Page 7 - Vibrations 3

= 5130 ( )
2

Not at simple as it seems. Both signals are likely to be very

noisy, you will not get a clean ellipse to measure .

_____________________________________

To perform phase measurements from the cross-

correlation function, use the Fourier Transform,

() = ∫ () −2

The phase spectrum will be given as,

[ ()]

Φ () = tan −1 ( )

[ ()]

The 35670A spectrum analysers has this option and you

can measure the phase at the frequency f.

The phase spectrum can be very confusing owing to the

fly-back of the trace on the screen [− < < ].
2 2

In principle you can generalise cross-correlation to include

several signals for example,

′
′
ℎ (, ) = ∫ () ( − ) ℎ( − )

6