Self-Injection-Locking Monopulse Radar for Physiological Motion Detection
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Solution Overview
Problem
Conventional monopulse radar systems struggle to detect small-scale physiological movements, such as cardiopulmonary activity, due to a weak difference signal that is not suitable for Doppler detection, limiting their application in human sensing.
Innovation Solution
A self-injection-locking monopulse radar system that utilizes a self-injection-locking oscillator (SILO) to enhance sensitivity by injecting the difference signal into the oscillator, combined with two demodulators for frequency and phase demodulation of sum and difference signals, and a processor to calculate a monopulse ratio signal for posture and motion analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional monopulse radar uses difference signal for Doppler detection, then the system structure remains simple, but the detection sensitivity is insufficient to capture tiny chest movement
Solution Approach 1:
The patent introduces a self-injection-locking oscillator (SILO) as an intermediary device between the difference signal and the detection system. The SILO converts the weak difference signal into a stronger oscillation signal through injection locking, enabling sensitive Doppler detection while maintaining relative system simplicity. This mediator amplifies the weak physiological movement signals without requiring complex signal processing hardware.
2Measurement precision
If the difference signal is amplified to improve detection sensitivity, then small-scale physiological movements can be detected, but signal noise and interference increase
Solution Approach 1:
The self-injection-locking oscillator employs feedback mechanisms where the output signal is fed back to control the oscillation frequency and amplitude. This feedback loop naturally filters out noise and interference by locking onto the stable frequency of the difference signal, thereby enhancing detection sensitivity while suppressing harmful signal noise and interference.
Solution Approach 2:
The SILO changes the frequency parameter of the oscillation signal to match the difference signal frequency through injection locking. By adjusting and stabilizing the frequency parameter, the system enhances the signal-to-noise ratio, allowing sensitive detection of physiological movements while rejecting broadband noise and interference.
3Measurement precision
If two demodulators are added for frequency and phase demodulation, then posture and motion identification accuracy improves, but device complexity increases
Solution Approach 1:
The patent segments the demodulation process into two independent demodulators: one for frequency demodulation and another for phase demodulation. Each demodulator handles a specific aspect of the signal analysis, allowing accurate extraction of posture and motion information from different signal components. This segmentation enables precise measurement while keeping each individual demodulator module relatively simple and manageable.
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 system achieves enhanced sensitivity to detect small-scale physiological movements, enabling accurate identification of human posture and motion by analyzing the monopulse ratio signal.
Implementation Method 1
The difference signal is injected into the SILO to achieve a SIL state
Implementation Method 2
The transmit antenna is coupled to the SILO to receive the oscillation signal and provided to transmit the oscillation signal to an object as a transmitted signal
Implementation Method 3
The two receive antennas are provided to receive a reflected signal reflected from the object as a first echo signal and a second echo signal
Implementation Method 4
enhance the sensitivity of extracting the Doppler phase shift from the difference signal
Data Source
AI summary
A SIL monopulse radar includes a self-injection-locking oscillator (SILO), a transmit antenna, two receive antennas, a hybrid coupler, a first demodulator, a second demodulator and a processor. The transmit antenna transmits the oscillation signal of the SILO to object. The two receive antennas receive a reflected signal from the object as a first echo signal and a second echo signal. The hybrid coupler outputs a difference signal and a sum signal. The difference signal is injected into the SILO. The first demodulator frequency-demodulates the oscillation signal to produce a first demodulated signal. The second demodulator phase-demodulates the sum signal by using the oscillation signal as a reference signal to produce a second demodulated signal. The processor processes the first and second demodulated signals to produce a monopulse ratio signal. The SIL monopulse radar can identify the posture and motion of a human body by analyzing the monopulse ratio signal.