# US 12,003,268 B2 · Apparatus and methods for power amplifier signal limiting > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,003,268 B2 - Document ID: US12003268B2 - Status: Granted - Kind: B2 - Application number: 17/663,067 - Filed: 2022-05-12 - Published: 2022-12-01 - Granted: 2024-06-04 - Earliest claimed: 2021-05-28 - Assignees: Skyworks Solutions, Inc. - Applicants: Skyworks Solutions, Inc. - Inventors: Philip John Lehtola - Web page: https://patentgrep.com/patent/US12003268B2 ## CPC - H04B 1/40: Circuits - H03F 1/52: Circuit arrangements for protecting such amplifiers {(monitoring arrangements G01R31/28; increasing reliability in communication systems, e.g. using redundancy H04B1/74)} - H03F 3/19: with semiconductor devices only - H03F 3/245: {with semiconductor devices only} - H03F 2200/105: A non-specified detector of the power of a signal being used in an amplifying circuit - H03F 2200/171: A filter circuit coupled to the output of an amplifier - H03F 2200/426: the amplifier comprising circuitry for protection against overload - H03F 2200/451: the amplifier being a radio frequency amplifier - H04B: TRANSMISSION - H03F: AMPLIFIERS ## Abstract Apparatus and methods for power amplifier signal limiting are disclosed. In certain embodiments, a power amplifier system includes a power amplifier that amplifies a radio frequency input signal, and a signal limiter operable to limit a signal power of the power amplifier when the radio frequency input signal exceeds a threshold. The signal limiter includes a radio frequency detector configured to generate a detection signal based on detecting a power level of the radio frequency input signal, and a latch configured to lock the signal limiter into an attenuating mode in response to the detection signal indicating that the threshold is exceeded. ## Claims ### Claim 1 A mobile device comprising: a transceiver configured to generate a radio frequency input signal; and a front-end system including a power amplifier configured to amplify the radio frequency input signal, and a signal limiter operable to limit a signal power of the power amplifier when the radio frequency input signal exceeds a threshold, the signal limiter including a radio frequency detector configured to generate a detection signal based on detecting a power level of the radio frequency input signal, and a latch configured to lock the signal limiter into an attenuating mode in response to the detection signal indicating that the threshold is exceeded, the signal limiter including an input connected to an input of the power amplifier and an output connected to an output of the power amplifier, the signal limiter further including an attenuator including a plurality of diodes connected in series between the output of the power amplifier and ground, the plurality of diodes including one or more selectable diodes that are bypassed in the attenuation mode. ### Claim 2 (depends on 1) The mobile device of claim 1 wherein the transceiver is configured to generate the radio frequency input signal during a transmit frame, and in response to the detection signal indicating that the threshold is exceeded the latch is operable to lock the signal limiter into the attenuation mode for a remainder of the transmit frame. ### Claim 3 (depends on 2) The mobile device of claim 2 wherein the power amplifier is biased by a bias signal that is activated during the transmit frame and deactivated during a receive frame, the latch selectively reset by the bias signal. ### Claim 4 (depends on 1) The mobile device of claim 1 wherein the front-end system further includes an acoustic wave filter configured to filter a radio frequency output signal from the power amplifier, the acoustic wave filter protected by the signal limiter. ### Claim 5 (depends on 1) The mobile device of claim 1 wherein the radio frequency detector includes a reference current source configured to generate a reference current that sets the threshold. ### Claim 6 (depends on 5) The mobile device of claim 5 wherein the reference current source includes a trimming circuit operable to trim the reference current. ### Claim 7 (depends on 5) The mobile device of claim 5 wherein the reference current source is configured to generate the reference current with a positive temperature coefficient. ### Claim 8 A method of signal limiting in a mobile device, the method comprising: generating a radio frequency input signal using a transceiver; amplifying the radio frequency input signal using a power amplifier; and limiting a signal power of the power amplifier when the radio frequency input signal exceeds a threshold using a signal limiter, including generating a detection signal based on detecting a power level of the radio frequency input signal using a radio frequency detector of the signal limiter, and locking the signal limiter into an attenuating mode in response to the detection signal indicating that the threshold is exceeded using a latch of the signal limiter; biasing the power amplifier with a bias signal that is activated during a transmit frame and deactivated during a receive frame; and selectively resetting the latch with the bias signal. ### Claim 9 (depends on 8) The method of claim 8 further comprising generating the radio frequency input signal during the transmit frame, and locking the signal limiter into the attenuation mode for a remainder of the transmit frame in response to the detection signal indicating that the threshold is exceeded. ### Claim 10 (depends on 8) The method of claim 8 further comprising filtering a radio frequency output signal from the power amplifier using an acoustic wave filter, and protecting the acoustic wave filter using the signal limiter. ### Claim 11 (depends on 8) The method of claim 8 further comprising generating a reference current that sets the threshold using a reference current source of the radio frequency detector. ### Claim 12 (depends on 11) The method of claim 11 further comprising trimming the reference current using a trimming circuit. ### Claim 13 (depends on 11) The method of claim 11 further comprising generating the reference current with a positive temperature coefficient using the reference current source. ### Claim 14 A power amplifier system comprising: a power amplifier configured to amplify a radio frequency input signal, the power amplifier biased by a bias signal; and a signal limiter operable to limit a signal power of the power amplifier when the radio frequency input signal exceeds a threshold, the signal limiter including a radio frequency detector configured to generate a detection signal based on detecting a power level of the radio frequency input signal, and a latch configured to lock the signal limiter into an attenuating mode in response to the detection signal indicating that the threshold is exceeded, the latch selectively reset by the bias signal. ### Claim 15 (depends on 14) The power amplifier system of claim 14 wherein an input and an output of the signal limiter are both connected to an input of the power amplifier. ### Claim 16 (depends on 14) The power amplifier system of claim 14 wherein an input of the signal limiter is connected to an input of the power amplifier and an output of the signal limiter is connected to an output of the power amplifier. ### Claim 17 (depends on 14) The power amplifier system of claim 14 wherein the radio frequency detector includes a reference current source configured to generate a reference current that sets the threshold. ### Claim 18 (depends on 17) The power amplifier system of claim 17 wherein the reference current source includes a trimming circuit operable to trim the reference current. ### Claim 19 (depends on 17) The power amplifier system of claim 17 wherein the reference current source is configured to generate the reference current with a positive temperature coefficient. ### Claim 20 (depends on 14) The power amplifier system of claim 14 further comprising an acoustic wave filter configured to filter a radio frequency output signal from the power amplifier, the acoustic wave filter protected by the signal limiter.