Sometimes the stocked Mini Circuits Lowpass / Highpass Filters do not meet the specificatins of our lab mice. It is then suiteable to have the components ready to hack together a lowpass (highpass) in no time. For this we designed a board which can hold any 9-pole (or less) filter type using the inductors (size 1030, 1050) of the Würth SMD WE-PD series Power Choke Coils. They are advertised for power supplies, but their shielding make them a good choice for filters, too. Capacitors can be used of size 0603, 0805 and 1206. Use NP0.

For the design you mayst want to use any calculator of your choice. We used RFSim99 which is a superb tool by Stewart Hyde. Calculate your filter and tweak the values to meet standard inductor / capacitor values.


A LOWPASS for 61 kHz, designed with RFSim99

The assembly is easy and can be done in a few minutes. Keep in mind, that you solder the capacitors first, as access to the soldering pads becomes challenging when the inductors are placed first.

As no device will leave the lab without proper testing, we verified the frequency response with our hp8753E network analyzer.

A LOWPASS for 1 MHz, designed with RFSim99

It can be seen, that the output stays down to more than 500 MHz. This speaks for the inductors by Wüth Electronics.

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