Active RC Filter Resistor Ladder Integration for Silicon Area Reduction
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Solution Overview
Problem
Active RC-type filters in FMCW radar devices face challenges in efficiently equalizing uneven spectral distributions and managing silicon area, with passive components required for discrete tuning, leading to area inefficiencies and potential distortion due to non-linear switch currents.
Innovation Solution
The implementation of an active RC-type filter with integrated capacitor and resistor banks, utilizing series-connected resistor ladders and T-switches to reduce silicon area and minimize distortion, along with a calibration controller to optimize component values for precise filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If discrete passive components are used for tuning the active RC-type filter, then filtering precision is improved, but silicon area consumption increases
Solution Approach 1:
The patent merges the resistor bank and capacitor bank into integrated structures where multiple resistors are connected in series to form resistor ladders, and multiple capacitors are connected in parallel to form capacitor banks. This integration reduces the total silicon area compared to using discrete passive components for each filter stage, while maintaining the ability to precisely tune filter characteristics through selective switching of individual resistor and capacitor elements.
Solution Approach 2:
The filter is segmented into multiple stages, each with its own resistor bank and capacitor bank. The resistor bank is divided into multiple resistor ladders with series-connected resistors, and the capacitor bank is divided into parallel-connected capacitor units. This segmentation allows independent tuning of each stage's filtering characteristics through controllable switches, achieving precise filtering control while using compact integrated structures that minimize silicon area consumption.
2Adaptability or versatility
If controllable switches are used to tune passive components, then adaptability is improved, but distortion increases due to non-linear switch currents
Solution Approach 1:
The patent introduces controllable switches as intermediary elements between the tuning control signals and the passive components. These switches enable dynamic reconfiguration of the resistor and capacitor networks to adapt filter characteristics to different frequency ranges and spectral conditions. The switch design and placement are optimized to minimize non-linear current effects, thereby reducing distortion while maintaining high tuning adaptability for equalizing uneven spectral distributions in radar signals.
3Measurement precision
If multiple resistor ladders with series-connected resistors are used, then filtering precision is improved, but device complexity increases
Solution Approach 1:
The resistor ladders and capacitor banks are designed as universal, reusable blocks that can be systematically replicated across multiple filter stages. Each resistor ladder consists of series-connected resistors that can be selectively switched, and each capacitor bank consists of parallel-connected capacitors. This modular, multi-functional design allows the same structural pattern to be applied throughout the filter, simplifying the overall design process and reducing device complexity while maintaining high filtering precision through systematic component arrangement and selective switching.
Data Source
AI summary
In accordance with a first aspect of the present disclosure, an active RC-type filter is provided, comprising: an input, an output and a signal path between said input and output; at least one capacitor bank and at least one resistor bank, wherein said capacitor bank and resistor bank are integrated into the signal path; wherein the resistor bank comprises a plurality of resistor ladders; wherein each one of said resistor ladders comprises a plurality of resistors connected in series; wherein each one of said resistors has an input node configured to be coupled selectively to the signal path through one of a plurality of controllable switches; and wherein said resistor ladders have output nodes directly coupled to each other and to the signal path. In accordance with a second aspect of the present disclosure, a corresponding method of implementing an active RC-type filter is conceived.