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test&measurementZONE Products for the week of August 11, 2008
Pico Technology Says…
PicoScope 9201, Dual-Channel PC Sampling Oscilloscope With Bandwidth Of 12 GHz Redefines Performance At This Price Level
The dual-channel PicoScope 9201 uses sequential equivalent-time sampling to achieve a sampling rate of 5 TS/s. The wide bandwidth allows acquisition and measurement of fast signals with a transient response of 50 ps or faster. Timebase stability, accuracy, and a sampling interval of 200 fs allow timing characterization of jitter in the most demanding applications. The ability to trigger on high frequencies up to 10 GHz allows measurements on microwave components with extremely fast date rates.
With excellent measurement repeatability, exceptional vertical resolution (16 bits) and fast display update rate, the PicoScope 9201 is a powerful measurement tool for semiconductor testing, TDR characterization of circuit boards, IC packages and cables, and high-speed digital data communications.
Data acquisition and measurement analysis are performed in parallel, enabling the instrument to achieve outstanding measurement throughput. The instruments provide fast acquisition speed up to 200 kS/s and waveform performance analysis with automated direct or statistical measurements on both single-valued signals (sine-wave, pulse, impulse) and multi-valued signals (NRZ, RZ). Markers and histograms, math and FFT analysis, colour-graded display, parametric limit testing, eye diagrams and mask template testing can be used independently or in concert.
Accurate eye-diagram analysis for NRZ and RZ signal types is essential for characterizing the quality of electrical and optical transmitters to beyond 7 Gb/s. The PicoScope 9201 was designed specifically for the complex task of analyzing digital communications waveforms. Compliance mask and parametric testing no longer require a complicated sequence of setups and configurations. The important measurements you need are right at your fingertips, including industry-standard mask testing with built-in margin analysis, extinction ratio measurements with improved accuracy and repeatability, automatic eye measurements - crossing %, eye height and width, one and zero levels, jitter, rise and fall times---and more. In addition, mask testing of SDH/SONET, Fibre Channel, Ethernet and other standards simplifies compliance testing. A full colour display helps you to discriminate waveform details. A colour-graded display mode adds a third dimension---sample density---to your signal acquisitions and analysis.
At less than half the price of a traditional bench-top instrument, with its small size (170 x 255 x 40 mm) and light weight (1 kg), the portable PicoScope 9201 offers the widest range of measurements and waveform processing capabilities of any multi-gigahertz PC Oscilloscope. It can be connected to the USB port of any Windows laptop or desktop PC.
Alan Tong, Managing Director of Pico Technology, commented: "The PicoScope 9201 really shows the benefit of Pico's approach to test and measurement. We have taken our understanding of low-cost PC oscilloscopes and applied it to a high-end, specialised instrument, and the result is a fully specified sampling scope that's within the budget of most engineering and test departments."
EN-Genius Says…
As a sampling scope, the PicoScope 9201 ADCs only have to be fast enough to capture a single sample for every cycle of a waveform. In contrast, true real-time oscilloscopes are fast enough to digitize hundreds of samples, but scopes such as Agilent Technologies' 12-GHz Infiniium DSO91204A digital storage scope, with its real-time sample rate of 40 Gsample/s, are priced at nearly $100,000. That's a far cry from the PicoScope 9201 at roughly $11,700. As such, the 9201 might be just the ticket if your need is the analysis of repetitive waveforms.
On the other hand, if you do need to capture fleeting random glitches, you will indeed want a scope with a high real-time sampling rate, and these are available from the likes of Tektronix, LeCroy, Agilent and others. If you were looking at a GHz signal, then a scope with a real-time sampling rate of 10 Gsample/s would typically be needed.
 Pico's press statement mentions that its 2-channel scope exhibits 12 GHz of bandwidth on both channels and its dual timebase is adjustable down to 20 ps/division. Not mentioned in the release is the fact that the Pico 9201 comes equipped with lots of memory. The scope buffer size can be set independently for each channel, too, from 32 samples to as many as 4096 samples (in multiples of two).
Sequential Equivalent-Time Sampling
The PicoScope 9201 also uses an unusual technique called sequential ETS (equivalent-time sampling). The 9201 ETS sampling rate is 5 Tera-sample/s, with a 100 ksample/s real-time sampling rate. Remember that ETS isn't the speed of the scope ADC, but an estimate of the speed of a theoretical front-end that could capture a single-shot waveform at the same timebase, and with the same number of samples, as a sampling scope.
If a sampling scope had perfectly accurate timing, it could achieve a high ETS rate by waiting for more cycles of the input waveform. However, in real life, ETS is limited by timing and trigger constraints. The smaller the timing uncertainty or jitter, the more non-overlapping samples the scope can take to form its on-screen image, and therefore the higher the ETS rate. In the case of the PicoScope 9201, its low internal jitter results in the 5 Tsample/s ETS rate.
Speaking of triggering and jitter, the 9201 direct triggering operates from dc to 1 GHz, but you can use a pre-scaled trigger out to 10 GHz. The hardware exhibits less than 3.5 ps rms of its own jitter.
Not incidentally, equivalent sample rate and buffer size work together, so if you use a small buffer with a high equivalent sample rate, you'll get fast throughput but little data in channel-memory. If more data points are needed, a waveform stored in a larger buffer will take longer to construct, but will yield a displayed waveform with higher horizontal resolution.
There Is A Difference
As you know, everything in engineering involves tradeoffs, and the nifty Pico 9201 is no exception. Having said that, there are significant differences between a PicoScope 9201 and a typical bench scope, but they’re not necessarily limitations.
For one thing, the 9201 uses threaded SMA connectors for signal inputs, instead of the common bayonet style BNC connectors found on most scopes. Pico cites its use of SMA connectors to keep impedance bumps low at microwave-domain frequencies. In addition to the SMA connectors, the 9201 input impedance is 50 Ω, rather than the customary high-Z inputs of most scopes. Again, the 50 Ω input impedance matches to typical 50 Ω coaxial cables and connectors as used at RF. No high-Z probes are needed, nor does Pico supply them.
There are additional differences between a 9201 and a conventional bench scope. Rather than a wide selectable vertical input span, the 9201 is quite limited. If the signal you intend to measure is greater in amplitude than the ±1 V maximum range, you must use an outboard attenuator or divider.
While mentioning vertical sensitivity, I might mention that the 16-bit front-end exhibits a full 12 GHz bandwidth, starting at dc. Risetime is specified at a fast 29 ps, and internally-generated noise is held below 2.5 mV rms. Vertical gain accuracy is within ±2%. On the horizontal, the 9201 dual timebases can sweep as slow as 2 ms/division. The timebase exhibits 0.4% (plus 15 ps) time-interval accuracy.
Windows Software
As for the Windows software that makes the 9201 play on your PC, it dishes up colorful eye diagrams and histograms, and also provides specialized measurements as well as industry-standard mask tests. It also handles IEEE automated testing. The software additionally supports infinite persistence and variable persistence displays, as well as grey-scaling and color grading.
 An on-screen timebase control lets you set the scope horizontal display through Main, Intensified, Delayed, or Dual Delayed timebases, and you can set conventional time/div and delay functions, too. Timebase windowing, similar to delayed or dual delayed sweeps on analog oscilloscopes, turns on an expanded timebase. The expanded timebase lets you pinpoint and horizontally expand a portion (or two portions) of an acquired waveform, in order to get a detailed high-resolution picture.
Three averaging algorithms can also be called into play to eliminate the effects of noise, thereby increasing resolution and accuracy. Averaging can actually extract signals that are below the noise. This feature will let you measure noisy signals to less than 0.5 ps standard deviation, which is extremely accurate.
Statistical Analysis
The PicoScope 9201 can also collect waveforms for statistical analysis, with results displayed as colored histograms against voltage or time. A vertical voltage histogram can reveal how much time a signal spends at a given amplitude. You can use that to ascertain things like rms noise and noise-margins. For its part, a horizontal time histogram can show how fast a signal level changes during a time interval. It can reveal things such as rms jitter and timing margins. A high-resolution cursor is also provided, and you can also take automatic waveform measurements with statistics.
Like most oscilloscopes these days, you can also run software to convert conventional time-domain measurements into the frequency domain. The 9201 FFT (fast Fourier transform) waveform processing function can be applied to any waveform, and you can select a number of window types, letting you choose the optimum bandwidth and shape for your FFT filter. In addition to rectangular FFT windowing, you can choose Hamming, Hanning, flat-top, Blackman-Harris, or Kaiser-Bessel windows.
To do all of this, all you need do is connect the 9201 front-end hardware to your PC USB 2.0 (Universal Serial Bus) port, connect an ac power source (supplied) to the hardware, and fire up Pico's unique scope software under Windows 2000, NT, or XP. Not mentioned in the press release is the fact you can optionally order a PicoScope 9201 to communicate over a LAN, instead of USB, should you so desire.
In conclusion, I think it’s fair to say the PicoScope 9201 will give major oscilloscope vendors a run for their money. The race should be fun to watch.
The PicoScope 9201 is available from local distributors, or direct from Pico Technology, priced in the UK at £5995 + VAT and delivery.
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