No abstract

No abstract

A wearable electromagnetic belt system for the detection of hepatic steatosis (lipid accumulation within the major liver cells, hepatocytes), is proposed. To satisfy the requirements of the belt system, an array of body matched antennas is designed. The belt, which goes around the lower chest and over the liver, requires compact, wideband, unidirectional antennas that operate at low microwave frequencies. To avoid using conventional bulky reflector structures, the designed antenna utilizes the loop-dipole combination concept. To enhance electromagnetic wave penetration, the antenna is designed to match the human body. Thus, thanks to the high dielectric loading from the human body, the dipole element of the antenna is easily miniaturized. Since the same principle does not apply on the loop structure, meandered arc-shapes are employed to increase the effective electrical length of the loop. The final antenna design has a measured wide operating bandwidth of 0.58-1.6 GHz with a compact size of 0.096×0.048×0.048λ 3 . The proposed structure is effective in irradiating the torso, where the signal can reach center of the liver at a depth of 90 mm, with 64% of the peak radiated power. An electromagnetic belt is built using twelve elements of the designed antennas. The belt is then tested on a 3D printed torso phantom that includes models of the lungs and liver. Due to close dielectric properties of the other tissues inside the torso, these are represented using an average tissue mimicking mixture with permittivity of 46. Measured data are analyzed using multivariate energy statistics method. A peak measured dissimilarity of 15.1% between steatotic and healthy liver is attained. These initial tests and obtained results indicate the potential of the proposed system as a method to diagnose hepatic steatosis.INDEX TERMS Body-matched antenna, electromagnetic belt, fatty liver disease, statistical based analysis, wearable system.

An ultrawideband receiver antenna system is proposed. The radiating element is a transverse electromagnetic horn antenna, featuring a negative impedance converter at lower frequencies. The voltage standing-wave ratio (VSWR) is less than 2.0 in the bandwidth from 20 MHz to 2.5 GHz. A good agreement between the measurements of the fabricated system and the simulated results is observed. Sample applications include direction finding, broadband communication systems, radar systems, and electromagnetic compatibility measurement systems.

A wideband beam-switching metasurface antenna using programmable unit-cells is proposed for electromagnetic torso scanning. The design aims at changing the intensity of the electric field inside the torso without any mechanical movements and thus enables fast electronic scanning of the torso. The antenna consists of an H-shape microstrip-fed slot as the radiator and a metasurface layer containing 5×5 programmable square ring resonator as the superstrate layer. Four PIN diodes are embedded in each cell to alter the electric field intensity within the metasurface layer and consequently switch the radiation pattern in the azimuth plane, elevation plane, and diagonal axis of the metasurface layer. As a proof of concept, a prototype antenna capable of switching the radiation pattern from-25 0 to +25 0 in the azimuth (x-z) plane is fabricated and measured. The antenna, which has the compact size of 0.9λ0×0.9λ0×0.06λ0 (where λ0 is the wavelength at the center operation frequency), achieves a wide bandwidth of 30% at 0.9-1.2 GHz. The peak measured gain is 9.5 dBi with maximum front to back ratio of 12 dB. The fabricated antenna is successfully tested on altering the intensity of the electric field at right, center and left sides of a torso phantom. INDEX TERMS Pattern reconfigurable antenna, metasurfaces, torso scanner, electronic beam switching

An ultra-wideband multibeam microwave lens antenna operating from 8 GHz to 18 GHz is proposed. The antenna consists of four excitation ports connected to a parallel plate waveguide filled with a cylindrical dielectric slab, which serves as a lens in order to modify the cylindrical wavefront launched by the excitation ports. The output of the lens is a plane wave guided to a radiation aperture with a linear tapered flare. Four distinct fan-beams covering 40 • in the azimuth plane with an elevation beamwidth of 30 • and a minimum gain of 15 dBi have been achieved. The main advantages of our design include its relative simplicity, ease of fabrication, having a low profile, not requiring an antenna feed, and high-power handling capability. The design procedure is presented together with the optimization procedures that have been applied to all parts of the antenna system to achieve the desired performance. The proposed structure has been simulated with CST Microwave Studio software. There is an excellent agreement between the simulation and measurement results.

No abstract

No abstract