Adaptive RF Matching Network Using Two-Point Impedance Sampling
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Solution Overview
Problem
Mobile handsets face performance limitations due to variations in antenna impedance caused by environmental changes and body effects, leading to impedance mismatches and reduced power radiated from the antenna, which existing systems struggle to address effectively without separate impedance sensing sections and accurate phase detectors.
Innovation Solution
An adaptive RF matching network module that uses two-point voltage sampling without a phase detector, employing a pi-type network with micro-electromechanical system (MEMS) capacitive switches and a dither clock to monitor and adjust impedance, allowing for real-time impedance measurement and matching without a separate sensing element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a phase detector is used to measure impedance, then measurement precision is improved, but device complexity increases and current consumption increases
Solution Approach 1:
The patent extracts and eliminates the phase detector component from the impedance measurement system. Instead of using a phase detector to measure both magnitude and phase of voltage, the invention only measures voltage magnitude at two different points using simple peak detectors, thereby removing the complex phase detection hardware while maintaining sufficient measurement accuracy for impedance matching.
Solution Approach 2:
The patent uses a simplified measurement approach that copies only the essential information needed for impedance matching. Rather than fully replicating the complex phase-detector-based measurement system, it uses two simple voltage magnitude measurements that provide sufficient data to determine impedance changes and adjust the matching network accordingly.
2Measurement precision
If a separate impedance sensing section is used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the impedance sensing function with the existing voltage sampling points in the RF signal path. Instead of adding a separate dedicated sensing section, it utilizes voltage measurements already available at two points in the signal path (before and after the matching network) to infer impedance changes, thereby combining measurement functions with existing circuit elements.
Solution Approach 2:
The voltage sampling points in the RF signal path serve multiple functions: they are used for both signal level monitoring and impedance measurement. By making these measurement points universal for both purposes, the patent eliminates the need for dedicated separate sensing hardware while maintaining measurement capability.
3Measurement precision
If phase detector accuracy is improved, then measurement precision is improved, but current consumption increases
Solution Approach 1:
The patent replaces the expensive and high-power phase detector with simple, low-power peak detectors that only measure voltage magnitude. These simpler detection elements consume significantly less current while providing sufficient measurement accuracy for the impedance matching application, effectively using a simpler substitute that meets the functional requirements.
4Power
If antenna impedance matching is optimized, then power radiated from antenna is improved, but device complexity increases due to separate sensing section
Solution Approach 1:
The patent combines the impedance measurement function with the existing RF signal path voltage sampling points. By using voltage measurements already present in the signal path for both signal monitoring and impedance sensing, it achieves optimized power transfer through accurate impedance matching without adding complex separate sensing hardware.
Data Source
AI summary
An adaptive impedance matching module having an adjustable impedance matching network with an input for receiving an RF power source and an output to be connected to an antenna, and first and second voltage measurement device configured to sense a voltage at respective first and second nodes on the impedance matching network. A network adjuster circuit is provided to switch the impedance matching network between a first state where first and second voltages are sensed on the respective first and second nodes and a second state where third and fourth voltages are sensed on the respective first and second nodes. Processing circuitry is provided which determines the matched load impedance based upon the first, second, third and fourth sensed voltages and including matching adjustment circuitry configured to adjust the matching impedance in the event the matched load impedance differs from a target load impedance by more that a predetermined amount.