Polyphase Basis DCT for Real-Time Heart Rate Radar
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Solution Overview
Problem
Current methods for measuring heart rate using continuous-wave Doppler radar face a tradeoff between real-time measurement and spectral resolution due to the need for long window lengths, which limits the ability to detect momentary changes in heart rate accurately.
Innovation Solution
The implementation of polyphase basis discrete cosine transform (PB-DCT) in a continuous-wave radar system, which allows for the use of short window lengths while reducing main-lobe and side-lobe widths in the spectrum, enhancing spectral resolution and accuracy of heart rate measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a long window length is used in traditional signal processing methods, then spectral resolution is improved, but real-time measurement capability deteriorates
Solution Approach 1:
The patent changes the fundamental parameter of the transformation method from traditional DFT/FFT to PB-DCT (polyphase basis discrete cosine transform). This parameter change enables the system to achieve high spectral resolution with short window lengths by utilizing the mathematical properties of polyphase bases and discrete cosine transform, which concentrate signal energy more efficiently in the frequency domain compared to traditional methods.
Solution Approach 2:
The patent replaces the traditional signal processing mechanism (DFT/FFT with long windows) with an alternative mathematical transformation mechanism (PB-DCT). This substitution fundamentally changes how spectral analysis is performed, allowing short-time analysis to achieve resolution previously only attainable with long integration periods, thus resolving the contradiction between temporal resolution and spectral resolution.
2Speed
If a short window length is used to achieve real-time measurement, then responsiveness to heart rate changes is improved, but spectral resolution deteriorates
Solution Approach 1:
The patent applies PB-DCT transformation which fundamentally changes the frequency concentration properties of the transform. The polyphase basis functions in PB-DCT are designed to concentrate signal components more tightly around their respective frequencies, effectively reducing main-lobe width in the spectral domain. This allows short window lengths to maintain both temporal responsiveness and spectral resolution simultaneously.
Solution Approach 2:
The patent exploits the asymmetric properties of polyphase basis functions in the PB-DCT transformation. By using specifically designed asymmetric basis functions with optimized phase characteristics, the transform achieves superior spectral concentration compared to symmetric transforms, enabling high resolution with short analysis windows and thus improving responsiveness to rapid heart rate changes.
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
This approach enables accurate and real-time heart rate measurement with improved spectral resolution, reducing errors and distinguishing between heartbeat and harmonic signals, even with short window lengths.
Implementation Method 1
Studies for detecting and analyzing cardiopulmonary movements using Doppler radar have been researched for many decades.
Implementation Method 2
Because two methods are based on quadrature demodulation, they may resolve the null point problem which is the typical problem in this field.
Data Source
AI summary
A method for measuring a high-accuracy and real-time heart rate based on a continuous-wave radar is provided. The method includes receiving an in-phase (I) signal and a quadrature (Q) signal for a receive signal received through the continuous-wave radar, selecting any one signal by comparing magnitudes of the received I signal and the received Q signal, performing frequency transform of each of bases respectively having predetermined phases with respect to the any one selected signal, and determining a heart rate based on a magnitude response of each of the bases by the frequency transform.