Mixed-Domain Oscilloscopes Go Mainstream

1405 Insight
1405 Insight

Dave Farrell General Manager, Mainstream Oscilloscopes, Tektronix

Engineers involved in mixed-signal embedded designs need to work in three domains, according to Dave Farrell, general manager, Mainstream Oscilloscopes, at Tektronix. Consequently, Tektronix has evolved its mainstream oscilloscope lineup to ensure that customers will have access to analog, logic, and RF capabilities.

In February, for instance, the company announced that its MDO4000B Series of mixed-domain oscilloscopes now are available at the same price point as MSO4000B mixed-signal oscilloscopes, which will be phased out. Introduced in August 2011, the Tektronix mixed-domain oscilloscopes can capture time-correlated analog, digital, and RF signals for a complete system view of a user’s device. Available analog bandwidth ranges from 100 MHz to 1 GHz with a 2.5- or 5-GS/s sample rate and a 20-Mpoints record length.

Also in February, the company debuted its MDO3000 Series of mixed-domain oscilloscopes, each of which includes a spectrum analyzer and an optional logic analyzer, protocol analyzer, arbitrary function generator, and digital voltmeter. The scopes offer 100-MHz to 1-GHz bandwidths along with a spectrum-analyzer channel matching the scope’s bandwidth. Optionally, the spectrum-analyzer channel on any model can be expanded to 3 GHz—along with a 3-GHz capture bandwidth.

According to Farrell, Tektronix has added RF capability to its mainstream oscilloscopes to accelerate the adoption of mixed-domain capability in the market and move it beyond niche applications. “It took 10 to 15 years for mixed-signal scopes as a category to capture the majority of the market,” he said. “We are two and a half years into this mixed-domain-oscilloscope endeavor, and our growth rates still look fantastic.”

Farrell said studies show that 45% of oscilloscope users employ a spectrum analyzer several times per month and 67% use one occasionally. “We see that percentage only going higher as more wireless is integrated into designs,” he said. RF capability is no longer needed just for EMI compliance—it’s needed throughout the mixed-signal project design and debug cycle, he added.

Thus far, competitors have not directly responded to Tektronix’s mixed-domain instruments beyond features such as new oscilloscope user interfaces that provide convenient access to FFT functionality. “We do expect our competitors to respond, but we are not surprised they haven’t responded yet,” Farrell said. “The MDO represents a significant technology shift and hardware development effort that’s not easily copied.” Tektronix has filed more than 30 patents on MDO technology, he said, adding that beyond patent protection, it is simply not easy to build a spectrum analyzer with a 3-GHz capture bandwidth—a specification important for EMI applications in which engineers don’t know the frequency of the noise source they are chasing.

As for comparison with oscilloscope-based FFTs, Farrell said a dedicated spectrum-analyzer channel provides “far better RF performance”—about 65 dB of dynamic range for the spectrum analyzer vs. about 45 dB for the FFT. Further, spectrum-analyzer bandwidth extends to 6 GHz on the MDO4000 models and 3 GHz on the MDO3000 instruments; with FFT, you are limited to the analog bandwidth of the scope you purchased with further degradation due to the scope’s 3-dB roll-off. To achieve RF performance comparable to the MDO models with an FFT, Farrell said, you probably would need to buy a 12.5-GHz scope—”and we know the price tag for that.”

Farrell said that mixed-domain oscilloscopes won’t replace dedicated instruments. In fact, he said, “We see a ton of overlap between our mainstream and performance oscilloscopes.” The mainstream scopes, he said, are personally assigned to engineers, who share lab-grade instruments that would not be cost-effective to assign individually. But, he said, a personally assigned MDO3000, which starts at $3,500, provides 80% to 90% of the functionality that an engineer needs. At the high end, a 1-GHz, four-channel model with AFG, MSO, and a 3-GHz spectrum analyzer would cost $18,650; Farrell estimated that similar standalone instrumentation would cost more than $27,500.

“Our goal is to make customers as efficient as possible throughout their design process, so we are going to provide features that provide faster time to insight,” Farrell said. Such features will include, for example, support for evolving serial standards. Finally, he said, “An often overlooked but highly valued part of the whole solution to the customer is the area of probing. You’ve got to think more and more about that probing experience, and that’s a big part of why we moved to active probes as a standard part of our lineup.”

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