Serial Patch Array Antenna for an FMCW Radar Housed in a White Cane

The design, realization, and test of the transmitting and receiving antennas for an FMCW radar operating between 24 and 24.25 GHz (ISM band), to be housed in a white cane for improving mobility of visually impaired subjects, have been performed. The coaxial-to-microstrip transition necessary for feeding the antennas has been studied together with the characteristics of serial arrays of increasing number of patches. Based on this study, a serial array with 8 patches has been selected for the transmitting and receiving antennas. The realized structures show a reflection coefficient lower than −10 dB in the ISM band. When the antennas are attached to an FMCW radar board, the radar is able to record reflections from a metallic panel up to a 5 m distance

A Comparison between Multiple-Input Multiple-Output and Multiple-Input Single-Output Radar Configurations for Through-the-Wall Imaging Applications

The performances of a multiple-input multiple-output (MIMO) radar, employing 16 equivalent antennas, and multiple-input single-output (MISO) radar, employing 10 antennas, for through-the-wall imaging applications are analyzed. In particular, imaging algorithms based on the Fourier transform (FT) and the multiple signal classification (MUSIC) available in the literature are compared with the FT-MUSIC hybrid algorithm recently developed by the authors. Three different investigations have been performed. The first, performed analytically, refers to a scenario in which a point scatterer is placed in free space, and the second, addressed numerically using the CST full-wave software, refers to a scenario in which two targets are present, while the last was executed in a real scenario where a metal panel is placed behind a tuff wall. All the algorithms and radar configurations were found to be suitable for accurately reconstructing the position of the investigated target. In particular, applying the FT technique, the MISO configuration has a lower cross-range half-power beamwidths (HPBW) than the MIMO one, while the range HPBW is the same for the two radar configurations. Despite the different number of elements present in the two radar configurations, similar range and cross-range HPBW are obtained for both configurations when MUSIC and FT-MUSIC techniques are employed. The field of view for FT and FT-MUSIC is about 45°, while it is less than 15° for the MUSIC algorithm. The HPBWs obtained with the experimental setup are very close to those obtained in the analytical study. Finally, the proposed experimental MISO radar acquires the data in half the time required by the MIMO one. The numerical results, confirmed by the experimental measurements, seem to indicate in the FT-MUSIC technique the one that provides the best performance for the considered radar configurations

Radiation-Enhancement Properties of an X-Band Woodpile EBG and Its Application to a Planar Antenna

A woodpile Electromagnetic Bandgap (EBG) material has been designed, by using an in-house code that implements the Fourier Modal Method (FMM). A couple of alumina-woodpile samples have been fabricated. Several results have been collected for the transmission behaviour of the woodpile and of resonators with woodpile mirrors, in a shielded anechoic chamber, by using a vector network analyzer, in the 8–12 GHz range. These new experimental data highlight interesting properties of 3D EBG resonators and suggest possible innovative applications. Comparisons of the collected results with FMM show a satisfactory agreement. An application of the EBG resonator has been considered, for gain enhancement of a microstrip antenna: an increase of about 10 dB in the broadside gain has been measured; experimental data and numerical results obtained with the commercial software HFSS show a good agreement. A comparison is presented between EBG resonator antennas and two-dimensional uniform arrays. Finally, HFSS results are provided for EBG resonator antennas working at higher frequencies or with a more selective superstrate: a gain enhancement of more than 18 dB is achieved by such antennas

Experimental Analysis of a Directive Antenna with a 3D-EBG Superstrate, Journal of Telecommunications and Information Technology, 2017, nr 3

A three-dimensional electromagnetic crystal is employed as a directivity-enhancing superstrate for planar antennas. The crystal is a woodpile made of alumina rods. In a shielded anechoic chamber, the performance of a patch antenna covered with the woodpile is measured. The superstrate is positioned at different distances from the antenna and its orientation is varied in the 8–12 GHz frequency range. The return loss, gain and radiation pattern in the E- and H-planes are measured. The electromagnetic behavior of Fabry-Perot cavities with woodpile mirrors, equivalent to the compound radiator, is also studied. The main effect of the crystal on the antenna performance is an enhancement of about 10 dB in maximum gain. A rather complete series of experiments is presented, highlighting the role of the periodic structure in the directivity enhancement and allowing a deeper understanding of the electromagnetic phenomena involved in EBG resonator antennas. Benefits and disadvantages of this kind of antennas are discussed and ideas for future research are given

A Comparative Analysis Between Customized and Commercial Systems for Complex Permittivity Measurements on Liquid Samples at Microwave Frequencies

In this paper, different customized systems for microwave permittivity measurements on liquid samples, based on reflectometric measurements, are presented and analyzed. Their performance is compared against the one deriving from the most widely adopted commercial measurement setup. The systems are designed with the aim of providing less expensive solutions without compromising measurement accuracy. The purpose of the first proposed solution is to replace the commercial measurement software exploiting a reformulation of the classical theory. Based on this alternative formulation, a "homemade" probe is built by properly modifying an N-type coaxial connector, thus providing a system requiring a lower quantity of liquid under test. Moreover, a different experimental approach which uses time-domain reflectometry (TDR) instrumentation is presented. Such solution is by far the least expensive, as it allows avoiding the use of costly instrumentation (such as a vector network analyzer). In order to metrologically characterize the proposed solutions, a series of repeated measurements is performed on a set of well-referenced liquids. After extracting the Cole-Cole parameters through each of the considered measurement methods, the resulting type A uncertainty is evaluated. Finally, comparison with literature data allows the estimation of measurement bias. The analysis evidences that custom solutions generally exhibit an accuracy comparable to the one of the commercial solution, with a slight degradation of performance for the TDR-based setup, which, however, compensates for this drawback with its appealing low cost

Interaction between 3-T MRI systems and patients with an implanted pacemaker

In this paper, a transverse electro-magnetic (TEM) coil operating at 128 MHz in a 3-T magnetic resonance imaging system has been studied in terms of the interaction with patients with or without an implanted pacemaker. The pacemaker has been simulated as a copper box with a catheter constituted by an insulated copper wire with an uncapped tip and it has been placed inside either box or anatomical models of the thorax. Electromagnetic and thermal simulations have been performed by using finite difference time domain codes. The obtained results show that in the absence of the pacemaker, and for a radiated power producing in the box a whole body specific absorption rate (SAR) of 1 W/kg, that is a typical value for MRI examinations, the coil produces in the anatomical models peak temperature values lower than the limits issued by the International Electrotechnical Commission (IEC). In the presence of the pacemaker, temperature increments at the catheter tip in excess of those issued by the IEC standard are obtained when the MRI scanned area involves the pacemaker region. The 3-T coil produces lower SAR and temperature increments with respect to a 64-MHz (1.5-T system) birdcage antenna in patients with implanted pacemaker

A PXI based system for electrical impedance tomography

In this paper, a PXI based system for electrical impedance tomography (EIT) will be presented. A virtual instrument based on the PXI platform is used to inject current and to acquire voltage data on a 16 electrode perspex phantom filled with saline or gelled solutions that mimic human body tissues. The admittance method is used for the solution of the direct problem and a modified Newton-Raphson algorithm is used for the image reconstruction. Experimental measurements have been performed on saline or gelled solutions to establish a link between the salt concentration and the solution conductivity. A set of measurements has been performed on phantoms simulating, at various levels of approximation, the human body anatomy. The results indicate that the proposed EIT system is efficient and accurate. Moreover its modular structure makes it possible to test various data collection protocols and inversion algorithms. © 2011 IEEE