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This article prepares, MgxCa(0.90-x)Zn0.10Fe2O4nanoparticle-based new flexible microwave substrate materials to build flexible antennas. The MgxCa(0.90-x)Zn0.10Fe2O4nanoparticles are synthesized using the sol–gel chemical method. There are three different weight percentages are chosen for “X” values i.e., X = 25%, 50%, and 75%. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) studies are used to evaluate the structural and morphological features of the produced nanoparticles. Dielectric Assessment Kit is also used to evaluate the nanoparticles' tunable dielectric characteristics (DAK). Loss tangents range from 0.00275 to 0.00675 while dielectric permittivity values range from 3.25 to 4.75. The magnetic characteristics of the produced samples are also investigated using the vibrating sample magnetometer (VSM). The Agilent 8501E module is used to calculate the adjustable magnetic permeability and magnetic loss tangent values. The magnetic permeability and magnetic loss tangent values obtained are in the range of 1.00–1.15 and 0.0035–0.0065, respectively. Later, a flexible antenna is designed on the prepared flexible substrate that operates within the frequency range of 1.60 GHz–3.00 GHz with a maximum gain of 5.15 dBi. After that, this antenna is incorporated with a nine-antenna array-based portable microwave head imaging system. Finally, successful brain tumor detection is observed by post-processing the collected scattering parameters with an image reconstruction algorithm. The overall results ensure that the MgxCa(0.90-x)Zn0.10Fe2O4nanoparticle-based new flexible microwave substrate materials can be a potential candidate for microwave head imaging and are suitable to fit with microwave devices.

In this work, CaxZn(0.90-x)Ni0.10Fe2O4nanopowder-based new flexible microwave substrates are prepared using the sol–gel method for metamaterial applications. Three different x values are chosen as x = 25, 50, 75 and termed as Ca25, Ca50,and Ca75respectively. The structural and morphology of synthesized materials are investigated with XRD and FESEM analysis. The dielectric properties were also determined and the obtained values for dielectric constant (εr) and loss tangents (Tδ) are ranges from 3.25 to 4.25 for εrand 0.0025 to 0.0065 for Tδfor Ca25, Ca50,and Ca75respectively. In addition, the magnetic permeability μrand magnetic loss tangent (Tδm) values are estimated from the scattering parameters S11and S21obtained by using Agilent module 85071E, and the achieved values of μrand Tδmare ranges from 0.875 to 1.00 and 0.0035 to 0.0075 respectively. Later, the proposed metamaterial unit cell consists of a square split ring resonator (SSRR) and a circular SRR (CSRR) loaded with a plus shape is designed and fabricated on the proposed flexible substrates obtained from the synthesized CaxZn(0.90-x)Ni0.10Fe2O4nanopowders to validate their application as metamaterials. The novelty of the proposed work is found in the unit cell being polarization-insensitive and having a multiband, low electrical dimension that improves the EMR, single-negative characteristics with high flexibility and lightweight and suitable for C, X, and Ku bands of microwave regime.

In this study, novel flexible microwave substrates based on CoxZn(0.90-x)Al0.10Fe2O4nanopowder having an average grain size of 20 nm–26 nm were prepared using the sol–gel synthesis technique for microstrip patch antenna applications. At first there are three different molecular composition were chosen having the chemical formula of CoxZn(0.90-x)Al0.10Fe2O4and specified as Co20,Co40and Co60for x = 20%, x = 40% and x = 60% respectively. Then the synthesized ferrites materials were characterized with XRD, FESEM, and VSM analysis, and single-phase spinel with high crystallinity were revealed. Besides, the dielectric and magnetic properties of the proposed Co–Zn ferrites samples were investigated for the affirmations of microwave applications. The values of dielectric constant εrand loss tangent (Tδ) are determined using dielectric assessment kit, and the obtained values are ranges from 3.5 to 4.5 for εrand 0.002 to 0.006 for Tδfor Co20, Co40,and Co60respectively. Also, the magnetic permeability μrand magnetic loss tangent (Tδm) values are determined to form the predetermined scattering parameters S11and S21obtained from rectangular substrate pellets and the obtained values of μrand Tδmare ranges from 0.90 to 1.00 and 0.003 to 0.007 respectively. Finally, a modified diamond-shaped microstrip patch antenna is designed and fabricated on the proposed flexible substrates obtained from the synthesized Co–Zn ferrites nanopowders by mixing with PVA binder to validate their application in the S-band of microwave regime. The finite element method based computer simulation technology software is used to design the proposed microstrip patch antenna; furthermore, the simulated prototype is fabricated, and their reflections coefficients are measured for verification. The simulated and measured result of the proposed flexible antennas exhibits a maximum of 3 GHz bandwidth in between 2.5 and 5.5 GHz. Thus, the proposed materials offers tunable dielectric and magnetic properties with soft magnetic behaviors and easy to use where arbitrarily electromagnetic values are required. Moreover, these materilas also can be played significant role in flexible microwave field as low cost flexible substrates for compact flexible antennas, metamaterials, absorbers, and sensors applications etc.