Time Difference of Arrival Signal Processing
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Solution Overview
Problem
Current direction- and position-finding methods lack a combination of high accuracy, sensitivity, immunity to distortions, and flexibility, with limitations in multi-path propagation, polarization rotations, and short-term signal handling.
Innovation Solution
A method that simultaneously uses time and frequency domains to determine the time difference of arrival (TDOA) by correlating time-domain and frequency-domain representations of signals, allowing for accurate sub-sample time difference calculation and minimizing phase jumps through interpolation and phase difference evaluation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional correlation methods are used to determine time difference, then the method is simple to implement, but the temporal resolution is limited to sample period
Solution Approach 1:
The patent transforms the time-domain correlation problem into the frequency domain using Fast Fourier Transform. By evaluating phase differences across multiple frequency components, the system achieves sub-sample temporal resolution without increasing time-domain complexity. The frequency domain representation allows precise time difference calculation through phase relationships rather than direct time-domain correlation.
Solution Approach 2:
The patent replaces direct time-domain correlation (mechanical approach) with frequency-domain phase analysis. Instead of correlating signals in the time domain with limited sample-period resolution, the system uses FFT to convert signals to frequency domain, where phase differences can be measured with much higher precision, effectively substituting a computational approach for a direct measurement approach.
2Measurement precision
If interpolation filters are used to obtain finer temporal resolution, then the accuracy of TDOA-based position determination increases, but different interpolation filters produce different time differences and hyperbolas
Solution Approach 1:
The patent changes the domain of analysis from time domain to frequency domain. Instead of using interpolation filters in the time domain (which introduce subjectivity and inconsistency), the system evaluates phase differences in the frequency domain after FFT transformation. This parameter change eliminates the need for arbitrary interpolation filter selection and provides consistent, objective time difference measurements based on fundamental signal properties.
Solution Approach 2:
The patent substitutes interpolation-based time difference estimation with phase-difference-based estimation in the frequency domain. Rather than mechanically interpolating between samples, the system uses the phase relationships inherent in the frequency domain representation, which provide a more reliable and consistent basis for determining time differences regardless of sampling rate.
3Adaptability or versatility
If satellite navigation systems are used for position determination, then global coverage is available, but the technology is becoming less important due to omni-present availability
Solution Approach 1:
The patent creates a universal position determination system that can work with any signal transmitter, not just satellite signals. By using TDOA measurements from multiple receivers and processing signals in the frequency domain, the system can determine positions of ground-based transmitters, mobile devices, or any other signal sources, making it adaptable to diverse applications beyond satellite navigation.
Solution Approach 2:
The patent substitutes satellite-based position determination with a ground-based multi-receiver TDOA system. Instead of relying on satellite signals that require line-of-sight and global infrastructure, the system uses local or distributed receivers that measure time differences of signals from any transmitter, providing reliable position determination independent of satellite system availability.
4Measurement precision
If directional antennas are used for direction finding, then sensitivity is improved due to antenna gain, but detection probability becomes reciprocal to directivity and rotating speed is limited
Solution Approach 1:
The patent merges the advantages of multiple receivers into a TDOA measurement system. Instead of using a single directional antenna that must physically rotate or steer to detect signals from different directions, the system combines signals from multiple fixed receivers, each providing a time difference measurement. This merging of spatial information from multiple locations achieves direction finding without the mechanical limitations of rotating antennas.
Solution Approach 2:
The patent substitutes mechanical rotation or steering of directional antennas with a stationary multi-receiver array. Instead of physically moving antennas to scan for signals, the system uses the time difference measurements from multiple fixed receivers to determine signal direction and transmitter position, replacing mechanical search methods with computational analysis of arrival time differences.
Data Source
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AI summary
A method for determining a time difference between a first and a second time of arrival of the signal is described, the method comprising: receiving (210) a first representation of the signal at the first time of arrival; receiving (220) a second representation of the signal at the second time of arrival; correlating (250) at least a first time-domain representation of the signal and a second time-domain representation of the signal to obtain a first time difference information; evaluating (270) a phase difference relation between a first frequency- domain representation of the signal and a second frequency-domain representation of the signal to obtain a second time difference information; and determining (290) the time difference between the first and the second time of arrival of the signal based on the first and the second time difference information, or based on a time difference information derived from the first time difference information and the second time difference information.