Signal interpolation method and measurement instrument

Abstract

A signal interpolation method is described. The method includes: receiving an analog input signal; digitizing the analog input signal received, thereby obtaining a digitized input signal having samples; determining a crossing of the digitized input signal with respect to a threshold that was set; and interpolating a signal between at least two successive samples, wherein the signal interpolated has two signal portions each having a linear slope, and wherein one of the signal portions crosses the threshold. A measurement instrument is also described.

Claims

1. A signal interpolation method, the method comprising: receiving an analog input signal; digitizing the analog input signal received, thereby obtaining a digitized input signal having samples; determining a crossing of the digitized input signal with respect to a threshold that was set; and interpolating a signal between at least two successive samples, wherein the signal interpolated has two signal portions each having a linear slope, and wherein one of the signal portions crosses the threshold, wherein the linear slopes of the two signal portions are variable, thereby construing a variable crosspoint at which the signal interpolated crosses the threshold.

2. The signal interpolation method according to claim 1, wherein the two signal portions are linearly combined, thereby obtaining the signal interpolated.

3. The signal interpolation method according to claim 1, wherein a first signal portion crosses the threshold.

4. The signal interpolation method according to claim 3, wherein a crosspoint associated with the first signal portion follows the equation $c_1=\frac{T-S}{m*a_1},$ wherein T relates to the level of the threshold, S relates to the level of the first sample, m relates to the steepness, relates to the fraction of the first signal portion between the levels of the samples, and c.sub.1 is the location of the crosspoint with respect to the first sample, wherein a.sub.1 amounts between 0.5 and 1.

5. The signal interpolation method according to claim 1, wherein a second signal portion crosses the threshold.

6. The signal interpolation method according to claim 5, wherein a crosspoint associated with the second signal portion follows the equation $c_2=\frac{E-T}{m*a_2},$ wherein E relates to the level of the second sample, T relates to the level of the threshold, m relates to the steepness, relates to the fraction of the second signal portion between the levels of the samples, and c.sub.2 is the location of the crosspoint with respect to a center between both samples, wherein a.sub.2 amounts between 0.5 and 1.

7. The signal interpolation method according to claim 1, wherein the slopes of the two signal portions depend on each other.

8. The signal interpolation method according to claim 1, wherein the slopes depend on each other in that the steeper the slope of the first signal portion, the flatter the slope of the second signal portion or vice versa.

9. The signal interpolation method according to claim 1, wherein the slope of the first signal portion ranges between 0 and a steepness, and wherein the slope of the second signal portion is the steepness minus the slope of the first signal portion.

10. The signal interpolation method according to claim 1, wherein the linear slopes of the signal portions are different from each other.

11. A measurement instrument, comprising: a reception interface configured to receive an analog input signal; at least one input channel; a sampling circuit configured to digitize the analog input signal received by the reception interface and to output a digitized input signal having samples; and an analysis circuit configured to: determine crossing of the digitized input signal with respect to a threshold that was set; and interpolate a signal between at least two successive samples, wherein the signal interpolated has two signal portions each having a linear slope, and wherein one of the signal portions crosses the threshold, wherein the linear slopes of the signal portions are different from each other or wherein the slopes depend on each other in that the steeper the slope of the first signal portion, the flatter the slope of the second signal portion or vice versa.

12. A measurement instrument having one or more circuits configured to perform the signal interpolation method according to claim 1.

13. A signal interpolation method, the method comprising: receiving an analog input signal; digitizing the analog input signal received, thereby obtaining a digitized input signal having samples; determining a crossing of the digitized input signal with respect to a threshold that was set; and interpolating a signal between at least two successive samples, wherein the signal interpolated has two signal portions each having a linear slope, and wherein one of the signal portions crosses the threshold, wherein the linear slopes of the signal portions are different from each other or wherein the slopes depend on each other in that the steeper the slope of the first signal portion, the flatter the slope of the second signal portion or vice versa.

Description

DESCRIPTION OF THE DRAWINGS

(1) The foregoing aspects and many of the attendant advantages of the claimed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

(2) FIG. 1 schematically shows a measurement instrument according to an embodiment of the present disclosure;

(3) FIG. 2 schematically shows steps of a signal interpolation method according to an embodiment of the present disclosure;

(4) FIG. 3 schematically shows an example of an overview illustrating the variable slopes of the signal portions, yielding a variable crosspoint; and

(5) FIG. 4 schematically shows further examples of overviews illustrating the variable slopes of the signal portions, yielding a variable crosspoint for different models.

DETAILED DESCRIPTION

(6) The detailed description set forth below in connection with the appended drawings, where like numerals reference like elements, is intended as a description of various embodiments of the disclosed subject matter and is not intended to represent the only embodiments. Each embodiment described in this disclosure is provided merely as an example or illustration and should not be construed as preferred or advantageous over other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the claimed subject matter to the precise forms disclosed.

(7) In FIG. 1, a measurement instrument 10 is shown that has a housing 12 that encompasses several circuits used for processing a signal received. For receiving the respective signal to be processed, the measurement instrument 10 has a reception interface 14 that is located at a front end 16 of the measurement instrument 10.

(8) The reception interface 14 is connected with at least one input channel 18 that connects the reception interface 14 with a sampling circuit 20. The sampling circuit 20 digitizes the analog input signal that has been received via the reception interface 14 in order to obtain a digitized input signal that has several samples.

(9) The sampling circuit 20 is connected with an analysis circuit 22 that receives the digitized input signal outputted by the sampling circuit 20. The analysis circuit 22 is configured to determine a crossing of the digitized input signal with respect to a threshold that was set, for example a threshold level. Thus, the threshold that was set corresponds to a predetermined threshold.

(10) The analysis circuit 22 is also configured to interpolate a signal, namely a waveform, between at least two successive samples associated with a symbol transition area, namely two successive samples located prior and after the crossing determined previously. Accordingly, the at least two successive samples have different levels, for example lower and higher than the threshold level respectively.

(11) The analysis circuit 22 is further configured to generate an arbitrary interpolated signal that has two signal portions that merge into each other. The respective signal portions each have a linear slope, wherein at least one of the signal portions crosses the threshold that was set, namely the predetermined threshold.

(12) In the embodiment shown in FIGURE, the measurement instrument 10 further comprises a display 24. The display 24 is connected with the analysis circuit 22 for graphically illustrating information provided by the analysis circuit 22.

(13) In general, the respective method steps performed by the measurement instrument 10 are shown, for example, in FIG. 2, as the analog input signal is received and digitized, thereby obtaining the digitized input signal that is compared with a threshold in order to identify crosspoints of the digitized input signal with respect to the threshold.

(14) Afterwards, the analysis circuit 22 generates or interpolates the interpolated signal between two successive samples located prior and after an identified crossing/crosspoint of the digitized input signal with respect to the threshold. The respective signal interpolated, namely the waveform derived, has two signal portions each having a linear slope.

(15) The respective signal portions may each have a variable linear slope, thereby construing a variable crosspoint at which the signal interpolated crosses the threshold.

(16) This concept is shown in more detail in FIG. 3 for different slopes of the two signal portions that together form the signal interpolated.

(17) Generally, the signal interpolated can be generated such that the first signal portion or rather the second signal portion crosses the respective threshold, resulting in an early edge or rather a late edge. The early edge is located closer to the first of the two successive symbols located around the symbol transition area, whereas the late edge is located closer to the second of the two successive samples.

(18) As shown in FIG. 3, the respective slopes of the two signal portions depend on each other, as the steeper the slope of the first signal portion, the flatter the slope of the second signal portion. Consequently, the flatter the slope of the first signal portion, the steeper the slope of the second signal portion.

(19) In some embodiments, the slope of the first signal portion ranges between 0 and the steepness that is defined by the levels of the samples, e.g., level “−1” and level “1”, namely 1−(−1)=2, and the shortest distance, e.g. a sample index step, namely 2−1=1, resulting in a steepness of 2/1=2. Then, the slope of the second signal portion corresponds to the steepness minus the slope of the first signal portion, thereby ensuring that both slopes together correspond to the steepness.

(20) In some embodiments, the crosspoint associated with the first signal portion follows the equation

(21) $c_1=\frac{T-S}{m*a_1},$
wherein T relates to the level of the threshold, S relates to the level of the first sample, m relates to the steepness, a.sub.1 relates to the fraction of the first signal portion between the levels of the samples, and c.sub.1 is the location of the crosspoint with respect to the first sample, wherein a.sub.1 amounts between 0.5 and 1.

(22) In the embodiment shown in FIG. 3, the parameters are as follows: T=0, S=−1, m=2 (as already described above). Then, the fraction of the first signal portion between the levels of the samples can be altered between 0.5 and 1, resulting in a variable crosspoint c.sub.1, which may be between 0.5 and 1 with respect to the first sample having the sample index 1 such that the crosspoint c.sub.1 has a sample index between 1.5 and 2.

(23) Hence, the formula provided above can be rewritten as follows for the respective example provided:
−1+c.sub.1*2*a.sub.1=0,

(24) as level of the first sample amounts to “−1”, the steepness amounts to “2” and the level of the threshold amounts to “0”.

(25) Accordingly, the dependency of the fraction of the first signal portion between the levels of the samples and the variable crosspoint c.sub.1 can be expressed as follows for the example given:

(26) $a_1=\frac{1}{2*c_1}.$

(27) Further, the crosspoint associated with the second signal portion follows the equation

(28) $c_2=\frac{E-T}{m*a_2},$
wherein E relates to the level of the second sample, T relates to the level of the threshold, m relates to the steepness, a.sub.2 relates to the fraction of the second signal portion between the levels of the samples, and c.sub.2 is the location of the crosspoint with respect to a center between both samples, wherein a.sub.2 amounts between 0.5 and 1.

(29) In the embodiment shown in FIG. 3, the parameters are as follows: E=1, T=0, m=2 (as already described above). Then, the fraction of the second signal portion between the levels of the samples can be altered between 0.5 and 1, resulting in a variable crosspoint c.sub.2, which may be between 0 and 0.5 with respect to a center of both samples having the sample index 2 such that the crosspoint c.sub.2 has a sample index between 2 and 2.5.

(30) However, it is also possible that the steepness amounts to 1 and/or that the levels of the symbols are different, e.g., “level 0” and “level 1” such that the threshold level amounts to “level 0.5”, as schematically indicated in the overviews shown in FIG. 4.

(31) Generally, a floating point accuracy of the respective crosspoint can be ensured due to the linear combining of two possible slopes of the signal portions, which in turn results in an interpolated signal/waveform that can be used for estimating the different jitter components in a simple and cost-efficient manner.

(32) For instance, the interpolated signal comprises a synthesized time interval error (TIE) signal.

(33) Certain embodiments disclosed herein utilize circuitry (e.g., one or more circuits) in order to implement standards, protocols, methodologies or technologies disclosed herein, operably couple two or more components, generate information, process information, analyze information, generate signals, encode/decode signals, convert signals, transmit and/or receive signals, control other devices, etc. Circuitry of any type can be used. It will be appreciated that the term “information” can be use synonymously with the term “signals” in this paragraph. It will be further appreciated that the terms “circuitry,” “circuit,” “one or more circuits,” etc., can be used synonymously herein.

(34) In an embodiment, circuitry includes, among other things, one or more computing devices such as a processor (e.g., a microprocessor), a central processing unit (CPU), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a system on a chip (SoC), or the like, or any combinations thereof, and can include discrete digital or analog circuit elements or electronics, or combinations thereof.

(35) In an embodiment, circuitry includes hardware circuit implementations (e.g., implementations in analog circuitry, implementations in digital circuitry, and the like, and combinations thereof). In an embodiment, circuitry includes combinations of hardware circuits and computer program products having software or firmware instructions stored on one or more computer readable memories that work together to cause a device to perform one or more protocols, methodologies or technologies described herein. In an embodiment, circuitry includes circuits, such as, for example, microprocessors or portions of microprocessor, that require software, firmware, and the like for operation. In an embodiment, circuitry includes one or more processors, such as, for example, microprocessors, or portions thereof and accompanying software, firmware, hardware, and the like.

(36) In the foregoing description, specific details are set forth to provide a thorough understanding of representative embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that the embodiments disclosed herein may be practiced without embodying all of the specific details. In some instances, well-known process steps have not been described in detail in order not to unnecessarily obscure various aspects of the present disclosure. Further, it will be appreciated that embodiments of the present disclosure may employ any combination of features described herein.

(37) The present application may reference quantities and numbers. Unless specifically stated, such quantities and numbers are not to be considered restrictive, but exemplary of the possible quantities or numbers associated with the present application. Also in this regard, the present application may use the term “plurality” to reference a quantity or number. In this regard, the term “plurality” is meant to be any number that is more than one, for example, two, three, four, five, etc. The terms “about,” “approximately,” “near,” etc., mean plus or minus 5% of the stated value. For the purposes of the present disclosure, the phrase “at least one of A and B” is equivalent to “A and/or B” or vice versa, namely “A” alone, “B” alone or “A and B.”. Similarly, the phrase “at least one of A, B, and C,” for example, means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C), including all further possible permutations when greater than three elements are listed.

(38) Throughout this specification, terms of art may be used. These terms are to take on their ordinary meaning in the art from which they come, unless specifically defined herein or the context of their use would clearly suggest otherwise.

(39) The principles, representative embodiments, and modes of operation of the present disclosure have been described in the foregoing description. However, aspects of the present disclosure which are intended to be protected are not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. It will be appreciated that variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present disclosure. Accordingly, it is expressly intended that all such variations, changes, and equivalents fall within the spirit and scope of the present disclosure, as claimed.