Complex Impedance Phase Measurement Using Delayed Signal Correlation
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Solution Overview
Problem
Existing methods for measuring the phase of a complex impedance require complex electronics, such as ASICs or FPGAs, and are not compatible with microcontroller-based solutions, necessitating specific power sensors and complex calculations.
Innovation Solution
A method and device using digital processing to generate a phase-shifted replica of voltage and current signals, employing a fixed delay and lookup tables to estimate and correct phase errors, allowing measurement with a microcontroller or FPGA.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If threshold comparator or zero-crossing device is used for phase measurement, then measurement precision is improved, but device complexity increases requiring ASIC or FPGA
Solution Approach 1:
The patent replaces complex electronic threshold comparators and zero-crossing detection circuits with a microcontroller-based digital system. The microcontroller samples voltage and current signals using ADCs, performs digital correlation calculations to determine phase difference, and outputs the result. This substitution of mechanical/electronic analog circuits with digital software-based processing resolves the contradiction by maintaining measurement precision while dramatically reducing hardware complexity to enable implementation on low-cost microcontrollers.
2Measurement precision
If specific power sensor and complex calculations are implemented, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent implements a universal measurement system where a single microcontroller performs multiple functions: signal generation (DAC outputting sinusoidal excitation), signal acquisition (ADC sampling voltage and current), digital signal processing (correlation calculations for phase and magnitude), and result output. This multi-functional integration eliminates the need for separate dedicated power sensors and complex calculation units, resolving the contradiction by achieving precise impedance measurement through a single low-cost microcontroller platform.
Solution Approach 2:
The patent uses digital copying of signals through the microcontroller's internal buffer and processing architecture. Instead of requiring complex analog power sensors, the system digitally captures and processes copies of the voltage and current waveforms through ADC sampling. The digital correlation algorithm then processes these copied signal representations to extract phase and magnitude information, achieving precise measurement while using only simple ADC hardware and software processing.
3Adaptability or versatility
If frequency sweep is performed to determine phase over spectral band, then adaptability is improved, but measurement precision deteriorates due to phase shift error
Solution Approach 1:
The patent implements a dynamic measurement system where the microcontroller can adaptively sweep through different excitation frequencies to characterize impedance across a spectral band. For each frequency point, the system dynamically adjusts the excitation signal frequency and performs complete measurement cycles (signal generation, sampling, correlation calculation). This dynamic frequency sweeping capability provides adaptability to measure phase characteristics across wide frequency ranges while maintaining precision at each individual frequency measurement point through the digital correlation method.
Data Source
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AI summary
Method for measuring the phase of a complex impedance comprising: a) applying an excitation signal (sex) at a frequency fex; b) acquiring a first analog signal (uv) representative of a voltage; c) acquiring a second analog signal (ui), representative of a current; d) converting said analog signals into a first (Uv) and a second (Ui) digital signal; e) generating a delayed replica (Ûj) of said second digital signal; f) calculating a third (Mn) digital signal by multiplying the first digital signal by the delayed replica of the second digital signal, and a fourth (Md) digital signal by multiplying the first digital signal by the second digital signal; g) applying low-pass digital filtering (FPB1, FPB2); h) determining said phase (φ̂) as a function of a ratio between the filtered signals and the frequency fex by applying a correspondence table (LUTDE). Apparatus for implementing such a method.