Sunday, February 7, 2016

Quick PCB: Crystal Ladder Filter

Here's a little board for making a four pole crystal ladder filter.

Four Pole Crystal Ladder Filter with SMA connectors

This type of filter has a very high Q and narrow bandwidth, allowing you to select a specific frequency from your signal. Because of the narrow bandwidth, selection of the capacitors and tuning of the filter is important to achieve the desired response. You will want to test your filter after designing and assembling it to verify performance.


Here are some links to cover the design theory. Many more can be found using an internet search.

Schematic of the board

Parts List

Crystals: Standard HC-49 through-hole crystals
C1 through C5: 0603 SMT capacitors
SMA Connectors: Edge-Launch SMA for 1.6mm/0.062" board thickness

If you make some interesting crystal filters with this board let me know!

- Dan W.

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