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By Louis
Y. Ungar, Editor-In-Chief, The BestTest Newsletter
Based on an Interview with Agilent Product Manager
for
the
Design Validation Division,
Takuya
Furuta.
At the APEX conference
in
Los Angeles
last month, Test & Measurement
World gave out its Best in Test awards at a breakfast they hosted.
The winners in various categories had already been named, but
the excitement mounted when they announced the winning test product …drums,
drums, drums… for 2006, is …more
drums… the Agilent Infiniium DSO80000B Oscilloscope.
Had the nice young man, Jun Chie from Agilent sitting next to
me not been as ecstatic, I admit I might have been a bit disappointed.
Not because the product doesn’t deserve to be a winner but
because inherently an oscilloscope did not strike me as all that big
of a deal. So, with this
article in mind, I did a bit of research, interviewed Mr. Takuya
Furuta, Product Manager of the Design Validation Division at Agilent
Technologies, and compared it to other scopes in the market.
My conclusion is that oscilloscopes aren’t even in the same
species that they used to be. This
article will highlight the oscilloscope that the editors of Test &
Measurement World found to be the Best, and now you, the readers of
BestTest can judge for yourself.
I was directed to Mr.
Furuta as the person who could answer my questions.
I bluntly asked him right off the bat what made this product
qualify to be the Best in Test in 2006.
His response was thorough.
“
Superior
signal integrity and probing for you application, is our key product
value and the reason for winning the award, I believe.
Our highest signal integrity provides the repeatable, stable,
and the largest design margins to the high speed digital application
engineers. Our InfiniiMax
probe system provides the highest flexibility and accuracy among all
probing solutions, and finally, our industry’s only ‘bandwidth
upgrade’ feature provides unmatched investment protection by
covering not only today’s application supports but future
applications,” Mr. Furuta explained.
His answer sounded good, but I had to understand his
terminology better. Superior
signal integrity is supported by what Agilent considers the
industry’s lowest noise floor (131 mV
rms noise at 5 mV/div with 2 GHz model or 387 mV
rms noise at 5 mV/div with 12 GHz model) and lowest trigger jitter (at
500 fs rms specified and 250 fs rms typical).
When I asked why Agilent considers this model to have the
flattest frequency response, he pointed to the picture of Figure 1.
The low noise figures are partly attributed to Agilent’s CMOS ADC
architecture, a monolithic 20 GSa/s ADC.
It is credited with achieving the lowest sampling noise and
error, while also reducing the power consumption.
Since “high power usage is always the worst enemy for the
signal quality,” Mr. Furuta feels this is an important distinction
from other scopes in the industry.
Figure
1 – DSO80000B Frequency Response “Flatness”
I continued to probe
into the probing prowess (pun intended) of the DSO800000B.
It is the uniqueness of the InfiniiMax probe system that in Mr.
Furuta’s view sets a new standard in the probe market.
“First of all, the unique topology of interchangeable probe
amps and probe heads took the flexibility of probe usage to the next
level. Then, InfiniiMax
probe was the first to provide a solder-in probing solution, which
changed the dynamics of the probing completely,” argues Mr. Furuta.
He points to three ways that solder-in probing is implemented
as shown in Figure 2.
Figure
2 – InfiniiMax Probe Solder-in Probe Solutions
The DSO80000B covers a
frequency range between 2 GHz and 13 GHz in eight different
“series,” namely 2, 3, 4, 6, 8, 10, 12, and 13 GHz.
But this does not imply eight different oscilloscope models,
nor even eight different plug-in modules.
Rather, the customer can buy the scope with a preferred initial
bandwidth and then “add” more bandwidth through a process Agilent
calls “bandwidth upgradeability.”
What I found
impressive and shared with my interviewee, was that with the
oscilloscope performing jitter analysis, vector analysis and other
forms of waveform analysis, why call it “just” an
“oscilloscope?” I
guess Agilent had recognized the multifaceted function of this product
as well, since it has released two different types of DSO80000B series
recently. One is the
DSA80000B and the other is a VSA80000A.
DSA stands for “digital signal analyzer” and comes with a
pre-installed jitter analysis package and a software clock data
recovery package. Similarly,
the VSA80000A is installed with VSA software that enables the user to
choose its function between a scope and an ultra wide band vector
signal analyzer.
“All this complexity
must have its impact on the user,” I argued, “who will need a
considerable amount of time to properly learn to utilize this
instrument.” Mr. Furuta
disagrees. He said that as
a result of an Agilent/HP usability study in the last decade, Agilent
made a commitment to “ease of use.”
Agilent scopes use a Wizard format so that even a novice
engineer can start his/her analysis immediately.
This idea for ease of use was expanded on further for the
DSO80000B, with a “SW event finder triggering solution, called
InfiniiScan.”
With so much going on in test, why
should an oscilloscope merit being the Best in Test product in the 21st
Century? “The scope is
the fundamental tool of hardware engineers -it’s like their arms and
legs,” maintained this Agilent product manager passionately.
“The signal rates are getting faster and faster.
The whole industry now understands the need for the high signal
integrity. The scope is
the tool to analyze the signal integrity of the customers’ device
under test (DUT).”
Well, with my renewed
respect for “just” an oscilloscope, I found myself asking how far
scopes are likely to go. Just
as passionately, his answers were rolling out.
“I believe the scope which can address the essential
application space the most will win the heart of customers.
Also, investment protection will become even more important in
coming years. These scopes
are pretty expensive.” When
I asked how much, he pointed me to the Agilent
web page for the product line, but estimated that a fully loaded
highest bandwidth scope with a full probe configuration will likely
cost around US$200,000.
That’s more zeros
that there are in the DSO80000B product’s part number.
So I asked why so many 0s and almost instantly regretted the
question. So for those of
you who also want to know, here is the answer.
“DSO80000B series have 8 models, DSO80204B, DSO80304B,
DSO80404B, DSO80604B, DSO80804B, DSO81004B, DSO81204B, and DSO81304B.
DSO stands for Digital Storage Oscilloscope, 8 is the family
number for Infiniium series, next three digits indicate the bandwidth,
and 4 stands for a four channel scope.
B is there since our previous product was A model.”
At Agilent “it is
the marketing department that develops the definition of the product
by collaborating with the planning team.”
In the case of the DSO80000B it was Lon Hintze, the Product
Planner for High Performance Oscilloscopes in the Design Validation
Division who filled this role. He
is known as the “owner” for defining this scope.
I came away with
something profound Mr. Furuta said that made this digital,
testability, built-in self test (BIST), automatic test equipment (ATE)
oriented test engineer reconsider my thinking about oscilloscopes.
He said, “there is no other tool that can replace a scope.”
But it looks like it doesn’t limit a scope’s ability to
replace other test tools.
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By
Gregory
Davis, Market Development Manager, Tektronix, Inc.
In
the computing and communications industries, a degree of
standardization at the system, subsystem, and component levels is the
foundation that technology builds upon. Examples of standardization
range from LVDS signaling to the PCI Express serial bus designed to
replace current PCI technology. Standards pervade semiconductor
architectures, network protocols, and software components. And for
every standard, there must be some means of certification, some way to
prove that new products are in compliance
with
the standard.
While
each of these standards has its own unique qualities, most of them
share some fundamental characteristics, particularly in the area of
testing where jitter tests and eye diagram measurements are critical
factor when determining the quality of a signal. Both measurements
require statistical analysis of vast amounts of data. And both are key
elements of serial compliance testing.
Eye
diagrams have been the province of sampling oscilloscopes for years.
The sampling methodology provides accurate measurements with a very
low jitter noise factor (JNF). However, the requirement for a stable,
uninterrupted signal makes the sampling instrument impractical when
performing industry standard jitter measurements. More recently, some
real-time oscilloscopes have incorporated clock recovery circuits
based on a
PLL
technology. They perform eye diagram tests using random Equivalent
Time sampling. This technique is similar to the technique used in
sampling oscilloscopes and requires repetitive trigger events to build
an eye diagram and is susceptible to trigger jitter.
Fortunately,
some real-time oscilloscopes offer another means of eye rendering.
They rely on the single-trigger nature of real-time acquisition,
capturing a contiguous series of complete waveform cycles as they
occur after the trigger event. The embedded clock is recovered in
software after the acquisition, and the actual waveform edges are
“redrawn” using the recovered clock as the reference. Figure 1 is
an eye diagram derived using this methodology.
There
are several advantages to this approach. It provides a JNF as low as
700 fs on certain real-time oscilloscope models, making it the equal
of sampling oscilloscopes in terms of eye diagram precision.
And
because the clock is recovered using software DSP, clock recovery is
not limited to a single algorithm. The software-based package provides
an interface for changing the method by which the clock is recovered,
a valuable asset in a world of constantly evolving standards.
Real-time clock recovery and eye rendering also provides a means for
separating transition bits from non-transition bits and performing
separate mask testing operations on each type of bit as is required
for PCI Express applications. Figure 4 shows the separation of
Transition and Non-Transition bits from the eye diagram shown in
Figure 1.
It
is often necessary to analyze the data more deeply in the context of
the compliance measurements. For example, an eye diagram test may fail
because the embedded clock signal has too much modulation. The eye
diagram shows only violations to the mask, but a Time Interval Error (
TIE
) waveform trend or frequency spectrum can reveal further clues. Other
built-in real-time oscilloscope tools such as cursor measurements and
zoom controls can aid the in-depth analysis.
Eye
diagrams and jitter measurements in particular produce a volume of
data that would be difficult to manage without the help of automated
analysis tools. Figure 2 shows the user interface of an integrated
analysis package running on a real-time oscilloscope. Key measurements
such as rise and fall time can be set up with just one on-screen
“button.” The acquisition window presents the raw serial waveform.
But Figures 3 and 4 bring out the true benefit of the analysis
package. In Figure 3 the automated tools work on the waveform from
Figure 4 to produce an information-rich jitter trend analysis.
Figure 1. Real-time
eye diagram displayed with post-processing techniques.
Figure 2. The
user interface window of a serial analysis tool running on a
real-time oscilloscope.
Figure 3. A jitter trend analysis. The real-time waveform is
shown in blue,
and the jitter trend in red.
Figure 4. Serial
compliance summary screen showing the eye pattern
mandated by the standard as
well as quantitative results in tabular form.
Summary
Serial
buses, components, and transmission elements are here to stay, and are
destined to grow in importance as technology markets continue to
demand ever-accelerating data rates. Design and validation engineers
have a new and perhaps unfamiliar discipline—serial compliance
measurement—to learn even as they confront aggressive development
schedules and fast-changing standards. Thanks to innovative, automated
oscilloscopes and other tools, engineers can perform serial compliance
and validation tests with the same ease and accuracy as any other
measurement.
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