LNA Gain Switching for TX Leakage and Duplex Linearity
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Solution Overview
Problem
Full duplex communication in radio access networks faces challenges due to crosstalk between frequency channels, leading to noise interference and suboptimal signal linearity, which affects the quality of end-to-end voice communications.
Innovation Solution
The implementation of adjustable gain low-noise amplifiers and a programmable filter circuit in user equipment (UE) that dynamically adjust gain and switch filter circuits based on digital signal thresholds, combined with reverse polarity digital-to-analog converter injection to reduce DC offset and enhance dynamic range, thereby improving noise figure and minimizing crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full duplex communication is implemented with simultaneous transmission and reception on frequency channels, then communication efficiency is improved, but crosstalk between frequency channels increases causing noise interference
Solution Approach 1:
The patent segments the receive signal path into multiple parallel paths: a first receive signal path for processing weak signals and a second receive signal path for processing strong signals. This segmentation allows the system to handle different signal strength conditions separately, reducing the impact of crosstalk from transmit leakage on the overall reception quality.
Solution Approach 2:
The patent implements preliminary detection of transmit signal leakage before the receive signal processing. A leakage detector measures the amount of transmit leakage, and based on this preliminary information, the system proactively switches between different receive signal paths or adjusts gain settings in advance, preventing crosstalk from degrading the receive signal quality.
2Reliability
If gain is increased to improve signal reception, then signal strength is improved, but noise figure deteriorates
Solution Approach 1:
The patent employs dynamic gain adjustment where the gain of the low-noise amplifier is adaptively changed based on the detected transmit signal leakage level. When leakage is high, gain is reduced to prevent saturation and maintain acceptable noise figure. When leakage is low, gain is increased to improve weak signal reception. This dynamic adaptation resolves the contradiction between signal strength and noise figure.
Solution Approach 2:
The system changes the operating parameters (gain settings) of the receive signal path based on the measured transmit leakage conditions. By adjusting the gain parameter dynamically according to external interference levels, the system optimizes the trade-off between signal amplification and noise figure degradation.
3Reliability
If filter circuits are used to reduce crosstalk, then signal purity is improved, but device complexity increases
Solution Approach 1:
The patent extracts the filtering function from dedicated hardware filter circuits and implements it through digital signal processing in the baseband. By removing the physical filter components and replacing them with software-based filtering algorithms, the system maintains signal purity while significantly reducing device complexity and component count.
Data Source
AI summary
An apparatus of user equipment (UE) includes a radio integrated circuit (IC), an adjustable external low noise amplifier (eLNA) external to the radio IC, and processing circuitry. The radio IC includes a receive signal circuit path including an adjustable gain internal low noise amplifier (iLNA), and a transmit signal circuit path including a digital-to-analog converter (DAC) circuit configured to convert digital signals to analog baseband signals for transmitting. The processing circuitry is configured to provide digital values of the digital signals to the DAC circuit and initiate adjusting gain of one or both of the iLNA and the eLNA according to the digital values.