Doppler wind measurements

In comparison to non-Doppler radars, a Doppler radar can provide clutter cancellation and wind products.

A Doppler radar measures the speed of the reflector by studying how the phase of microwaves compared to the sent pulse changes between samples.

A non-moving target has no phase shift.
A target whose movement has no component in direction of the radar beam, has no phase shift.
A phase shift of exactly 2p looks like no phase shift.
A phase shift of 2p+d looks like phase shift d.
A phase shift of n*2p+d looks like phase shift d. This is called aliasing.

To get good Doppler measurements, many samples must be processed together (64 is good). This sets limits to antenna speed.

The maximum speed which can be measured unambiguously is

V_{\max} = \frac{P R F \times λ}{4}

where λ (lambda) denotes wavelength.