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Time-domain reflectometer measures paths for serial data to 12.5 Gbps

Designers who are working with the latest serial-data standards such as PCI Express, Serial ATA, Infiniband and XAUI are the target market for Tektronix’ new DSA8200 digital serial analyser. Getting a signal across even a relatively short length of backplane track and achieving a good eye opening at the termination requires a precise characterisation of the signal path, its impedance and all its discontinuities. There are two methods of doing so: in the frequency domain, the vector network analyser is the appropriate instrument—in the time domain, the TDR is the appropriate tool. Tektronix has equipped its latest introduction with a suite of S-parameter-measurement routines, as a simpler way of characterising signal paths, with easier setup and fewer calibration routines. The TDR is essentially a pulse generator that launches fast-rise-time edges into the signal path, combined with a sampling oscilloscope that measures the reflections that return along the path from discontinuities and impedance mismatches. Tek’s 8200, which it calls the most significant advance in TDRs in 20 years, updates the key parameters of the instrument to a 15-psec reflected-edge rise time, 50 GHz measurement bandwidth with 600
V noise floor, and a 1-million-point record length for high resolution. This, Tek says, is sufficient for all current serial-data standards up to 10G Base-R FEC. The instrument takes the form of a mainframe comprising a PC, a controller and a sampling-scope display, plus pulse-launch and sampling-head modules. Measurement modules can be fully differential and can de-skew signals by up to 250 psec. The fact that the key technology is in the pulselaunch and sampling modules is reflected in the starting prices of €13,000 for the mainframe, €24,400 for the TDR modules and €19,800 for the sampling modules.

Tektronix, www.tektronix.com