Teledyne LeCroy DFP2 - Digital Filter Package 2 - Manual (Page 15)

DFP2 Option
923134 Rev A ISSUED: June 2013 13
CUSTOM FILTERS
Custom Filter Setup
If the standard filters provided with DFP2 are not sufficient for your needs, you can create filters
with virtually any characteristic, up to 2000 taps.
The required custom filter can be designed with a digital filter design or math package such as
MATLAB or Mathcad. The filter coefficients can then be loaded into the scope from an ASCII file.
The file consists of numbers separated by spaces, tabs, or carriage returns.
Note: Do not use commas as separators.
For a custom IIR filter there needs to be a multiple of 6. Each stage consists of 3 numbers for the
numerator polynomial followed by 3 numbers for the denominator polynomial. They are in the
order a b c where the polynomial is of the form: a + b * z
-1 + c * z -2 .
Example 1: Creating an FIR Filter Coefficient File Using Mathcad
N := 200 i := 0..N
sinx(x) := sin(x)/x
200 point sin(x)/x, a low-pass filter.
Note: Real world filters would either be windowed or made by the Remez exchange algorithm.
The point of this example is to show how to transfer a filter to the scope.
check = 0.987 This is the DC gain of the filter