SDR Receiver TOA Precision via PN Code Correlation
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Solution Overview
Problem
Current radio receivers face challenges in accurately determining the location of a signal source due to limitations in Time Of Arrival (TOA) measurement accuracy, especially in dynamic Doppler environments, which affects the precision of beacon location estimation in search and rescue systems.
Innovation Solution
The implementation of a Software Defined Radio (SDR) system that demodulates carrier signals with Pseudo Noise (PN) code sequences, computes high accuracy TOA through time delay offset correlations, and refines it by curve fitting and accounting for atmospheric and relativistic delays, enabling precise location determination of signal sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional TOA measurement methods are used in dynamic Doppler environments, then the system is simpler to operate, but the measurement precision deteriorates significantly
Solution Approach 1:
The patent segments the TOA measurement process into multiple stages: initial coarse TOA estimation, Doppler effect removal using the coarse estimate, refined TOA calculation, and iterative improvement. This segmentation allows complex signal processing to be broken down into manageable steps, achieving high precision without overwhelming system complexity
Solution Approach 2:
The patent performs preliminary actions by first estimating a coarse TOA value before attempting to measure the precise TOA. This preliminary estimate is then used to remove Doppler effects from the signal, which in turn enables more accurate TOA measurement. The preliminary action creates a foundation for subsequent precision measurements
2Measurement precision
If conventional TOA measurement methods are used, then the device complexity is lower, but the beacon location estimation accuracy deteriorates
Solution Approach 1:
The patent implements feedback mechanisms where the calculated TOA values are used to update and improve subsequent measurements. The refined TOA estimates are fed back into the system to adjust Doppler compensation parameters, creating an iterative improvement loop that enhances location estimation accuracy while managing algorithm complexity through structured feedback cycles
Solution Approach 2:
The patent transitions from one-dimensional TOA measurement to multi-dimensional analysis by incorporating Doppler frequency shifts, signal amplitude variations, and temporal patterns. This dimensional expansion allows the system to extract more information from the same signal, improving location accuracy without proportionally increasing device complexity
3Measurement precision
If high accuracy TOA measurement is achieved through multiple processing stages, then measurement precision improves, but the processing time increases
Solution Approach 1:
The patent applies partial action by performing Doppler removal and refined TOA calculation only after obtaining a sufficient coarse estimate, rather than processing the entire signal at maximum precision from the start. This staged approach achieves necessary accuracy while minimizing total processing time by applying computational intensity only where needed
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 achieves a measurement accuracy of 100 ns, which is three orders of magnitude better than existing search and rescue receivers, significantly improving the accuracy of beacon location estimation.
Implementation Method 1
computing, by the receiver, time delay offsets using correlations of PN code windows for each symbol of the original information-bearing signal
Implementation Method 2
using, by the receiver, the high accuracy TOA to determine an accurate location of the original information-bearing signal's source of transmission
Data Source
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AI summary
Systems and methods for determining an accurate location of a signal's source of transmission. The methods involve: demodulating a detected carrier signal modulated with a Pseudo Noise ("PN") code sequence to obtain an original information-bearing signal therefrom; computing time delay offsets using correlations of PN code windows for each symbol of the original information-bearing signal; determining a high accuracy Time Of Arrival ("TOA") of the detected carrier signal using the time delay offsets; and using the high accuracy TOA to determine an accurate location of the original information-bearing signal's source of transmission.