Crystal Devices

What Exactly Is Oscillator Jitter? (Part 1)

In this segment, we will define "oscillator jitter," a term that emerges during the evaluation of ICs and the design of circuits.

What is Jitter?

Jitter, as defined by a crystal oscillator, represents the deviation between the ideal waveform of a specific frequency and the waveform actually observed from the oscillator.
The jitter value is derived from the observation of this waveform deviation through various methods. What is Jitter?

Jitter Types and Measurements

Jitter Types

There are many kinds of jitter.
Various terms are used, including period jitter, cycle-to-cycle jitter, phase jitter, RMS jitter, and 1σ (sigma) jitter. Generally speaking, when we say jitter, it often means period jitter or phase jitter. These differences also depend on how you measure jitter. First, let's take a look at the differences between jitter measurement methods and equipment.

Jitter Measurements

Measuring Instrument	Group	Features	Disadvantages
Time Interval Analyzer (TIA)	Time Domain	Measure the time interval between input signals. Measure the time between the crossing point of the input signal with the threshold level (voltage level). Additional processing may be performed on measurement results.	Generally, unobserved time occurs between consecutive gate times (signal acquisition times). Signals with slow rise times (such as those with low frequencies) tend to have poorer values. This is a statistical value and may be affected by the signal acquisition time.
Digital Storage Oscilloscope (DSO)	Time Domain	Measure the time interval between input signals. Waveform data from an input signal, subjected to digital signal processing, is stored in a memory, and analysis processing (time analysis) is performed. Measure the time between the crossing point of the signal with the threshold level. Complementary processing of measurement results can be incorporated. Continuous data acquisition and analysis without unmeasured time is possible depending on the memory capacity.	The measurement results may depend on the performance of the oscilloscope and the setting of the measuring instrument. Major Influences: Voltage Axis Resolution, Sampling Rate, Interpolation Function Settings, and Bandwidth. Depending on the measurement settings, unobserved time may occur between the gate times (signal acquisition times). This is a statistical value and may be affected by the signal acquisition time.
Signal Source Analyzer(SSA)	Freq. Domain	The phase noise is measured and integrated over the bandwidth (Typically 12 kHz to 20 MHz) to calculate 1-sigma jitter. Fast Fourier Transforms (FFT) are used to transform time signals into frequencies. Processing is performed on the frequency axis. Convert to values on the time axis by performing integration processing.	The jitter value is averaged. The value varies depending on the environment at the time of measurement. (Sensitive to environment)

Measuring Instrument

Group

Features

Disadvantages

Time Interval Analyzer (TIA)

Time Domain

Measure the time interval between input signals.
Measure the time between the crossing point of the input signal with the threshold level (voltage level).
Additional processing may be performed on measurement results.

Generally, unobserved time occurs between consecutive gate times (signal acquisition times).
Signals with slow rise times (such as those with low frequencies) tend to have poorer values.
This is a statistical value and may be affected by the signal acquisition time.

Digital Storage Oscilloscope (DSO)

Time Domain

Measure the time interval between input signals.
Waveform data from an input signal, subjected to digital signal processing, is stored in a memory, and analysis processing (time analysis) is performed.
Measure the time between the crossing point of the signal with the threshold level.
Complementary processing of measurement results can be incorporated.
Continuous data acquisition and analysis without unmeasured time is possible depending on the memory capacity.

The measurement results may depend on the performance of the oscilloscope and the setting of the measuring instrument.
Major Influences: Voltage Axis Resolution, Sampling Rate, Interpolation Function Settings, and Bandwidth.
Depending on the measurement settings, unobserved time may occur between the gate times (signal acquisition times).
This is a statistical value and may be affected by the signal acquisition time.

Signal Source Analyzer(SSA)

Freq. Domain

The phase noise is measured and integrated over the bandwidth (Typically 12 kHz to 20 MHz) to calculate 1-sigma jitter.
Fast Fourier Transforms (FFT) are used to transform time signals into frequencies.
Processing is performed on the frequency axis.
Convert to values on the time axis by performing integration processing.

The jitter value is averaged.
The value varies depending on the environment at the time of measurement. (Sensitive to environment)

List of Basic Knowledge About Timing Devices Articles

vol.1 What is Crystal Unit Matching?

vol.2 What Are the Equivalent Circuit Constants of a Crystal Unit?

vol.3 What Exactly Is Oscillator Jitter? (Part 1)

vol.4 What Exactly Is Oscillator Jitter? (Part 2)

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# Trivia # Matching # Simulation

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What Exactly Is Oscillator Jitter? (Part 1)

What is Jitter?

Jitter Types and Measurements

Jitter Types

Jitter Measurements

Related Keywords

Technical information View All

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TCXO for Automotive Communications Applications

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