RIGOL 
Copyright ©1998-2008 RIGOL Technologies, Inc. 
  User’s Guide for DS1000CA Series 
3-9
 
 
Figure 3-6 
Ellipse method to observe the phase difference 
 
Sinθ = A/B or C/D, where θ = phase shift (in degrees) between the two signals. 
From the formula above, you could get: 
θ = ±arcsine (A/B) or ±arcsine (C/D) 
If the main axis of the ellipse is at I and III quadrant, θ must be in the range of 
(0~π/2) or (3π/2~2π). If the main axis is at II and IV quadrant, θ must be in the 
range of (π/2~π) or (π~3π/2). 
 
A
B
C
D 
 
Signal must be 
centered in X