Abstract
Jamming of GNSS signals is lately treated as essential threat for GNSS users. It is especially dangerous in the face of common usage of GPS-like systems in everyday life, and the great belief of everyday users in the truth of devices indications. In spite of the legal prohibition of using them, jammers are commonly accessible, especially in the Internet. Last years showed however that such threat generated purposely also some governments, what is clearly visible in armed conflicts, and during military exercises. Of course this creates the great threat for civilian users if will be in the vicinity.
Applications and services based upon GNSS are becoming increasingly embedded in modern society, so community have now become critically dependent upon their correct operation. This refers positioning first of all, but telecommunications networks, power grids, financial transactions, whole world of logistics are dependant as well. The main users of GNSS, both professional and non-professional smartphones users are not prepared on such situation, and usually have no technical possibilities to detect of jamming. For operators of critical installations, for example seaports, or airfields, the detection of jamming cases is extremely important. It can be provided with special devices, which are usually based on specific antennas, and deep analysis of signal. In this paper experiments in detection of the jamming with helical antennas are discussed
Impedance Matching of Axial Mode Helical Antennas