Teledyne LeCroy DFP2 - Digital Filter Package 2 - Manual (Page 12)

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ISSUED: June 2013 923134 Rev A
In the setup of these filters, you have control of cutoff frequencies, transition region width, and
stop band attenuation.
FILTER SETUP
To Set Up a DFP Filter
1. Touch Math in the menu bar then Math Setup... in the drop-down menu.
2. Touch the Fx tab (F1 for example) for the math trace you want to display
your filtered waveform.
3. Touch the Single function button if you want to perform just one filtering function on
the trace, or touch the Dual function button to perform math on, or apply another
filter to, the filter output.
4. Touch inside the Source1 field and select a source waveform from the pop-up menu.
5. Touch inside the Operaor1 field and select Filter from the pop-up menu. A mini-dialog
to set up the filter will open at right.
Note: Other math choices in the Operator1 menu include Boxcar, ERES, and interpolation. The boxcar "filter" is a simple
average taken over a user-specified number of points (the "length").
6. Touch inside the FIR/IIR field and select finite or infinite response filter FIR (non-recursive)
filters require a limited number of multiplications, additions, and memory locations. On the
other hand, IIR (recursive) filters, which are dependent on previous input or output values, in
theory require an infinite number of each..
7. Whether you selected FIR or IIR, touch inside the Filter Kind field and select a filtering
operation. Some choices are not available for IIR.
8. If you selected FIR, touch inside the Type field and choose an FIR filter type. Then touch
inside the Taps
2
data entry field and enter a value, using the pop-up numeric keypad.
Alternatively, you can touch the Auto Length checkbox; the Taps field is grayed out and the
scope calculates the optimum number of coefficients. If you selected IIR, touch inside the
Type field and choose an IIR filter type. Then touch inside the Stages data entry field and
enter a value, using the pop-up numeric keypad. Alternatively, you can touch the Auto
Length checkbox; the Stages field is grayed out and the scope calculates the optimum
number of stages.
2 The number of coefficients. The number of coefficients. The suggested number of taps is a minimal suggestion: using
even more taps can give a more desirable response. Using less than the suggested number of taps will not meet the
requested specifications.