# Butterworth Operator

The Butterworth operator applies a low-pass filter to the waveform. Butterworth filters have a very flat passband response with little ripple when compared to other filter designs.

To enter the Filter Order and Filter Cutoff Frequency, double click on the operator.

The Show Transfer Function, Show Impulse Response, or Show Step Response options automatically load the operator's network into Freq-Mag, Impulse Response, or Step Response chart windows (like you can do with de-embedding transfer functions — see S-Parameter/Transfer Function Viewer).

The Butterworth operator requires a single-valued waveform, as opposed to an eye diagram. Be sure that your trigger setup results in a single-valued waveform at the input to this operator.

Jitter measurements can be made on the Butterworth operator's output waveform.

## Display Setup

Each operator's setup includes a Setup section that has the selections that are shown in the following generic setup dialog box. Use these settings to control the display of the operator's output waveform, including turning the display on or off. Use the Name field to display an identifying name to the waveform which can be helpful for screen captures or when multiple waveforms are displayed. The settings also include the output waveform's color, scaling, and signal type. The scaling Automatic selection allows the output waveform to track changes to the scaling of the input waveform. This is the setting that you would normally want to use.

The signal Pattern can be used for BER (Bit Error Ratio), SNDR (Signal to Noise and Distortion Ratio), and other measurements. You can specify the math function has the same pattern as the input waveform (Track Input), Auto Detect the pattern, choose a Known Pattern from a list, or specify your own pattern using a Pattern File.