2018 Volume 138 Issue 2 Pages 100-105
Because radiation patterns of conventional antennas at the security gates are not enough sharp, many false operations are pointed out to recognize the RF-tags located in short distance away from the security gates. In this paper, a technique to narrow down the radiation patterns of the antenna operationally was proposed while keeping antenna size to be small based on the monopulse system at 920MHz. From the numerical and experimental investigations, it was obvious that this system guaranteed the narrow beam operation to be less than the range of the arrival angle of 20° although an antenna with a half power beamwidth of 150° was used. And moreover, influence of the interference waves from other unchecked RF-Tags located in short distance away from the security gate was considered, the shoplifted RF-Tag passing through the security gate.