Multi-Stage Isolation Subsystem for Remote Antenna Units
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Solution Overview
Problem
Remote antenna units in distributed antenna systems face signal distortion due to simultaneous transmission and reception of radio signals in multiple frequency bands, leading to downlink leakage into uplink paths, which existing solutions like cavity filters are large, expensive, and undesirable, or require power reduction that limits system performance.
Innovation Solution
A multi-stage isolation sub-system that models the air interface between uplink and downlink paths to generate cancellation signals, reducing or eliminating distortions by using adaptive filters and non-linear equalizers to attenuate downlink leakage and intermodulation products, thereby increasing isolation without the need for cavity filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cavity filters are used to provide signal isolation between transmit and receive paths, then isolation performance is improved, but device size and cost increase
Solution Approach 1:
The patent replaces the mechanical cavity filter system with an electronic isolation subsystem that uses signal processing techniques. The canceller generates anti-phase signals to actively cancel leakage signals, substituting passive mechanical filtering with active electronic cancellation, thereby reducing device size while maintaining isolation performance.
Solution Approach 2:
The invention changes the approach from fixed passive filtering to dynamic active cancellation. The isolator adaptively adjusts cancellation signals based on varying transmit power levels and channel conditions, allowing the system to maintain optimal isolation performance across different operating conditions without requiring large fixed-size cavity filters.
2Reliability
If cavity filters are used to provide signal isolation between transmit and receive paths, then isolation performance is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive precision-manufactured cavity filters with electronically implemented isolation circuits that can be integrated using standard PCB techniques and digital signal processing components, significantly reducing manufacturing complexity and cost while achieving comparable or superior isolation performance.
Solution Approach 2:
The invention uses cost-effective electronic components and integrated circuits to implement the isolation function, replacing expensive precision-machined cavity filters with cheaper electronic alternatives that can be manufactured using standard production processes.
3Device complexity
If uplink or downlink power is reduced to avoid using cavity filters, then device complexity is reduced, but system power capability is limited
Solution Approach 1:
The patent substitutes power reduction with active electronic cancellation. The canceller generates anti-phase signals that actively neutralize leakage, allowing the system to maintain full transmit and receive power levels without requiring cavity filters, thus preserving system power capability while avoiding complex filtering hardware.
Solution Approach 2:
The isolation subsystem uses feedback from the receive path to generate appropriate cancellation signals. The system continuously monitors leakage signals and adjusts the cancellation signals accordingly, enabling full power operation while maintaining isolation through adaptive feedback control rather than passive power limiting.
4Adaptability or versatility
If simultaneous transmission and reception in multiple frequency bands is implemented, then system functionality is improved, but signal distortion increases
Solution Approach 1:
The patent replaces passive frequency-selective filtering with active cancellation that works across multiple frequency bands. The canceller processes signals in the digital domain, allowing simultaneous multi-band operation without the need for complex multi-band cavity filters, thereby maintaining signal quality while preserving full system functionality.
Solution Approach 2:
The isolation subsystem is designed to handle multiple frequency bands and duplexing modes (FDD, TDD, half-duplex) through a single universal architecture. The digital signal processing approach provides universal isolation capability across different operating modes and frequency ranges, maintaining signal quality without requiring separate filtering solutions for each band.
Data Source
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AI summary
Certain features relate to a remote antenna unit having a multi-stage isolation sub-system for isolating uplink and downlink signal paths. A multi-stage isolation sub-system in the remote antenna unit can include a first stage device that is configured to generate a cancellation signal for canceling unwanted downlink signals received at the uplink antenna. The isolation sub-system can also include a second stage device configured to generate a cancellation signal that attenuates residual noise and intermodulation products generated in the downlink path and received in the uplink path. The multi-stage isolation sub-system can combine the cancellation signals with signals received on the uplink path in order to cancel or attenuate downlink leakage signals and residual noise present on the uplink path.