Abstract
This article addresses the practical problem of selecting a GSM antenna for an electronic navigation seal intended for the control and monitoring of cargo transportation. Unlike traditional approaches based on datasheet specifications, the focus is placed on investigating antenna performance within a fully assembled device, taking into account the influence of the plastic enclosure, internal metallic components, and the overall electronic layout. For this purpose, laboratory tests were conducted on 28 commercially available planar GSM antennas operating in the GSM 900 band under conditions closely approximating real-world operation in a navigation seal. The antenna characteristics were evaluated using a standardized measurement setup with a housing mock-up and a reference antenna. The main comparison criterion was the standing wave ratio, which reflects the quality of antenna matching with the radio module and the level of power losses. Dimensional constraints of the enclosure, which are critically important for practical integration, were also considered during the selection process. Based on a comprehensive analysis, antennas providing stable communication and sufficient energy efficiency were selected and recommended for use in mass-produced electronic navigation seals. The obtained results confirm that a proper antenna selection is not possible without considering the installation conditions within a specific device, while testing under conditions close to the actual layout represents an important stage in the development of navigation systems operating under constraints of limited internal volume and dense component integration.