User`s guide

Jitter - Jitter is a period / frequency displacement of a signal from its ideal location. These displacements can occur in
amplitude, phase or pulse width and are generally categorized as either deterministic or random in nature. The
reference event is the differential zero crossing for electrical signals and the nominal receiver threshold power
level for optical systems. Jitter is composed of both deterministic and Gaussian (random) content.
Total jitter is the convolution of Deterministic Jitter (DJ) and Random Jitter (RJ). (See Fibre Channel Methodologies
for Jitter Specification REV 10 page 30, at ftp://ftp.t11.org/t11/member/fc/jitter_meth/99-151v2.pdf). Deterministic
Jitter is composed of Duty Cycle Distortion (DCD), Inter-Symbol Interference (ISI), Periodic Jitter (PJ) and Bounded
Uncorrelated Jitter (BUJ).
At very high frequencies, unchecked jitter causes:
• Flicker in video devices
• Clicks and glitches in audio devices
• Disparity between input and output serial data in network applications
• Devices such as computers to operate slowly and potentially crash.
Currently, some semiconductor devices require jitter tolerances as low as 50 picoseconds and allow one bit error
per 10 thousand billion clock cycles. Therefore, jitter measurements are critical during the prototyping and
developmental stages of the semiconductor devices. The more accurately device performance is measured and
errors corrected prior to production, the faster the device can ultimately operate.
© WAVECREST Corporation 2005
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Jitter Amplitude - Jitter amplitude applied to the OUTPUT and OUTPUT signals. Amplitude Jitter is defined as the
peak-to-peak jitter in one clock cycle (or period) of the Frequency control value.
Jitter Distribution - Selects the Jitter Distribution type that is loaded into jitter memory and applied to the OUTPUT
and OUTPUT signals when jitter is enabled. There are six jitter distribution choices: Sine, Triangle, Sawtooth,
Random and Psuedo Random.
Jitter Frequency (MHz) - Sets the Jitter frequency (MHz).
Jitter Mode - Period Jitter is defined as the peak-to-peak jitter in one clock cycle (or period) of the Frequency
control value. Cumulative jitter is defined as the peak-to-peak jitter in one cycle of the Jitter Frequency control
value. (See theory of jitter generation section.) The Summary Units control specifies how the amplitude will be
displayed: Unit Interval (Where a Unit Interval is defined as one clock cycle of the Clock Frequency control
value); Nanoseconds (nanoseconds peak-to-peak) and Degrees (degrees peak-to-peak where one clock cycle
equals 360°). Changing the value in one jitter amplitude control will affect the other.
Jitter Output - This control turns the jitter On or Off for the OUTPUT and OUTPUT signals. The current values in
the Jitter Amplitude, Jitter Frequency and Distribution controls determine the amount and type of jitter applied.
Glossary