Through the DDA 260’s powerful PRML channel-emulation, you can view a channel starting from the raw head signal to the output of the Viterbi Detector. 

Head Signal Filtering

A 7-pole, continuously-selectable cutoff frequency filter emulator is available to remove head signal noise. 

Noisy head signal

Byte Number

No more guessing which part of a PRML head signal you are viewing. View the byte number of the head signal at the center of the display.

Same signal with 95 MHz 3 dB cutoff selected

PRML Channel Insight

View your head signal from a PRML channel’s point of view. The DDA displays the head signal equalized, based on the selected PRML target levels (PR4, EPR4, E2PR4) or others (PRI,PR2) via the user-defined trellis (UDT) capability. The DDA 260 also provides PRML sample targets (‘+’ signs) indicating where the ideal PRML sample points are. Visual comparison of the equalized head signal and PRML targets gives a rapid visual indication of head signal quality from a PRML viewpoint. In addition, the DDA 260 provides the channel emulation quality metric Sequenced Amplitude Margin (SAM) for the 100 head-signal samples with the poorest SAM.

Equalizer head signal and Viterbi sample targets ('+')

The DDA’s channel emulation takes the mystery out of complex PRML signal processing. See the PRML head signal and —through channel emulation — the PRML signal as it gets processed through the equalizer, sampler, and Viterbi Detector. Quality metrics such as SAM histograms and media noise can then be viewed.