

Low Phase Noise
We have the best GPSderived lowphasenoise specs in the world.
The lowphasenoise specifications of the Meridian II and Tycho II 5 MHz and 10 MHz sine wave outputs are dependent
on the installed oscillator. We design and manufacture our own ovencontrolled crystal oscillators (OCXO)
because we cannot find the quality or performance we need elsewhere. These OCXOs excel in low phase noise and
shortterm stability. We offer three OCXO oscillator options  the MediumStability OCXO (MSOCXO), the High
Stability OCXO (HSOCXO), and the UltraStable OCXO (USOCXO) that is suitable for the most demanding applications.
Rubidium atomic frequency standards excel in temperature stability, ageing, and mediumterm stability. The UltraStable
Rubidium (USRb) with a low phase noise output and a standard compact rubidium (Rb) are available:
1 Hz 
95 
105 
113 
80 
92 
10 Hz 
120 
130 
138 
100 
135 
100 Hz 
135 
140 
148 
135 
148 
1 kHz 
145 
150 
152 
145 
154 
10 kHz 
145 
150 
153 
145 
155 
100 kHz 
145 
150 
153 
145 
155 
What is phase noise?
Shortterm stability is an important quality in sine wave outputs for many military and broadcast
applications. Shortterm stability refers to the movement of the zero crossings of a signal relative to those
of a reference frequency standard, measured over observation intervals that are typically shorter than one
second. When measured in units of time, in a broad bandwidth, it is commonly called jitter. When
measured in units of phase, in a 1 Hz bandwidth centered at specific frequencies, it is called phase noise.
Frequency Multiplication
Most applications requiring the lowphasenoise characteristic of our products involve phase lock loop (PLL) frequency
multiplication. When the output from one of our products is used as the reference in such a PLL multiplier,
the phase noise that is inside of the PLL bandwidth will be present on the synthesized output signal and its level
will be raised by the frequency multiplication factor. Due to typical limitations of the much higher frequency
oscillator that is being phase locked to the reference, the PLL bandwidth cannot be made arbitrarily narrow so as to
filter out the reference phase noise. This is why it is crucial to have a reference signal with very low
closein phase noise, as this is the noise that cannot be removed by the filtering action of the PLL.
Calibration and Metrology
Another application for the outstanding closein phase noise performance of our products is in calibration
and metrology. The phase noise level at a 1 Hz offset from the carrier is directly related to the time domain
stability for averaging times on the order of 1 second. The 113 dBc level achieved in our UltraStable OCXO
will yield a measurement uncertainty of 4x1013 for 1 second duration measurements. This level of stability is
not achievable using atomic frequency standards, so our GPSdisciplined OCXO can outperform them for many types
of measurements.


