LeCroy DDA 7 Zi series, Operator'S Manual

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WavePro 7Zi
359
WP700Zi-OM-E-RevA
package such as MATLAB or Mathcad. Filter coefficients can be directly downloaded from the program into the
scope, using the DSOFilter utility. It is also possible to specify the filter coefficients on an Excel spreadsheet and
to use DSOFilter to download them from the spreadsheet to the scope.
DFP2's flexibility is shown by the following example:
Figure 5-16. 1. A 25 kHz square wave
combined with an unwanted 60 Hz
sinusoidal component.
Figure 5-17. 2. A high-pass filter set
to attenuate signals lower than 1 kHz
is applied to remove the unwanted 60
Hz component.
Figure 5-18. 3. FFT of the unfiltered
trace.
Figure 5-19. 4. FFT of the filtered
trace. Note the absence of the 60 Hz
component.
Enhanced Solutions
DFP2 can be coupled with other LeCroy software products such as JTA2 or DDM2 to enhance the capabilities of
these products and to provide improved solutions. For Jitter Measurement, for example, the DFP2 Band-pass
Filter can be coupled with the JTA2 package to measure jitter over a narrow frequency range.
KINDS OF FILTERS
1
1. Filters are optimal FIR filters of less than 2001 taps, according to the Parks-MacLellan
algorithm described in Digital Filter Design and Implementation by Parks and Burrus, John Wiley & Sons, Inc.,
1987, and then adjusted by windowing the start and end 20% with a raised cosine for improved time domain
characteristics and better ultimate rejection in the frequency domain, slightly increasing 1st stop-band ripple
height.
Low-pass Filter
Low-pass filters are useful for eliminating accumulated high-frequency
noise and interference, and for canceling high-frequency background
noise.
Sample applications are in datacom, telecommunications, and disk drive
and optical recording analysis for accurate RF signal detection.
Band 1: Pass Band — DC to top of the transition region; signal passes
unattenuated.
Band 2: Transition Region — edge frequency to edge frequency plus
width; increasing attenuation.
Band 3: Stop Band — above end of transition region; signal is highly
attenuated.
High-pass Filter
High-pass filters are useful for eliminating DC and low-frequency
components. Sample applications include Disk Drive and Optical
Recording analysis (emulation of the SLICING function).
Band 1: Stop Band — DC to bottom of the transition region; highly
attenuated.
Band 2: Transition Region — edge frequency minus width to edge
frequency; decreasing attenuation.
Band 3: Pass Band — above edge frequency; signal passes unattenuated.