|
Frequency
Standards or oscillators are available in different
types. This document gives a brief overview of
each type supplied by Precision Test Systems.
OXCO
Crystal Oscillator
An oven
controlled crystal oscillator (OXCO) can be used in
applications where a moderate degree of frequency
accuracy is needed or where ultra low phase noise is
required.
OXCO
oscillators operate from 100 kHz to 500 MHz.
Higher frequencies can be obtained by the use of
multipliers.
The
oscillator is enclosed in an oven to reduce the effects
of ambient temperature changes.
The
typical drift of our OXCO oscillators varies from 1
parts on 10E-10 / day (our lowest drift) to 1 ppm
/ year (our lowest cost). So an oscillator with a
specification of 1 x 10E-10 will drift a maximum amount
of 0.001 Hz per day or 0.36 Hz / year (worse case) for a 10 MHz
oscillator.
Phase
noise is an important parameter and we manufacture some
of the lowest phase noise oscillators available on the
market. Phase noise of -115 dBc/Hz @ 1 Hz is
available with a -174 dBc/Hz floor noise (10 kHz
offset).
Most of
our OXCO oscillators are housed in a 1U rack and have
from one to fifteen sinewave outputs. All outputs
are isolated from each other.
However
we can supply OXCO's in smaller packages or bespoke
designs.
Our
range of OXCO oscillators include:
Rubidium Frequency Standard
A
rubidium oscillator is an atomic oscillator. It
uses rubidium vapor to discipline a 10 MHz OXCO
oscillator. By multiplying the 10 MHz OXCO to
6.8346826128 GHz and feeding it to a resonance cell that
also has a Rb87 enriched discharge lamp, the resultant
output is used to control the 10 MHz OXCO.
Rubidium
oscillators have the advantages of very low drift (about
60 times better than the best OXCO oscillator).
However, in the past, rubidium oscillators had the
disadvantages of high cost, limited life and poor phase
noise.
The
rubidium used in our GPS10RBN frequency standing
overcomes these disadvantages due to a unique design.
The cost is reduced, the rubidium has been designed for
a twenty year life and the phase noise is up to 30 dB
better than competitive units.
Thus,
our rubidium oscillators offer significant advantages
over competitive units at a cost effective price.
By using
the GPS satellite system, rubidium frequency standards
can approach the performance of a cesium frequency
standard but at a fraction of the price.
Details
of our GPS10RBN GPS Disciplined, rubidium frequency
standard are available by clicking
here
Cesium Frequency Standard
Cesium
clocks are again atomic clocks similar to rubidium but
using cesium instead. The advantages of cesium
frequency standards is that they don't drift in
frequency. They do have an offset but this is very
small (parts in 10E-13). Cesium oscillators form
the basis for world time.
The
disadvantages are that cesium frequency standards cost
at least ten times the price and the tubes have a very
limited life 5 to 10 years). Replacing a tube is
very expensive.
We
supply cesium frequency standards. Click
here
for
details.
Hydrogen Maser Frequency Standard
Hydrogen
masers offer the ultimate in frequency accuracy with
offsets to parts in 10E-16. They are very
expensive and are only made in limited quantities around
the world.
Precision Test Systems is able to supply hydrogen masers
on special order. |
