TEST, MEASUREMENT & ANALYSIS
Technological advances are helping digital oscilloscopes keep pace
with the demanding world of electronics R&D.
During the development of the tran- sistor, which launched the computer age, oscilloscopes were a key tool for engineers and scientists who needed to
understand the behavior of complex electronics. Now, computers are returning the favor
by revolutionizing how test and measurement
instrumentation, including oscilloscopes, is
constructed and how it performs. The software-defined digitizer, which can not only
perform the measurement tasks of an oscilloscope, it can be a frequency counter, ultrasonic
receiver or spectrum analyzer, hints at the
future direction of waveform measurement.
Factor in features like open-source software
and instantaneous upgrades through software
updates, and it’s not difficult to conjecture the
days of traditional benchtop oscilloscopes are
numbered. Not so fast. The standalone oscilloscope is still the instrument of choice for
intensive and reliable waveform analysis and
digital-signal processing. While the transition
to digital-signal instrumentation is nearly
complete, the development road for these
devices is still wide open. Several key advances
have transformed these instruments in areas
of performance, adaptability and accessibility.
These range from improvements in electronics architecture to the adoption of advanced
materials and software.
Rise of the digital microscope and
A year ago, Research and Markets predicted the
global digital oscilloscope market will experience market growth of nearly 20% through
2016. This growth represents more than just
a transition from older technologies. More
companies require sophisticated electronic
test equipment to eliminate errors or bugs,
and as digital oscilloscopes become more user
friendly in terms of the ability to test and store
electrical signals, more developers will harness
One of the more obvious trends in high-end digital oscilloscopes is the rise in frequency bandwidth handled by the instrument.
Most of the major oscilloscope vendors carry
instruments that offer 33 GHz or more of
bandwidth. In 2012, the 60-GHz threshold
was passed for commercial oscilloscopes, and
in 2013 instruments exceeding 90 or 100 GHz
have been demonstrated.
The maximum bandwidth, whether 20
MHz or 10 GHz, describes the highest frequency sine wave that can be digitized with
Delivering signal integrity to high-frequency electronics, however, is a major design
challenge for oscilloscope manufacturers. Flat
frequency response from direct current is difficult at frequencies of 63 GHz or more. When
designing its Infiniium 90000 oscilloscope
series, Agilent Technologies, Billerica, Mass.,
had to develop a new set of technologies,
called RealEdge, that preserved signal integrity
to the oscilloscope’s graticule.
The X-Series, introduced in 2011, incorporated several advances that replaced the three
key chips in the oscilloscopes front-end: the
pre-amplifier, sampler and trigger chips. By
elevating the capabilities of all three ( 32 GHz
for the pre-amplifier, 20 GHz for the trigger
and 80 GS/sec for the sampler), Agilent was
able to preserve the input electronic waveform at higher frequencies. The key to these
improvements was transistor speed, up to 200
GHz, made possible with the use of indium
phosphide in the chips, packaged using a new
These chips played a part in Agilent’s next
advance, the 2013 R&D 100 Award-winning
Q-Series oscilloscope. This 63-GHz update
to the 90000 Infiniium line also incorporates
RealEdge, which uses a hybrid filter bank to
accurately capture rise times as fast as 5 psec
and data rates up to 120 Gbit/sec. This permits
applications in gigabit Ethernet development.
Sample rates and visualization
Bandwidth alone does not dictate the most
appropriate digital oscilloscope for a given
application. The buyer must make a host of
considerations for specifications like sample
rate, sampling modes, memory, dynamic
range, resolution, and special capabilities, such
as multi-instrument synchronization.
Sample rate is one of the most important,
and plays a big part in determining how much
of an oscilloscope’s bandwidth offers useful
This rate, which is clocked to digitize the
incoming signal to either the digitizer or the
ADC in a digital oscilloscope, determines
how effectively an oscilloscope can accurately
reproduce time-domain signals.
One way to achieve a higher sampling rate
is to expand the bandwidth of the instrument’s
analog-to-digital converter (ADC). In 2012,
Teledyne LeCroy, Chestnut Ridge, N. Y.,
introduced a 12-bit ADC in its HDO4000 and
HDO6000 oscilloscopes, which offer bandwidths from 200 MHz to 1 GHz. The goal of a
higher acquisition rate for the ADC is a clean,
crisp waveform display. This allows a higher
sampling (up to 2. 5 GS/sec), deeper memory
(250 Mpt/sec) and lower noise.
The new ADCs were deployed as part of
Teledyne LeCroy’s High Definition Technology, which includes high signal-to-noise
amplifiers and low-noise system architecture
along with the new ADCs. The combination
of improvements is able to deliver a 16-fold
improvement in resolution compared to prior
oscilloscopes of similar bandwidth.
Rigol’s DS6104 Digital Oscilloscope uses
field-programmable gate array circuitry coupled
with sophisticate algorithms to allow better
acquisition and data capture rates. Image: Rigol
North America Inc.