Creating and Using Math Waveforms
CSA7000B Series & TDS7000B Series Instruments User Manual
3- 191
--35 dB
0 °
Magnitude vs. frequency
Suppression threshold
Phase vs. frequency
Figure 3- 52: Example of the effects of setting the phase suppression threshold
H Group Delay. When the phase spectrum is a continuous function of
frequency, group delay may be computed. This is true of impulse response
testing where an impulse is fed into the system and the spectrum of the
response of the system output is computed.
Group delay measures how well a system passes a signal in terms of phase
distortion. Group delay is the negative derivative of the phase with respect to
frequency.
This feature is not useful for analysis of harmonic content of signals where
the phase response is not continuous.
H Impulse Response Testing. When performing impulse response testing of a
system, place the impulse at the zero-phase reference position of the
acquisition. This produces a correct phase display. Because the Tek
Exponential window has its zero phase reference position at the 20% point,
more of the impulse response is captured. All other window functions have
their phase reference position at the 50% position in the gated region.
There are several ways to adjust the position of the zero phase reference
point with respect to your input signal:
H Adjust the spectral analyzer gate position
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