RF Front-End Circuit With Tunable Filtering for TV White Space
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Solution Overview
Problem
In wireless communication systems utilizing TV white space, the narrow bandwidth and varying channels make it difficult to effectively attenuate interference waves in adjacent and alternate adjacent channels.
Innovation Solution
A radio frequency front-end circuit is designed with a predistortion process and a tunable filter, specifically an acoustic wave resonator filter, to attenuate spurious waves in adjacent and alternate adjacent channels, allowing for precise interference reduction while simplifying the filter design and maintaining low loss in the use channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a conventional filter design is used to attenuate spurious waves in narrow bandwidth TV white space channels, then the filter complexity and design difficulty increase significantly, but the attenuation performance in alternate adjacent channels remains insufficient
Solution Approach 1:
The patent divides the filtering function into two separate stages: a predistortion circuit that pre-processes the signal to reduce spurious wave generation, and a tunable filter that provides final attenuation. This segmentation allows each component to be simpler while achieving overall superior performance in alternate adjacent channel suppression.
2Device complexity
If the tunable filter attenuates spurious waves in adjacent channels, then the filter design becomes more complex, but the predistortion process can be simplified
Solution Approach 1:
The predistortion circuit performs preliminary processing on the signal before it reaches the tunable filter, pre-reducing the spurious wave content. This preliminary action allows the subsequent filter to operate with reduced complexity while maintaining effective attenuation performance.
3Device complexity
If a fixed filter is used for TV white space communication, then the filter design is simpler, but the system cannot adapt to varying channels and districts
Solution Approach 1:
The patent employs a tunable filter whose characteristics can be dynamically adjusted to match different TV white space channels and regional variations. This dynamic capability allows the system to adapt to varying districts and channels while maintaining relatively simple overall design through the assistance of the predistortion circuit.
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 solution effectively reduces interference in adjacent and alternate adjacent channels, ensuring high-quality communication with reduced adjacent-channel leakage ratio and intermodulation distortion, even with narrow frequency bands and varying channel conditions.
Implementation Method 1
a transmission-side circuit that produces, from a transmitted signal after being subjected to a predistortion process, a transmitted signal corresponding to the use channel
Implementation Method 2
a tunable filter that attenuates a radio frequency signal of a spurious wave at least in an alternate adjacent channel relative to the use channel
Implementation Method 3
an acoustic wave resonator filter, to attenuate spurious waves in adjacent and alternate adjacent channels
Data Source
AI summary
A radio frequency front-end circuit performs, in a communication band made up of a plurality of communication channels within a particular frequency band used in a system, wireless communication through a use channel selected from among empty communication channels in the plurality of communication channels, the radio frequency front-end circuit including a transmission-side amplifier circuit and a transmission circuit both serving as a transmission-side circuit that produces, from a transmitted signal after being subjected to a predistortion process, a transmitted signal corresponding to the use channel, and a frequency variable filter serving as a tunable filter that attenuates a radio frequency signal of a spurious wave at least in an alternate adjacent channel relative to the use channel.