Software Defined Radio-Based ELINT System for Geolocation of RF Emitters

A Software Defined Radio (SDR) is a radio where digitizing the signal allows circuitry previously implemented in dedicated hardware to be moved in to the digital domain. After the signal is digitized, software can control the channel frequency, bandwidth and modulation format. The combination of wideband front ends and powerful processors makes software radios an ideal platform for ELINT, COMINT, SIGINT applications. This paper aims at introducing SDR-based ELINT system for geolocation of RF emitters from space and airborne platforms. The ELINT system proposed consists of three receivers placed in a defined configuration to receive the signal from the RF emitter simultaneously. For precise geo location of the RF emitters, it is required to time synchronize the three receivers to an accuracy of < 5 ns. A novel method of relative time synchronization based on Time to Digital Conversion (TDC) technology is discussed to enable the SDR receiver to time stamp the received RF pulse data precisely to get its Time of Arrival (TOA) information. The Time of Arrival information of the received RF pulse at each receiver is used to extract the Time Difference of Arrival (TDOA) and hence used in geolocation of RF emitters by solving the hyperbolic equations.