A proposed model for frequency tuned antennas used in mobile communication systems

The antenna is considered as one of the most fundamental elements in wireless communication systems, especially in mobile devices. Desirable specifications of antennas include covering wide range of operating frequencies, while maintaining high quality of system performance over the whole range of operating frequencies. Therefore, the ability of tuning the resonant frequency of the antenna without altering its physical dimensions would be highly recommended in up-and-coming designs of antennas in mobile devices. This research work proposes a model for tuning the operating frequency of the inverted F-antenna over a reasonably wide range of frequencies, via altering the electromagnetic properties of its ferrite material. In this proposed model, it will be shown that the electronic control of the permeability of the ferrite material of the antenna leads effectively to a significant shift in its resonant frequency, and hence to an overall improvement in the performance of the communication system.

Determination of the surface tension coefficient of ferrites 600NN upon sintering

The manufacturing process of ferrite production consists in a chain of structural and phase transformations resulted in formation of ferrite ceramics from disperse systems (their solid phase is represented by metal oxides). The forces of surface tension play a crucial role at all stages of the technological process. A decrease in surface tension forces during grinding due to the use of surfactants (surface active substances) leads to better disaggregation of the components (both original and ferritized). The use of surfactants reduces interparticle friction and provides manufacturing of more dense workpieces at the stage of pressing. Microadditives promote faster formation of contact isthmuses. The goal of the study is to develop a method for determining the surface tension coefficient of 600NN ferrite material during sintering. The proposed approach is based on measurements of the shrinkage of various fragments of a vertically sintered ferrite rod, which are used to determine the values of the coefficient. It is shown that the surface tension coefficient of the studied ferrite material during sintering was σ = 65.2 ± 13.0 N/m with a confidence probability of 95%. The results obtained can be used to study the effect of the sintering temperature, the size of sintered particles, the amount and quality of alloying additives on the forces of surface tension. Moreover, the data can be used in the study of the relationship between the value of the surface tension coefficient and the parameters of the microstructure.

Ferrite-Loaded Spidron Fractal Loop VHF Antenna for UAV Applications

In this letter, an electrically small Spidron fractal loop antenna operating in the VHF band is proposed. The ferrite material, which consists of a nickel-zinc combination, is loaded into inside of the loop antenna to increase the gain of the antenna in the low frequency band. To minimize the magnetic loss of the ferrite in the high frequency band, the amount and configuration of the ferrite are optimized using a genetic algorithm. Through this optimization step, the amount of the ferrite is decreased to 37.5% and the gain of the antenna in the high frequency band is improved. The size of the proposed antenna is 0.0242 × 0.0242 × 0.0051 λL3 at the lowest operating frequency. The proposed antenna was fabricated to verify the performance, and the simulated and measured results are in good agreement. The measured peak gains varied from −31.6 to −1.9 dBi within the measured frequency band. To examine the performance of the proposed antenna mounted on an unmanned aerial vehicle model (UAV), the antenna on a UAV was also simulated and the results were discussed. The simulated realized peak gains of the antenna on the UAV and on flat ground are similar.