CW Radar Sensor Calibration for Crosstalk Delay Compensation
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Solution Overview
Problem
Existing CW radar systems, particularly FMCW radars, suffer from inaccuracies in distance measurements due to group propagation delays between transmitting and receiving antennas, leading to measurement errors that are not adequately addressed in conventional methods.
Innovation Solution
A calibration method is employed to determine the error propagation delay by operating the radar sensor in a measurement mode where no target is present, using a predefined modulation scheme to isolate the crosstalk signal, digitizing the output signal, and applying spectral filtering to identify the error frequency, which is then used to correct distance measurements during operational mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional CW radar systems are used without calibration, then the device complexity is low, but the measurement precision deteriorates due to group propagation delays
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements before actual distance measurements. The system determines error propagation delays through calibration measurements taken in the absence of targets, then uses these pre-determined values to correct subsequent distance measurements. This preliminary calibration step eliminates measurement errors without adding complexity to the core measurement function.
Solution Approach 2:
The patent converts the harmful effect of crosstalk signals (which carry error propagation delay information) into a beneficial calibration source. By intentionally measuring the crosstalk signal in calibration mode, the system extracts the error propagation delay values that would otherwise be mere measurement errors. This transforms a harmful interference into a useful calibration reference.
2Measurement precision
If calibration measurements are performed continuously, then the measurement precision is maintained, but the productivity deteriorates due to time loss
Solution Approach 1:
The patent implements periodic action by performing calibration measurements at specific intervals rather than continuously. The system executes calibration measurements during activation phases when no targets are present, then performs actual distance measurements during operational modes. This periodic alternation between calibration and measurement modes maintains measurement precision while maximizing productivity by minimizing time spent in calibration.
3Measurement precision
If crosstalk suppression measures are implemented, then the measurement precision improves by reducing interference, but the device complexity increases
Solution Approach 1:
The patent applies the extraction principle by separating the crosstalk signal measurement from the target signal measurement through mode switching. During calibration mode, the system extracts and measures only the crosstalk signal to determine error propagation delays. During operational mode, the system extracts and measures only the target echo signals. This temporal separation allows precise measurement of each signal type without requiring complex spatial or frequency domain suppression techniques.
Data Source
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AI summary
In a calibration procedure for determining a fault propagation time (LFa,b) of a CW radar sensor (2), the sensor is operated in a measurement mode (BM) in which a measurement signal (SM) is fed into the input (6), wherein a cross-signal (SQ) and an antenna crosstalk signal (SÜa,b) are mixed at a mixer (16a,b) in a receive path (12a,b) to form a fault signal (SFa,b) in an output signal (SAa,b), a fault frequency (ffa,b) of the fault signal (SFa,b) is identified in the frequency spectrum (SPa,b) of the output signal (SAa,b), and from this the difference of the group propagation delays (t1-4) of the crosstalk signal (SÜa,b) and the cross-signal (SQ) in the radar sensor (2) from the node (8) to the mixer (16a,b) is determined as the fault propagation time (LFa,b) of the radar sensor (2).In an operating procedure for operating the CW radar sensor (2), the fault travel time (LFa,b) is determined accordingly and in an operational operation (BO) a distance (A) to a detected target (28) is determined taking into account the fault travel time (LFa,b).