# How to implement a Bessel filter with ModelingToolkit?

**URL:** <https://discourse.julialang.org/t/how-to-implement-a-bessel-filter-with-modelingtoolkit/101220>\
**Category:** Modelling & Simulations\
**Tags:** question, package, modelingtoolkit\
**Created:** [July 5, 2023, 5:27pm UTC](https://discourse.julialang.org/t/how-to-implement-a-bessel-filter-with-modelingtoolkit/101220 "2023-07-05T17:27:31Z")\
**Posts on this page:** 1\
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**Author:** ![baggepinnen](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/baggepinnen/32/693_2.png) [@baggepinnen](https://discourse.julialang.org/u/baggepinnen)\
**Post date:** [July 5, 2023, 7:40pm UTC](https://discourse.julialang.org/t/how-to-implement-a-bessel-filter-with-modelingtoolkit/101220/5 "2023-07-05T19:40:20Z")

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This answer

> [@Designing a band pass filter with modeling toolkit](https://discourse.julialang.org/t/designing-a-band-pass-filter-with-modeling-toolkit/99118/6):
>
> Before doing analog filter design with DSP, beware of [analogfilter design seems to be broken · Issue #341 · JuliaDSP/DSP.jl · GitHub](https://github.com/JuliaDSP/DSP.jl/issues/341) TLDR; analog filter design is quite broken in DSP but the problem can be worked around. Having said that, here’s how you can convert a filter to an MTK system with the PR [#843](https://github.com/JuliaControl/ControlSystems.jl/pull/843) using DSP, ControlSystemsBase # Digital filter fs = 100 df = digitalfilter(Bandpass(5, 10; fs), Butterworth(2)) G = tf(df, 1/fs) bodeplot(G, xscale=:identity, yscale=:identity, hz=true) …

demonstrates one particular way of obtaining an MTK model for a transfer function.

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