RF Module Switching Topology for TDD Multi-Mode Impedance Matching
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Solution Overview
Problem
Existing radio frequency modules struggle to achieve impedance matching between the antenna and filter in both transmit and receive states, as well as between different transmit modes, particularly in multi-band systems, due to limitations in adjustable matching networks.
Innovation Solution
A radio frequency module with a switch circuit and a variable impedance element, such as a digital tunable capacitor, that allows for impedance adjustment between the transmit and receive paths and between different transmit modes, enabling effective impedance matching for both time division duplex and frequency division duplex systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional adjustable matching network is used, then impedance matching between antenna and filter can be achieved in transmit or receive path, but impedance matching between transmit circuit and filter cannot be adjusted for multiple transmit modes
Solution Approach 1:
The matching network is divided into two independent segments: a first matching network for adjusting impedance between antenna and filter, and a second matching network for adjusting impedance between transmit circuit and filter. Each segment can be independently controlled to serve different functions, resolving the contradiction by enabling multi-mode impedance matching without requiring a completely redesigned complex system.
Solution Approach 2:
The patent employs variable impedance elements (such as variable capacitors or inductors) that can dynamically adjust their impedance values based on control signals. This dynamic adjustment capability allows the matching networks to adapt to different transmit modes and impedance conditions, achieving versatile impedance matching while maintaining a relatively simple fixed structure.
2Reliability
If impedance matching is optimized for one transmit mode, then performance in that mode improves, but performance in other transmit modes deteriorates
Solution Approach 1:
The second matching network is designed with universal adaptability to handle multiple transmit modes. By providing a dedicated matching network that can be adjusted for different transmit modes, the system achieves multi-functionality where the same hardware structure serves multiple impedance matching requirements, ensuring reliable signal transmission across all modes.
Solution Approach 2:
The patent utilizes variable impedance elements whose electrical parameters (capacitance or inductance values) can be changed based on the selected transmit mode. Control circuits adjust these parameters dynamically to optimize impedance matching for each specific transmit mode, thereby maintaining high signal transmission efficiency across diverse operating conditions.
3Device complexity
If a simple fixed impedance network is used, then device complexity is reduced, but impedance matching accuracy for multiple modes is insufficient
Solution Approach 1:
The patent introduces dynamic adjustment capabilities through variable impedance elements that can change their electrical characteristics based on control signals. This allows the system to maintain a relatively simple fixed physical structure while achieving precise impedance matching through dynamic parameter adjustment, effectively resolving the contradiction between structural simplicity and matching accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables accurate impedance matching in both transmit and receive modes, as well as between different transmit modes, improving signal transmission and reception efficiency across multiple communication bands.
Implementation Method 1
a variable impedance element connected to the first selection terminal, the variable impedance element changing an impedance thereof according to connection switching of the switch circuit
Data Source
AI summary
A radio frequency module includes: a switch circuit including a transmit terminal, a receive terminal, a selection terminal, and a common terminal, the switch circuit being capable of switching between (A) a connection between the transmit terminal and the common terminal, (B) connections between the transmit terminal and the common terminal and between the selection terminal and the common terminal, (C) connections between the receive terminal and the common terminal and between the selection terminal and the common terminal, and (D) a connection between the receive terminal and the common terminal; a transmit/receive filter connected to the common terminal and to be used for a time division duplex system, a pass band of the transmit/receive filter being a transmit/receive band of Communication Band A; and a DTC connected to the selection terminal, the DTC changing its capacitance value according to connection switching of the switch circuit.