Loop Antennas for Use On/Off Ground Planes

Many applications benefit from the ability of an RFID tag to operate both on and off a conducting ground plane. This paper presents an electrically small loop antenna at 433 MHz that passively maintains its free-space tune and match when located a certain distance away from a large conducting ground...

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Bibliographic Details
Published in:IEEE access 2020-01, Vol.8, p.138763-138770
Main Author: Borchardt, John J.
Format: Article
Language:English
Subjects:
Antenna
Antennas
dual-environment
ENGINEERING
Equivalent circuits
Geometry
Ground plane
Integrated circuit modeling
loop antenna
Loop antennas
Mathematical model
metal tag
Metals
on/off metal
Parasitic elements (antennas)
platform-tolerant
Radio frequency identification
Radiofrequency identification
radiofrequency identification (RFID)
Reactance
Resonant frequencies
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Summary:Many applications benefit from the ability of an RFID tag to operate both on and off a conducting ground plane. This paper presents an electrically small loop antenna at 433 MHz that passively maintains its free-space tune and match when located a certain distance away from a large conducting ground plane. The design achieves this using a single radiation mechanism (that of a loop) in both environments without the use of a ground plane or EBG/AMC structure. An equivalent circuit model is developed that explains the dual-environment behavior and shows that the geometry balances inductive and capacitive parasitics introduced by the ground plane such that the free-space loop reactance, and thus resonant frequency, does not change. A design equation for balancing the inductive and capacitive parasitic effects is derived. Finally, experimental data showing the design eliminates ground plane detuning in practice is presented. The design is suitable for active, "hard" RFID tag applications.
ISSN:2169-3536
2169-3536
DOI:10.1109/ACCESS.2020.3011280