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Oscilloscope Reference Spectral math phase controls

Reference level offset

This changes the value of Ref in the equation for dB s

hown

above. Unlike the Reference Level control, this control

actually changes the output data values in the spectrum.

Zero dB is shown on the display screen by the marker

associated with the spectral waveform. Adjusting the

Reference Level Offset causes the spectral waveform to

move vertically with respect to the waveform ref

erence

marker as shown. This moves the waveform without

changing the Reference Level control setting. Sometimes

it is beneﬁcial to adjust this control so that the

peak of a

fundamental is at zero dB. Then you can measure other

harmonics in terms of how many dB they are away from the

fundamental. Click the dBm button to preset th

is level to the

equivalent of 1 m W into 50 ohms.

xxx

Real and imaginary magnitudes

You can display the linear magnitude of the real data or the imaginary data in the spectrum. This is useful

if you process the spectrum off line and transform i t back into a time domain trace. You can save the real

and the imaginary spectrum into reference memory, and export the waveforms directly into Mathcad,

MATLAB, or Excel documents to update in real time.

To turn on a real or imaginary spectrum, click the Math menu button, select Deﬁne/Edit Expression

Editor, and select the Freq tab. Click either the Real or the Imag buttons and enter an expression. Click

the appropriate channel button, and cl

ick Apply.

What do you want to do next?

Go to a list of all spectral math controls. (see page 760)

Learn more about spectral math controls. (see page 766)

Go to a step-by-step procedure for deﬁning a spectral math waveform. (see page 623)

Spectral math phase controls

Select the phase controls

You can set the vertical units to Degrees, Radians, o rGroupDelayinseconds.Todothis,clicktheMath

toolbar button, click Spectral Analysis Setup, and select the Phase tab. Then select the desired scale type

from Degrees, Radians, or Group Delay.

766 DSA/DPO70000D, MSO/DPO/DSA70000C, DPO7000C, and MSO/DPO5000 Series

Tektronix DPO5000 Series User Manual

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