Abstract: Electronic Intelligence (ELINT) is the result of observing the signals by radar systems to obtain information about their capabilities. ELINT provides timely information about threatening system such as radar that guide aircraft or missile to target. It can be installed in all kinds of airborne, sea based, and ground based assets and is used for identifying and avoiding threats. Amplitude comparison direction finding method is used in this design to determine the Angle of Arrival of the received signals by distributing eight antennas circularly. Determining the direction or Angle of Arrival of a radar signal is fundamental to electronic intelligence. It uses eight directional antennas circularly distributed, whose boresight are pointed in different directions. The boresights are typically offset from each other such that the gain patterns overlap along the 3dB edge. When the signals arrived, it is down converted to intermediate frequency using Digital Down Converter (DDC) and Fast Fourier Transform (FFT) is taken. The ratio of power amplitudes of the antennas are compared to known antenna gain patterns which is then used to calculate the Angle of Arrival. The equation of Angle of Arrival was derived by taking the ratio of signal amplitudes between each two adjacent antennas due to their associated Angle of Arrival over 360 directions. This method makes the system simple in analysis and implementation and gives good accuracy and resolution over a wide range of frequencies. This system provides the horizontal (azimuth) direction of the arrived signal as related to the reference direction automatically without steering antennas and then overcomes the mechanical problems. The proposed system in this paper operates over a wide band of frequency (0.5 to 18GHz) and covers the whole 360 degrees.
Keywords: Amplitude comparison, AOA, Direction Finding, ELINT, Multi Emitter.