Different RX image calibration values depending on if the Spur Reduction is on or off
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Different RX image calibration values... Expand / Collapse
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Posted Thursday, October 12, 2006 4:17 PM


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I have notice that the RX image calibration values differ a bit depending on if the spur reduction is on or off. The differrent isn't much +/- 5 0n the gain and +/- 4 on the phase.

It "seems" to give better image reduction with SR on, but I do not have to tools to really tell.

First question, does this small change really make an difference?



-----
Tim - W4TME
Post #12
Posted Monday, October 16, 2006 12:57 PM
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You are correct.  The values will be slightly different.  The reason for this is because depending on whether spur reduction is on or not, it will put the tone in a different part of the passband.  This will result in slightly different values.  The long and the short of it is that the image rejection is not completely flat across the whole passband.  This is why after you calibrate, you can tune up or down a few kHz and the last 5dB that you worked so hard to get will come back up.  It's just the nature of how we are doing the image rejection.  Eventually we will model the rejection in a better manner that takes care of this.
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