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A planar sensor designed using the fourth Hilbert fractal curve iteration for solid material characterization at multiple frequencies is reported in this paper. The fractal curve is self-similar with space filling properties. The Hilbert fractal geometry is used to form a compact resonator, with a multiband frequency response where miniaturization is achieved, since a large transmission line length is effectively confined in a limited area. The sensor provides five resonances in the frequency range from 0 to 5 GHz. The resonant frequencies are 0.56, 1.68, 2.72, 3.69 and 4.72 GHz, all used to measure the real permittivity of known samples with a sensitivity of 7, 20, 27, 43 and 50 MHz/permittivity, respectively. The sensor is used to measure dielectric samples with 20 x 20 mm2 areas with several thicknesses. Simulations and measurements demonstrate that the Hilbert fractal geometry can be used to design a multiband planar sensor for solid dielectric material characterization.

This work proposes the use of the Particle Swarm Optimization method (PSO) to maximize the main beam of an intelligent, switched array of four Yagi-Uda antennas. The antenna feeds, amplitude and phase, are the PSO input variables, which not only maximizes the main lobe for a given direction, but also minimizes all secondary ones. The MATLAB software is used to make the simulations. Radiation patterns are here produced, which show that PSO is efficient for maximizing lobes in the range from 0° to 180°. Suggestion of an arrangement for a 360° coverage around the array is also presented.

This paper reviews the application of microwave signal-interference techniques to interferometers for frequency measurement and filters. The microwave interference takes place when the input-signal components pass through two different electrical paths to be then recombined and produce an interference pattern. Path lengths define the interference-based power-transmission maximum and minimum, which are calculated to obtain the desired device frequency response. Reconfigurable interferometers, wide-band, and dual-band filters designed using interference principles are described in this overview paper.

A planar dual-band circular antenna for a chemical wireless sensor network is described in this paper. Four antennas compose the wireless sensor package and one antenna is selected at a given time using an SP4T switch. This work describes the unit antenna used to transmit sensor information to a nearby hub that operates in the ISM bands. The antenna is composed of concentric shorted annular rings using substrate integrated waveguides and includes a circular patch at its center. The antenna presents two types of radiation patterns, one omni-directional in the azimuth plane at 2.4 GHz, and one uni-directional in the elevation plane at 5.8 GHz. The simulated gains obtained at 2.4 GHz and 5.8 GHz are 2 dB and 7 dB, respectively., Grant numbers : Generalitat de Catalunya grant 2017 SGR 891 project.

A novel Sierpinski carpet fractal dipole is here investigated. The new geometry of the fractals used in this study has slots suitably located, so that currents now flow near the edges of the squares which have been defined by the slots, and, as a result, resonances occur at frequencies which correspond to the dimensions of the fractal generator at different scales. The dipole is then verified to operate effectively as a multiband antenna. Simulation results for the return loss, current density distribution and radiation pattern are here reported.