Abstract
This paper proposes CAF algorithm to estimate localisation accuracy of a stationary emitter which is being monitored by a pair of sensors mounted on high altitudes. It computes joint Time Difference of Arrival (TDOA) and Frequency Difference of Arrival (FDOA) using Cross Ambiguity Function (CAF) and measures geolocation accuracy in presence of biasing in sensor position and velocity. Previous work in this area utilizes TDOA and FDOA measurements with known sensor kinematics which is fed to Maximum Likelihood or Least Squares algorithm for post processing. However it is computation demanding. In the present work, surface peaks of TDOA and FDOA values are directly mapped to geographic coordinates. This method is computationally efficient. As sensor and emitter geometry keeps changing over time due to moving sensors, multiple CAF snapshots are taken for emitter geolocation. Simulations are carried out using MATLAB. It is observed that at 30 dB SNR, location accuracy of stationary emitter is 100 m at known sensor kinematics and by introducing bias in the receiver position and velocity, it is 200 meters. These measurements are well within and in accordance with theoretical developments.
Highlights
Estimating precise geographical location of a stationary emitter is critical for both military and civilian applications
Received Signal Strengths (RSS), Time Of Arrival (TOA), Time Difference Of Arrival (TDOA) and Angle Of Arrival (AOA) are some of the techniques used for localisation, each with its associated strengths and weakness
In this paper we have proposed an algorithm for geolocating a stationary RF emitter observed that is steered by a set of moving receivers placed on high altitudes
Summary
Estimating precise geographical location of a stationary emitter is critical for both military and civilian applications. Localisation using joint TDOA and FDOA measures is quite popular Classical methods of localisations based on TDOA and FDOA was a two-step process. Differential delay and Doppler frequency shifts between pair of sensor is measured In the second step, these estimates are used in statistical signal processing algorithms for emitter location But these methods were computationally too extensive and gave accurate results only in special conditions. Conventional TDOA and FDOA methods based on CAF using higher order statistics, wideband signals and uncorrelated signals is covered in literature the problem of joint TDOA and FDOA is studied in widely.
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