ADC Reception Chain Gain Calibration to Prevent Amplifier Saturation
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Solution Overview
Problem
Existing methods for calibrating reception chains with variable-gain amplifiers are inadequate in determining optimal gains, particularly in adapting to varying signal conditions and preventing amplifier saturation.
Innovation Solution
A calibration method that adjusts the gain of the input amplifier based on the average power of the digital signal, using formulas to calculate a gain adjustment increment and convert it into logarithmic form, allowing for rapid gain adjustment during packet detection without knowing the packet arrival time, and incorporating an infinite impulse-response filter for power calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gain of the amplifier is increased to improve signal detection sensitivity, then the ability to detect weak signals is improved, but the amplifier enters saturation zones causing signal distortion
Solution Approach 1:
The patent implements dynamic gain adjustment by continuously monitoring the average power of the digital signal and adjusting the amplifier gain accordingly. The gain is set to a first value when signal power is low and reduced to a second value when signal power exceeds a threshold, preventing saturation while maintaining sensitivity for weak signals.
Solution Approach 2:
The system uses feedback by calculating the average power of the digital signal from the analogue-to-digital converter and using this information to adjust the amplifier gain. This closed-loop control ensures the amplifier operates in its linear region while maximizing signal detection capability.
2Speed
If the gain is adjusted rapidly upon packet detection to capture signal variations, then the response speed is improved, but the complexity of determining optimal gain increases
Solution Approach 1:
The patent performs preliminary calculations by pre-determining the relationship between signal power and optimal gain values. The system calculates average power using a running average filter and compares it against thresholds to determine gain adjustment, avoiding complex real-time optimization algorithms.
Solution Approach 2:
The system simplifies gain determination by changing parameters from complex multi-variable optimization to simple threshold-based control. The gain is adjusted based on whether the average signal power exceeds a predetermined threshold, making the control logic simple and computationally efficient.
3Measurement precision
If the average power calculation uses more signal samples to improve measurement accuracy, then the precision of power measurement is improved, but the time delay in detecting signal changes increases
Solution Approach 1:
The patent uses a running average filter that processes a limited number of recent samples rather than all available samples. This partial action approach provides sufficiently accurate power measurement while maintaining fast response to signal changes, avoiding excessive computation time.
Solution Approach 2:
The system dynamically adjusts the measurement window by using a running average that continuously updates with new samples. This allows the power measurement to adapt to changing signal conditions in real-time, balancing accuracy and response speed.
Data Source
AI summary
A calibration method for calibrating a reception chain comprising an input amplifier of an analogue-to-digital converter, and including the following successive steps: determining a rest gain as a function of the average power of the noise present on a digital signal from said converter; and setting the gain of the input amplifier at said rest gain when the average power of said digital signal is lower than a first threshold.