Tektronix 11801C User Manual page 402

Appendix D: Algorithms
D 6
scallop loss is the attenuation of the windowing function at the odd
numbered (interpolated) points in the FFT waveform.
worst loss is the worst case processing loss (the sum of the scallop
loss and the equivalent noise bandwidth, in dB).
Filter
Filter(n) + Smooth(Smooth(n))
Centered Mode (Non Causal) Filter Algorithm
Smooth(n) + (1 s)
for n t h
Smooth(n) + (1 s)
for h v n v R * 1 * h
Smooth(n) + (1 s)
for n u M * 1 * h
where:
n = index into record of data points
W(n) = input sampled data point
s = smoothing interval = Round (sf)
risetime
sf +
(time per dot)
risetime = the second argument to Filter
where:
risetime > 10 ps and < 50 ms
h = half interval: (s - 1)/2 rounded up
R = record length in points
The centered mode, smoothed trace is derived by computing the average
value of the corresponding point of the original trace and some number of
points of the original trace on either side of the corresponding point. The
number of points on either side is derived from the smoothing interval, the
second argument of the Smooth function. Near the ends of the trace, nonex
istent points beyond the ends of the trace are required for averaging. The
nonexistent points are assumed to be the value of the corresponding end
points. This method of extending the trace is arbitrary, so the results within a
smoothing interval of the ends of the trace must be interpreted accordingly.
n)h
W(m) ) (h * n) W(0)
m+0
n)h
W(m)
m+n*h
R*1
W(m) ) (M * 1 * n)
m+n*h
1.10557
W(M * 1)
Appendices