Pressure Sensor Signal Chain With Digital Down-Conversion Noise Suppression
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Solution Overview
Problem
Existing measuring devices for physical variables face challenges in effectively suppressing noise and offset in measurement signals, particularly due to the complexity of analog circuitry required for chopper concepts.
Innovation Solution
The solution involves using an analog square-wave frequency mixer for up-converting the measurement signal and a digital sine frequency mixer for down-converting the signal, shifting the hardware effort into the digital domain, which simplifies the circuitry and improves noise suppression by utilizing a combination of square-wave up-conversion and sine-wave down-conversion, along with additional filtering to suppress odd harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an analog sine frequency mixer is used for up-converting the measurement signal, then noise suppression is improved, but the circuit complexity increases significantly
Solution Approach 1:
The patent replaces the mechanical/analog sine frequency mixer with a digital frequency mixer implemented in the digital domain. The analog measurement signal is first converted to digital form, then frequency mixing operations are performed using digital signal processing techniques. This substitution eliminates the need for complex analog circuitry while achieving the same noise suppression效果 through digital algorithms.
Solution Approach 2:
The patent changes the domain parameter from analog to digital. By converting the measurement signal to digital form before frequency mixing, the system can utilize digital signal processing capabilities to achieve precise frequency manipulation without the hardware complexity of analog mixers. This parameter change enables simpler implementation while maintaining or improving measurement precision.
2Device complexity
If a square-wave frequency mixer is used for up-conversion, then hardware complexity is reduced, but signal-to-noise ratio deteriorates due to harmonic distortion
Solution Approach 1:
The patent replaces the square-wave frequency mixer with a digital frequency mixer that can precisely control the mixing waveform. By implementing the frequency mixing operation in the digital domain, the system can use ideal sine wave mixing without the harmonic distortion inherent in square-wave mixers, thereby improving signal-to-noise ratio while keeping hardware complexity low.
Solution Approach 2:
The patent introduces an analog-to-digital converter as an intermediary between the analog measurement signal and the frequency mixing operation. This intermediary enables the transition from analog to digital domain, allowing precise frequency control and filtering to eliminate harmonic distortion while maintaining simple hardware architecture.
3Device complexity
If down-conversion is performed using an analog frequency mixer, then the processing chain remains simple, but noise suppression effectiveness is reduced
Solution Approach 1:
The patent replaces the analog frequency mixer for down-conversion with a digital frequency mixer. The down-conversion operation is performed in the digital domain after analog-to-digital conversion, enabling precise frequency control and effective noise suppression through digital signal processing while maintaining a streamlined processing chain.
Solution Approach 2:
The patent changes the domain of the down-conversion operation from analog to digital. By performing frequency mixing in the digital domain, the system achieves superior noise suppression effectiveness through precise digital control of the mixing process, while the overall processing chain remains simple due to the integration of these operations in the digital signal processing unit.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in improved signal-to-noise ratio and reduced hardware complexity, achieving approximately 5 dB improvement over traditional square-wave mixers while minimizing signal loss and noise reintroduction.
Implementation Method 1
an analog square frequency mixer for up-converting the measurement signal
Implementation Method 2
a digital sine frequency mixer for down-converting the signal
Implementation Method 3
a first filter is provided at the output of the signal processing unit... for the suppression of signal points caused by the analog square frequency mixer and shifted down in frequency by the digital sine frequency mixer
Data Source
Figure 1~2
AI summary
The device for measuring a changing physical variable, such as pressure, is provided with a sensor (10) which emits an analogue measurement signal which has frequencies below a limit value. Furthermore, the device is provided with a signal processing unit with an input receiving the measurement signal of the sensor (10) and an output for outputting the processed measurement signal. The signal processing unit is provided with an analog square-wave frequency mixer (12) arranged at its input for frequency shifting the measurement signal of the sensor (10) by a shift frequency fD towards higher frequencies, an amplifier for amplifying the frequency-shifted measurement signal, the amplifier generating an amplifier offset , an analog-digital converter for converting the amplified analog signal of the amplifier into a digital signal and a digital-sine frequency mixer arranged at the output of the signal processing unit for shifting the output signal of the analog-digital converter by the shift frequency fD towards lower frequencies.