Journal
IEEE TRANSACTIONS ON MAGNETICS
Volume 47, Issue 10, Pages 3720-3723Publisher
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/TMAG.2011.2148109
Keywords
Antennas substrates; ferrite materials; microwave materials
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Low-loss Ni-Zn porous ferrite ceramics have been obtained (porosity close to 40%) after appropriate heat treatment and shaping of nanosized powders. The key point in this process is a moderate reaction sintering that promotes desired value of porosity. Measured complex permeabilities and permittivities in the [10(7) Hz-10(10) Hz] frequency range are presented. The developed materials show almost constant refractive index value f, close to 5 up to 900 MHz. The sum of the magnetic and dielectric losses shows moderate values up to a frequency value f, unusual for spinel ferrites: tan delta(mu) + tan delta(epsilon) < 0.083 at f = 600 MHz. Their efficiency for miniaturization and performances improvement of several new antennas for Digital Video Broadcasting Handheld (DVB-H) devices (frequency ranging: 470-862 MHz) are presented. High miniaturizations (about 40% to 60% when compared to not loaded antenna) are obtained. Low loss, wide bandwidth and good radiation efficiency are measured. Antennas performances are enhanced. A new antenna is also presented. Its dimensions are very small and it covers the entire DVB-H band. Suitability of Ni-Zn porous ferrites ceramics for antenna miniaturization for DVB-H applications is demonstrated.
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