RF Module Band Elimination Filter for TDD-FDD Interference
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Solution Overview
Problem
When a transmission signal in a wide communication band for time division duplex (TDD) and a reception signal in a communication band for frequency division duplex (FDD) are simultaneously transmitted, there is a possibility that unnecessary waves within the FDD communication band, included in the TDD transmission signal, enter the reception path, leading to a decrease in the reception sensitivity of the FDD reception signal.
Innovation Solution
A radio frequency module is designed with a band elimination filter having a stop band that includes the reception band of the FDD communication band, placed between the transmission input terminal and the switch, to attenuate noise components in the FDD reception band, thereby preventing them from entering the reception path and improving signal sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a wide communication band filter is used for TDD transmission, then the transmission signal can pass through, but unnecessary waves in the FDD reception band enter the reception path causing reception sensitivity deterioration
Solution Approach 1:
The patent divides the signal path into separate TDD transmission path and FDD reception path, and introduces a band elimination filter specifically for the FDD reception path to eliminate unnecessary waves from the TDD transmission signal. This segmentation allows each path to be optimized independently, preventing interference between different communication modes.
Solution Approach 2:
The band elimination filter acts as an intermediary component between the TDD transmission signal and the FDD reception path. It selectively attenuates frequencies in the FDD reception band while allowing TDD transmission frequencies to pass through, thereby mediating the interaction between the two signal types and preventing harmful interference.
2Object-affected harmful factors
If a band elimination filter is added to suppress unnecessary waves, then reception sensitivity is improved, but device complexity increases
Solution Approach 1:
Instead of using a complex wideband filter that would affect the entire frequency range, the patent applies a band elimination filter with specific local characteristics - it only attenuates the FDD reception band frequencies while preserving TDD transmission frequencies. This localized approach achieves the desired function with minimal impact on other signal paths.
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
This configuration effectively suppresses the deterioration of the reception sensitivity of the FDD reception signal during simultaneous TDD transmission and FDD reception, while minimizing the increase in transport loss for the FDD signal.
Implementation Method 1
a first band elimination filter connected between the first transmission input terminal and the first switch, the first band elimination filter having a stop band including the reception band of the second communication band
Data Source
AI summary
A radio frequency module, capable of simultaneously transporting a transmission signal in a communication band B for TDD and a reception signal in a communication band A for FDD, includes a filter connected to an antenna connection terminal and having a pass band, the communication band B, a filter connected to the antenna connection terminal and having a pass band, a reception band of the communication band A, a switch to change over between the filter and a transmission input terminal to receive a transmission signal in the communication band B from an outside and the filter and a reception output terminal to supply a reception signal in the communication band B to the outside, and a band elimination filter connected between the transmission input terminal and the switch and having a stop band including the reception band of the communication band A.