Jitter

Jitter is a change in the characteristic of pulses in a high-frequency signal. This digital deviation can be caused by conditions in phase timing, amplitude, or signal-pulse width. Electromagnetic interference (EMI) and signal crosstalk are some of the sources of jitter.

In personal computing, jitter can make a monitor or display flicker, affect a processor’s performance, change audio signals, and induce the loss of transmitted data.

In Voice-over Internet Protocol (VoIP), jitter is the variance in time of packet arrival, often rooted in high network traffic, route changes, or timing drift.

Procedures of jitter measurement and evaluation depend on the circuitry being tested. Eye diagrams are used to measure jitter in Serial Bus (SB) architecture. The data stream of digitized analog waveforms on the other hand, is analyzed in the measurement of pixel jitter. The objective of jitter measurement is to make sure that jitter will not upset the circuitry’s normal operation.

Types of Jitter

  • Constant Jitter – a near-constant level of variation in packet-to-packet delay.
  • Transient Jitter – a single packet incurring an incremental yet substantial delay.
  • Short Term Delay Variation – a number of packets incurring increase in delay, accompanied by an increase in variation of packet-to-packet delay.

Types of Jitter Prevention

  • Anti-jitter Circuits (AJC) – electronic circuits that reduce jitter level in a normal pulse signal. AJCs retime output pulses to align with a standard pulse signal.
  • Jitter Buffers – also known as de-jitter buffers, these counter jitter from packet-switched networks to ensure a continuous stream of audio or video transmission over the network.
  • Dejitterizer – a device that lessens digital signal jitter. It consists of a buffer where the signal is stored temporarily, then resent based on the average rate of the incoming signal.