IQ Mixer Signal Demodulation with Differential DC Offset Cancellation
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Solution Overview
Problem
Conventional CW radar systems with a single mixer for signal demodulation face issues with null detection points at specific distances, leading to inaccurate measurement of subject displacement due to DC offset in IQ signals, which cannot be calibrated effectively due to varying conditions.
Innovation Solution
A signal demodulation device incorporating an IQ mixer, differential element, and signal processor to differentiate and demodulate mixed signals, canceling DC components and obtaining subject displacement without DC offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two mixers are used to mix detection signals in quadrature and output IQ signals for arctangent demodulation, then the Doppler shift components can be acquired, but hardware imperfections and clutter effects cause DC offset in the IQ signals that cannot be calibrated, leading to inaccurate measurement of subject displacement
Solution Approach 1:
The patent extracts and removes the DC offset component from the IQ signals by utilizing the differential element to differentiate the mixed signals, which eliminates the DC component while preserving the AC components containing displacement information. This extraction of harmful DC offset enables accurate displacement measurement.
Solution Approach 2:
The patent applies preliminary differentiation to the mixed signals before demodulation. By differentiating the IQ signals in advance, the DC offset is eliminated prior to the demodulation process, preparing the signals for accurate subsequent processing and displacement measurement.
2Device complexity
If a single mixer is used for signal demodulation, then the device complexity is reduced, but null detection points occur at particular distances preventing accurate measurement of subject displacement
Solution Approach 1:
The patent merges the functionality of two separate mixers into a single mixer that outputs both in-phase and quadrature components. This combined mixer architecture maintains the ability to perform accurate displacement measurement across all distances while reducing the number of hardware components.
3Measurement precision
If DC offset calibration is performed, then the measurement accuracy can be improved, but the calibration is unavailable because the DC offset varies in different conditions
Solution Approach 1:
The patent implements self-service by having the system automatically eliminate DC offset through the differential element without requiring external calibration procedures. The differentiation process inherently removes DC components, making the system自适应 to varying conditions without manual intervention or calibration.
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
The solution effectively cancels DC components in mixed signals, allowing accurate measurement of subject displacement by intensifying high-frequency clutter and eliminating DC offset, thereby improving the precision of displacement monitoring.
Implementation Method 1
The differential element is electrically connected to the IQ mixer for receiving the first and second mixed signals and configured to differentiate the first and second mixed signals to output a first derivative signal and a second derivative signal
Implementation Method 2
The signal processor is electrically connected to the differential element for receiving the first and second derivative signals and configured to demodulate the first and second derivative signals to output a first demodulated signal
Implementation Method 3
the conventional CW radar usually uses two mixers to mix the detection signals in quadrature and output IQ signals
Data Source
AI summary
A signal demodulation device includes an IQ mixer, a differential element and a signal processor. The IQ mixer is configured to output a first mixed signal and a second mixed signal. The differential element is electrically connected to the IQ mixer for receiving the first and second mixed signals and configured to differentiate the first and second mixed signals and output a first derivative signal and a second derivative signal. The signal processor is electrically connected to the differential element for receiving the first and second derivative signals and configured to demodulate the first and second derivative signals and output a first demodulated signal.