Multi-Stage Sample Rate Converter with Constant Anti-Aliasing Filter
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Solution Overview
Problem
Existing architectures for sample rate converters in wireless communication systems, such as WiMAX, face challenges in efficiently converting signal sampling rates while preventing aliasing, particularly due to the need for complex anti-aliasing filters and variable converting ratios.
Innovation Solution
A multi-stage sample rate converter architecture is introduced, featuring an anti-aliasing filter with a constant cut-off frequency and a series of halfband filters, which limits the converting ratio to ensure simple implementation and prevent aliasing by adjusting the passband of the anti-aliasing filter according to the sample rate converter's converting ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a variable anti-aliasing filter is used to prevent aliasing across different converting ratios, then aliasing prevention is improved, but device complexity increases
Solution Approach 1:
The sample rate conversion process is segmented into multiple stages, each with a fixed converting ratio (e.g., 3/2, 5/4, 7/6). Each stage uses a dedicated anti-aliasing filter designed for its specific converting ratio, eliminating the need for a single complex variable filter while maintaining effective aliasing prevention across the full range of converting ratios.
Solution Approach 2:
The system dynamically selects which stage to operate based on the required converting ratio, but each individual stage maintains a fixed, simple filter design. This dynamic stage selection combined with static filter designs resolves the contradiction between handling variable converting ratios and maintaining simple filter implementations.
2Device complexity
If a constant anti-aliasing filter is used to simplify implementation, then device complexity is reduced, but the converting ratio range is limited
Solution Approach 1:
The overall converting ratio range is segmented into multiple sub-ranges, each handled by a dedicated conversion stage with its own constant filter. For example, one stage handles 3/2 conversions, another handles 5/4 conversions, and so on. This segmentation allows each filter to be optimized for a specific range while the system as a whole achieves versatility through stage combination.
Solution Approach 2:
Multiple conversion stages, each designed for a specific converting ratio, work together to provide universal support for a wide range of converting ratios. The system can achieve any converting ratio within the supported range by appropriately selecting and combining stages, making the overall system versatile despite each individual stage having a specialized, simple design.
3Manufacturing precision
If multiple down-sampling converters are used in series to achieve desired sampling rate, then sampling rate conversion precision is improved, but device complexity increases
Solution Approach 1:
The down-sampling process is segmented into multiple stages, each performing a moderate decimation ratio rather than a single large decimation. Each stage includes its own anti-aliasing filter and down-sampler, allowing for gradual reduction of the sampling rate while maintaining signal quality and preventing aliasing at each step, thus improving overall conversion precision.
Data Source
AI summary
Architectures of multi-stage sample rate converters are disclosed. According to one aspect of the present invention, a received signal with a higher sampling rate is converted to a lower sampling rate. To prevent aliasing in the resultant signal, an anti-aliasing filter is introduced. The passband of the anti-aliasing filter is so adjusted according to the conversation rate of a sample rate converter. To keep the implementation relatively simple, the coefficients of the filter are kept constant. Therefore, the conversation rate of a sample rate converter is constrained in a limited range, thus requiring only a constant anti-aliasing filter. A series of halfband filters are then used to convert the signal to a desired sampling rate.