Adaptive Impedance Matching Network for RF Power Amplifiers

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Solution Overview

Problem

Small transmitters with high efficiency power amplifiers are susceptible to performance degradation due to antenna impedance perturbations, and conventional impedance matching solutions require additional space and add loss to the transmission path, especially when dealing with electrically small antennas.

Innovation Solution

An adaptive impedance matching network using a tunable matching network with a current sensor, RF power sensor, and tuner to optimize the impedance match between the transmitter and antenna, allowing for complex impedance matching without the need for bulky monitoring devices, thereby maximizing RF power delivery while minimizing loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional impedance matching circuitry is added to resolve antenna detuning, then impedance matching capability is improved, but transmission loss increases and physical space is occupied

Engineering Contradiction:

Improveimpedance matching capabilityVSAvoidtransmission loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent employs a feedback mechanism where a sensor detects the actual impedance of the antenna and feeds this information back to a control system. The control system then adjusts the matching network components (variable capacitors or inductors) to optimize the impedance match, thereby maintaining low transmission loss while adapting to impedance variations.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent uses dynamically adjustable matching network components (variable capacitors and inductors) that can change their electrical characteristics in real-time based on the detected antenna impedance. This dynamic adjustment allows the system to maintain optimal matching without requiring bulky fixed circuitry for all possible impedance conditions.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If conventional impedance matching circuitry is added to resolve antenna detuning, then impedance matching capability is improved, but physical space is occupied

Engineering Contradiction:

Improveimpedance matching capabilityVSAvoidphysical space

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

The patent integrates multiple functions into a compact system: the sensor serves dual purposes for both detection and control, the microcontroller handles both sensing data processing and actuator control, and the matching network components serve both impedance transformation and tuning functions. This multi-functionality reduces the overall space requirement compared to conventional separate dedicated circuits.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent replaces bulky mechanical impedance matching devices (such as large directional couplers and mechanical tuners) with electronic components including microcontrollers, digital-to-analog converters, and electronically controlled variable capacitors/inductors. This substitution dramatically reduces the physical footprint while maintaining or improving matching performance.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Area of stationary object

If miniaturized monitoring devices are fabricated to reduce space, then physical space is reduced, but transmission loss increases

Engineering Contradiction:

Improvephysical spaceVSAvoidtransmission loss

Core Design Contradiction:

Area of stationary objectVSLoss of energy

Solution Approach 1:

The patent introduces a microcontroller-based control system as an intermediary between the sensor and the matching network actuators. This intermediary processes sensor data, determines optimal matching parameters through algorithms, and controls the actuators accordingly. This approach allows the use of smaller, lower-loss passive components while maintaining matching accuracy through intelligent control.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the operating parameters of the monitoring and control system by using digital signal processing and microcontroller-based control instead of analog circuitry. This allows for more efficient use of smaller components, as digital processing can compensate for the reduced performance of miniaturized sensors and actuators, thereby reducing transmission loss despite the smaller component size.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10431889B2Low-loss compact transmit impedance matching tuning technique

Publication Date: 2019.10.01 THE CHARLES STARK DRAPER LABORATORY INC

AI summary

An adaptive impedance matching network to implement an impedance match between an RF power device and an antenna comprises a matching network having at least one tunable component, a current sensor providing a current value corresponding to the supply current associated with the RF power device, a power sensor configured to provide an RF power sensor value monotonically related to power delivered to the antenna, and a tuner to provide a tuning signal to the matching network as a function of the current and RF power values. The tuner may adjust the tuning signal so that the RF power sensor value is at least as large as for other settings of the tuning signal, while maintaining the supply current at a predetermined amount corresponding to an amount of supply current occurring when the RF power device is driving a load that produces the desired RF output power and amplifier efficiency.