To Next Page

To Previous Page

Creating and Using Math Waveforms

3- 158

TDS5000 Series User Manual

waveform reference marker. 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 this level to the equivalent of 1 mW into 50 ohms.

0dB

20 dB 20 dB 20 dB

Figure 3- 46: Effects of adjusting the reference level offset control

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 it 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. C lick the appropriate channel button,

and click Apply.

Using the Phase Controls. You can set the vertical units to Degrees, Radians, or

Group Delay in seconds. To do this, click the Math toolbar button, click Spectral

Analysis Setup, and select the Phase tab. Then select the desired scale type from

Degrees, Radians, or Group Delay.

Phase Reference Position: Phase is a relative measurement that must have a time

domain reference point. The phase value is specified with respect to this phase

reference position.

For the spectral analyzer, the phase reference position is the 50% position of the

gate, that is, the middle of the gate interval of the data that is input to the spectral

analyzer. This is true for all window functions except for the Tek Exponential

window. This window has a the reference point at the 20% position of the gate.

Phase Unwrap: The spectral analyzer produces phase values from --π to

π radians or --180 to 180 degrees. However, when you perform impulse response

testing and the phase is continuous, then phase values outside these ranges may

occur. The spectral analyzer then wraps the data with discontinuities in the

Tektronix TDS5052 User Manual

Other manuals for Tektronix TDS5052