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RF Filter for STM32WLE5

Associate III

I'm using a STM32WLE5 processor in my design. I had an RF consultant tell me that I needed to add a SAW filter to the design to protect against potential interference with 800 MHz cell phone transmissions so I placed a B39921B3728U410 SAW filter at the RF input/output. Is this really necessary? I don't see any similar filter on the Semtech eval boards for the SX126x series. In addition, I lose 2.2-4 dB through the filter. Is it worth it or did my consultant give me bad advice?

ST Employee

Hello @DWalk.3 and welcome to ST Community.

The need for a SAW filter depends on the specific requirements of your design and the environment in which it will operate. If your design is not particularly sensitive to interference from cell phone transmissions, or if it will not be operating in an environment where such interference is likely, then the filter may not be necessary.

As for the loss through the filter, it is not uncommon for filters to have some insertion loss. However, the amount of loss will depend on the specific filter and its design. If the loss is too great for your application, you may want to consider a different filter or a different approach to mitigating interference.

I hope this is helpful for you.


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