The problem concerns the use of the Gilbert cell type VGA in a continuous time feed back loop including a peak detector followed by an integrator integrating the error (between peak detector output and a reference level).
The gain is controlled by the voltage difference between the LO switches. The gain switches sign when the control voltage crosses zero. So the gain versus control voltage is not monotonic. So how can such a VGA be included in a feedback loop with the peak detector and integrator.

Raja Prabhu