Howtosignalprocessing
- Why do we use Allan variance?
- How do you read Allan variance?
- What is Tau in Allan variance?
- How do you measure Allan deviation?
Why do we use Allan variance?
Allan deviation is widely used for plots (conventionally in log–log format) and presentation of numbers. It is preferred, as it gives the relative amplitude stability, allowing ease of comparison with other sources of errors.
How do you read Allan variance?
An Allan deviation of 1.3×10−9 at observation time 1 s (i.e. τ = 1 s) should be interpreted as there being an instability in frequency between two observations a second apart with a relative root mean square (RMS) value of 1.3×10−9. For a 10-MHz clock, this would be equivalent to 13 mHz RMS movement.
What is Tau in Allan variance?
Allan variance is used to measure the frequency stability of oscillation for a sequence of data in the time domain. It can also be used to determine the intrinsic noise in a system as a function of the averaging time. The averaging time series τ can be specified as τ = m/fs.
How do you measure Allan deviation?
The beat frequency method is the standard method to measure Allan variance, or more precisely to measure the frequency deviation of the DUT from the frequency standard. The total power at the respective offset frequency is read from the spectrum analyzer display.
