RF Module Filter Impedance Stabilization for Signal Integrity
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Solution Overview
Problem
Conventional radio-frequency modules experience variations in bandpass phase when switching between communication modes, affecting signal integrity during simultaneous communications using different filters.
Innovation Solution
A radio-frequency module configuration with a first switch, first filter, and second filters, where the first filter includes a common filter section for both transmission and reception, and an additional filter section for either transmission or reception, coupled in a time division duplex configuration, with a second amplifier connected to a branching signal path to reduce impedance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the first filter includes both a common filter circuit and an additional filter circuit that are selectively used, then the communication device can flexibly adapt to different communication modes, but the impedance on the first filter side varies between when both circuits are used and when only the common filter circuit is used, causing signal variations
Solution Approach 1:
A third filter is introduced as an intermediary component connected in parallel with the first filter. This third filter provides a stable impedance path that compensates for impedance variations caused by selective use of the common and additional filter circuits, thereby maintaining signal stability while preserving communication mode flexibility
Solution Approach 2:
The impedance characteristics of the filtering system are modified by adding the third filter with specific impedance properties. This parameter change ensures that the overall impedance remains stable regardless of whether the additional filter circuit is connected, resolving the contradiction between adaptability and signal stability
2Manufacturing precision
If the additional filter circuit is coupled between the amplifier and the common filter circuit, then the filter device can provide enhanced filtering performance, but the configuration of the resonator at the antenna switch side end varies between communication modes, affecting the impedance observed from the first switch
Solution Approach 1:
The third filter serves as a mediator that decouples the impedance variability from the antenna switch. By providing a consistent parallel path, it allows the additional filter circuit to be selectively connected without affecting the resonator configuration at the antenna switch side, thereby reducing device complexity while maintaining filtering performance
3Productivity
If simultaneous communications using both the first filter and the second filter are performed, then the communication device can handle multiple communication bands concurrently, but signals passing through the second filter may vary with the state of the first filter due to impedance coupling
Solution Approach 1:
The third filter acts as an intermediary that isolates the second filter from impedance variations in the first filter. This parallel connection provides a stable reference impedance that prevents signal variations in the second filter path, enabling reliable simultaneous communications across multiple bands
Solution Approach 2:
The filtering system is segmented into independent parallel paths (first filter and third filter). This segmentation allows each filter to operate independently with stable impedance characteristics, enabling concurrent communications without mutual interference while maintaining signal integrity
Data Source
AI summary
A radio-frequency module includes a first switch, a first filter, second filters, a power amplifier, and a low-noise amplifier. The first switch has a first terminal, a second terminal, and a third terminal. The first terminal is coupled to an antenna terminal. The first filter is coupled to the second terminal. The second filters are coupled to the third terminal. The first filter includes a common filter circuit and an additional filter circuit. The additional filter circuit is coupled between the power amplifier and the common filter circuit. The low-noise amplifier is coupled to a path that branches off from a path connecting between the common filter circuit and the additional filter circuit. The common filter circuit is coupled between the additional filter circuit and the first switch.