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Strange AGC behavior

Question asked by Olegis on Jun 2, 2015
Latest reply on Jun 3, 2015 by Olegis

Hello,

 

I use a fast AGC mode in my design (TDD mode). I monitor the AGC state machine states via the control outputs, as described in documentation. When register 0x035=7, the control outputs 3, 2 and 1 should indicate the AGC state in real time.

In most scenarios the AGC works very well, but sometimes I see strange behavior, as illustrated in the screenshot below -

 

AGC_SM.jpg

 

Red trace is control output 3 (AGC SM bit 2), blue trace is control output 2 (AGC SM bit 1) and green trace is control output 1 (AGC SM bit 0). In the scenario above, the AGC state is locked (101b=state 5) until something happens that unlocks the gain (in this case a large Rx signal arrives). Then the AGC starts oscillating between 110b (state 6 ? What is state 6 ?) and 001b (state 1), as shown.

After quite a few such oscillations the AGC manages to lock the gain again.

 

What would cause such behavior ? What is this state 6 that the AGC goes to ? Any help would be appreciated.

 

Thanks,

Oleg C.

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