RF Multiplexer Filter Layout for Intermodulation Distortion Reduction
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Solution Overview
Problem
Existing radio-frequency circuits face challenges in managing simultaneous transmission of multiple bands, leading to signal distortion and degradation due to unwanted waves of second-, third-, and fourth-order distortion modes, which affect signal quality.
Innovation Solution
A multiplexer design incorporating bulk acoustic wave (BAW) and surface acoustic wave (SAW) filters, strategically positioned to absorb and reduce these distortion modes by including their frequencies within specific pass bands, thereby minimizing signal interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple filters are connected to an antenna via a switch, then multiple radio-frequency signals with different pass bands can be transmitted, but unwanted waves of second-, third-, and fourth-order distortion modes occur causing signal quality degradation
Solution Approach 1:
The patent divides the filtering function into multiple separate filters (first filter, second filter, third filter), each targeting specific distortion modes. The first filter handles second-order distortion, the second filter handles third-order distortion, and the third filter handles fourth-order distortion. This segmentation allows each filter to be optimized for its specific frequency range and distortion type, effectively reducing unwanted waves while maintaining multiband transmission capability.
Solution Approach 2:
The patent introduces multiple intermediary filtering components between the antenna and the radio-frequency signals. These filters act as mediators that selectively remove unwanted distortion waves while allowing desired signals to pass. The filters are positioned in the signal path to intercept and attenuate distortion products before they can interfere with the main communication signals.
2Reliability
If filters are added to reduce distortion modes, then signal quality improves, but device complexity increases
Solution Approach 1:
The patent applies local quality by assigning specific filtering characteristics to each filter based on the distortion mode it targets. Each filter is designed with particular pass bands and stop bands tailored to its function: the first filter for second-order distortion frequencies, the second for third-order, and the third for fourth-order. This localized optimization allows effective distortion reduction without requiring a single complex filter to handle all frequencies and distortion types.
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 multiplexer effectively reduces unwanted waves of multiple distortion modes, enhancing signal quality and sensitivity by isolating and filtering signals across different frequency bands.
Implementation Method 1
The first filter is a bulk acoustic wave filter
Implementation Method 2
The second filter is a surface acoustic wave filter
Implementation Method 3
strategically positioned to absorb and reduce these distortion modes
Data Source
AI summary
A multiplexer includes first, second, and third filters. The first filter has a first pass band including a first band to send a signal. The second filter has a second pass band including a second band to send a signal. The third filter has a third pass band including a third band. An unwanted frequency of a second-order or fourth-order distortion mode, generated when a first transmitted signal of the first band and a second transmitted signal of the second band are simultaneously transmitted, is included in at least one of the first, second, and third pass bands. An unwanted frequency of a third-order distortion mode, generated when the first transmitted signal and the second transmitted signal are simultaneously transmitted, is included in at least one of the first, second, and third pass bands. The first filter is a BAW filter. The second filter is a SAW filter.