

a processing unit programmed to determine an intrinsic skew of the deskew device between the first deskew probe point and the second deskew probe point using the first and second digitized calibration signals and to adjust a timing of at least one of the first calibration signal or the second calibration signal.

2. The deskewing apparatus of claim 1, further comprising:

at least one signal generation circuit for generating the first and second calibration signals received by the first deskew detection point and the second deskew detection point.

3. The deskewing apparatus of claim 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.

4. The deskewing apparatus of claim 1, further comprising:

a signal conditioning circuit connected to at least one of the first or second deskew detection points and 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.

5. The deskewing apparatus of claim 2, wherein the at least one signal generation circuit comprises a first signal generation circuit and a second signal generation circuit, and wherein the first calibration signal is generated by the first signal generation circuit and the second calibration signal is generated by the second signal generation circuit.

6. The deskewing apparatus of claim 2, further comprising:

at least one Variable Gain Amplifier (VGA) connected between the at least one signal generation circuit and the first deskew probe and configured to amplify at least one of the first calibration signal or the second calibration signal.

7. The deskewing apparatus of claim 4, wherein the signal conditioning circuitry 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.

8. The deskewing apparatus of claim 4, wherein the signal conditioning circuitry 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 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 deskewing apparatus of claim 5, further comprising:

a switch 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 deskewing apparatus of claim 2, wherein the at least one signal generation circuit comprises at least one Arbitrary Waveform Generator (AWG).

11. The deskewing apparatus of claim 2, further comprising:

a synchronization clock configured to provide synchronization between the at least one signal generation circuit and each of the first and second ADCs.

12. The deskewing apparatus of claim 1, wherein each of the first deskewing probe point and the second deskewing probe point is modular such that the first deskewing probe point and the second deskewing probe point can be removed and replaced according to the type and bandwidth of the first probe and the second probe, respectively.

13. The deskewing apparatus 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 deskewing apparatus for improving the accuracy of deskew calibrations performed on a first probe and a second probe by a test instrument for measuring electrical parameters of a Device Under Test (DUT), the deskewing apparatus comprising:

a base;

a first modular deskew probe point removably connected to the base and configured to contact the first probe during the deskew calibration, the first modular deskew probe point being customized according to geometry and Radio Frequency (RF) characteristics of the first probe;

a second modular deskew probe point removably connected to the base and configured to contact the second probe during the deskew calibration, the second modular deskew probe point being customized according to geometry and RF characteristics of the second probe;

at least one signal generation circuit on the base for respectively generating at least one calibration signal that is respectively provided to the first and second modular deskew detection points;

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; and

a processing unit programmed to determine 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 deskewing apparatus 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 deskewing 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 deskewing apparatus of claim 14, further comprising:

a signal conditioning circuit connected between the at least one signal generating circuit and at least one of the first and second modular deskew detection points and configured to adjust 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 deskewing apparatus for improving the accuracy of deskew calibrations performed on a first probe and a second probe by a test instrument for measuring electrical parameters of a Device Under Test (DUT), the deskewing apparatus comprising:

a first deskew probe point configured to receive a first calibration signal upon contact with the first probe;

a second deskew probe point configured to receive a second calibration signal upon 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; and

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

wherein the deskewing apparatus provides deskewing information to the test instrument for the deskewing calibration of the first probe and the second probe, wherein the test instrument uses the deskewing information to adjust the deskewing calibration to compensate for an inherent skew of the deskewing apparatus.

19. The deskewing apparatus of claim 18, further comprising:

a processing unit programmed to determine the inherent skew of the deskewing apparatus using the first and second digitized calibration signals and to provide the deskew information including the determined inherent skew to the test instrument for the deskew calibration of the first probe and the second probe.

20. The deskewing apparatus of claim 18, wherein the deskewing information comprises the first and second digitized calibration signals, and the test instrument determines the inherent skew of the deskewing apparatus from the deskewing information using the first and second digitized calibration signals.

In the following detailed description, for purposes of explanation and not limitation, example embodiments disclosing specific details are set forth in order to provide a more thorough understanding of an embodiment according to the present teachings. However, it will be apparent to one having ordinary skill in the art having had the benefit of the present disclosure that other embodiments according to the present teachings that depart from the specific details disclosed herein remain within the scope of the appended claims. In addition, well-known devices and methods are not described in detail herein in order to avoid obscuring the description of the example embodiments. Such methods and apparatus are clearly within the scope of the present teachings.

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

Unless otherwise specified, when a first element is said to be connected to a second element, this includes the case 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 includes only the case where the two elements are connected to each other without any intervening or intermediate device. Similarly, when a signal is referred to as being coupled to an element, this includes the case where one or more intermediate elements may be employed to couple the signal to the element. However, when a signal is said to be directly coupled to a component, this includes only the case where the signal is directly coupled to the component without any intervening or intermediate devices.

As used in this specification and the appended claims, the terms "a" and "an" and "the" include both singular and plural referents unless the context clearly dictates otherwise. Thus, for example, the case where "one device (a device)" includes one device and a plurality of devices. As used in the specification and the appended claims, the term "substantially" or "approximately" is intended to be within an acceptable limit or degree, except to the extent it is conventionally used. As used in the specification and the appended claims, and in addition to their ordinary meaning, the term "about" means within acceptable limits or amounts for those skilled in the art. For example, "about the same" means that one of ordinary skill in the art would consider the items to be the same after comparison.

Relational terms such as "above," "below," "top," "bottom," and the like may be used to describe the relationship between various elements as illustrated in the figures. These relational terms are intended to encompass different orientations of the elements thereof in addition to the orientation depicted in the figures. For example, if the apparatus (e.g., signal measurement device) depicted in the drawings is inverted with respect to the view in the drawings, an element described as "above" another element, for example, will now be below that element. Similarly, if the device were rotated 90 ° relative to the views in the drawings, an element described as "above" or "below" another element would now be "adjacent" the other element; where "adjacent" means adjoining another element or having one or more layers, one or more materials, structures, etc. between the elements.

Generally, a test instrument (e.g., an oscilloscope) may 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 deskew calibration on the probes before the probes are used to measure the DUT. Deskew calibration accounts for timing differences (deskewing) between signals respectively provided by the probes, so that subsequent measurements by the probes on the DUT are aligned in time (deskew). For deskew calibration, according to various embodiments, a test instrument is connected to a deskew device while probes are placed in contact with corresponding deskew probe points on the deskew device. The calibration signal generated by the integrated signal generating circuit of the deskewing apparatus is applied to the probe point. The test instrument receives signals from the probes and timing information from the deskewing apparatus that enables the test instrument to determine skew between the probes and calculate a deskew function to eliminate the skew. According to various embodiments, the timing information from the deskewing apparatus includes deskewing information that accounts for the skew introduced by the deskewing apparatus itself during deskewing calibration of the probe. Thus, the test instrument is able to perform more accurate deskew calibration than conventional deskew calibration techniques that do not account for the skew introduced by conventional deskew devices.

Fig. 1 is a simplified block diagram of a deskewing apparatus with self-calibration functionality in accordance with a representative embodiment.

Referring to fig. 1, deskewing apparatus 100 includes first and second deskewing probe points 110 and 120 configured to contact first and second probes 115 and 125, respectively. The first probe 115 may be connected to a first channel of the test instrument 160 and the second probe 125 may be connected to a second channel of the test instrument 160. The test instrument 160 may 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. Deskewing apparatus 100 also includes integrated signal generation circuit 130, signal conditioning circuit 140, and processing unit 150.

The test instrument 160 is configured to perform deskew calibration on the first probe 115 and the second probe 125, which includes accounting for skew introduced by the deskew device 100. This deskew calibration enables test instrument 160 to accurately deskew signals passing through first probe 115 and second probe 125 during subsequent testing (not shown) of the DUT. For purposes of illustration, although the first probe 115 may be a voltage probe and the second probe 125 may be a current probe, the deskewing apparatus 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.

The first deskew detection point 110 is connected to a first analog-to-digital converter (ADC)118 and 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, such 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 and second ADCs 118, 128 need not be collocated with the respective first and second deskew detection points 110, 120, in general, the closer they are to the first and second deskew detection points 110, 120, respectively, the more accurate the deskew. Deskewing apparatus 100 may also include a synchronization clock (not shown) configured to provide synchronization between signal generation circuit 130 and each of first ADC 118 and second ADC 128.

First ADC 118 and second ADC 128 provide timing for the digitized calibration signal, thereby enabling deskewing apparatus 100 to automatically self-calibrate, as discussed below with reference to processing unit 150. In general, self-calibration eliminates inherent skew between the two physical locations of the first deskew probe point 110 and the second deskew probe point 120, thereby making the final deskew calibration performed by the test instrument 160 more accurate. Moreover, self-calibration allows the physical location of the first deskew probe point 110 and the second deskew probe point 120 to vary widely, thereby eliminating the need for deskew probe points to be very close together in conventional deskew devices. Self-calibration thus provides the deskewing apparatus 100 with the ability to know when the calibration signal reaches the first deskewing probe point 110 and the second deskewing probe point 120 and automatically remove the deskewing error inherent to the deskewing apparatus 100.

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 105 of the deskew apparatus 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 105 are indicated to some extent by dashed lines as being optional. The first and second probe point modules 101 and 102 are removably connected to the base 105 using first and second connectors (not shown), respectively. For example, particularly suitable for probes requiring proper deskewing of large amplitude signals, the first and second connectors may be high quality RF connectors, such as, for example, subminiature version a (sma) connectors, micro-coaxial (MCX) connectors, or subminiature coaxial (MMCX) connectors.

In one embodiment, the first and second probe point modules 101 and 102 may include digital connectors in addition to RF connectors so that auxiliary digital signals may be sent to the processing unit 150 to enable automatic detection and configuration of the first and second probe point modules 101 and 102. Additionally, the processing unit 150 may be programmed to identify the type of module and may communicate information to the test instrument 160. The identification of the module type may be performed, for example, by using resistor values and look-up tables and/or using auxiliary digital signals.

The first probe point module 101 and the second probe point module 102 may have different physical dimensions and/or may include first deskew probe points 110 and second deskew probe points 120 having different physical dimensions and form factors to accommodate different types, bandwidths, and/or sizes of probes that may be connected to the test instrument 160. That is, one or both of the first probe point module 101 and the second probe point 102 may be customized according to the geometry and RF characteristics of the first probe 115 and the second probe 125, respectively. Deskewing apparatus 100 supports arbitrary probe geometries, allowing first probe 115 and second probe 125 to be assembled precisely and more conveniently, resulting in more accurate and repeatable deskew measurements. Furthermore, the architecture allows the physical location of the first deskew probe point 110 and the second deskew probe point 120 to be decoupled from the circuitry. The self-calibration discussed above enables the use of different sizes of the first and second probe point modules 101, 102 because if the self-calibration were not performed, the first and second probe point modules 101, 102 would introduce excessive, uncorrectable errors due to skew. Also, unlike conventional deskewing apparatus, deskewing apparatus 100 can be used to measure high frequency (e.g., frequencies greater than 100 MHz) current probes using corresponding first deskewing probe points 110 or second deskewing probe points 120. In this case, the signal generation circuit 130 would be configured to generate the high frequency calibration signal and the signal conditioning circuit 140 would be configured to support the additional bandwidth of the high frequency calibration signal.

Also, in the depicted embodiment, the first ADC 118 and the first deskew detection point 110 are on the first detection point module 101, and the second ADC 128 and the second deskew detection point 120 are on the second detection point module 102. This configuration brings the first ADC 118 and the second ADC 128 in close proximity to the first deskew detection point 110 and the second deskew detection point 120, respectively, which in turn reduces or prevents the effects of additional skew based on the relative positions of the first ADC 118 and the second ADC 128. Additionally, the first ADC 118 and the second ADC 128 may have various characteristics (e.g., sampling rates) that are specific to complementary characteristics of the first deskew detection point 110 and the second deskew detection point 120. In alternative embodiments, rather than being modular, the first ADC 118 and the second ADC 128 may be included in the base 105 of the deskewing apparatus 100.

The signal generation circuit 130 may be, for example, a signal generator, an Arbitrary Waveform Generator (AWG), or other RF signal source whose output may be controlled by a user and/or the processing unit 150. The signal generation circuit 130 generates electrical calibration signals that are applied to the first deskew detection point 110 and the second deskew detection point 120 by the signal conditioning circuit 140. In one embodiment, the characteristics of the calibration signal generated by the signal generation circuit 130 may be controlled by signal generation and/or signal conditioning inputs from the test instrument 160.

When implemented as a signal generator, the signal generation circuit 130 generates, for example, a sine wave as a calibration signal. The user is able to control the fundamental characteristics of the sine wave, such as amplitude and frequency. When implemented as an AWG, the signal generation circuit 130 can generate a wide variety of calibration signals, thereby enabling adequate customization of calibration signal characteristics (including, for example, amplitude, frequency, shape, bandwidth, and rise time). This in turn enables very accurate deskew calibration for different probe types and different applications. For example, the signal generation circuit 130 may be controlled to generate a calibration signal with a low repetition rate, which is useful for coarse deskew adjustments. Further, the signal generation circuit 130 may be controlled to generate a square wave for a wideband signal and to generate a sine wave that varies in frequency across the bandwidth for improved overall accuracy. The AWG may also be controlled to generate custom calibration signals that are similar or identical to the expected signals on the DUT. In general, the ability to adapt the calibration signal to different probes and/or different applications can optimize deskewing performance.

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 desirable 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 inductive windings, and/or may pre-reduce the skew between the first deskew probe point 110 and the second deskew probe point 120, thereby minimizing deskewing to be performed by the test instrument 160. The signal conditioning circuit 140 may include one or more of the amplifiers, low pass filters, band pass filters, delay lines, and rise time converters discussed below with reference to fig. 2. 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 probe point 110 and the second deskew probe point 120. The low pass and band pass filters are configured to pass only calibration signals of certain frequencies. A 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 in order to delay the arrival of the calibration signal at 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 may be removed prior to processing 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. Notably, to the extent that the first deskew detection point 110 and the second deskew detection point 120 are modular, the signal generation circuit 130 and/or the signal conditioning circuit 140 may be adjusted to account for form factor variations of the first detection point module 101 and the second detection point module 102.

Processing unit 150 may include one or more processor devices, such as Field Programmable Gate Arrays (FPGAs), Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), microprocessors, computer processors, or any combinations thereof, using any combination of hardware, software, firmware, hard-wired logic circuits, or combinations thereof. 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 enable the various functions described herein to be performed. For example, the memory may store software instructions/computer-readable code executable by a processing unit (e.g., a computer processor) for performing some or all aspects of the functions and methods described herein.

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 that may be executed by processing unit 150. The various types of ROM and RAM can 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 transitory propagating signals).

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 aspects of deskewing apparatus 100 (e.g., signal generation circuitry 130, signal conditioning circuitry 140, and/or processing unit 150), and also enables the one or more processor devices to indicate the effects of the user control or manipulation. The user interface may provide information and data to a user via a display, which may include a graphical user interface. The user interface may receive information and data from a user, for example, via one or more of a keyboard, a mouse, a trackball, a joystick, a touchpad, and a touchscreen.

The processing unit 150 is programmed to determine the intrinsic skew of the deskew device 100 between the first deskew detection point 110 and the second deskew detection point 120 caused by the physical separation. Processing unit 150 provides deskew information regarding the deskew determination to test instrument 160. Test instrument 160 then performs deskew of first probe 115 and second probe 125 using one of the well-known deskew algorithms, and adjusts the deskew calibration using deskew information provided by deskew device 100 to compensate for the inherent skew between first deskew probe point 110 and second deskew probe point 120. For example, assuming that the second deskew probe point 120 is determined to lag the first deskew probe point 110 by 1 nanosecond (ns), the processing unit 150 communicates such determination to the test instrument 160 as deskew information. When deskewing calibration is performed on first probe 115 and second probe 125, test instrument 160 references the deskew information and adds another 1ns to the overall skew of first probe 115 based on the deskew information, thereby accounting for the inherent skew in deskewing apparatus 100.

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

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

To the extent that adjustments made by signal generation circuitry 130 and/or signal conditioning circuitry 140 can remove inherent skew from deskewing apparatus 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 thus may use conventional deskew algorithms (which would otherwise not account for the inherent deskew of deskew device 100) to perform deskew for first probe 115 and second probe 125. This is useful when test instrument 160 does not support data communication with a deskewing device. In one embodiment, both the feedback loop and test instrument 160 may be used to compensate for the inherent skew, where the feedback loop substantially reduces the inherent skew and information about any remaining skew is provided to test instrument 160, which accounts for the inherent skew remaining when calibrating first probe 115 and second probe 125.

Although shown in deskewing apparatus 100, it is understood that processing unit 150 and all or a portion of the processing performed by processing unit 150 may be included in test instrument 160, rather than deskewing apparatus 100, without departing from the scope of the present teachings. That is, processing unit 150 may be implemented by a processing unit within test instrument 160 itself, or one or more functions that processing unit 150 is programmed to perform may be performed by a processing unit within test instrument 160. In this case, the deskew information provided by deskewing apparatus 100 to test instrument 160 via a digital connection includes the first and second digital calibration signals provided by first and second ADCs 118 and 128. Test instrument 160 then determines the inherent skew of deskewing apparatus 100 using the first and second digitized calibration signals retrieved from the deskew information.

In various embodiments, one or more of the signal generation circuit 130, the signal conditioning circuit 140, and the processing unit 150 may be modular in addition to or in place of the first deskew detection point 110 and the second deskew detection point 120 discussed above. For example, the modular signal generation circuit 130 may be altered to provide different types of calibration signals to different probes, such as calibration signals having higher speeds and/or frequencies. Also, for example, all or a portion of modular signal conditioning circuit 140 may be altered to provide higher amplitudes through different amplifiers.

Fig. 2 is a simplified block diagram of a deskewing apparatus including self-calibration in which a test apparatus includes or otherwise accesses a plurality of signal generation circuits, according to a representative embodiment. The deskewing apparatus of fig. 2 also includes signal conditioning circuitry, which can be provided in various combinations.

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

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

Deskewing apparatus 200 also includes two sets of signal conditioning circuits, each of which may be implemented as signal conditioning circuits 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 may be selectively connected to the first AWG 230 (or the first signal input 233) through a switch 271 located between the first AWG 230 and the first VGA 241. Also, in the depicted embodiment, the second signal conditioning circuit may be selectively connected to the second AWG 232 (or second signal input 234) through switches 272 and 273 located between the second AWG 232 and the second VGA 246, and may be further connected to the first AWG 230 (or first signal input 233) through 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.

The deskewing apparatus 200 also includes a switch 274 that selectively connects the second delay line 247, the filter 248, and the second rise-time converter 249 to the output of the first VGA 241, thereby bypassing the second VGA 246. The switch 274 enables both the first signal conditioning circuit 240 and a portion of the second signal conditioning circuit 245 to be connected to the first AWG 230 (or the first signal input 233) and the first VGA 241 after being connected to the second VGA 246, such that the first calibration signal can be provided to the first deskew probe point 110 and the second deskew probe point 120 using one RF signal source and one amplifier. In alternative embodiments, deskewing apparatus 200 may not include switch 273 and/or switch 274 without departing from the scope of the present teachings, in which case first AWG 230 (or first signal input 233) is dedicated to first signal conditioning circuit 240 and second AWG 232 (or second signal input 234) is dedicated to second signal conditioning circuit 245.

The first VGA 241 and the second VGA 246 may 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 may amplify the current of the calibration signal, so that the added windings may be excluded from the deskewing device 200, which would otherwise be necessary to increase the current to a level sufficient to perform deskew measurements and calibrations. The reduction in windings avoids unnecessary inductance that would otherwise interfere with the performance of deskewing apparatus 200. Moreover, the first VGA 241 and the second VGA 246 may have different amplification requirements depending on the characteristics of the first probe 115 and the second probe 125. 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.

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

The first filter 243 and the second filter 248 may be any type of filter to limit the frequency and/or bandwidth of the first and second calibration signals, respectively. When one AWG (e.g., the first AWG 230) is used to generate both the first and second calibration signals, a first filter 243 and a second filter 248 are typically incorporated. For example, the first filter 243 and the second filter 248 may be low pass filters that condition the first and second calibration signals within the bandwidth of the first probe 115 and the second probe 125, respectively. Alternatively, the first filter 243 and the second filter 248 may be band pass filters that remove DC components and additionally 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 may be tunable filters controllable by the processing unit 150. For example, the cutoff frequency of the band-pass filter or the low-pass filter may be adjusted in response to the type of probe used (e.g., the first probe 115 and the second probe 125).

The first rise-time converter 244 and the second rise-time converter 249 are configured to adjust the pulse edge rise times of the first and second calibration signals for different bandwidths of the first probe 115 and the second probe 125. It will be apparent to one of ordinary skill in the art that the first rise-time converter 244 and the second rise-time converter 249 are essentially low-pass filters having different frequency responses (as discussed above). The first rise-time converter 244 and the second rise-time converter 249 may be controlled by the processing unit 150.

The adjusted first and second calibration signals are provided to the first deskew probe point 110 and the second deskew probe point 120, respectively, while the first probe 115 and the second probe 125 are in contact with the first deskew probe point 110 and the second deskew probe 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, thus forming a first feedback loop 251, e.g., 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, thus forming a second feedback loop 252, e.g., to control the second AWG 232 and the second signal conditioning circuit 245.

Fig. 3 is a simplified flow diagram of a deskewing method of a deskewing apparatus with self-calibration functionality according to a representative embodiment. As discussed above, the deskewing apparatus includes at least two deskewing detection points (e.g., first deskewing detection point 110 and second deskewing detection point 120) having corresponding ADCs (e.g., first ADC 118 and second ADC 128) for digitizing calibration signals received at the deskewing detection points. The deskewing apparatus also includes a processing unit (e.g., processing unit 150) that performs the signal processing steps of the flow chart.

Referring to fig. 3, calibration signals are received at deskew probing points while probes to be calibrated are respectively brought into contact with the deskew probing points in block S311. As discussed above, the deskew detection point may receive the same calibration signal from one signal generation circuit or different calibration signals from separate signal generation circuits, with at least one of the signal generation circuits being integrated with the deskew device. In block S312, the calibration signals at the deskew probe points are sampled and digitized, respectively, by the ADC.

In block S313, the processing unit receives the digitized calibration signal and the timing information and, in block S314, determines the inherent skew of the deskewing apparatus. For example, the processing unit may receive digitized calibration signals (samples) from the ADC and resolve both digitized calibration signals in time. For example, assuming that the calibration signal is a pulse and that the pulse at the second deskew detection point occurs 1ns after the 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. Timing differences may be due to, for example, physical separation of the deskew probe points from each other, from the deskew probe points and from one or more signal generation circuits and from the processing unit.

In block S315, one of more adjustments to be made to one or more components of the deskewing apparatus is determined in order to reduce or eliminate the determined inherent skew. In response to one or more control signals provided by the processing unit, the adjustment is implemented in block S316. 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 needed to compensate for the detected inherent skew. To the extent that delay adjustments result in substantially simultaneous reception of calibration signals at the deskew probe points, or introduction of skew after the deskew probe points, delay adjustments may result in reception of calibration signals at the deskew probe points at different times.

Meanwhile, in block S317, the determined intrinsic skew is provided to a test instrument (e.g., test instrument 160). The test instrument is configured to perform a known deskew algorithm during calibration to deskew the probes for subsequent testing. The test instrument is capable of compensating for any inherent skew of the deskewing apparatus using the determined skew provided by the processing unit. In various embodiments, the method may include performing blocks S315, S316, and/or S317.

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 present invention is not limited to the disclosed embodiments.

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 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.

Although representative embodiments are disclosed herein, those skilled in the art will appreciate that many variations in accordance with the present teachings are possible and remain within the scope of the appended claims. Accordingly, the invention is not to be restricted except in light of the attached claims.