Protection circuit for acoustic filter and power amplifier stage

A mobile communication device comprising:

• an antenna;
• a baseband processor (BBP);
• an integrated circuit (IC) coupled to the BBP and the antenna, the IC comprising:
• an antenna switch coupled to the antenna and configured to receive a signal from a filter;
• a conductor coupled to the antenna switch and configured to be coupled to an antenna;
• and
• a four-port coupler configured to sense current indirectly on the conductor, where sensed current is indicative of a signal reflected from the antenna, wherein each port includes an associated transient voltage suppression diode;
• and
• a detection circuit coupled to an isolation port of the four-port coupler and configured to generate an alert signal when a reflected signal sensed by the four-port coupler exceeds a threshold, wherein the alert signal is configured to trigger a debias of a power amplifier stage to protect the filter.

A method comprising:

• receiving a signal at a power amplifier stage;
• outputting an amplified output signal from the power amplifier stage;
• adjusting a power level of the amplified output signal by selectively biasing and debiasing the power amplifier stage based on an alert signal;
• filtering the amplified output signal with a filter;
• passing the amplified output signal to an antenna from the filter;
• indirectly sensing current of the amplified output signal before the antenna with a four-port coupler, where sensed current is indicative of a signal reflected from the antenna, wherein each port includes an associated transient voltage suppression diode;
• generating the alert signal with a detection circuit responsive to sensed current exceeding a threshold.

A method comprising:

• receiving at antenna switch a signal from a filter;
• passing the signal from the antenna switch to an antenna through a conductor;
• indirectly sensing current on the conductor using a four-port coupler, wherein sensed current is indicative of a signal reflected from the antenna, wherein each port includes an associated transient voltage suppression diode;
• detecting an overcurrent condition in the sensed current using a detection circuit;
• and
• generating an alert signal responsive to detecting the overcurrent condition.