Abstract
The article presents the results of a comparative study of 28 types of commercial flat GSM antennas and a self-developed antenna "Zmeyka" fabricated on a 1 mm FR-4 substrate operating in the GSM 900 band (Uplink 890 MHz, Downlink 960 MHz) for integration into the housing of a navigation seal intended for real transportation conditions. Particular attention is paid to the influence of housing materials, layout constraints, and the electromagnetic environment on impedance matching parameters and signal reception quality. The study was conducted in several stages. Laboratory measurements in an anechoic chamber using a Keysight FieldFox N9915A analyzer showed that in the reference housing made of 2 mm ABS plastic, the "Zmeyka" antenna achieved an average VSWR of 1.2, whereas several commercial samples exhibited VSWR values exceeding 6. Subsequently, selected antennas were tested in field conditions using a proprietary software tool "GSM Antenna Tester" to record CSQ/RSSI parameters. This approach enabled a comparative analysis of antenna performance not only under controlled laboratory conditions but also in scenarios close to real operating environments. Experimental results demonstrated that the integration of antennas into a housing made of reinforced polyamide PA12+GF ([Formula: see text]-4.5) with 3.5 mm wall thickness and dense internal layout causes a downward shift of the resonance frequency by approximately 50 MHz, as well as an increase in VSWR up to 3.5 and a reduction of the transmission coefficient in the main lobe by 6-7 dB. Against this background, the self-developed "Zmeyka" antenna showed the highest resistance to layout and environmental effects, maintaining acceptable impedance matching and stable signal reception. Field tests using the "GSM Antenna Tester" software recorded a decrease in the signal level of commercial antennas to the "Weak" category (CSQ 7-11, RSSI from [Formula: see text] to [Formula: see text] dBm), while the adaptive design of the "Zmeyka" antenna compensated for environmental effects. The obtained results confirm that the design of navigation seals with integrated GSM communication cannot rely solely on the nominal antenna specifications provided by manufacturers. The electromagnetic environment inside the housing, material properties, and layout features have a significantly stronger impact on antenna performance than is typically assumed. It has been demonstrated that the possibility of adjusting the topology of the radiating elements in the "Zmeyka" antenna makes it possible to reduce insertion losses from 6-7 dB to an acceptable level of 1-2 dB, thereby ensuring stable data transmission under challenging transportation operating conditions.