Variable Filter High-Frequency Front-End Circuit for FDD and TDD Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current high-frequency front-end circuits face challenges in efficiently handling both FDD-scheme and TDD-scheme communication signals using a common antenna, leading to increased circuit scale and cost due to the need for multiple duplexers and separate paths, as well as difficulty in achieving isolation between overlapping frequency bands.
Innovation Solution
A high-frequency front-end circuit with adjustable variable filters and impedance settings allows for the transmission and reception of both FDD-scheme and TDD-scheme signals using a common antenna, ensuring isolation and reducing signal loss by adjusting pass bands and impedance characteristics, eliminating the need for multiple duplexers and switch devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple duplexers and switch devices are used to handle both FDD and TDD communication signals, then the circuit can transmit and receive multiple communication signals, but the circuit scale increases and cost increases
Solution Approach 1:
The patent combines multiple duplexer functions into a single duplexer by using a variable filter that can dynamically change its frequency characteristics. The variable filter replaces what would traditionally require multiple fixed-frequency duplexers, allowing one duplexer to serve multiple communication schemes (FDD and TDD) by adjusting its filter characteristics according to the selected communication mode.
Solution Approach 2:
The patent employs a variable filter whose frequency characteristics can be dynamically adjusted based on the selected communication scheme. When FDD mode is selected, the variable filter configures itself for FDD frequency separation; when TDD mode is selected, it reconfigures for TDD time-division operation. This dynamic adaptability eliminates the need for multiple static duplexers.
2Adaptability or versatility
If multiple duplexers and switch devices are used to handle both FDD and TDD communication signals, then the circuit can transmit and receive multiple communication signals, but the cost increases
Solution Approach 1:
The patent merges the functions of multiple duplexers into a single duplexer unit, reducing the total component count and associated manufacturing costs. By using one duplexer with a variable filter instead of multiple fixed duplexers, the circuit reduces bill of materials costs, assembly complexity, and overall manufacturing expense while maintaining multi-mode communication capability.
3Device complexity
If a common antenna is used for both transmission and reception, then the circuit configuration is simplified, but isolation between transmission and reception circuits becomes difficult to achieve when frequency bands overlap
Solution Approach 1:
The variable filter dynamically adjusts its frequency characteristics based on the operational mode. When transmitting, it creates sufficient attenuation in the reception frequency band to prevent transmit signals from overwhelming the sensitive receive circuit. When receiving, it allows the reception frequency band to pass through while attenuating transmission frequencies. This dynamic adjustment maintains reliable isolation despite using a common antenna.
Solution Approach 2:
The patent changes the frequency parameters of the variable filter according to the selected communication mode. For FDD operation, the filter is configured with specific passbands and stopbands appropriate for frequency-division duplexing. For TDD operation, the filter parameters are adjusted to support time-division duplexing with overlapping frequency bands. These parameter changes enable the common antenna to maintain proper isolation characteristics.
Data Source
AI summary
A high-frequency front-end circuit includes a first variable filter and a second variable filter. One end of each of the variable filters is connected to a common terminal. The other end of the first variable filter is connected to a transmission individual terminal and the other end of the second variable filter is connected to a reception individual terminal. At the time of transmission of a transmission signal, the impedance of the second variable filter is adjusted such that the impedance seen on the second variable filter side from a connection point between the variable filters is open. At the time of transmission of a reception signal, the impedance of the first variable filter is adjusted such that the impedance seen on the first variable filter side from a connection point between the variable filters is open.