Self-Injection-Locked Vital Sign Sensor Design
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Solution Overview
Problem
Current non-contact self-injection-locked vital sign sensors face challenges in size, cost, and sensitivity due to large frequency discriminators and high operation frequency requirements, which restrict their miniaturization and comfort for long-term wear, and are affected by ambient light and operation frequency.
Innovation Solution
A non-contact self-injection-locked vital sign sensor design incorporating a self-injection-locked integrated circuit with a voltage-controlled oscillator, mixer, harmonic-frequency power combiner, and amplifiers for generating and processing RF signals, allowing for high-frequency and high-sensitivity vital sign detection without the need for large frequency discriminators, integrated into a low-cost IC fabrication process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photoelectric sensing method is used for vital sign detection, then detection capability is achieved, but the sensor must be in contact with human skin tightly which causes discomfort and restricts design flexibility
Solution Approach 1:
The patent replaces the mechanical contact-based photoelectric sensing system with a non-contact microwave radar sensing system. The microwave sensor detects vital signs through radio wave reflection from the body without requiring physical skin contact, thereby eliminating discomfort while maintaining detection capability. The microwave signal reflects off the body surface and captures respiratory and cardiac movements without mechanical interaction.
2Measurement precision
If higher operation frequency is used to increase sensitivity, then detection sensitivity improves, but circuit cost and complexity increase significantly
Solution Approach 1:
The patent optimizes the operating frequency parameter to 24 GHz, which provides an optimal balance between sensitivity and cost. This frequency offers sufficient sensitivity for vital sign detection while avoiding the prohibitively high costs associated with 5.8 GHz or higher frequencies. The 24 GHz band achieves adequate signal reflection from the body without requiring expensive high-frequency circuit components.
Solution Approach 2:
The patent employs a frequency discriminator that generates multiple frequency outputs (first frequency, second frequency, third frequency) from a single input signal. This allows the system to derive multiple detection capabilities from one oscillator, reducing the need for multiple independent high-frequency circuits and thereby lowering overall system cost while maintaining sensitivity.
3Measurement precision
If frequency discriminator is used for frequency demodulation, then vital sign retrieval is achieved, but the device size becomes too large for miniaturization
Solution Approach 1:
The patent integrates the frequency discriminator functionality directly into the microcontroller unit (MCU). By combining the frequency demodulation capability with the existing control processor, the system eliminates the need for a separate discrete frequency discriminator circuit. This integration significantly reduces device volume while preserving the ability to retrieve vital signs through frequency analysis of the reflected microwave signal.
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 enables a compact, cost-effective, high-sensitivity vital sign sensor that operates at high frequencies, improving detection accuracy and comfort by reducing size and increasing sensitivity while minimizing the impact of ambient light and operation frequency.
Implementation Method 1
a voltage-controlled oscillator for generating two oscillation RF signals with opposite phases
Implementation Method 2
a mixer for receiving the two oscillation RF signals and the reflected RF signal, the two oscillation RF signals and the reflected RF signal being mixed in the mixer to generate a frequency-divided RF signal
Implementation Method 3
two amplifiers for receiving and amplifying the frequency modulated and amplitude modulated signal
Implementation Method 4
a harmonic-frequency power combiner for receiving and combining the two amplified RF signals and generating the frequency-multiplied RF signal
Implementation Method 5
the transmitting antenna transmits the frequency-multiplied RF signal to a living body
Implementation Method 6
a receiving antenna for receiving a reflected RF signal
Data Source
AI summary
A non-contact self-injection-locked vital sign sensor is disclosed, which includes transmitting antenna, receiving antenna, self-injection-locked integrated circuit and demodulator. The self-injection-locked integrated circuit includes voltage-controlled oscillator, mixer, two amplifiers and harmonic-frequency power combiner. A frequency-multiplied signal is produced by amplifiers and harmonic-frequency power combiner then transmitted to a living body by transmitting antenna. A frequency-divided signal is produced by voltage-controlled oscillator and mixer then transmitted to voltage-controlled oscillator, then a frequency- and amplitude-modulated signal is produced by the voltage-controlled oscillator then transmitted to demodulator to produce a vital sign. So as to detect vital sign with a higher frequency to increase measurement sensitivity by using a low-cost integrated circuit process. A centrifugal compressor includes a volute base block, a volute cover plate, an impeller, a diffuser-adjusting assembly, a radial constraint assembly, an axial constraint assembly and a driving assembly.