MIMO RF Front End Reusing Receive Paths for 4x4 MIMO
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Solution Overview
Problem
Current RF communication systems face challenges in achieving 4×4 downlink MIMO for the B46 frequency band due to limited antenna resources, as they typically support only 2×2 DL MIMO, especially in the 5 GHz WiFi band, which is common for both cellular and WiFi operations, limiting data rates and complexity in radio front-end designs.
Innovation Solution
The system re-uses existing n79 receive paths to extend B46 receive paths to four, achieving 4×4 DL MIMO by bandpass filtering, amplifying, and splitting signals, allowing concurrent operation without adding additional antenna units, thereby leveraging adjacency of frequency bands for improved MIMO performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If additional antenna units are added to achieve 4×4 DL MIMO for B46 band, then MIMO performance and data rates are improved, but device complexity and cost increase
Solution Approach 1:
The patent makes existing n79 receive paths perform dual functions by enabling them to process both n79 band signals and B46 band signals through frequency conversion. The same hardware infrastructure (receive paths, amplifiers, filters) is utilized for multiple frequency bands, eliminating the need for separate dedicated hardware for B46 band while achieving 4×4 DL MIMO capability.
Solution Approach 2:
The patent changes the operating frequency parameter of existing n79 receive paths to enable B46 band operation. By using frequency conversion techniques (downconversion or upconversion), the receive paths are configured to process signals at different frequency parameters, allowing the same physical hardware to support multiple bands with different frequency characteristics.
2Device complexity
If the same antenna system is used for both 5G n79 and LTE B46 bands, then device complexity is reduced, but signal isolation and intermodulation distortion worsen
Solution Approach 1:
The patent introduces frequency conversion as an intermediary mechanism between the antenna system and the receive paths. By converting frequencies before processing, the system creates a separation in the frequency domain that reduces intermodulation distortion between B46 and n79 band signals, allowing shared antenna usage without significant harmful interactions.
3Device complexity
If 4×4 DL MIMO is implemented for B46 band with only two physical antennas, then device complexity is reduced, but signal reception capability deteriorates
Solution Approach 1:
The patent transitions from spatial dimension to frequency dimension by utilizing frequency conversion. Instead of adding physical antennas in space, the system creates additional reception paths through frequency domain manipulation. The two physical antennas are processed through frequency conversion to generate four virtual reception paths, achieving 4×4 MIMO capability without increasing physical antenna count.
Data Source
AI summary
A radio frequency front end includes a first receiver system including a first receive path connected to a first antenna and configured to output a first receive signal in a first band, a second receive path connected to a second antenna and configured to split a first filtered receive signal to output a second receive signal in the first band and to output a third receive signal in a second band, the second band adjacent to the first band, and a third receive path connected to a third antenna and configured to output a fourth receive signal in the second band. The system can includes a second similar receiver system connected to three additional antennas, and be configured for 4×4 downlink MIMO operation.