N-path Mixer Receiver for Transmitter Self-Interference Rejection
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Solution Overview
Problem
Emerging 5G applications face increased in-band or co-channel interference due to spectrum reuse, which existing technologies struggle to manage effectively, particularly in the absence of analog spatial filtering, leading to high ADC dynamic range requirements and power consumption.
Innovation Solution
A scalable, reconfigurable receiver architecture using parallel spatio-spectral notch filtering (PSNF) with Walsh function sequences and impedance translation of passive mixers, combined with N-path filtering, to concurrently reject multiple blockers at independent frequencies and angles of incidence, thereby reducing interference before the analog-to-digital conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If phased-arrays with digital beamforming are used, then spatial filtering capability is improved, but ADC dynamic range requirements increase due to absence of analog spatial filtering
Solution Approach 1:
The patent applies preliminary action by implementing analog spatial filtering through N-path filters before the ADC stage. This pre-processing of the signal in the analog domain removes interferers early in the signal chain, reducing the dynamic range burden on subsequent ADC and digital beamforming stages while maintaining spatial filtering capability.
Solution Approach 2:
The N-path filter serves as an intermediary component between the antenna array and the ADC/digital beamforming system. It provides analog spatial filtering functionality that bridges the gap between physical array geometry and digital processing, enabling both spatial selectivity and reduced ADC requirements simultaneously.
2Object-affected harmful factors
If notched-arrays with spatio-spectral notching are implemented, then CCI rejection is improved, but device complexity increases
Solution Approach 1:
The N-path filter structure achieves multi-functionality by simultaneously providing both spatial filtering (through antenna element weighting) and spectral filtering (through notched frequencies in the baseband equivalent response). This single structure replaces what would otherwise require separate spatial and spectral filtering stages, reducing overall system complexity.
Solution Approach 2:
The patent merges spatial filtering and spectral filtering functions into a unified N-path filter architecture. The filter combines elements of both spatial beamforming and spectral notching in a single analog processing stage, achieving dual functionality with reduced component count compared to implementing separate filtering stages.
3Measurement precision
If analog spatial filtering is added before ADC, then ADC dynamic range requirements are reduced, but power consumption increases
Solution Approach 1:
The patent replaces power-intensive digital signal processing with analog N-path filtering that operates at lower frequencies with simpler circuitry. By performing filtering in the analog domain using passive and active RC networks rather than high-speed digital processors, the system achieves equivalent interference rejection with significantly reduced power consumption.
4Adaptability or versatility
If reconfigurable concurrent multiple beams are implemented, then adaptability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The N-path filter implements dynamic reconfigurability through electronically controllable switches that can programmably connect different RC network configurations. This allows concurrent multiple beam patterns and notched frequencies to be dynamically adjusted without physical reconfiguration, achieving high adaptability while avoiding the precision constraints of fixed analog components.
Data Source
AI summary
An apparatus comprising: a receiver; and one or more N-path filters coupled to an input of the receiver, wherein the one or more N-path filters apply a combination of non-overlapping pulses and a pseudo noise (PN) code.