Background: a set of 110.51 MHz filters were acquired on eBay per usual, and I ended up with around 400 of them. Part number was 110E39.
No data sheet was available, though a potentially related data sheet for 90 MHz filters in the same package was available from NDK.
Here is the response when used in a 50 ohm system with no matching:
It can be seen that this filter is approximately 40 kHz wide, with a set of spurs on the high side of the filter. As with the SAW filter design, any image frequencies should be set up to be below the center. Using a 21.4 MHz IF from this design with a low-side LO would give excellent performance.
Measurements indicate this filter is around 400 ohm in/out, but the amount of ripple and insertion loss is low enough for IF use that the matching components aren’t really needed.
I built a test board using matching components and while it did reduce the amplitude ripple, the total performance was worse. The high side peaks were also still there.
This article was updated on 2017-08-04T16:53:53+0200