LeCroy DIGITAL FILTER PACKAGE Software
In today’s complex environment, data is frequently composed of
a mixture of analog and digital components spread over a broad
range of frequencies. In many applications, the relevant data is
encoded or obscured. Capturing the right signals becomes a
challenge. Engineers find it increasingly difficulty to examine only
those parts of the data they are interested in. Traditional (or even
triggering cannot always provide a
For example, servo motors from disk drives add a low frequency
component to the high frequency data output. It is hard to achieve
an accurate analysis of data unless the low component is
Another common example is switched Power supply
inject the switching frequency component into many system
parts. Viewing digital signals mixed with this switching frequency
component could be very difficult. Filtering is definitely required.
Yet another example is in ADSL residential connectivity, where
data is transmitted over 256 narrow bands. Each band is only
4.7kHz wide, and the gap between two adjacent bands is also
4.7kHz. Examining such complex waveforms with regular DSOs
is almost impossible; filtering out unwanted frequency
components is necessary.
At present, these needs are addressed in two ways. One way is
building analog filters and placing them in front of the
oscilloscope, providing an already filtered signal to the DSO. The
disadvantages of this approach are many. Analog filters depend
heavily on the accuracy and stability of analog components.
Although in some cases analog filters are easily implemented,
they are quite impractical for low (< 100 Hz) or high (> 100 MHz)
frequency ranges. In comparison, digital filters can provide the
desired results in those cases.
The second approach, practiced by many engineers, is using the
DSO as a digitizer. The digitized data output is then transferred to
a PC for processing. This solution frequently provides the
required results, but it might be too slow or too limited in flexibility
for some applications.
With the DIGITAL Filter
provides a solution that
combines the best of both worlds. This package includes seven
of the most useful Filter
types, in addition to a custom design
feature. You can easily set the edge (or corner) frequency in
addition to the transition region width for each Filter
. It is possible
to use single filters or multiple (up to four) filters cascaded for
even more complex filtering. Once filtered, waveforms include
mostly relevant frequency components, undesired parts being
If filters with special characteristics are desired, the custom
design feature allows you to design unique filters tailored to your
specific needs. The required Filter
can be designed with a digital
design or math package such as MATLAB® or Mathcad®.
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.
DFP can be coupled with other LeCroy Software
products — such
as AORM, JTA, PMA1
or DDA — to enhance the capabilities of
these products and to provide improved solutions.
Jitter Measurement: the DFP Band-pass Filter
coupled with the JTA package to measure jitter over a narrow
Optical Recording: In some cases equalization with a
different response is required. In such a case, the DFP
feature can be used in conjunction with AORM.
The required custom Filter
can be easily implemented to
provide the necessary equalization, while all other AORM
functions remain unchanged.
Power Measurement: A Band-stop Filter
can be coupled with
package to eliminate the switching Power supply
frequency component from power lines. The Band-stop Filter
can be tuned to match a specific Power supply