LNA Gain Control Using PAPR Under Out-of-Band Interference
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Solution Overview
Problem
In burst communication systems, existing methods for adjusting the gain level of low-noise amplifiers (LNAs) fail to accurately handle out-of-band interference, leading to nonlinear distortion or increased noise figures, which degrade signal-to-noise ratios due to differences in frequency between target signals and interference.
Innovation Solution
An apparatus and method that measure the peak-to-average power ratio (PAPR) and total average power of both target signals and interference, adjusting the LNA gain level in conjunction with the maximum-linear-input-power point to keep the total power peak just below this point, optimizing signal-to-noise ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the LNA gain level is adjusted according to PAPR of the target signal only, then the LNA level becomes too high, causing nonlinear distortion, but the target signal amplification is sufficient
Solution Approach 1:
The patent combines the PAPR values of both the target signal and interference into a total PAPR value, and combines their power values into a total power value. This merging approach allows the LNA gain to be adjusted based on the composite characteristics of all signals, preventing nonlinear distortion caused by overlooking interference while ensuring sufficient amplification for the target signal.
Solution Approach 2:
The system measures the actual PAPR and power values of received signals, feeds this information back to the AGC module, which then adjusts the LNA gain level accordingly. This closed-loop feedback mechanism enables dynamic optimization of the LNA level, preventing both nonlinear distortion and insufficient amplification by continuously adapting to signal conditions.
2Object-generated harmful factors
If the LNA gain level is adjusted according to PAPR of the target signal only, then the LNA level becomes too low, resulting in larger noise figure, but nonlinear distortion is reduced
Solution Approach 1:
By merging the power values of target signal and interference into a total power value, the system ensures that the LNA gain is set high enough to amplify the target signal sufficiently while accounting for the presence of interference. This prevents the noise figure from becoming excessively large while maintaining acceptable levels of nonlinear distortion.
Solution Approach 2:
The feedback mechanism continuously monitors the total power and PAPR, adjusting the LNA gain to optimize the signal-to-noise ratio. This ensures that the gain is never set so low that the noise figure becomes excessive, while also preventing it from being set so high that nonlinear distortion occurs.
3Device complexity
If the LNA gain level is adjusted without considering total power, then the maximum-linear-input-power point is exceeded, causing nonlinear distortion, but device complexity is reduced
Solution Approach 1:
The system performs preliminary measurement of the total power value and total PAPR before adjusting the LNA gain level. By having these measurements ready in advance, the AGC module can quickly determine the appropriate gain level without complex real-time calculations, simplifying the control logic while preventing nonlinear distortion through proactive power management.
Solution Approach 2:
The patent changes the parameter used for gain control from considering only target signal characteristics to considering the composite parameters (total power and total PAPR) of all signals. This parameter change simplifies the decision-making process by providing a single comprehensive metric while effectively preventing nonlinear distortion.
Data Source
AI summary
This disclosure relates to an apparatus and a method for adjusting a level of a low-noise amplifier (LNA), a terminal device, and a network-element device. The apparatus includes a LNA, a peak-to-average power ratio (PAPR) module, and an automatic gain control (AGC). The LNA is configured to amplify a received signal to obtain a first signal, where the received signal includes out-of-band interference and a target signal. The PAPR module is configured to measure a PAPR value of the first signal. The AGC module is configured to adjust a gain level of the LNA, according to the PAPR value, a maximum-linear-input-power point of the LNA, and a strength of the first signal.