Electronic Design

With 33-GHz Bandwidth, Tek Reaches For Upper Scope Echelon

After a year or two of watching its key competitors zoom past in the scope-bandwidth race, Tektronix is answering back in the form of its DPO/DSA70000D scope family (Fig. 1). The family comprises four models with real-time sampling rates of up to 100 Gsamples/s on two channels and an analog bandwidth up to 33 GHz on four channels. With this launch, Tektronix firmly injects itself back into the conversation about who’s got the upper hand in the high-end scope market.

⇒  Watch interview with Tek's Chris Loberg and demo of the DPO/DSA70000D scope family.

Engineers are seeing an across-the-board need for more bandwidth from their test equipment. Not only that, but they need high bandwidth on multiple channels, due to the growing prevalence of multi-lane bus architectures. Further, it’s no longer just about bandwidth, but about more overall accuracy. Designers are evaluating high-end scopes on a combination of sampling rates, rise-time performance, and bandwidth. Scopes must perform in demanding measurement environments in which users expect absolute accuracy.

So Tek’s answer to its customers’ needs, and to the pressure applied by Agilent and LeCroy in the marketplace, is a line of scopes that is based on IBM’s 8HP SiGe ADC/track-and-hold front-end chipset (Fig. 2). Tek installs this chipset on the scopes’ acquisition boards using a very low-loss and low-noise attachment. Signals are taken from the scope’s front end directly to the SiGe chipset by means of a special cable from the front end to the four posts on the corners of the MCM; those posts have a bandwidth of 100 GHz. The goal here is to minimize instrument noise and achieve the flattest possible passband.

The tight front-end integration also contributes to the high sampling rate with removal of as much interleaving error as possible. Interleaving errors are the source of spurs in the dynamic range, which in turn introduces noise on measured signals. The scopes use 100-Gsample/s, eight-way interleaved track-and-hold amplifiers with dual 33-GHz preamplifiers.

A closer look at the scope’s key specs shows that the 33-GHz analog bandwidth is achieved without use of DSP boosting. This is a result of a 2X speed bump in the front-end chipset. The instrument supports a 9-ps rise time on all four channels. It also can be put into equivalent time mode at a sample rate of up to 10 terasamples/s on all four channels, taking sampling down to an astounding 100 fs. Input sensitivity is specified at 6.25 mV/div, enabling users to look at very small signals without using the full screen. The result is good visibility into signal performance when looking for anomalies such as overshoot or ringing.

The instruments sport a waveform acquisition rate of over 300,000 waveforms/s while still doing an excellent job of managing internal noise and jitter. The jitter noise floor is specified as <250 fs typical for the DPO/DSA73304D models. Time base accuracy is ±1.5 ppm and trigger jitter is <100 fsRMS typical with enhanced triggering enabled.

At bandwidths as high as 33 GHz, connectivity to the DUT is a critical aspect of the measurement. Tektronix has chosen to support its TekConnect modular adapter system in the DPO/DSA70000D series, and has added a new adapter, the TCA292D, for direct coaxial-cable connection that supports the full 33-GHz bandwidth. The scopes also support Tek’s P7500 Series TriMode probing system for use with browsers or solder-down probes.

Serial data signals are becoming incredibly complex, and so is triggering on those signals. A new tool in the DPO/DSA70000D series is what Tek calls Visual Trigger (Fig. 3), which enables users to define shapes on the scope’s screen and then tell the instrument to trigger on the signal either when it passes inside or outside of that shape. Additionally, a new 8b/10b serial decode feature allows triggering or searching on decoded traffic, making it easier to debug generic 8b/10b protocols. Of course, the scopes also perform serial decoding on standard protocols such as USB and MIPI.

Thanks to enhancements to its DPOJET technology, Tek has added support for bounded uncorrelated jitter (BUJ) separation to these instruments. BUJ is a version of deterministic jitter that is uncorrelated to the data stream. It’s a factor in Gigabit Ethernet signals, where periodic jitter tends to show up from excessive crosstalk. The DPO/DSA70000D scopes give users more visibility into this relatively new source of jitter.

Prices for the DPO/DSA70000D Series scopes starts at $202,000 for a 25-GHz DPO version and tops out at $295,000 for theDSA73304D, a 33-GHz digital serial analyzer. Shipments will begin in the fourth quarter of 2011.


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