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W_We_C_Room5: Challenges in Special Applications of Electrically Small, HF Vehicular Antennas (III)
Vehicular, mobile HF (short wave 1.5/3 to 30 MHz, 200/100 to 10m) communication is up today still in beneficial use. Due to ionospheric propagation conditions, under presently low sunspot activities, only the lower spectrum part can mostly be used. Exactly this is a technical challenge, because here electrically short, vertical HF mobile antennas are, from antenna theory basically known, to be inefficient. There is however very little practical, experimental or simulation data available in the open literature. Aside from the military, emergency disaster relief organizations (humanitarian, medical, technical aid) depend on HF mobile on the go. In troubled areas communication infrastructure is mostly gone. Improvised, quick, reliable and still cost-effective deployment is vital. Sat-Com or 3 or 4G mobile phones are often no option. Our detailed experimental and EM-simulation investigations include Automotive EMC, analysis of electrically short HF Antennas, critical communications S/N-ratio, antenna performance impacting parameter studies, rubber tire impact, antenna input impedance, radiation pattern, the impact of soil/ground under the automobile, far-field simulations with absolute antenna efficiency, incl. vertical elevation angle. Validation measurements (groundwave, sky-wave) were performed in the critical low bands of shortwave spectrum around 1.8/3.5/7MHz and above. These representative bands were used base on existing government Amateur Radio transmitting licenses. Antenna efficiency tests by ground-wave propagation were conducted over 2.8 km flat farmland. Sky-wave antenna efficiency test lead to estimates, via statistics, from extended, real world, EU Ionospheric Propagation experiments. The only successful way to address antenna elevation patterns, without having H-field sensing drones available, was to use validated, professional EM-Simulation Codes. Agreement between tests and simulation results are very reasonable, given the many impacting parameters. Innovative antenna design concepts will be discussed.
The general content structure of the workshop is:
Dr. Diethard Hansen
President and Principal Consultant
EURO EMC SERVICE (EES)
EMCoS Ltd. HQ, Georgia
|External Resource: https://bit.ly/2HfkTnx|
|No contributions were assigned to this session.|
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