New sampling technique underpins 100-GHz-bandwidth scopes - Embedded.com

New sampling technique underpins 100-GHz-bandwidth scopes

World's Highest Performance Digital Oscilloscopes with 100 GHz Bandwidth Introduced by LeCroy Corporation

New Sampling Method Exclusive Coherent Interleaved Sampling Mode Allows WaveExpert 9000 and SDA 100G to Capture and Display Very Long Serial Data Waveforms Without External Pattern Trigger Jitter

Chestnut Ridge, NY—LeCroy Corporation introduces the WaveExpert 9000 and SDA 100G, the world's highest performance digital oscilloscopes that feature 100 GHz bandwidth and an exclusive coherent interleaved sampling mode that enables the capture and display of very long serial data waveforms without the need for an external pattern trigger. The WaveExpert 9000 and SDA 100G have an acquisition rate of 10M samples per second, which is a 100x improvement over existing instruments in this class. Additionally, the oscilloscopes can output a TDR pulse with a 20 ps incident rise time which is 50% faster than existing instruments, making them the instruments of choice for time domain reflectometry (TDR) measurements.

This breakthrough in bandwidth is enabled by a new monolithic sampling head design developed by Picosecond Pulse Laboratories (Boulder, CO). These sampling heads employ a patented non-linear transmission line (NLTL) in the sampling strobe generation circuit, creating what results in a rectangular sampling aperture. Previous sampler designs produced approximately Gaussian apertures. The rectangular sampling strobe results in nearly 100% efficiency, better bandwidth control and lower jitter over previous designs. The monolithic design of the samplers allows much higher sampling rates to be achieved compared to previous discrete designs.

The Coherent Interleaved Sampling time base developed by LeCroy derives the sampling gate by phase locking to the clock signal. This technique results in very fast sampling rates and precise tracking of the signal bit rate. The coherent nature of the sampling gate allows the system to lock to the data pattern simply by knowing its length. The resulting waveform can be measured and processed in the same manner as a real-time oscilloscope trace. The random interleaved sampling mode (RIS), a first for this type of instrument, allows pulsed signals to be measured without an external trigger signal.

WaveExpert 9000 and SDA 100G have been specifically designed to meet the measurement needs of today's high-speed designs. With serial data rates moving well beyond 3Gb/s, high bandwidth instruments capable of measuring signals with very fast rise times are needed. The instruments feature real-time waveform displays and a special jitter measurement mode that measures total jitter as well as random and deterministic jitter components. The basic waveform memory in this mode is 4M samples per channel, which enables jitter component breakdown and equalization on long serial data patterns. It can be expanded to 2G samples per channel so that the oscilloscopes can capture, display and measure bit patterns that are millions of bits in length.

WaveExpert 9000 and SDA 100G also feature a coherent interleaved sampling timebase. This feature enables single valued waveforms (v-t) to be captured in a manner similar to that found in real-time digital oscilloscopes (DSOs).

Both WaveExpert 9000 and SDA 100G use LeCroy's award-winning user interface (UI), which provides quick and easy access to over 50 measurements and math functions. Similar to a UI found on real-time oscilloscopes, the interface makes it a very simple transition for engineers who are new to sampling oscilloscopes. The UI also allows functions and measurements to be combined to create an almost unlimited number of more complex measurements.

The real time waveform (voltage vs. time) available from the WaveExpert 9000 and SDA 100G are ideal for evaluating high-speed serial buses. These include next-generation PCI Express, SAS, Fibre channel and FB-DIMM.

WaveExpert 9000 is aimed at general purpose signal integrity applications, including TDR and eye pattern analysis. A jitter and eye measurements package is also available. With the software, WaveExpert 9000 can perform eye pattern analysis faster than any other comparable instrument and analyze jitter in accordance with many standards. The SDA 100G specifically targets serial data applications and includes the coherent interleaved time base as well as a full jitter application standard.

In addition to the two mainframes, several plug-in modules are available for measuring electrical or optical signals. The electrical modules have bandwidths of 20 GHz, 30 GHz, 50 GHz, 70 GHz, and 100 GHz while the optical modules have optical bandwidths of 25 GHz and 50 GHz. The module design allows customers to configure WaveExpert 9000 and the SDA 100G for their existing testing needs while maintaining the flexibility to extend the instruments' capabilities as analysis requirements expand.

The instruments include a full set of compliance masks, along with measurements for both RZ and NRZ signaling formats. The coherent time base enables a rapid mask testing feature that measures up to 3M samples per second against a compliance mask—a 30X speed improvement over existing mask testing solutions. This level of acquisition throughput gives the highest level of confidence in measurement accuracy.

Engineers and technicians who would like to know more can contact LeCroy at 1-800-4LeCroy (1-800-453-2769) or visit the LeCroy web site (www.lecroy.com).

Wow. LeCroy 's new 100-GHz bandwidth WaveExpert 9000 and SDA 100G mainframes combine the high bandwidth and accuracy of sampling oscilloscopes with the speed—and utility—of realtime scopes.

You even get a realtime oscilloscope user interface that sports a set of math functions. What's more, it's based on the same user interface used in the company's WaveMaster realtime scopes.

The on-screen interface gives you access to more than 50 measurements and math functions, and you can create additional custom functions using applications such as Matlab, Mathcad or Excel , or any other Windows-compatible programming language for that matter.

Interleaved Timebases

Thanks to the contribution from Picosecond Pulse Laboratories , these scope's sampling rates, coupled with the patented NLTL (non-linear transmission line) interleaved timebases, lets a complete signal waveform be displayed without a separate pattern trigger. That can be a boon when observing long bit streams where you want to measure signal components such as jitter.

These scopes also have an inherent jitter spec that's less than a picosecond. Jitter measurements in the SDA 100G (jitter measurement is optional for the WaveExpert) let you analyze total jitter, random jitter, and deterministic jitter, as well as the component parts of deterministic jitter. A summary display then shows an eye pattern along with several views of jitter components.


Click to view typical jitter view

The coherent interleaved timebase, in conjunction with the scope's long memory (optionally up to 512-Msamples; standard memory length is 4-Mpoints), is what's responsible for extending the jitter analysis capability to very long data patterns, too.

Automatic Pattern Locking

Automatic pattern-lock capability in the coherent interleaved timebase, as discussed in the press statement (on the left), also makes it possible to capture waveforms without that aforementioned pattern trigger. With the optional clock recovery module, an external clock just isn't needed.

The company's press release also notes that these scope's RIS (random interleaved sampling) mode let pulsed signals be measured without an external trigger signal (RIS supports the display and measurement of the rising edge of a pulse that's simultaneously triggering the instrument; The RIS timebase has a time resolution of 250-femtoseconds).

Fast Eye Patterns

LeCroy also notes that its newest scope's fast acquisition speed will let you make eye patterns containing hundreds of millions of samples—in mere seconds. In fact, LeCroy says that's up to fifty times faster than currently available instruments. As such, you could take 28 million samples in ten seconds, for example. With that kind of speed, eye patterns reveal meaningful statistics, and you also get reduced aliasing.

The scope's eye pattern mode also uses a standard-persistence display, with acquisition triggered by an external clock, or the previously mentioned recovered clock. The trigger input can accommodate signals from DC to 5-GHz. Once the interleaved time base and the jitter analysis software (which comes standard in the SDA 100G) measures a complete voltage-vs-time waveform, it's then folded to create an eye pattern.

LeCroy claims this technique dramatically improves measurement throughput and enables the display of specific symbols within the data pattern that might cause mask violations. Compliance masks are included for most standards, but additional masks can also be created as emerging standards appear and get adopted.

LeCroy's release notes also mention that these oscilloscopes can output a TDR (time domain reflectometry) pulse with a 20-ps incident risetime. Moreover, TDR traces can be scaled in volts, reflectance, and ohms, and any capacitive reactance (XC ), or inductive reactance (XL ) portions of a trace can be displayed using markers. Finally, the scopes support both single-ended and differential TDR measurements, as well as TDT (time domain transmission) measurements.

Plug-In Modules

Kudos to LeCroy for making these products modular. Their modular design lets you configure a WaveExpert 9000 or SDA 100G for existing testing, yet it gives you a route to extend their capabilities on an as-needed basis, which can be cost-effective.

The electrical modules offer bandwidths of 30-GHz, 50-GHz, 70-GHz, and 100-GHz. The single-mode optical modules have bandwidths of 25-GHz and 50-GHz. You can also buy a 10-GHz high-sensitivity optical head. It spans 750-nm to 1750-nm wavelengths, and includes reference receiver plug-ins. There's also an optional 12.5-Gbit/s PRBS (pseudo-random bit sequence) source, and a 600-Mbit/s to 12.5-Gbit/s clock recovery module.

The TDR/sampling head operates out to 20-GHz, with 20-ps steps. It has a maximum input signal range of 2-V (p-p), which is twice that of most sampling heads. What's more, it exhibits an aberration spec of 10-percent, which is less than 40-ps from an edge; most sampling heads have 10-percent specs to 300-ps after a step. This graph compares TDR step responses of the WaveExpert 9000 with Agilent Technologies 54653A and a Tektronix SD24 wares.


Click for larger step response image

Reflected risetime specs for the head are also 30-ps, with incident risetime specs at just 20-ps. Compare that to most heads with 35-ps and 28-ps specs, respectively. Finally, the 20-GHz/TDR head has 10-MHz pulse rate specs as opposed to most heads with 200-kHz pulse rate specs.


Click for larger risetime image

For more details, contact product marketing manager Mike Schnecker at LeCroy Corp., 700 Chestnut Ridge Rd., Chestnut Ridge, New York 10977. Phone: 800-453-2769 or 845-425-2000. Fax: 845-425-8967. E-mail: contact.corp@lecroy.com.

Be sure to visit LeCroy's Web site for more details on this and related products.

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