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Chapter 3 Demo Waveforms
Demo 1: Voltage-Controlled Oscillator (VCO) Frequency Step Response
and Settling
The step response, frequency overshoot, and settling characteristics can
be seen clearly on this display.
Cursors and Markers
The software lets you easily find the (x,y) coordinates of any point on the
display (it doesn't have to be a measurement point.) Position the
"crosshair" (+) using the mouse at a point of interest, for example the peak
of the VCO step waveform, hold the SHIFT key and click the left mouse
button. The bottom entry in the log area (bottom of the display) will show
MRK1>, the x value (time in this case), the y value (frequency deviation
from Fo), and the absolute frequency value.
Now move the cursor to a point at the bottom of the "ringing" of the
waveform, hold the SHIFT key and click the right mouse button.
The data log now shows MRK2> and MRK1to2> with the difference in
both x (Dtime) and y (Dfreq) from the previous cursor position (D= delta).
The peak-to-peak ringing is about 130 kHz. You can continue positioning
the cursor at various points and, while holding the SHIFT key, clicking
the right mouse button; each new log entry will be the x,y difference from
the previous cursor position. To clear a marker, hold down the CONTROL
key while clicking on the appropriate mouse button. Both markers may be
cleared in one operation by clicking both mouse buttons together.
Zooming
Any portion of the data display may be arbitrarily magnified using the
zoom feature. You simply define two diagonal corners of a rectangle which
will be the new, magnified display.
1
To magnify the peak overshoot and settling of the VCO response, position
the cursor just to the left of the overshoot of the waveform. Click and drag
the mouse to define the area you wish to magnify as follows. Click the left
mouse button (you've just defined the upper left hand corner position of
the magnified display) and drag the mouse to a point just to the right of
the ringing portion of the waveform, and slightly beneath the 10 MHz
frequency level. Release the mouse button. You have defined the lower
right hand corner position of the magnified display. The green box
outlines the region that will be magnified when you click the "zoom"
button.
Getting Started Guide
3-7
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