Measurement of equivalent circuit parameters of avalanche beacons antennas for rapid prototyping

Abstract

This work deals with a measurement procedure for a fast and low-cost characterization of antennas for "Appareil de Recherche de Victimes d'Avalanches" (ARVAs). ARVA antennas are usually simple coil antennas tuned at 457 KHz. Such a low frequency ensures robust signal detection even in extremely harsh conditions, i.e. when the transmitter is buried under meters of snow and debris. Till now, the form factor has been one of the most critical design constraint of such antennas, since they are supposed to fit into handheld devices. However, in the near future, ARVA receivers could be mounted on Unmanned Aerial Vehicles (UAVs) flying over the avalanche areas to speed up the search for victims. In this context, new-generation and more sensitive antennas are needed, which require considerable design efforts. Unfortunately, the measurement systems commonly used to characterize radio frequency (RF) or microwave antennas can be hardly used to this purpose, due to the low operating frequency and the short range of ARVA devices. To overcome these problems, a measurement procedure able to characterize the equivalent circuit parameters as well as the Q-factor of antennas for avalanche beacons has been developed, and finally validated experimentally by means of a Virtual Instrument implemented in LabVIEW. The results obtained using two different antennas confirm that the proposed approach can provide accurate results, once the main systematic contributions are estimated and compensated.