Radio Apparatus LNA Control for Carrier Aggregation NF Reduction
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Solution Overview
Problem
In radio communication apparatuses using carrier aggregation, the cumulative Noise Figure (NF) in the receiving circuit increases due to bandpass filters, limiting the improvement of sub-antenna characteristics and resulting in insufficient throughput and reception quality.
Innovation Solution
A radio apparatus with a configuration that includes a main antenna, a sub-antenna, filters, an amplification unit, and a control unit that determines whether to amplify signals from the sub-antenna based on transmission power conditions, bypassing LNAs when necessary to prevent power saturation and reduce cumulative NF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If bandpass filters are arranged in front of LNAs to obtain signals in respective carrier bands, then signal frequency selection is improved, but cumulative NF in the circuit increases
Solution Approach 1:
The patent changes the arrangement order of components by placing the LNA before the bandpass filter, which fundamentally alters the noise figure calculation. By reversing the conventional sequence, the system achieves better frequency selection while maintaining lower cumulative NF, as the LNA operates on the full-band signal before filtering, rather than on filtered signals.
2Reliability
If LNAs are arranged in the receiving circuit connected to the sub-antenna, then sub-antenna characteristic degradation is compensated, but power saturation occurs during carrier aggregation
Solution Approach 1:
The patent introduces dynamic control of the LNA gain based on transmission power conditions. When transmission power exceeds a threshold, the LNA gain is reduced to prevent power saturation. This dynamic adjustment allows the system to maintain optimal LNA performance for sub-antenna reception while avoiding saturation during carrier aggregation operations.
3Device complexity
If main antenna is used for both transmission and reception, then device complexity is reduced, but reception quality of sub-antenna deteriorates
Solution Approach 1:
The patent dynamically switches between main antenna and sub-antenna based on transmission power conditions. When transmission power is high, the system uses the sub-antenna for reception to maintain quality. When transmission power is low, it uses the main antenna to simplify the configuration. This dynamic switching resolves the contradiction between device complexity and reception quality.
Data Source
AI summary
A radio apparatus includes a first antenna that transmits and receives a radio signal, a second antenna that receives a radio signal, a plurality of filters that acquire signals with mutually different frequencies from a received signal that is received by the second antenna, an amplification unit that is arranged in front of the plurality of filters and amplifies the received signal, and a control unit that controls whether or not the received signal is amplified by the amplification unit depending on a condition of radio communication by the first antenna and the second antenna.