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AD936x Digital Filtering Path (halfbands)

Question asked by ltechief55 on Jun 1, 2015
Latest reply on Jun 2, 2015 by tlili

I'm using the AD9361 as an LTE radio. I'm configuring it in a mode similar to the example on page 36 in the reference manual, with all the decimation stages set to decimate by 2. I've set the analog bandwidth to 10 MHz and fs = 30.72 MHz, 128 tap FIR with 65 dB rejection. Once I insert an interferer just outside the band it degrades the EVM performance dramatically.

I'm wondering if the provided halfband filters don't provide enough image rejection for decimation. The filters HB2 and HB3 especially only have 5 and 7 taps and very gradual transitions when plotted in Matlab.

What's a recommended configuration for 10 MHz LTE being mindful of adjacent channel rejection?

Thanks

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