Miniaturization of body worn antenna using nano magneto-dielectric composite as substrate in C-band

•Nickel zinc ferrite-LLDPE composite is developed as substrate for body worn antennas.•Its suitability is determined by physical, thermal and microwave characterization.•S11 of -31.44 dB and -10 dB BW of 8.30% is observed for 7 wt% NZF-LLDPE composite

It is preferable to have small size conformal microstrip patch antenna for body worn applications. Size reduction is generally carried out by using magneto-dielectric material. Nanosized Ni1−xZnxFe2O4 (x=0.25, 0.50 and 0.75) of crystallite size ~32 nm is synthesized as magnetic filler and dispersed in flexible linear low density polyethylene (LLDPE) matrix. The filler concentrations are varied as 1, 3, 5 and 7 wt% in the composite. The developed composite is tested for suitability to be used as substrate for microstrip antenna by determining its permittivity, permeability and losses in the C-band (4–8 GHz). Other relevant parameters like, tensile strength, water absorbance and decomposition temperature of the composite are also determined. The real part of complex permittivity of the composite varies from 2.23 to 2.38 and complex permeability from 1.25 to 1.46 for different filler concentrations. Verification of the composites as potential substrates for body worn antenna is carried out by fabricating simple rectangular patch antenna at 6 GHz on it using transmission line model. Rectangular patch for x=0.50 for 7 wt% shows S11 of −30.44 dB and −10 dB bandwidth of 8.30% at 6.02 GHz. Directivity of 10.14 dBi and negligible side lobe level for both E and H plane radiation pattern is observed. A size reduction of 27.09% as compared to patch on LLDPE and tensile strength of 50 MPa is observed.