Directional Antenna Calibration for Accurate Living-Body Position Sensing
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Solution Overview
Problem
Existing methods for calibrating directional antennas for estimating the position of a living body using radio signals are difficult and lack accuracy due to varying radiation characteristics with angle, limiting the effective use of calibrated values.
Innovation Solution
A sensor system with N transmitting and M receiving antenna elements, including complex-transfer-function, reflection-coefficient, normalized-reflection-coefficient, and interpolated-reflection-coefficient calculators, and a position estimator, which calculates and corrects position estimates using steering vectors and interpolated reflection coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration is performed at one point using conventional methods, then calibration is simple and quick, but the angular range in which the calibrated value can be effectively used is limited
Solution Approach 1:
The calibration space is segmented into multiple discrete positions (L positions) around the antenna. By performing calibration at each segmented position and storing separate calibrated values for each position, the system achieves accurate position estimation across the entire angular range while maintaining simple point-by-point calibration procedures.
Solution Approach 2:
The calibration approach transitions from a single-point calibration to a multi-dimensional calibration space defined by L discrete positions. This dimensional expansion allows calibrated values to be stored and applied for different angular positions, thereby extending the effective angular range while maintaining calibration simplicity through systematic multi-position measurement.
2Adaptability or versatility
If multiple calibration positions are used to extend angular range, then adaptability improves, but calibration time and complexity increase
Solution Approach 1:
The system performs calibration in advance at L discrete positions and stores the calibrated values in memory before actual position estimation operations. This preliminary calibration action eliminates the need for real-time calibration during operation, thereby extending the angular range while maintaining efficient operation during actual use.
Solution Approach 2:
The calibration is performed at L discrete positions which is sufficient to cover the required angular range, rather than attempting continuous calibration across all possible angles. This partial action approach achieves adequate adaptability while significantly reducing calibration time and complexity compared to exhaustive calibration methods.
3Reliability
If directional antennas with physical lengths are used, then radiation characteristics are improved, but angular characteristics are introduced that limit calibration effectiveness
Solution Approach 1:
The system accepts that each directional antenna has specific angular characteristics at different positions, and instead of trying to create uniform radiation patterns, it calibrates and stores position-specific characteristics for L discrete positions. This local quality approach allows the use of directional antennas with improved radiation characteristics while compensating for their angular dependencies through position-specific calibration.
Solution Approach 2:
The calibration process measures and stores parameters (complex transfer functions) that characterize the antenna's radiation properties at each of L positions. By changing and storing these parameters for different angular positions rather than assuming uniform characteristics, the system effectively handles the angular characteristics of directional antennas while maintaining calibration effectiveness.
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
Enables accurate and efficient calibration of directional antennas for position estimation of living bodies, even with wider radiation ranges, improving accuracy and reducing calibration time.
Implementation Method 1
a transmitting antenna unit that includes N transmitting antenna elements that transmit a signal to a predetermined space
Implementation Method 2
by using Fourier transform to analyze components including Doppler shift
Implementation Method 3
PTL 1 discloses a living-body detection method using a Doppler sensor
Data Source
AI summary
A sensor includes a complex-transfer-function calculator that calculates a complex transfer function from received signals, a reflection-coefficient calculator that calculates a reflection coefficient using a complex transfer function when an object to be detected is arranged at one of L positions and an ideal complex transfer function which is a theoretical value for the position at which the object to be detected is arranged, various normalizers that calculate a normalized reflection coefficient by normalizing the reflection coefficient, a reflection-coefficient interpolator that calculates an interpolated reflection coefficient by interpolation calculation of the reflection coefficient using the normalized reflection coefficient for each coordinates used in position estimation of the object to be detected, and a position estimator that corrects the position estimation, using a steering vector and the interpolated reflection coefficient that are determined based on the position of each of the transmitting antenna elements and the receiving antenna elements.