Miniaturization of long-term evolution antenna fostered by NiMn_xFe_2−xO₄ nanocomposite coating

The synthesis and characterization of NiMn_xFe_2−xO₄(x = 0, 0.2 and 0.4) with insitu generated Fe₃O₄ composite coatings for miniaturization of Printed Inverted F antenna (PIFA) has been reported. The intended ferrite powder samples were synthesized using urea assisted self-propagating high temperature synthesis. The structural analysis of the sintered powders analyzed through x ray diffraction and FTIR characterization methods confirm the substitution of trivalent Mn ion in tetrahedral site in ferrite lattice and also the presence of Fe₃O₄/NiMn_xFe_2−xO₄ nano composite. The x ray photoelectron spectral studies had further confirmed the presence of divalent and trivalent Fe ions in the compound accounting for the presence of composite phase. The Mn substitution had resulted in higher magnetic permeability at GHz frequencies. The permeability value of 2.5 is achieved in the UHF frequencies used for LTE applications for a Mn doping concentration of 0.2. The synthesized material is coated as a superstrate on a LTE antenna and is observed to result in miniaturization by 20% with a bandwidth of 90 MHz (80% increment) covering the entire LTE band 12 and LTE 13. The antenna has a gain of 1.8 dBi in the peak and a near omni-directional pattern. (paper)