Multiband RF Circuit Antenna Isolation for 5G Sub-6 GHz
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Solution Overview
Problem
Current radio-frequency circuits fail to provide effective signal isolation between frequency bands above 3 GHz, leading to an increase in the number of antennas required, which results in degradation of isolation between signals in multiband communication systems, especially for 5G NR sub-6 GHz systems.
Innovation Solution
The use of separate antennas for each frequency band, with multiplexers including filters that isolate signals into specific frequency bands, allowing each antenna to share multiple frequency bands, thereby reducing the overall number of antennas needed while maintaining signal isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acoustic wave filters are used for frequency bands above 3 GHz, then signal isolation should be improved, but current technology cannot achieve the required isolation performance
Solution Approach 1:
The frequency bands are segmented and assigned to different antennas based on their isolation requirements. Frequency bands that cannot be adequately isolated using traditional filters (above 3 GHz with narrow spacing) are assigned to separate physical antennas, effectively segmenting the communication system into multiple independent signal paths.
Solution Approach 2:
Multiple antennas act as intermediaries to provide physical isolation between frequency bands that cannot be isolated by filters alone. The antennas serve as mediators that separate signals in the spatial domain when filter-based separation in the frequency domain is insufficient.
2Reliability
If separate antennas are used for each frequency band above 3 GHz, then signal isolation is improved, but the number of antennas increases
Solution Approach 1:
Frequency bands with sufficient spacing (greater than 10% of the lower frequency) are merged and assigned to the same antenna, reducing the total number of antennas. The multiplexers combine multiple filter paths into single antenna interfaces where filter-based isolation is adequate.
Solution Approach 2:
Each antenna is designed to serve multiple frequency bands through the use of multiplexers and filters, making the antenna system universal. A single antenna can handle multiple frequency bands either through direct radiation (when spacing is sufficient) or through filter-based selection (when spacing is narrow).
3Device complexity
If LC filters are used for frequency bands with narrow spacing, then device complexity is reduced, but signal isolation deteriorates
Solution Approach 1:
The system changes the isolation parameter from filter-based frequency separation to antenna-based physical separation when dealing with narrow-spaced frequency bands above 3 GHz. This parameter change allows the use of simpler LC filters while maintaining adequate isolation through the antenna assignment strategy.
Data Source
AI summary
First and second frequency bands used for multiband communication are both higher than or equal to about 3 GHz, and do not overlap each other. The spacing between the first and second frequency bands is less than or equal to about 10% of the lower one of the lower-bound frequency of the first frequency band and the lower-bound frequency of the second frequency band. A radio-frequency circuit includes a first antenna, a second antenna, a first multiplexer connected to the first antenna, and a second multiplexer connected to the second antenna. The first multiplexer includes a first filter with a pass band including the first frequency band, and a third filter with a pass band different from the first filter. The second multiplexer includes a second filter with a pass band including the second frequency band, and a fourth filter with a pass band that differs from the second filter.