Agilent Technologies 8753ET User Manual page 23

Figure 1-4 Example Insertion Phase Response Measurement
The phase response shown in
between frequency points. If the   180, incorrect phase and delay information may result.
shows an example of phase samples being with 
 less than 180 and greater than 180.
Figure 1-5 Phase Samples
Undersampling may arise when measuring devices with long electrical length. To correct this problem, the
frequency span should be reduced, or the number of points increased until  is less than 180 per point.
Electrical delay may also be used to compensate for this effect (as shown in the next example procedure).
Measuring Magnitude and Insertion Phase Response
Figure 1-5 is undersampled; that is, there is more than 180 phase delay
Making Measurements
Figure 1-5
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