Communications analyzers build on real-time scopes

Textronix's CSA (Communications Signal Analyzer) scopes have for years addressed the needs of engineers working with high-performance communication systems. Until now, however, CSA scopes have achieved bandwidth as high as 50 GHz through the use of sequential sampling, which reconstructs waveforms by acquiring one sample during each signal iteration that follows a trigger event. Sequential-sampling scopes provide amplitude resolution as great as 14 bits, but, because they need hundreds or even thousands of signal iterations to reconstruct each waveform, they respond relatively slowly to signal changes.

Tektronix calls units in the CSA7000 series the first communications scopes based on real-time-sampling (Picture). The top-of-the-line, $57,500 CSA7404 achieves a bandwidth of 4 GHz and in single-channel mode takes 20G samples/sec. The sampling rate and bandwidth are adequate for real-time capture of signals that convey the 2.5-Gbps data streams of such standards as OC-48, Gigabit Ethernet, Fibre Channel, and InfiniBand. The $37,500 CSA7154 also captures 20G samples/sec and 400,000 waveforms/second and provides a 32M-sample waveform memory but offers 1.5-GHz bandwidth for viewing 1-GHz data streams.

Each CSA7000 instrument includes a built-in optical-reference receiver (optical-to-electrical converter), obviating the need for an external receiver with its critical calibration routines. The instrument also includes a library of DSP-based filters, and, because of the DSP-based implementation, modifying the filter characteristics requires no additional hardware. A clock-recovery facility extracts the clock from the input data stream and a 32-bit serial-triggering facility simplifies navigating through serial streams and isolating pattern-dependent effects. Compliance-mask-testing capabilities handle eye-diagram and pulse-shape masks.

Many of the CSA7000 capabilities, not including the built-in optical-reference receiver, are now also available as options on the TDS7000 family of general-purpose, high-performance, real-time-sampling scopes.

Tektronix Inc, 1-800-426-2200, www.tektronix.com.