Apple Inc.
RF Power Detector With A Variable Threshold

Abstract:

A radio frequency (RF) power detector with a variable threshold for dynamic power detection. The RF power detector includes stacked transistors of an input stage and stacked transistors of an output stage. A DC bias voltage plus an input RF signal are applied to a control electrode on the input stage and the same DC bias voltage plus an additional DC bias voltage are applied to a control electrode on the output stage. Depending on the input power of the RF signal, a .DELTA. current is generated in the output stage, and the output capacitor is either charged or discharged, and the output capacitor voltage is compared to a threshold to generate an output signal. The output signal may be averaged over time by two capacitors, miller capacitor and output capacitor. The output voltage of the RF power detector is an integration over time of the input RF power.