In designing filters and antenna feeds at microwave frequency, the energy density and stop bands are of vital importance. To this development, this work is set out to determine the transmission coefficients behavior of substrates along with their energy density for a microstrip structure using finite element method (FEM) and Vector network analyzer (VNA). In this work, a 15, 30 and 50 mm PTFE samples were used as an overlay substrate material on a patch microstrip antenna. Simulations and measurement were then carried using FEM and VNA, respectively. Transmission coefficient obtained via FEM and VNA were compared and the behavior of the substrates at 10 GHz were noted which is the area of broad stop band. Results from simulation and measurement showed that the energy density of the 50 mm thick substrates was 1.67 x 10-5 J/m3 while the attenuated power for the 15, 30 and 50 mm thick substrates at 10 GHz were 6.8, 8.0 and 14.6 dB, respectively. Based on these findings, it is concluded that the 50 mm thick PTFE substrates has the deepest stopband at 10 GHz and more suitable for filter designs and antenna feeds.

Ferrite are conventional materials used for microwave absorption, however, they are expensive, constitute health hazard and pollutes the environment. For these reasons, there is need to explore safe and environmental friendly materials that can serve as radiation absorbers and be used in fabricating microwave devices. In the light of the above, this work was geared towards exploring the use of Unripe Plantain Husk (UPH) waste material for microwave absorber applications. The usability was determined by investigating the dielectric properties and attenuation of the UPH powder with respect to particle size and frequency of operation. The nano particle of the UPH was prepared aseptically by washing in water and acetone, sliced, sundried and grinded. The grinded UPH powder was then subjected to high energy milling using a SPEX 8000D shaker for 4 hours, 8 hours, 10 hours and 12 hours. The milled powder was then prepared into pellets by suppressing with hydraulic press and mold which were then used for characterization. Results from investigation and analysis showed that the milled powder was in nano dimension using transmission electron microscope (TEM). The UPH powder sizes were in the range of 63.35 nm, 52.05 nm, 42.86 nm and 21.43 nm for the 4, 8, 10 and 12 hours milling, respectively. The dielectric constants for the as produced, 4, 8, 10 and 12 hours milled powder were 2.96, 4.97, 5.66, 6.97 and 10.36, respectively. The highest magnitude for attenuation was calculated for the 12 hours milled powder with a value of 14.92 dB and the least attenuation was calculated for the as produced powder with a value of 6.72 dB. Based on the results obtained it is concluded that nano particles of UPH powder is good for microwave attenuation and is a potential for fabricating electronic components.

This study involves an investigation to ascertain the effect of ZnO nano inclusion on the evolution and dielectric properties of ZnO-PCL nanocomposites. The effect of the nano inclusion towards attenuation of the composites is also reported. In this study, ZnO nano particles and polycaprolactone (PCL) were blended to form composites using melt blending technique. The composites were employed to study the effect of nano inclusion on the materials. Further analysis was done using FTIR to investigate the band positions and absorption peak of the prepared samples, SEM and EDX for the morphology and elemental composition of samples. The FTIR spectra indicated a strong interaction at the interface of the ZnO nano particles with the polymer matrix. Amongst other findings, it was confirmed that the dielectric constant increases as the ZnO nano content increases where the average values for the different compositions are 4.39, 4.14, 3.62, 3.31 and 3.21 from highest to lowest filler percentage respectively. The high dielectric properties of the composites makes it suitable for small microwave absorption devices

Dielectric materials have many important functions in the microelectronics industry. The aim of this research is to characterize the dielectric constant of doped zinc-oxide composites using solid state method at microwave frequency. The methods used in this research are solid state method for sample preparation, open ended coaxial probe (OECP) for determining the dielectric constant and FTIR for bonding and IR absorption properties. The OECP results shows a sequential increase in dielectric constant as pure ZnO is doped incrementally with the filler (NiO). It also shows a sequential decrease in dielectric constant as the frequency increases. The FTIR result shows an increase in IR absorption as NiO content increases. The result from SEM was able to distinguish between the filler and matrix for each composition. Therefore NiO can be used as a filler for improving dielectric constant of ZnO as a matrix. The composite can also serve as a good agent for constructing capacitors and other dielectric materials which are hence used in manufacturing electronic and telecommunication gadgets. It was also proven that solid state method is a good method for synthesis of powdered sample like ZnO and NiO for determining their dielectric constant.

Knowledge of materials behaviour placed in an electromagnetic field was found to be of immense significant especially as it is attributed to military hardware, electronics, communication and industrial applications. An overlay microstrip antenna was employed in this study to determine scattering parameters of an overlay microstrip antenna using finite element method (FEM). The substrate thickness used on the microstrip was 10 mm thick and 8 x 12 cm (width and length). All simulation was carried at X band frequency range (8-12 GHz) using FEM. The result amongst others showed that the transmission coefficient depends on the permittivity of the sample. The result also showed that lowest permittivity of material produced the greatest transmission coefficient. It is then concluded that the results obtained for the transmission and reflection coefficients can be used for the prediction of complex permittivity of materials used as overlay on a microstrip antenna.