Mitigating Multipath Distortions in TDOA Geolocation via Receiver Trajectories
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Solution Overview
Problem
Radiolocation techniques face significant accuracy issues in multipath environments due to multipath distortion, which is exacerbated in urban terrain where reflected and delayed signals interfere with direct signals, affecting the precision of location estimates.
Innovation Solution
A method and system that involves spatially separated RF receivers repositioned along a circular trajectory to collect measurements at varying relative phase differences between direct-path and multipath reflections, calculating and averaging Time Difference of Arrival (TDOA) measurements to mitigate multipath distortions and improve location accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If ground-level receivers are used for TDOA-based geolocation, then the device complexity and deployment constraints are reduced, but measurement precision deteriorates due to multipath distortions from reflected and delayed signals
Solution Approach 1:
The patent applies the Dynamics principle by moving the receivers along circular trajectories instead of keeping them stationary. The receivers are repositioned repeatedly along circular paths with ranges of at least half the wavelength of the detected RF signal, creating dynamic measurement conditions that enable multipath distortion cancellation through averaging.
Solution Approach 2:
The patent implements Periodic action by having receivers repeatedly traverse circular trajectories at sufficiently rapid rates. This periodic motion creates multiple measurements at different phase differences between direct-path and multipath reflections, allowing the system to average out the multipath effects over complete cycles.
2Measurement precision
If receivers are repositioned along circular trajectories to mitigate multipath effects, then measurement precision improves through averaging, but productivity decreases due to the time required for repeated repositioning and measurement cycles
Solution Approach 1:
The patent applies Preliminary action by pre-planning and pre-positioning receivers along specific circular trajectories before measurements begin. The circular paths are designed in advance with ranges of at least half the wavelength, allowing the system to efficiently collect the necessary measurement diversity without trial-and-error adjustments during the actual location determination process.
Solution Approach 2:
The patent maintains Continuity of useful action by having receivers continuously move along circular trajectories and continuously collect measurements throughout the repositioning cycles. Rather than stopping between measurements, the system maintains uninterrupted data collection, maximizing the utility of the measurement period and reducing idle time.
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 approach effectively cancels out multipath distortions by averaging TDOA measurements, reducing bias and improving the accuracy of transmitter location determination, even in environments with substantial multipath interference.
Implementation Method 1
obtain a sequence of measurements of the RF signal by each of the receivers at different positions along the circular trajectory at a diversity of relative phase differences between the direct-path and the multipath reflections of the RF signal
Implementation Method 2
reflected and delayed replicates of the signal arrive at the receiver antenna. The obstructed signal undergoes constructive and destructive interference along multiple paths before reaching the receiver
Implementation Method 3
averaging the TDOA measurements for each of the pairs of receivers to provide a respective updated TDOA measurement value
Implementation Method 4
The obstructed signal undergoes constructive and destructive interference along multiple paths before reaching the receiver, causing variations in both the amplitude and phase of the signal
Data Source
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AI summary
Method and system for radiolocation of RF transmitter in the presence of multipath interference. RF receivers are spatially separated at known locations in a moderate multipath environment in the vicinity of the transmitter. Upon detection of a received active RF signal associated with the transmitter, the receivers are directed to acquire measurements of the detected RF signal. Each receiver obtains a sequence of measurements of the RF signal at different positions along a trajectory that provides multiple measurements at relative phase differences between the direct-path and the multipath reflections of the detected RF signal. The receivers may be repositioned automatically or manually, or prearranged or selectively deployed at fixed positions along the trajectory. TDOA measurements between pairs of receivers are calculated based on the obtained measurements, and are averaged to provide a respective updated TDOA measurement value for each receiver pair, which is used to determine the transmitter location.