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Suitability of Ni-Zn Ferrites Ceramics With Controlled Porosity as Granular Substrates for Mobile Handset Miniaturized Antennas

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11 Author(s)
Mattei, J.-L. ; Lab.-STICC, Univ. of Brest, Brest, France ; Huitema, L. ; Queffelec, P. ; Pintos, J.-F.
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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 [107 Hz -1010 Hz] frequency range are presented. The developed materials show almost constant refractive index value n 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: tanδμ+tanδε <; 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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Magnetics, IEEE Transactions on  (Volume:47 ,  Issue: 10 )