Polyphase Tapped Filter for Receiver Sampling Frequency Offset Compensation
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Solution Overview
Problem
In ultra-high-speed wireless communication, frequency offsets between transmitter and receiver clocks lead to inaccurate symbol determination and data restoration failures, as existing compensation methods are slow and require large circuit configurations.
Innovation Solution
A method for on-the-fly compensation using a tapped filter and adaptive algorithm to adjust tap coefficients based on error vectors, allowing for polyphasing of received symbol sequences without matching the receiver clock to the transmitter clock, enabling efficient sampling frequency and phase offset correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital resampling circuit is used to compensate frequency offset, then data restoration accuracy is improved, but circuit complexity and processing time increase
Solution Approach 1:
The received symbol sequence is divided into multiple polyphased sequences (e.g., even and odd phases) through down-sampling at different phases. This segmentation allows the system to process frequency offset compensation in parallel across multiple phases rather than requiring a single complex resampling operation, thereby reducing overall circuit complexity while maintaining accuracy.
Solution Approach 2:
The tap coefficients of the tapped filter are dynamically adjusted based on the polyphased sequences to compensate for frequency offsets in real-time. This dynamic adaptation eliminates the need for fixed complex resampling circuits, as the system adapts its filtering characteristics to match the actual frequency offset conditions, reducing circuit complexity while improving restoration accuracy.
2Reliability
If analog PLL is used for symbol time recovery, then frequency synchronization is achieved, but synchronization speed is too slow for ultra-high-speed communication
Solution Approach 1:
The patent replaces the mechanical analog PLL system with a digital signal processing approach using tapped filters and polyphased sequences. This substitution enables frequency synchronization to be achieved through digital computation rather than mechanical feedback, dramatically increasing synchronization speed to match ultra-high-speed communication requirements while maintaining reliable frequency synchronization.
Solution Approach 2:
The system performs preliminary down-sampling of the received symbol sequence into multiple polyphased sequences before applying the tapped filter. This preliminary action prepares the data in a format that enables rapid frequency offset compensation, allowing the system to achieve fast synchronization without requiring slow analog feedback loops.
3Measurement precision
If oversampling is performed multiple times to compensate frequency offset, then sampling accuracy is improved, but processing time and power consumption increase
Solution Approach 1:
Instead of performing multiple sequential oversampling operations that consume significant power, the patent segments the single oversampled sequence into multiple polyphased sequences through down-sampling. This segmentation achieves equivalent or superior sampling accuracy by distributing the processing across parallel phases, thereby reducing overall power consumption while maintaining precision.
Solution Approach 2:
The system performs a single oversampling operation followed by polyphase down-sampling rather than multiple oversampling operations. This partial action approach achieves the necessary sampling accuracy for frequency offset compensation without the excessive power consumption that would result from repeated oversampling, optimizing the balance between precision and energy efficiency.
Data Source
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AI summary
Problem To restore data in a transmitted symbol sequence without aligning the clock of the receiver with the clock of the transmitter. Solution Received data oversampled twice is polyphased by the receiver, feedback is applied using an adaptive algorithm, and the filter coefficients (tap coefficient sequence) of a compensation filter are simultaneously shifted when the data shifts. The sampling frequency and the phase offset can be compensated for on the fly using a filter combining a tapped filter whose initial value is a correlation value obtained from the preamble and header of a received signal, and a wavefront aligner. In this configuration, a resampling filter circuit, an equalization filter circuit and a decimation filter circuit are realized in a single compensation filter circuit, which is much smaller than the prior art circuits in terms of size.