# TIE Filter

In the Advanced tab of the Jitter Measurement Setup dialog box, in the Random Jitter/Interference (RJ/RN) area, the TIE Filter tab lets you apply a filter to the jitter measurements. Select Filter TIE and then specify the filter parameters using these controls:

- TIE Filter Type — Selects Low-pass, Band-pass, or High-pass.

- Start Frequency — Frequencies below this value are filtered out of the TIE measurement.

- Stop Frequency — Frequencies above this value are filtered out of the TIE measurement.

- TIE Filter Shape — You can select from these TIE filter edge shapes:

  - Rectangular — The TIE filter is a brickwall filter.

  - 20dB/Decade — The TIE filter edge(s) roll off at 20 dB per decade.

  - 40dB/Decade — The TIE filter edge(s) roll off at 40 dB per decade.

  - 60dB/Decade — The TIE filter edge(s) roll off at 60 dB per decade.

  - First Order — Available with the High-pass and Low-pass filter types only, this is similar to the 20 dB per decade roll off, but the response is more curved. See:

    - Equation for the First Order High-pass TIE filter
    - Equation for the First Order Low-pass TIE filter

  - Second Order — Available with the High-pass and Low-pass filter types only, this is similar to the 40 dB per decade roll off, but the response is more curved. See:

    - Equation for the Second Order High-pass TIE filter
    - Equation for the Second Order Low-pass TIE filter

    When the Second Order TIE filter edge shape is selected, you can also specify the Damping Factor:

    < 1 | underdamped
    > 1 | overdamped
    = 1.0 | critically damped
    = 0.707 | Often considered ideal or optimal because of its fast settling time (optimally flat) and Butterworth type response.