Adaptive Decimation Control in ASRCs to Prevent Signal Folding
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Solution Overview
Problem
Existing asynchronous sample rate converters face challenges in preventing signal folding from the passband of the input sample rate into the output sample rate without increasing the order of the low pass filter or the interpolation ratio, leading to inefficiencies in area and power consumption.
Innovation Solution
Adaptive decimation rate control in asynchronous sample rate converters, utilizing a digital phase-locked loop to determine the input to output sampling rate ratio, allowing for dynamic adjustment of the decimation rate and bypassing stages to maintain low pass filter performance while reducing power and area requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the order of the low pass filter is increased to prevent signal folding, then signal folding is prevented, but chip area and power consumption increase significantly
Solution Approach 1:
The patent implements dynamic adjustment of the decimation ratio based on the relationship between input sampling rate (Fsin) and output sampling rate (Fsout). When Fsin > Fsout, the system automatically increases the decimation ratio to prevent signal folding, and when Fsin ≤ Fsout, it reduces the decimation ratio to minimize resource usage. This dynamic control mechanism allows the system to adapt to different operating conditions without requiring a permanently high-order low pass filter, thereby preventing signal folding while optimizing chip area and power consumption.
2Reliability
If the decimation ratio is increased to prevent signal folding, then signal folding is prevented, but power consumption and chip area increase
Solution Approach 1:
The system dynamically adjusts the decimation ratio based on the ratio of input to output sampling rates. When signal folding risk is detected (Fsin > Fsout), the decimation ratio is increased to prevent folding. When folding risk is absent (Fsin ≤ Fsout), the decimation ratio is reduced to minimize power consumption. This conditional dynamic adjustment ensures signal folding prevention only when necessary, optimizing power efficiency.
Solution Approach 2:
The patent changes the decimation ratio parameter dynamically based on operating conditions. By monitoring the relationship between Fsin and Fsout, the system adjusts the decimation ratio to appropriate levels, ensuring sufficient attenuation of folded signals only when needed. This parameter adaptation allows the system to maintain signal integrity while minimizing power consumption during normal operation.
3Reliability
If a fixed temporary sampling rate is used with external decimation, then signal folding is prevented, but the system requires additional external components and increases complexity
Solution Approach 1:
The patent merges the decimation functionality directly into the ASRC chip by integrating the decimation filter and control logic. Instead of requiring an external decimation filter as a separate component, the system combines interpolation, filtering, and decimation operations within a single integrated device. This integration eliminates the need for external components while maintaining signal folding prevention capabilities, thereby reducing system complexity.
Solution Approach 2:
The ASRC system is designed to perform multiple functions within a single device: interpolation, low pass filtering, adaptive decimation, and signal folding prevention. By making the system universal and self-sufficient, it eliminates the need for external decimation filters and reduces overall system complexity while maintaining all necessary signal processing capabilities.
Data Source
AI summary
An asynchronous sample rate converter prevents the folding back of a signal in the passband of an input sample rate into the passband of the output sample by adaptively controlling the decimation rate. The ASRC includes an adaptive decimation rate controller that selectably controls a decimation filter based on the ratio of the input sampling rate to the output sampling rate. By adaptively controlling the decimation rate in the ASRC, a significant amount of area and power is saved.