Band Elimination Filter for High-Frequency Module IMD Reduction
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Solution Overview
Problem
High-frequency modules in communication devices experience Inter-Modulation Distortion (IMD) due to the interaction between multiple bands, leading to deteriorated receiving sensitivity, especially in devices compatible with multiple communication systems like UMTS.
Innovation Solution
Incorporating a band elimination filter with a specific configuration that includes a series arm and parallel arms, featuring one-port type surface acoustic wave resonators, to attenuate interfering signals and reduce IMD by aligning the stop band with the pass band of the transmission filter in one duplexer and the reception filter in another.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple duplexers are mounted in an RF circuit to support multiple bands and communication systems, then the communication device can handle multiple bands and systems, but Inter-Modulation Distortion occurs and receiving sensitivity deteriorates
Solution Approach 1:
A band elimination filter is introduced as an intermediary component between the antenna and the first demultiplexer. This filter mediates the signal path by selectively eliminating specific frequency bands that cause inter-modulation distortion, allowing the system to maintain multi-band compatibility while protecting receiving sensitivity by blocking interfering signals before they reach the demultiplexer
Solution Approach 2:
The harmful frequency bands causing inter-modulation distortion are extracted and removed from the signal path using the band elimination filter. By taking out the problematic frequency components (specifically the pass band of the transmission filter in the second demultiplexer) before they interact with other signals, the system maintains its multi-band functionality while eliminating the source of distortion
2Reliability
If a band elimination filter is added to reduce IMD, then receiving sensitivity is improved, but device complexity increases
Solution Approach 1:
The band elimination filter is designed to perform multiple functions simultaneously: it eliminates the specific frequency band causing inter-modulation distortion while also serving as part of the overall frequency selection architecture. The filter's stop band is strategically positioned to coincide with the transmission filter pass band of the second demultiplexer, allowing one component to address multiple potential interference scenarios
Solution Approach 2:
The band elimination filter is integrated into the existing demultiplexer architecture rather than being added as a completely separate system. The filter shares the common terminal connection point with the demultiplexers and works in conjunction with the existing transmission and reception filters, merging the interference elimination function with the existing frequency separation architecture
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 proposed solution effectively reduces and prevents IMD, thereby enhancing the receiving sensitivity of communication devices by ensuring that interfering signals are attenuated, allowing for improved performance across multiple communication bands.
Implementation Method 1
the band elimination filter preferably includes a series arm and a plurality of parallel arms. At least some resonators from among the plural resonators are provided as parallel arm resonators in the plural parallel arms
Data Source
AI summary
A high-frequency module includes first and second demultiplexers and a band elimination filter. The first and second demultiplexers include common terminals, transmission filters, and reception filters, respectively. In the band elimination filter, a demultiplexer-side terminal is connected to the common terminal of the first demultiplexer. The band elimination filter includes a first pass band, and a second pass band and a stop band that are located adjacent to each other within the first pass band. The band elimination filter is configured so that the second pass band includes the pass band of each of the transmission filter and the reception filter in the first demultiplexer and the stop band includes the pass band of the transmission filter in the second demultiplexer.