Multi-Antenna LO Frequency Allocation for Spurious Emission Control
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Solution Overview
Problem
The use of equally configured transmit and receive paths for all antenna elements in multi-antenna systems leads to imperfections such as LO-leakage, flicker noise, DC offset changes, spurious responses, and spurious emissions, which reduce the overall gain and compliance with spectral emission requirements in 5G cellular systems.
Innovation Solution
Operating transmitters and receivers connected to different antenna elements at distinct local oscillator (LO) frequencies, while maintaining alignment with the frequency grid of the radio communications system, to reduce these imperfections and improve system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If equally configured transmit and receive paths are used for all antenna elements, then hardware design becomes simple and modular, but imperfections such as LO-leakage, flicker noise, and spurious emissions are added in a correlated way, reducing overall gain
Solution Approach 1:
The patent applies local quality by configuring transmit and receive paths differently for different antenna elements. Specifically, antenna elements are divided into groups (e.g., first group and second group) with different path configurations - such as different LO frequencies, different filtering, or different amplification characteristics. This ensures that imperfections in one group do not correlate with imperfections in another group, preventing the additive effect of correlated noise and interference, thereby improving overall system reliability and gain.
2Device complexity
If equally configured transmit and receive paths are used for all antenna elements, then device complexity is reduced, but spectral emission compliance becomes difficult to achieve due to correlated spurious emissions
Solution Approach 1:
The patent implements local quality by assigning different configurations to different antenna element groups. For example, the first group of antenna elements uses a first transmit path with specific LO frequency and filtering characteristics, while the second group uses a second transmit path with different characteristics. This differentiation causes spurious emissions from different groups to occur at different frequencies or with different characteristics, preventing them from adding up in a correlated manner, thus facilitating compliance with spectral emission requirements.
3Reliability
If distinct LO frequencies are used for different antenna elements, then imperfections are reduced and signal-to-noise ratio is enhanced, but hardware complexity increases
Solution Approach 1:
The patent applies local quality by assigning distinct LO frequencies to different groups of antenna elements. The first group uses a first LO frequency while the second group uses a second LO frequency. This local differentiation ensures that imperfections such as LO-leakage and flicker noise do not correlate across all antenna elements, improving signal-to-noise ratio and overall system performance, while the modular group-based approach keeps the complexity manageable.
Data Source
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AI summary
A communication circuit (10) for communication at a carrier frequency via multiple antenna elements (5a-d) of a radio apparatus (1) is disclosed. The communication circuit (1) comprises a plurality of radio units (15a-d), wherein each radio unit (15a-d) of said plurality of radio units (15a-d) is arranged to be connected to a separate antenna element (5a-d). An LO signal generation unit (20) is arranged to generate a plurality of LO signals (LOa-d) at distinct frequencies (fLOa-fLOd), and supply a unique LO signal (LOa-d) of the plurality of LO signals (LOa-d) to each radio unit (15a-d) of the plurality of radio units (15a-d). A corresponding radio apparatus and method are also disclosed.