Fourth-Order N-Path Filter Using Active All-Pole Impedance
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Solution Overview
Problem
Current filtering technologies face challenges with high-order N-path filters, including limited RF selectivity, increased complexity, and area-intensive solutions, which fail to effectively address multiple access interference and spectral efficiency in multi-channel wireless communications.
Innovation Solution
Implementing a fourth-order N-path filter with an active all-pole driving point impedance, which provides up to 80 dB/decade RF selectivity and high linearity, reducing complexity and area requirements while effectively blocking internal and external blockers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional SAW filters are used to achieve highly selective filtering, then filtering performance is improved, but area footprint and device complexity increase significantly
Solution Approach 1:
The patent replaces traditional mechanical SAW filter structures with an electrical N-path filter implementation using switched capacitors and operational amplifiers. This substitution achieves comparable filtering selectivity through electrical circuitry rather than acoustic wave mechanics, significantly reducing area footprint while maintaining filtering performance.
Solution Approach 2:
The patent employs variable switching frequencies and可调 capacitor values to achieve tuning capability across multiple frequency bands. By changing operational parameters (switching frequency, capacitor values) rather than physical structure, the filter can be reconfigured for different applications without requiring multiple fixed filters, reducing overall area.
2Measurement precision
If higher order N-path filters are implemented to improve RF selectivity, then filtering performance is improved, but circuit complexity and area requirements increase
Solution Approach 1:
The patent combines multiple filtering functions and signal processing operations into a single integrated N-path filter structure. By merging the switching network, capacitive elements, and operational amplifiers into one cohesive circuit block, the design achieves high-order filtering performance without proportionally increasing overall circuit complexity or area requirements.
Solution Approach 2:
The N-path filter circuit is designed to perform multiple functions simultaneously: RF filtering, signal multiplexing, and frequency translation. This multi-functionality allows a single circuit implementation to replace what would traditionally require multiple separate components, reducing overall system complexity while maintaining high RF selectivity.
3Object-affected harmful factors
If multiple filters are deployed to address interference in crowded spectrum, then interference rejection is improved, but area footprint and device complexity increase
Solution Approach 1:
The patent implements dynamically reconfigurable filtering through time-variant switching networks that can adapt their transfer characteristics based on operating conditions. This dynamic capability allows a single filter structure to provide interference rejection across multiple frequency bands and scenarios, replacing what would traditionally require multiple static filters and reducing total area footprint.
Data Source
AI summary
Embodiments may comprise N-path filter circuitry with tunable radio frequency selectivity and up to 80 decibels per decade roll-off. The N-path filter may comprise at least one input transistor, wherein the at least one input transistor comprises a channel and a gate. A first end of the channel is coupled with a receiver circuitry input, wherein a second end of the channel is coupled with a load. The gate of the at least one input transistor is coupled with a clock circuitry input. The load may comprise a fourth order, all-pole driving point impedance. The impedance may shunt the second end of the channel to a circuit ground or a low voltage circuit rail via the impedance. And the impedance may comprise a first active impedance circuit coupled in series with a second active impedance circuit.