A consideration on influence of interference waves at security gate using monopulse system at UHF band

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. Having this fact in mind, a technique to narrow down the radiation patterns of the antenna operationally while keeping antenna size to be small has been proposed based on the monopulse system at 920 MHz. In this paper, to verify the usefulness of this system, the 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.