Power Amplifier Signal Limiter With Latched RF Overdrive Protection

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Solution Overview

Problem

Power amplifiers in RF communication systems face challenges in handling high RF input signals that exceed thresholds, potentially damaging downstream components like acoustic wave filters, especially under varying temperature and voltage conditions.

Innovation Solution

Implementing a signal limiter with an RF detector and latch mechanism that locks the power amplifier into an attenuating mode when the input signal exceeds a threshold, using a reference current source with a positive temperature coefficient for adaptive threshold adjustment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the power amplifier operates without signal limiting, then efficiency and gain are maintained under normal conditions, but downstream components may be damaged when RF input signals exceed thresholds

Engineering Contradiction:

Improveprotection of downstream componentsVSAvoidcomplexity of signal limiter circuitry

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent introduces an acoustic wave filter as an intermediary component between the power amplifier and downstream circuitry. This filter serves as a protective mediator that can handle excessive RF signals without damaging sensitive downstream components, thereby resolving the contradiction between component protection and system simplicity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The signal limiter is designed to automatically activate when RF input signals exceed predetermined thresholds, without requiring external control or complex monitoring systems. The circuit self-regulates by detecting overdrive conditions and engaging attenuation mechanisms, thus protecting downstream components while maintaining relatively simple device architecture

Inventive Principle:

Principle #25Self-service

2Reliability

If a signal limiter is implemented to protect against excessive RF signals, then downstream components are protected, but the circuit complexity increases

Engineering Contradiction:

Improveruggedness against worst-case scenariosVSAvoidnumber of components in signal limiter

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The signal limiter functionality is segmented into distinct operational modes rather than requiring a completely new complex system. The power amplifier operates in normal mode under standard conditions and automatically transitions to a limited mode when overdrive is detected, providing protection through functional segmentation rather than additional hardware complexity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The acoustic wave filter serves multiple functions: it acts as a normal signal processing component during regular operation and simultaneously provides protection against excessive RF signals. This multi-functionality reduces the need for dedicated protection components, thereby limiting circuit complexity while maintaining reliability

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Power

If the power amplifier handles high RF input signals, then signal strength is maintained, but the amplifier and downstream components may be damaged

Engineering Contradiction:

ImproveRF signal power handlingVSAvoiddamage to amplifier and downstream components

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The signal limiter implements preliminary protective action by detecting when RF input signals approach dangerous levels and preemptively activating attenuation mechanisms. This prevents excessive power from reaching the power amplifier and downstream components before damage can occur, rather than responding after damage has already happened

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The system provides beforehand cushioning through the acoustic wave filter and signal limiter circuitry that can absorb and dissipate excessive RF energy. This cushioning mechanism is in place before any potential damage occurs, allowing the system to handle power fluctuations and worst-case scenarios without component damage

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS12451920B2Apparatus and methods for power amplifier signal limiting

Publication Date: 2025.10.21 SKYWORKS SOLUTIONS INC

AI summary

Apparatus and methods for power amplifier signal limiting are disclosed. In certain embodiments, a front-end system includes a low noise amplifier that amplifies a radio frequency receive signal during a receive frame, a power amplifier that amplifies a radio frequency transmit signal during a transmit frame, and a signal limiter operable to limit a signal power of the power amplifier in an attenuating mode. The signal limiter includes a radio frequency detector configured to generate a detection signal based on detecting a power level of the radio frequency transmit signal, and a latch that locks the signal limiter in the attenuating mode in response to activation of the detection signal. The latch is reset by a bias signal of the power amplifier that is activated during the transmit frame and deactivated during the receive frame.