Time Data - Agilent Technologies 89410A Operator's Manual

Time data

The 89400 series analyzers provide the ability to view and analyze the time domain
data. Time measurement data provides a time domain view of the input data before
FFT processing. The following points will help you interpret time data:
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Time data is available in Vector and Demodulation modes but not in Scalar
mode.
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Time data may look similar to an oscilloscope display in some cases but you
will see distortion, particularly at high frequencies. The distortion occurs
because the waveform is made up of the discrete samples from a time record
which is optimized for FFT measurements. FFT measurements require a lower
sample rate than would be required for an optimum time domain display.
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The analyzer must be in baseband mode to display data similar to an
oscilloscope. In other words the measurement must start at 0 Hz and the
center frequency must not be set explicitly. If you enter zoom mode either by
setting the center frequency explicitly or by pressing the zoom/baseband key, a
notice will flash on the screen which indicates that time data is in zoom mode.
In zoom (band-selectable) measurements the time data is displayed relative to
the center (local oscillator) frequency rather than relative to DC. Therefore,
zoom time data has a different appearance because baseband data is real while
zoom data is complex. Because the local oscillator is tuned to the center
frequency for zoom measurements, the time data is represented as the
difference frequency between the local oscillator and the input signal
frequencies.
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Time and time exponential averaging are the only types of averaging which
affect time data displays. Other average types only display the most recent
time record.
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In baseband mode with maximum span, some signals, particularly square
waves and transients, may appear to have excess distortion or ringing because
of the abrupt frequency cut-off of the anti-alias filters. In this case the time
data display can be improved by turning off the anti-alias filter under the [
menu. Make sure you turn the filter back on before viewing frequency domain
data.
Fundamental Measurement Interactions
Input
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