Sub-band Separation Circuit for Distributed Antenna Systems
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Solution Overview
Problem
Distributed antenna systems (DASs) face interference issues due to a small frequency gap between downlink and uplink communications signals, which can lead to signal distortion and oscillations when using conventional duplexers, especially when the gap is 10 MHz or less.
Innovation Solution
The implementation of a sub-band separation circuit that splits downlink and uplink communications signals into sub-bands, providing increased frequency separation between them, thereby isolating downlink signals from uplink paths using multiple sub-band isolation circuits and duplexers, allowing for effective band separation and reduced interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a small frequency gap (10 MHz or less) is used between downlink and uplink signals, then spectrum efficiency is improved, but signal interference and oscillations increase
Solution Approach 1:
The patent segments the downlink signal into multiple sub-bands and processes each sub-band separately through dedicated isolation circuits. This segmentation allows for more precise frequency-specific isolation, enabling the system to maintain small overall frequency gaps while preventing interference through targeted sub-band handling.
Solution Approach 2:
The patent introduces sub-band isolation circuits as intermediary components between the downlink and uplink paths. These isolation circuits act as mediators that selectively filter and isolate specific frequency sub-bands, allowing close frequency spacing while preventing harmful interference through the intermediary filtering action.
2Device complexity
If conventional duplexers are used with small frequency gaps, then device complexity is reduced, but signal isolation and system reliability deteriorate
Solution Approach 1:
Instead of using a single complex duplexer, the patent segments the isolation function into multiple simpler sub-band isolation circuits. Each circuit handles a specific frequency sub-band, reducing the complexity of individual components while collectively providing superior isolation performance across the entire frequency range.
Solution Approach 2:
The patent changes the operational parameters of the isolation system by working in the sub-band domain rather than handling the full frequency range at once. This parameter change allows each isolation circuit to be optimized for specific frequency ranges, improving overall isolation performance while maintaining reasonable device complexity.
3Productivity
If downlink and uplink signals are closely spaced in frequency, then spectrum utilization is improved, but leakage between paths increases
Solution Approach 1:
The patent segments the frequency spectrum into multiple sub-bands and applies dedicated isolation to each sub-band. This segmentation enables the system to maintain close overall frequency spacing for better spectrum utilization while preventing leakage through targeted isolation of each sub-band pathway.
Solution Approach 2:
The patent changes the frequency domain parameters by processing signals in discrete sub-bands rather than as a continuous spectrum. This parameter transformation allows for more precise control of leakage in each sub-band while maintaining high overall spectrum utilization through efficient frequency packing.
Data Source
AI summary
Separation of sub-bands of communications signals to reduce interference in distributed antenna systems (DASs) is disclosed. A sub-band separation circuit coupled to a plurality of antennas is configured to distribute and receive and transmit a pair of downlink and uplink sub-band signals. The sub-band separation circuit is coupled to a duplexed port of a remote unit that distributes uplink communications signals to the DAS and receives downlink communications signals from the DAS. In order to isolate the downlink communications signals from the uplink communications path in the remote unit, the isolation circuit includes a plurality of sub-band isolation circuits. Each sub-band isolation circuit is configured to isolate at least one sub-band of the downlink communications signal to generate a downlink sub-band signal that has a desired frequency separation or gap with uplink communication signals received at the duplexed port.