Switched-Capacitor Filter Network for High-Order Passive RF Filtering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing discrete-time filter networks face limitations in achieving high-order filters with complex poles and efficient power consumption, particularly in RF circuits, where they struggle to provide sharp transition between passband and roll-off and are often power-intensive due to the use of active components.
Innovation Solution
A discrete-time filter network with a capacitor bank and clock-driven switches that implements multiple feedback paths and sequential connections between sampling and history capacitors, allowing for the creation of fully passive, reconfigurable filters with enhanced transfer functions, including low-pass and band-pass filters, without active components, thereby improving filter order and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active components are used in discrete-time filter networks, then filter performance and transfer function can be achieved, but power consumption increases
Solution Approach 1:
The patent removes active components (operational amplifiers, transistors) from the filter network and replaces them entirely with passive components (capacitors and switches). This extraction of active elements directly eliminates the primary source of power consumption while maintaining filter functionality through switched-capacitor charge transfer mechanisms.
Solution Approach 2:
The patent employs simple passive components (capacitors and switches) that consume no power during operation, replacing complex active components. These passive elements act as 'cheap' alternatives in terms of power consumption, enabling the filter to operate without continuous energy supply for active devices.
2Manufacturing precision
If high-order filters with complex poles are implemented, then sharper transition between passband and roll-off is achieved, but device complexity increases
Solution Approach 1:
The patent segments the filter into multiple history capacitors (CH0, CH1, CH2, etc.) arranged in a systematic pattern, where each capacitor corresponds to a specific pole location in the z-plane. This segmentation allows high-order filters with complex poles to be constructed by simply adding more capacitors following the established pattern, rather than designing complex interconnected circuits.
Solution Approach 2:
The patent creates a universal filter structure where the same basic building block (switched-capacitor connection between input, history capacitors, and output) can generate any desired filter order and pole configuration by adjusting the number and arrangement of history capacitors. This multi-functionality allows a single design approach to serve multiple filter requirements.
3Productivity
If multiple feedback paths are added to achieve high-order filters, then filter order and transition sharpness improve, but number of components and circuit complexity increase
Solution Approach 1:
The patent merges multiple feedback paths into a unified switched-capacitor architecture where a single sampling capacitor sequentially connects to multiple history capacitors in a systematic pattern. This consolidation achieves the same high-order filtering effect as multiple separate feedback paths but with fewer discrete components and simpler control logic.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution enables the creation of high-order filters with improved transfer functions and reduced power consumption, achieving sharper transitions between passbands and roll-offs, while maintaining low energy consumption, making it suitable for RF circuits and scalable with advancements in technology.
Implementation Method 1
a sampling capacitor or sampling capacitors CS which operate at a predetermined cycling rate to couple a sampling capacitor to at least one history capacitor CHi, which history capacitor CHi and sampling capacitor CS are selected from the capacitor bank so as to share electrical charge between such selected history capacitor CHi and selected sampling capacitor CS
Data Source
Figure 1(a)~2
Figure 3(a)~4(c)
Figure 5(a)~6
AI summary
A discrete time filter network with an input signal connection and an output signal connection and comprising a capacitor bank with a plurality of history capacitors, and at least one sampling capacitor which operates at a predetermined cycling rate to couple to at least one history capacitor at a time, which history capacitor is selected from the capacitor bank so as to share electrical charge between such selected history capacitor and the sampling capacitor, wherein there is a plurality of sampling capacitors that are provided in the capacitor bank, and the discrete time filter network is pro- vided with at least one switch network comprising a plurality of clock driven switches for making selected cyclical connec- tions between the sampling capacitors and the history capaci- tors in the capacitor bank at the predetermined cycling rate.