U.S. patent application number 12/056133 was filed with the patent office on 2008-10-30 for apparatus and method for sampling eye diagrams with window comparators.
Invention is credited to Andrei POSKATCHEEV, Thomas Eugene WASCHURA.
Application Number | 20080270053 12/056133 |
Document ID | / |
Family ID | 25542797 |
Filed Date | 2008-10-30 |
United States Patent
Application |
20080270053 |
Kind Code |
A1 |
WASCHURA; Thomas Eugene ; et
al. |
October 30, 2008 |
APPARATUS AND METHOD FOR SAMPLING EYE DIAGRAMS WITH WINDOW
COMPARATORS
Abstract
Apparatus and method for determining characteristics of a bit
stream of binary pulses. The apparatus has control apparatus for
defining a window comparator and logic apparatus for accumulating
and mapping numbers derived from a count of the number of times the
bit stream pulses fall at points inside the window comparator and
drawing an eye diagram defining characteristics of the bit
stream.
Inventors: |
WASCHURA; Thomas Eugene;
(Menlo Park, CA) ; POSKATCHEEV; Andrei; (Menlo
Park, CA) |
Correspondence
Address: |
DOUGKLAS A. CHAIKIN;PENINSULA IP GROUP
26150 BUCKS RUN
CORRAL DE TIERRA
CA
93908
US
|
Family ID: |
25542797 |
Appl. No.: |
12/056133 |
Filed: |
March 26, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09996342 |
Nov 21, 2001 |
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12056133 |
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11376485 |
Mar 14, 2006 |
7386405 |
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09996342 |
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Current U.S.
Class: |
702/65 |
Current CPC
Class: |
H04L 1/24 20130101 |
Class at
Publication: |
702/65 |
International
Class: |
G01R 13/00 20060101
G01R013/00 |
Claims
1. Apparatus for measuring characteristics of a bit stream of
binary pulses comprising control means for defining a window
comparator, and logic means for accumulating time and voltage
counts of the bit stream pulses falling within voltage thresholds
and points inside the window comparator during durations of the
binary pulse bit stream and drawing eye diagrams therefrom defining
the bit stream characteristics.
2. The apparatus for measuring characteristics of a bit stream of
binary pulses set forth in claim 1 wherein the control means
comprises: programmable means for establishing an array of columns
and rows defining the points for accumulating counts of pulse
voltage levels at time offsets during the duration times and for
creating a voltage threshold window that moves between a minimum
and maximum voltage with changes of rows of the array.
3. The apparatus for measuring characteristics of a bit stream of
binary pulses set forth in claim 2 wherein the logic means
comprises: logic circuitry for detecting voltage levels of the
binary pulses occurring at various time offsets of the bit stream
when the pulse voltage levels are within the voltage threshold
window at each row and column point of the array.
4. The apparatus for measuring characteristics of a bait stream of
binary pulses set forth in claim 3 wherein the logic means
comprises: first counter means for accumulating counts of the
detected binary pulse voltage levels at the time offsets during
each duration part of the binary pulse bit stream in a column and
row point of the array.
5. The apparatus for measuring characteristics of a bit stream of
binary pulses set forth in claim 4 wherein the logic means
comprises: second counter means for defining duration times of the
bit stream of binary pulses to accumulate the counts of the
detected binary pulse voltage levels falling within the voltage
threshold window at each point of the array.
6. The apparatus for measuring characteristics of a bit stream of
binary pulses set forth in claim 5 further comprising: apparatus
for displaying the array column and row points of accumulated time
and voltage counts as an eye diagram defining characteristics of
the bit stream of binary pulses.
7. Apparatus for measuring characteristics of a bit stream of
binary pulses comprising: control means for defining a window
comparator of an array of columns and rows defining points for
accumulating voltage counts of the binary pulse bit stream at time
offsets during defined durations of the binary pulse bit stream,
and apparatus for creating a voltage threshold window that moves
between minimum and a maximum voltage levels with each row of the
array and for accumulating counts of voltage levels of the binary
pulses occurring at the time offsets of the bit stream during a
duration time when the pulse voltage levels are within the voltage
threshold window at each row and column point of the array and
displaying the array column and row points of the accumulated time
and voltage counts as an eye diagram defining characteristics of
the bit stream of binary pulses.
8. Apparatus for measuring characteristics of a bit stream of
binary pulses comprising: first control means for defining a window
comparator of an array of columns and rows defining points for
accumulating event counts at time offsets during defined duration
times of the binary pulse bit stream, second control means for
creating a voltage threshold window that moves between a minimum
and maximum voltage threshold with each row of the array, logic
means for detecting voltage levels of the binary pulses occurring
at time offsets of the bit stream when the pulse voltage levels are
within the voltage threshold at each row and column point of the
array, first counter means for accumulating counts of the detected
binary pulse voltage levels at time offsets during each defined
duration time of the binary pulse bit stream in a column and row
point of the array, second counter means for determining duration
of periods of the binary bit stream in which to accumulate the
detected binary pulse voltage levels at each point of the array,
and monitor apparatus for displaying the array column and row
points of the accumulated event counts as an eye diagram defining
characteristics of the bit stream of binary pulses.
9. A method for determining characteristics of a bit stream of
binary pulses comprising the steps of defining a window comparator,
and accumulating various voltage counts of the bit stream pulses at
time offsets during defined duration times of the binary pulse bit
stream within voltage thresholds at points inside the window
comparator and drawing an eye diagram therefrom defining the bit
stream pulse characteristics.
10. The method for determining characteristics of the bit stream of
binary pulses set forth in claim 9 wherein the window comparator
defining step comprises the step of: establishing an array of
columns and rows defining the points for accumulating the event
counts at time offsets during the defined duration times.
11. The method for determining characteristics of the bit stream of
binary pulses set forth in claim 10 wherein the window comparator
defining step comprises the step of: creating a voltage threshold
window that moves with respect to a minimum and maximum voltage
threshold wherein the voltage threshold window changes with respect
to the rows of the array.
12. The method for determining characteristics of the bit stream of
binary pulses set forth in claim 11 wherein the event count
accumulating step comprises the step of: detecting voltage levels
of the binary pulses occurring at the time offsets of the bit
stream when the pulse voltage levels are within the voltage
threshold window at each row and column point of the array.
13. The method for determining characteristics of the bit stream of
binary pulses set forth in claim 12 wherein the event count
accumulating step comprises the step of: accumulating counts of the
detected binary pulse voltage levels at the time offsets during
each duration part of the binary pulse bit stream in a column and
row point of the array.
14. The method for determining characteristics of the bit stream of
binary pulses set forth in claim 13 wherein the event count
accumulating step comprises the step of: displaying the array
column and row points of accumulated event counts as an eye diagram
defining characteristics of the bit stream of binary pulses.
15. A method for determining characteristics of a bit stream of
binary pulses comprising the steps of: defining a window comparator
of an array of columns and rows defining points for accumulating
event counts of the binary pulse bit stream at time offsets during
defined durations of the binary pulse bit stream; creating a
voltage threshold window that moves between a minimum voltage and a
maximum voltage at each row of the array; and accumulating counts
of voltage levels of the binary pulses occurring at time offsets of
the bit stream during a duration time when the pulse voltage levels
are within the voltage threshold window at each row and column
point of the array and displaying the array column and row points
of the accumulated event counts as an eye diagram defining
characteristics of the bit stream of binary pulses.
16. A method for determining characteristics of a bit stream of
binary pulses comprising the steps of: defining a window comparator
of an array of columns and rows defining points for accumulating
event counts at time offsets during defined duration times of the
binary pulse bit stream; creating a voltage threshold window that
moves between defined voltage levels at each row of the array;
detecting voltage levels of the binary pulses occurring at the time
of the bit stream when the pulse voltage levels are within the
voltage threshold window at each row and column point of the array;
accumulating counts of the detected binary pulse voltage levels at
the time offsets in a column and row point of the array; and
displaying the array column and row points of the accumulated time
and voltage counts as an eye diagram defining characteristics of
the bit stream of binary pulses.
Description
FIELD OF THE INVENTION
[0001] This invention relates to apparatus and a method for
analyzing a waveform and in particular to apparatus and method for
creating eye diagrams of a high speed binary pulse coded bit stream
with window comparators.
BACKGROUND OF THE INVENTION
[0002] High-speed communication systems typically communicate with
each other by sending serial bit streams of data between
transmitters and receivers. These bit streams are usually binary
coded pulse signals represented by zeros and ones which may be
electrical voltages or optical signals derived from the signals
created by the transmitters and which pulse coded signals are
applied to a transmission facility connecting the transmitters with
the receivers. The receivers decode the received pulse code signal
data to obtain the information therein.
[0003] If a receiver receives pulse code signals that have been
deformed by errors occurring in the transmission facility or if the
receiver improperly decodes the received pulse coded signals, the
effect is that bit errors may occur in the communications thereby
resulting in wrong information being received by the receiver.
Thus, designers, engineers, installers and maintenance personal
need to evaluate the stream of pulse coded signals, oftentimes
called binary pulse bit streams, to monitor system performance and
to help in diagnosing system problems. It is typical to monitor the
quality of such bit streams by using a sampling oscilloscope.
[0004] In the monitoring operation, the binary pulse bit stream and
a trigger input in the form of a clock signal having a repetition
rate identical to the repetition rate of the binary pulses in the
bit stream and synchronous therewith are applied to the inputs of
the sampling oscilloscope. Samples of the voltage levels of the
binary pulses of the bit stream are taken at various time offsets
from the repetitive trigger input and are plotted as sample points
on the display of the oscilloscope. Voltage samples are
continuously taken of the bit stream and added to the sampling
oscilloscope in combination with the older sample points which
continue to exist on the sampling oscilloscope display. Over a
relatively short period of time, hundreds or thousands of the
sample points on the sampling oscilloscope display plot the
possible voltage distributions at each time offset from the trigger
input. By sweeping all time offsets in the range of interest, a
diagram appears on the sampling oscilloscope display which reveals
the quality or characteristics of the measured high-speed bit
stream. This type of diagram, oftentimes called an "eye" diagram,
is often used to view high speed binary pulse bit streams during
the various development, installation and maintenance phases of
high-speed communications systems.
[0005] A problem exists in using sampling oscilloscopes in this
manner to measure the quality of high-speed communication systems.
As the bit stream data rate increases, the bandwidth of the
sampling oscilloscopes needed to create the eye diagrams increases
proportionally thereby resulting in a higher cost. Another problem
arises in that as the cost of the sampling oscilloscopes increases
and due to the design issues of super high-speed systems, the
present sampling methods takes samples at a relatively few of all
the possible edges of the bit stream pulses thereby limiting the
current effective sampling rate to the range of one hundred to two
hundred thousand samples per second.
[0006] Another type of apparatus has been developed to create an
eye diagram for statistically measuring the quality of high speed
binary pulse bit streams. A problem exists with this apparatus in
that it requires that multiple histrograms be created and combined
to establish an eye diagram and that two histograms are required to
be created to make an eye diagram. Subtractions from neighboring
vertical elements in the first histrogram are required to make the
second histrogram which is what is used to make the eye diagram. If
the data count of the user signal passing through the device under
test changes drastically between the times the two vertical
elements are taken, noise can be added to the subtracted results
causing noise in the eye diagram. Accordingly, a need exists in the
art for apparatus and a method for creating a noise free single
histrogram actively determining an eye diagram for measuring the
characteristics of high-speed binary pulse bit streams used to
transfer information and data between communications systems.
SUMMARY OF THE INVENTION
[0007] It is an object of the invention to provide apparatus and a
method for measuring characteristics of a bit stream of binary
pulses with control apparatus arranged to define a window
comparator and with logic apparatus for accumulating event counts
of the bit stream pulses falling within points inside the window
comparator during durations of the binary pulse bit stream at
different time offsets and voltage window positions and drawing eye
diagrams therefrom defining the bit stream characteristics.
[0008] It is also an object of the invention to establish a window
comparator of an array of columns and rows defining points for
accumulating event counts of a binary pulse bit stream at times
during defined durations of the binary pulse bit stream.
[0009] It is also an object of the invention to create a voltage
threshold window that moves between a minimum voltage and a maximum
voltage with changes of rows of a column and row array and to
accumulate counts of voltage levels of the binary pulses occurring
within the voltage threshold and at time offsets of a binary bit
pulse stream during a duration time at each row and column point of
the array and to display the array column and row points of the
accumulated counts as an eye diagram defining characteristics of
the bit stream of binary pulses.
[0010] In a preferred embodiment of the invention, apparatus
defines a window comparator of an array of columns and rows
defining points for accumulating event counts at time offsets
during defined duration times of a binary pulse bit stream and
creates a voltage threshold window that that moves between a
minimum voltage and a maximum voltage with changes of the rows of
the array. Logic apparatus detects voltage levels of binary pulses
occurring at time offsets of the bit stream when the pulse voltage
levels are within the voltage threshold window at each row and
column point of the array. Counter apparatus accumulates counts of
the detected binary pulse voltage levels at the time offsets during
each defined duration time of the binary pulse bit stream in a
column and row point of the array wherein counter apparatus
determines durations of the bit stream of binary bit stream in
which to accumulate the detected binary pulse voltage levels at
each point of the array. Monitor apparatus displays the array
column and row points of the accumulated event counts as an eye
diagram defining characteristics of the bit stream of binary
pulses.
[0011] Also in accordance with the preferred embodiment of the
invention, a method for determining characteristics of a bit stream
of binary pulses defines a window comparator of an array of columns
and rows defining points for accumulating voltage counts at times
during defined duration time offsets of the binary pulse bit
stream. The method creates a voltage threshold window between a
minimum voltage threshold and a maximum voltage threshold wherein
the voltage threshold window changes with each change of the rows
of the array. Voltage levels of binary pulses occurring at time
offsets of the bit stream are detected when the pulse voltage
levels are within the voltage threshold window at each row and
column point of the array. Counts of the detected binary pulse
voltage levels are accumulated at the time offsets during each
defined duration time of the binary pulse bit stream in a column
and row point of the array and displayed as an eye diagram defining
characteristics of the bit stream of binary pulses.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For a further understanding of the objects and advantages of
the present invention, reference should be had to the following
detailed description, taken in conjunction with the accompanying
drawing figures, in which like parts are given like reference
numerals and wherein:
[0013] FIG. 1 is a block diagram of binary pulse coded waveform
measuring apparatus in accordance with the principles of the
invention connected to a communication system for generating eye
diagram measurements of a binary pulse coded waveform bit stream
transmitted from a system transmitter to a system receiver,
[0014] FIG. 2 is a block diagram of count logic circuitry set forth
in FIG. 1,
[0015] FIG. 3 is a diagram of a symbolic histogram formed by the
measurement of the binary pulse bit stream set forth in FIG. 1,
and
[0016] FIGS. 4, 5 and 6 is a flow chart of the method of operation
of the binary pulse coded waveform measuring apparatus set forth in
FIG. 1.
[0017] The logic component circuitry of the threshold logic
apparatus set forth in FIG. 2 of the drawing is performed by logic
circuitry and central processor units, the individual operation of
which are well known in the art and the details of which need not
be disclosed for an understanding of the invention. Typical
examples of these logic circuitry are described in numerous
textbooks. For example, such types of logic circuitry, among
others, are described by J. Millman and H, Taub in Pulse, Digital
and Switching Waveforms, 1965, McGraw-Hall, Inc., H. Alex
Romanowitz and Russell E. Puckett in Introduction to Electronics,
1968, John Wiley & Sons, Inc., E. J. Angelo, Jr. in Electronic
Circuits, Second Edition, 1958, McGraw Hill, Inc. and in The TTL
Data Book for Design Engineers, Second Edition, 1976, Texas
Instruments Incorporated.
DETAILED DESCRIPTION
[0018] Referring to FIG. 1 of the drawing, high speed communication
system 1 consists of a transmitter 10 interconnected by a
transmission facility 12 with a receiver 11. Information is
transmitted to receiver 11 by transmitter 10 in a binary coded
pulse format as a high speed binary pulse bit stream 13 applied to
the input of transmission facility 12. Transmission facility 12 may
be any one of a large number of high speed transmission facilities
such as printed circuit board traces, coaxial cables, optical
fibers, radio and satellite links or the like. In a typical
application, the binary pulses of input binary bit stream 13 may be
reconfigured by the characteristics of the transmission facility 12
and appear as the rounded binary coded pulse format shown as the
binary bit stream 14 received by receiver 11. The binary pulse
coded waveform measuring apparatus may be connected to transmission
facility 12 at either the output of transmitter 10, the input of
receiver 11, at various locations along transmission facility 12 or
at various locations within transmitter 10 and receiver 11 wherein
it is desired to measure the quality and characteristics of the
transmitted and received binary pulse coded bit streams 13 and 14.
In operation, control apparatus 3 controls the operation of count
logic 2 to generate an eye diagram representing the quality
characteristics of the measured the binary pulse coded bit streams
13 and 14 on display apparatus 4 which may be any one of a number
of well known display devices such as a computer, stand alone
monitors, plotters, various storage devices, work stations or the
like. The configuration of the eye diagram displayed on monitor 4
shows the characteristics of the measured binary pulse bit
stream.
[0019] In general, a binary pulse coded bit stream consists of a
series of succeeding "0" and "1" pulses wherein each "0" pulse is
transmitted at one voltage level and each "1" pulse is transmitted
at another voltage level. The specific sequence of the "0" and "1"
pulses define the information or data transmitted by transmitter 10
to receiver 11. The pulses have a repetition rate wherein each
pulse has a period of time, hereinafter referred to as the pulse
period, and follows a preceding pulse at the repetition rate
determined by the communication system clock. In an exemplary
embodiment of the invention, apparatus in accordance with the
invention for measuring the characteristics of the bit stream of
binary pulses 13, 14 has control apparatus 3 for defining a window
comparator. Control apparatus 3 may be a computer, processor, work
station, or the like, the details of which are well known, and
which is specifically programmed or configured to establish an
array, FIG. 3, of columns and rows defining the points for
accumulating event counts at time offsets during the defined
durations of the measured binary pulse bit stream. Data collected
from the measured waveform of the binary pulse bit stream is
accumulated at each column and row location, hereinafter called
points, for a defined duration of a part of the binary pulse bit
stream. The accumulated data is then drawn as an eye diagram, FIG.
1, on monitor 4 to define characteristics of the binary pulse bit
streams 13 and 14.
[0020] Control apparatus 3, FIG. 1, is programmed to create a
voltage threshold window that moves between a minimum voltage
V.sub.MIN and a maximum voltage V.sub.MAX with row changes of the
array and which has an incremental voltage .DELTA.V difference
equal to the value of (V.sub.MIN-V.sub.MAX) divided by the maximum
number of rows in the array. Count logic apparatus 2 detects
voltage levels of the binary pulses occurring at time offsets of
the bit stream when the pulse voltage levels are within the voltage
threshold window and accumulates the counts during the duration
times at each row and column point of the array. In particular,
control apparatus 3, FIG. 2, applies a value of voltage V+.DELTA.V,
200, to the plus input of comparator 202 and a value of voltage V,
201, to the minus input of comparator 203 to create a voltage
threshold window. The count logic apparatus 2 responds to a signal
occurring during the duration of a part of the binary pulse bit
stream by detecting the voltage level of a pulse at a time offset
and determines if the measured pulse voltage level is within the
voltage threshold window levels defined by the window comparator of
the array. When the measured pulse voltage level is below the
threshold voltage level V+.DELTA.V, comparator 202 operates to set
logic device 204. If the measured pulse voltage level is above the
threshold voltage level V, comparator 203 operates to set logic
device 203. The setting of logic devices 204 and 205 enable AND
gate 206 to indicate that the measured pulse level is within the
voltage threshold window between the value of V and V+.DELTA.V for
each column and row of the array. Logic counter 207 accumulates
counts of the detected binary pulse voltage levels within the
voltage threshold window at time offsets during each duration part
of the binary pulse bit stream in a column and row point of the
array.
[0021] Count logic 2 has a duration counter 210 that responds to a
repetitive trigger by counting the repetitive trigger up to a value
of duration.sub.MAX. The value of duration.sub.MAX is defined as
the duration time of the binary pulse bit stream during which
events of the pulse voltage count levels are accumulated within the
voltage threshold window at each column and row point of the array.
The value of duration.sub.MAX defines how much total time will be
required to gather enough event counts to complete the eye diagram.
Typically, the value of duration of duration.sub.MAX for each
column and row point may be the number of pulses themselves. When
the column and row point sample is to be taken or started, counters
207 and 210 are reset to their initial count value of zero. The
initial count for a particular array column and row point is
started by identifying a column 1 and row 1 and starting an event
count of the pulse voltage levels that are within the voltage
threshold window. A repetitive initialization starts each count of
the measurement of the pulse events by resetting logic devices
which then records pulse voltage levels within the voltage
threshold window voltage levels. Each valid count is accumulated by
logic counter 207 and recorded at the end of the duration period
determined by duration counter 210 in the array column 1 and row 1
point. The row count is advanced to row 2, the voltage threshold
window thresholds incremented by .DELTA.V, and the count sequence
repeated for a change of the voltage threshold window during the
duration time and recorded in array column 1 and row 2 point.
Although the count as herein described started at array column 1
and row 1 it is exemplarily only and it is to be understood that in
accordance with the invention, the count could be started at array
column 1 and row.sub.MAX point or at any random array column and
row point as long as all column and row point counts are completed.
The measuring apparatus thus accumulates event counts of the bit
stream pulses falling within points inside the voltage threshold
window comparator during durations of the binary pulse bit stream
and draws eye diagrams therefrom defining the bit stream
characteristics.
[0022] The method of operation, FIGS. 4, 5 and 6, defines the
window comparator and accumulates various event counts of the bit
stream pulses at time offsets during defined duration times of the
binary pulse bit stream at points inside the window comparator and
then draws an eye diagram therefrom defining the bit stream pulse
characteristics. In operation, the method, FIG. 4, sets the value
of duration.sub.MAX, step 300, wherein the duration.sub.MAX, is the
period in which it is desired to accumulate event counts at an
array column and row point. In accordance with embodiments of the
invention, the value of duration.sub.MAX, may be designed into
duration counter 210, FIG. 2, or duration counter 210 may be a type
of counter wherein a user may set a value of duration.sub.MAX into
the counter which will generate an output when the accumulated
count reaches the value that the user set into the counter 210.
[0023] The method continues to define the window comparator by
letting the initial value of the array column be zero, step 301,
and setting the value of the minimum and maximum voltage thresholds
V.sub.MIN and V.sub.MAX, step 302. The values of V.sub.MIN and
V.sub.MAX depend upon the type of binary pulse bit stream to be
measured and varies with the particular application. The size of
the array is established by setting the values of row.sub.MAN and
col.sub.MAX, step 304. Again the size of row.sub.MAN and
col.sub.MAX will depend upon the apparatus and the particular
application. Delay.sub.Max and delay.sub.MIN are set to the user's
requirement, step 305, and the value of .DELTA.V is set equal to
the value of (V.sub.MAX-V.sub.MIN) divided by the value of
row.sub.MAX, step 306. The value of .DELTA.delay is established as
equal to the value of (delay.sub.Max-delay.sub.MIN) divided by the
value of col.sub.Max, step 307, and the value of delay is set to
the value of delay.sub.MIN, to initialize it, step 308.
[0024] At this point the window comparator, FIG. 3, has been
defined by establishing an array of columns and rows defining the
points for accumulating events such as pulse voltage level counts
at times during the defined duration times. Although it is to be
understood that the array column and row points could be selected
randomly or started at column one and at the maximum row in
accordance with the invention, the present invention will start at
column one and row one. Thus, the value of V is set equal to
V.sub.MIN, step 309, the row initially set to zero, step 311, FIG.
5, and the column set to one, step 312, The method, step 313,
determines that the measurement sequence is complete, or done, step
314, if the column and row points have reached the values of
col.sub.Max, step 313 and row.sub.MAX, step 325, FIG. 6. If not,
the value of row is set to row plus one, step 315, FIG. 5.
[0025] The measurement for the specific array (col, row) point is
started, step 317, by initializing the accumulated data count of
counter 207, FIG. 2, to zero and initializing the duration count to
zero, step 318. At step 319, the logic apparatus, FIG. 2, detects
voltage levels of the binary pulses occurring at time offsets of
the bit stream when the pulse voltage levels are within the voltage
threshold window between V and V+.DELTA.V at each row and column
point of the array. If the detected pulse voltage level is greater
than the threshold level V and less than or equal to the threshold
value V+.DELTA.V, step 319, the accumulated data count of counter
207, FIG. 2, is incremented, step 320, and the value of duration
incremented, step 322. If the value of duration has not reached
duration.sub.MAX, step 323, the method waits for the next trigger,
step 321, and repeats steps 319, 320, 321, 322 and 323 until the
value of duration reaches duration.sub.MAX. When the value of
duration reaches duration.sub.MAX, the value of counter 207, FIG.
2, has recorded the number of times that the pulse voltage level of
the binary pulses of the measured bit stream have been detected as
being within the voltage threshold window during the total period
of the duration interval at the specified time offset.
[0026] When it is determined that the value of duration has reached
duration.sub.MAX, step 323, the array[row, col] point, step 324, is
set to the value of the data accumulated by counter 207, FIG. 2.
The voltage threshold window, step 316, is then advanced between
V.sub.MIN and V.sub.MAX by letting V equal V+.DELTA.V in
preparation for accumulating event counts for the next row of the
column. If the array row has not reached row.sub.MAX, step 325, the
value of row is increased by one, step 315, FIG. 5, and steps 316
through 324 repeated to accumulate the pulse level data for the
next row point of the column. If the value of the rows in a column
has reached row.sub.MAX, step 325, steps 309 through 325 are
repeated to accumulate data for each of the rows of the next
column. Thus, counts of the detected binary pulse voltage levels
within the voltage threshold window are accumulated at time offsets
during each duration part of the binary pulse bit stream in each
column and row point of the array. When count data has been
accumulated in the array row and column points, FIG. 3, the
histrogram of the array is displayed as column and row points of
accumulated event counts as an eye diagram defining characteristics
of the measured bit stream of binary pulses.
[0027] It is obvious from the foregoing that the facility, economy
and efficiently of binary pulse coded waveform measuring apparatus
has been improved by apparatus arranged to use a window comparator
to measure a high speed binary pulse bit stream and to generate a
single histrogram for creating an eye diagram showing the
characteristics and quality of the measured high speed binary pulse
bit stream.
[0028] While the foregoing detailed description has described an
embodiment of specific apparatus for measuring characteristics of a
bit stream of binary pulses, it is to be understood that the above
description is illustrative only and is not limiting of the
disclosed invention. Particularly other configurations are within
the scope and spirit of this invention. Thus, the invention is to
be limited only by the claims set forth below.
* * * * *