Q-Tech MILITARY TCXO - Manual (Page 6)

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Q-TECH
CORPORATION
QPDS-0009 (Revision F, April 2013 ) (ECO# 10834)
HIGH STABILITY DIGITAL TCXO
SURFACE MOUNT CRYSTAL OSCILLATORS
3.3 to 5Vdc - 1MHz to 125MHz
6 of 7
Phase noise is measured in the frequency domain, and is expressed as a ratio of signal power to noise power measured in a 1Hz bandwidth
at an offset frequency from the carrier, e.g. 10Hz, 100Hz, 1kHz, 10kHz, 100kHz, etc. Phase noise measurement is made with an Agilent
E5052A Signal Source Analyzer (SSA) with built-in outstanding low-noise DC power supply source. The DC source is floated from the
ground and isolated from external noise to ensure accuracy and repeatability.
In order to determine the total noise power over a certain frequency range (bandwidth), the time domain must be analyzed in the frequency
domain, and then reconstructed in the time domain into an RMS value with the unwanted frequencies excluded. This may be done by
converting L(f) back to Sφ(f) over the bandwidth of interest, integrating and performing some calculations.
The value of RMS jitter over the bandwidth of interest, e.g. 10kHz to 20MHz, 10Hz to 20MHz, represents 1 standard deviation of
phase jitter contributed by the noise in that defined bandwidth.
Figure below shows a typical phase noise/phase jitter of a QT3103C, 3.3Vdc, 10.000MHz and a QT3103C, 3.3Vdc, 27.48MHz TCXO
at offset frequencies 10Hz to 5MHz, and phase jitter integrated over the bandwidth of 1kHz to 5MHz. Typical phase noise jitter (1kHz
to 20MHz) smaller than 1psec
Phase Noise and Phase Jitter Integration
Symbol Definition
∫L(f) Integrated single side band phase noise (dBc)
Sφ (f) (180/Π)x √ 2 ∫L(f)df Spectral density of phase modulation, also known as RMS phase error (in degrees)
RMS jitter Sφ (f)/(fosc.360°) Jitter(in seconds) due to phase noise. Note Sφ (f) in degrees.
QT3103C-27.48MHz QT3103C-10.000MHz