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Invert Bypassed LNA Polarity and RF DC Offset issues

Question asked by omek on Apr 15, 2016
Latest reply on Jul 8, 2016 by omek

I have an application where I would like to utilize the Invert Bypassed LNA Polarity (reg 0x22 bit[6]). I found that when I have this setting enabled and I have a Rx gain setting where the LNA is bypassed, then the RF DC offset algorithm seems to fail. The correction registers (in my case I'm using Rx 2A) in 0x176 = 0x10, 0x177 = 0x60, 0x178 = 0x80. They have these values for any gain setting where the LNA is bypassed. Basically they are railed at a high DC offset correction value.

 

I'm using a workaround where I edited my Rx gain table to always leave the internal LNA on, but this reduces my Rx dynamic range by about 11 dB.

 

Has anyone else come up with a solution that allows them to

     - avoid a phase rotation when bypassing the internal LNA

     - avoid corruption of the automatic RF DC offset correction algorithm

     - get the full dynamic range in the receiver?

 

Thanks

-Steve

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