Frequency-Offset Self-Injection-Locked Radar EMI Mitigation
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Solution Overview
Problem
Conventional self-injection-locked (SIL) radar systems experience electromagnetic interference (EMI) due to frequency swings in the wireless signals they transmit, which can interfere with other devices in the environment.
Innovation Solution
A frequency-offset self-injection-locked (FOSIL) radar system is designed with two injection-locked oscillators and mixers to cancel out frequency drifts caused by Doppler shifts, maintaining a constant transmit frequency by mixing the oscillation signals from these oscillators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SIL radar uses injection-locking technique to achieve high sensitivity to tiny vibration, then measurement precision is improved, but frequency swing causes electromagnetic interference to other wireless devices
Solution Approach 1:
The radar system is divided into two separate injection-locked oscillators (first ILO and second ILO) instead of using a single oscillator. Each oscillator independently generates oscillation signals that are later mixed together. This segmentation allows the system to maintain the frequency drift特性 needed for sensitivity while enabling frequency cancellation through mixing, thus resolving the EMI issue.
Solution Approach 2:
The oscillation signals from the first ILO and second ILO are merged through a mixer to produce a transmitted signal. The mixing process combines the two signals in such a way that their frequency drifts cancel each other out, resulting in a constant frequency transmitted signal. This merging approach preserves the sensitivity benefits of injection-locking while eliminating the EMI problem.
2Measurement precision
If oscillator frequency drifts are used to detect subject's displacement with high sensitivity, then measurement precision is improved, but frequency stability deteriorates
Solution Approach 1:
The system uses two oscillators with frequency drifts that act as counterweights to each other. When the oscillation signals from the first ILO and second ILO are mixed, the frequency drifts cancel out like opposing forces, resulting in a stable constant frequency transmitted signal while preserving the displacement detection capability through the injection-locking mechanism.
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 FOSIL radar effectively reduces EMI issues while maintaining high sensitivity to detect vital signs by ensuring the transmitted signal has a constant frequency, enhancing its ability to detect tiny vibrations without interfering with other wireless devices.
Implementation Method 1
frequency drifts of the first and second oscillation signals caused by the Doppler shifts
Implementation Method 2
The first mixer is coupled to the first and second ILOs to receive the first and second oscillation signals, and mix the first and second oscillation signals to produce a mixed signal
Implementation Method 3
The second mixer is coupled to the signal transceiver and the second ILO, receives and mix the received signal and the second oscillation signal to output a first injection-locking signal. The first injection-locking signal is injected to lock the first ILO.
Implementation Method 4
The third mixer is coupled to the signal transceiver and the first ILO, receives and mix the received signal and the first oscillation signal to produce a second injection-locking signal. The second injection-locking signal is injected to lock the second ILO.
Data Source
AI summary
In a frequency-offset self-injection-locked (FOSIL) radar, a first mixer is provided to mix a first oscillation signal of a first injection-locked oscillator (ILO) and a second oscillation signal of a second ILO so as to cancel out the frequency drifts of the first and second oscillation signals. Accordingly, the transmit frequency of the FOSIL radar can remain constant to mitigate the EMI issue.