Variable Matching Circuit for Wireless Front End Impedance Tuning
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Solution Overview
Problem
Wireless communication devices face challenges in maintaining impedance matching across multiple communication bands, especially when near a human body, due to shifts in normalized impedance, leading to signal distortion and reduced reception sensitivity.
Innovation Solution
A front end circuit with a variable matching circuit and an antenna tuner, where the matching circuit can switch between different impedance settings to achieve conjugate matching, allowing for impedance adjustment across a wide range without increasing the number of control elements, and includes a proximity sensor to detect changes in the antenna's environment and adjust accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the normalized impedance of the antenna circuit is set to near 1 in a predetermined communication band, then matching with the front end circuit is ensured, but when the antenna is near a human body or when handling multiple communication bands, the normalized impedance shifts away from 1, making matching difficult
Solution Approach 1:
The patent applies dynamics by making the impedance matching circuit adjustable and adaptive rather than fixed. The antenna tuner includes variable capacitors and inductors that can be dynamically controlled to change the impedance characteristics of the antenna circuit according to different communication bands and environmental conditions, allowing the system to maintain matching across multiple bands despite impedance shifts
Solution Approach 2:
The patent implements parameter changes by modifying the electrical parameters (capacitance and inductance values) of the matching circuit components. The controller adjusts the capacitance of variable capacitors and the inductance of inductors based on detected communication band and impedance conditions, enabling the antenna circuit to adapt its normalized impedance to maintain matching with the front end circuit across different frequency bands
2Reliability
If an antenna tuner is provided to maintain normalized impedance near 1, then signal reflection is reduced, but the circuit complexity increases due to additional control elements
Solution Approach 1:
The patent applies segmentation by dividing the impedance matching function into separate controllable modules within the antenna tuner. The matching circuit is segmented into discrete variable capacitors, inductors, and switches that can be independently controlled, allowing precise impedance adjustment without requiring a completely complex redesign of the entire antenna system
Solution Approach 2:
The patent implements feedback through the controller that monitors the communication band and impedance conditions, then automatically adjusts the antenna tuner components to maintain optimal matching. This closed-loop control reduces signal reflection and improves transmission quality while keeping the complexity management centralized through intelligent control rather than purely passive circuit design
Data Source
AI summary
A front end circuit includes a variable matching circuit connected to a diplexer and a switch connector connected between an antenna port and the diplexer. The variable matching circuit selectively connects matching circuits to a signal path. When one of the matching circuits is connected, the impedance as viewed from the switch connector matches an impedance of a measurement circuit near a normalized impedance of 1 in a predetermined communication band, whereas when the other matching circuit is connected, the impedance viewed from the antenna port conjugate-matches the impedance of an antenna circuit in a predetermined communication band.