Coherent Radar Signal Combining Without Position Calibration
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Solution Overview
Problem
Existing radar systems face challenges in improving signal-to-noise ratio (SNR) for target detection and identification, as they require redesigning new radars with different characteristics, which is costly and time-consuming, and calibrating multiple radar antennas is complex due to large distances and internal electrical phase shifts.
Innovation Solution
A method and system for coherent in-phase combining of multiple radars without requiring knowledge of their relative positions, using a reference radar and paired radars to generate calibration and initialization values, adjust signals, and coherently sum composite signals for improved signal gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple radars are combined to improve signal-to-noise ratio, then detection and tracking performance is improved, but the complexity of calibrating relative positions and electrical phase shifts increases
Solution Approach 1:
The system uses the radars themselves to perform calibration by having them transmit test signals and process their own returned echoes. Each radar measures the phase and time delay of signals from other radars using its own receiver, eliminating the need for external calibration equipment and complex mechanical positioning systems.
Solution Approach 2:
The patent replaces mechanical calibration methods (measuring physical distances between antennas) with electrical signal processing. By transmitting test signals and measuring phase shifts and time delays through the radar's own electronics, the system substitutes mechanical measurement with electrical measurement, simplifying the calibration process.
2Loss of information
If mechanical measurement of radar antenna positions is used, then relative position information is obtained, but measurement accuracy deteriorates due to large distances compared to wavelength
Solution Approach 1:
The system substitutes mechanical distance measurement with electrical phase measurement. Instead of measuring physical distances between antennas (which are large compared to wavelength and difficult to measure accurately), the patent measures phase shifts of radar signals, which provide precise relative position information through wavelength-based measurements.
Solution Approach 2:
The patent changes the measurement parameter from mechanical distance to electrical phase. By measuring phase shifts of test signals transmitted between radars, the system obtains relative position information with accuracy proportional to the wavelength, which is much finer than the mechanical measurement capability for large distances.
3Reliability
If calibration is performed manually, then radar alignment is adjusted, but time consumption increases substantially
Solution Approach 1:
The radars perform their own calibration automatically by transmitting test signals and processing returned echoes. The system eliminates manual calibration operations and uses the radars' own transmit and receive electronics to measure phase and time delay, significantly reducing calibration time compared to manual procedures.
Solution Approach 2:
The system performs calibration using test signals that are transmitted and processed as part of the normal radar operation sequence. By incorporating calibration measurements into the standard signal processing workflow, the patent eliminates separate calibration steps and reduces overall time consumption.
Data Source
AI summary
Systems and techniques for coherent combining radars include generating a phase and range calibration and initialization values for adjusting a time delay and a phase of a transmitted pulse from one of the radars, resulting in received composite target echoes at each of the radars having contributions from monostatic and bistatic echoes. The method further includes predicting phase and range correction values for further adjusting the time delay and the phase of subsequent radar pulses transmitted by one of the radars to continue to result in received composite target echoes at each of the radars. The method further includes coherently summing the composite target echoes.