Step 10: Create The Fit - HP 3563A Operating Manual

Figure 16-14 shows an example of a weighting function where a valley (caused by a conjugate pair of
zeros near the jw axis) is emphasized by the curve fitter.
M : F R E O
1 4 4
d B
8 0 . 0
o
M : WE I G H T
1 . 0
M o g
0 . 0
Y 0
F x d
Figure
Step 1 0: Create the Fit
The fit is created when CREATE FIT in the CURVE FIT menu is pressed. The message "Curve Fit in
Progress" is displayed while the fit is
viewed in the curve fit table; press EDIT TABLE.
zero locations can be
You can fit any portion of the displayed frequency response trace. Use the
for instructions) to identify the band of interest, then press CREATE FIT. The curve is then fitted
only inside the marker band.
If an acceptable fit is achieved before the specified number of poles and zeros have been extracted,
the fit can be stopped by pressing STOP FIT. It is helpful to press FRONT BACK while the fit is
progress. This superimposes the measured response and the fit results so you can monitor the
progress. The fit can also be stopped if it becomes clear that the setup is inappropriate. Because
fitting high-order systems can
curve fit does not factor the last polynomial fit into a table of poles and zeros - the previous table is
left.
R E S P
,
I
16-13. Example Auto Weight Emphasizing Both
Poles and Zeros
in
progress. When the fit is complete, the extracted pole and
be time consuming, stop the fit if it is obviously incorrect. The aborted
O % O v I P
H o n n
H z
i
H z
X
Curve Fit
Curve Ftt Setup Steps
2 0 k
2 0 k
marker (see Chapter 8
in
1 6-45