An anti-intrusion protection barrier based on 2D radar technology

Abstract

The 2D (range and azimuth) radar system here presented has been developed for civilian and industrial anti-intrusion applications and has been designed to provide an impassable protection barrier with controllable width (down to one meter). It is based on a CW double chirp technique: a linearly changing frequency signal is transmitted and the signals reflected by possible intruders (targets) are properly processed to determine, by analyzing their frequency content, the position in azimuth and range of the target itself. The system is mainly composed of a 24 GHz transceiver module for the transmission and reception of the signals, a real-time processing DSP-based board and an interface board for communication with the user and with external devices. The transceiver module includes one transmitting (TX) and two receiving (RX) antennas and an MMIC chip for the generation of the radar signals and the reception of echoes and their coherent pulse compression and filtering. The TX and RX antennas are patch 2D arrays with a designed beam-width of approximately 6° and side-lobe suppression achieved through appropriate elements power tapering. The main element of the transceiver is an MMIC chip which converts the triangular continuous wave generated by the DSP board into a varying frequency (24-24.250 GHz) wave for feeding the TX antenna. The high frequency received echo signals are then pulse compressed by the MMIC, filtered and sent back to the DSP board. The processing board is equipped with a DAC, four ADCs, a 300 MHz DSP and many peripherals. The received echo signals, converted into frequency domain through complex FFT, are processed with sophisticated algorithms for background removal (MTI filter), thresholding (CFAR algorithms, RCS analysis and more) and range determination. The determination of the azimuthal position of the target is based on a phase comparison mono-pulse technique. The analysis allows to determine both the range and the azimuth position and to accurately achieve the desired 2D shape of the detection area (usually a very narrow BLADE shape). The sophisticated processing algorithm makes the system resilient to atmospheric events such as wind, snow and rain, and capable of discriminating between human targets and small animals. The interface board gives the user the possibility to properly configure the radar system by setting all the parameters through an appropriate GUI and regulate the radar sensitivity all over the protection area. Furthermore, it allows the system to be integrated in a network of sensors, video cameras and other devices.