Programmable RF Decimation for Active Alias Interference Removal
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Solution Overview
Problem
Current wireless digital communications systems face challenges in integrating anti-aliasing filters due to their complexity, size, and cost, and they are static, unable to adapt to changing spectral environments, leading to issues with aliasing frequency components that interfere with signal processing.
Innovation Solution
A method and apparatus that actively detect and eliminate aliasing frequency components by computing powers at different decimated sample streams, determining the decimating ratio, and using a programmable sample stream decimating circuit to generate a decimated sample stream, allowing for dynamic adjustment of sampling ratios to avoid or remove interferers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If anti-aliasing filters are integrated into the wireless transceiver, then aliasing frequency components can be removed, but the device complexity, area, and manufacturing cost increase significantly
Solution Approach 1:
The patent replaces the mechanical/analog anti-aliasing filter with a digital signal processing approach. The system samples the RF signal directly without analog filtering, then uses digital processing to identify and remove aliasing frequency components from the digitized signal, substituting a software-based solution for hardware-based filtering.
Solution Approach 2:
The patent extracts and removes the harmful aliasing frequency components from the signal after digitization. By identifying the aliased components in the digital domain and selectively eliminating them, the system achieves aliasing removal without requiring complex analog filters to be integrated into the transceiver.
2Object-affected harmful factors
If static anti-aliasing filters are used, then aliasing can be reduced, but the system cannot adapt to changing spectral environments
Solution Approach 1:
The patent implements a dynamic system that continuously monitors the spectral environment and adapts its aliasing removal strategy accordingly. The digital signal processing approach allows the system to identify changing interference patterns and adjust the aliasing component removal in real-time, making the system adaptable to varying spectral conditions unlike fixed analog filters.
Solution Approach 2:
The system employs feedback mechanisms where the digitized signal is analyzed to detect aliasing frequency components, and this information is used to adjust the signal processing parameters. The feedback loop enables the system to respond to changing spectral environments by continuously optimizing the aliasing removal process based on actual signal conditions.
3Object-affected harmful factors
If analog anti-aliasing filters are placed external to the integrated circuit, then aliasing can be filtered, but the signal must go off-chip reducing overall system performance
Solution Approach 1:
The patent replaces external analog filtering with internal digital signal processing. By directly sampling the RF signal into the integrated circuit and performing aliasing component removal digitally, the system eliminates the need for external analog filters, keeping the signal path entirely on-chip and maintaining superior system performance.
Data Source
AI summary
When a sample stream is decimated, frequency components from outside of a desired frequency band are aliased into the desired band, causing interference and loss of information. Different decimating ratios result in different frequencies aliasing into the desired frequency band. A current-mode sampling mixer 800 with capacitor banks 811 and 812 that are controlled by a digital control unit 820 with a capability to integrate and decimate an RF current at different decimating ratios is able to measure the frequency spectrum with different decimating ratios. The measured frequency spectrum is then analyzed to detect the presence of interferers aliased into the desired frequency band. The interferers can then be eliminated or avoided.