Integrated Signal Generator Calibration for Linear-in-dB Power Detection
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Solution Overview
Problem
Conventional power detector circuits introduce log-conformance error, process variation, and temperature drift, leading to deviations in the relationship between input signal power and output voltage, necessitating accurate calibration to achieve a linear-in-dB transfer function.
Innovation Solution
A detecting circuit with a signal generator and detector integrated in the same chip, utilizing a test signal generated by an adjusting circuit and resistor ladder circuit to calibrate the transfer function by producing candidate output signals with varying amplitudes, allowing for piecewise linear-in-dB transfer function calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional power detector circuit is used to detect input signal power, then the detection function is achieved, but log-conformance error and deviation from ideal linear-in-dB transfer function occur
Solution Approach 1:
The patent applies preliminary action by performing calibration before actual power detection. A calibration mode is implemented where test signals with known power levels are input to the detector, and the measured output values are used to pre-calculate calibration parameters (a0, a1, a2) that compensate for log-conformance errors. This preliminary calibration establishes an accurate transfer function before normal operation begins.
Solution Approach 2:
The patent implements feedback by using the detector's own output to adjust its transfer function. The calibration process feeds back the relationship between known input power levels and actual detector responses to generate correction parameters. During operation, this feedback mechanism ensures the transfer function accurately reflects the detector's actual behavior, compensating for non-ideal characteristics.
2Measurement precision
If process variation and temperature drift are considered, then more accurate calibration is needed, but calibration complexity increases
Solution Approach 1:
The patent addresses process variation and temperature drift by changing the calibration approach to use multiple test signals with different power levels instead of a single calibration point. The calibration parameters (a0, a1, a2) are derived from measurements at multiple power levels, making the transfer function robust against variations. This parameter-based calibration adapts to different operating conditions without requiring complex hardware changes.
Solution Approach 2:
The patent segments the calibration process into distinct phases: calibration mode and normal detection mode. During calibration, multiple test signals at different power levels are sequentially applied to establish the transfer function. This segmentation allows comprehensive calibration without complicating the normal operation, as the complex multi-level testing is confined to the calibration phase only.
3Measurement precision
If a test signal calibration method is implemented, then transfer function accuracy is improved, but additional circuit components are required
Solution Approach 1:
The patent applies universality by designing the signal generator to serve multiple functions: it generates both the oscillating signals for normal detector operation and the test signals for calibration. The same detector circuit is used for both calibration measurements and normal power detection. This multi-functionality allows accurate calibration without adding separate dedicated calibration hardware, reducing overall circuit complexity.
Solution Approach 2:
The patent merges the calibration function with the normal detection function by integrating the test signal generation capability into the existing signal generator. The calibration process uses the same signal path and detector as normal operation, combining what could be separate systems into one unified circuit. This merging eliminates redundant components while maintaining calibration accuracy.
Data Source
AI summary
A signal generator includes: an adjusting circuit arranged to adjust a first amplitude of an oscillating signal to generate an adjusted oscillating signal; and a resistor ladder circuit arranged to receive the adjusted oscillating signal to generate a plurality of candidate output oscillating signals having a plurality of different amplitudes respectively and output an output oscillating signal selected from the candidate output oscillating signals.