Adaptive RF Hybrid Filter Structure With Digital Closed-Loop Tuning
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Solution Overview
Problem
Digital filters introduce noise and processing delays, and require high-speed converters, making them unsuitable for all applications, while traditional analog filters are inflexible and difficult to control digitally.
Innovation Solution
A digitally controlled analog filter device that combines digitally controlled analog signal amplifiers and time delay circuits with digital closed-loop control, allowing for adaptive compensation of non-idealities in analog components, such as variable delays and gains, using algorithms like the Least Mean Squares (LMS) adaptive algorithm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If digital filters are used to achieve controllable filtering functionality, then adaptability is improved, but noise floor increases and processing delays occur
Solution Approach 1:
The system segments the filtering function into two separate domains: analog filtering for signal processing (to avoid quantization noise) and digital control for adaptability (to provide controllability). The analog filter handles the signal path while digital processors handle only the control signals, thus separating the harmful quantization effect from the useful filtering function.
Solution Approach 2:
Digital-to-analog converters (DACs) serve as intermediaries that translate digital control commands into analog control signals for the filter components. This intermediary allows digital systems to control analog filters without directly processing the main signal through digital conversion, thereby avoiding the introduction of quantization noise into the signal path.
2Adaptability or versatility
If digital filters are used to achieve controllable filtering functionality, then adaptability is improved, but processing delays increase
Solution Approach 1:
The system segments the signal processing function from the control function. The analog filter processes signals in real-time without digital conversion delays, while digital processors handle only control parameter adjustments at lower data rates, thereby minimizing processing delays in the critical signal path.
3Object-generated harmful factors
If traditional analog filters are used to achieve low noise and real-time processing, then noise floor is reduced and processing speed is improved, but adaptability deteriorates
Solution Approach 1:
The analog filter components are made dynamically adjustable through digital control. Variables such as cutoff frequencies, gain, and filter order can be changed in real-time by adjusting analog control voltages or component values based on digital commands, transforming static analog filters into adaptive systems that maintain low noise while gaining flexibility.
Solution Approach 2:
Digital closed-loop control circuits monitor the filter's performance and automatically adjust control parameters to optimize filtering behavior. This feedback mechanism enables the analog filter to adapt to changing conditions while maintaining low noise characteristics, as the digital system only adjusts control signals rather than processing the entire signal stream.
4Manufacturing precision
If digital closed-loop control is applied to compensate for component non-idealities, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
Digital closed-loop control circuits continuously monitor the actual performance of analog components and automatically adjust control parameters to compensate for manufacturing variations and non-idealities. This feedback mechanism allows the use of less precise, lower-cost components while achieving the desired overall system performance through active compensation.
Solution Approach 2:
The system performs self-calibration and self-adjustment through automated digital control algorithms that compensate for component drift and variations without requiring manual intervention. The digital control circuitry automatically adapts to component non-idealities, enabling the system to maintain high precision while using standard manufacturing tolerances.
Data Source
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AI summary
A digitally controlled analog filter device. The digitally controlled analog filter device includes one or more digitally controlled analog signal amplifiers. The digitally controlled analog signal amplifiers are configured to have a gain of the digitally controlled analog signal amplifiers controlled by digital signals. The digitally controlled analog filter device further includes one or more analog time delay circuits coupled to signal input nodes of the digitally controlled analog signal amplifiers. The analog time delay circuits are configured to implement an analog signal delay. The digitally controlled analog filter device further includes a digital closed loop control circuit coupled to the digitally controlled analog signal amplifiers to digitally control the gain of the digitally controlled analog signal amplifiers.