Giuseppe Ruvio

A Novel GPS Patch Antenna on a Fractal Hi-Impedance Surface Substrate

A compact high-performance circularly-polarized microstrip antenna for the global positioning system application is proposed. It comprises a fractal hi-impedance surface electromagnetic bandgap (EBG) structure printed on a high permittivity substrate. Measurements and simulation of return loss and axial ratio are in good agreement. It is shown that the proposed Global Positioning System antenna has good axial ratio performance in the upper half-plane, an improvement in gain and a significantly wider axial ratio bandwidth when compared to the same antenna without EBG

Wideband Reconfigurable Rolled Planar Monopole Antenna

A novel technique to reconfigure the frequency range of a planar monopole antenna is presented. By adjusting the degree of spiral tightness, a shift of the well-matched operating frequency range is achieved. The proposed antenna is capable of covering the frequencies in the range from 2.9 to 15 GHz, depending on the degree of spiral tightness. The antenna yields a high-efficiency across the full operating bandwidth. Radiation patterns show good omni-directional features in all primary cuts and remain relatively stable with the change of antenna configuration, so that it is a remarkable candidate for indoor or mobile applications where a large frequency range and omnidirectional radiation are required.

A Printed Triangular Monopole With Wideband Circular Polarization

A printed triangular monopole antenna with wideband circular polarization is presented. The wideband circular polarization is achieved by asymmetrical excitation of a triangular ground plane and planar triangular monopole. The combined radiation provides a wide axial-ratio bandwidth spanning from 1.42 to 2.7 GHz (62%). A parametric study of key geometric parameters is given for clear understanding of the radiation mechanism.

A Novel Wideband Semi-Planar Miniaturized Antenna

A semi-planar miniaturized antenna which operates over the FCC allocated UWB spectrum is presented. The small antenna comprises a folded conducting element connected to a printed section. Several solutions are introduced which create different current paths increasing the effective dimensions of the antenna. The antenna is examined for the stand-alone case and for the antenna mounted in various locations on a larger handset-type groundplane. The impedance and radiation characteristics show a relative independence of the groundplane size and the antenna location on it. The proposed antenna is a valuable candidate for handset applications due to its compactness. The proposed antenna may be employed in UWB communications systems and exhibits quasi-omnidirectional radiation patterns over the full impedance bandwidth.

Breast cancer detection using interferometric MUSIC: experimental and numerical assessment.

PURPOSE In microwave breast cancer detection, it is often beneficial to arrange sensors in close proximity to the breast. The resultant coupling generally changes the antenna response. As an a priori characterization of the radio frequency system becomes difficult, this can lead to severe degradation of the detection efficacy. The purpose of this paper is to demonstrate the advantages of adopting an interferometric multiple signal classification (I-MUSIC) approach due to its limited dependence from a priori information on the antenna. The performance of I-MUSIC detection was measured in terms of signal-to-clutter ratio (SCR), signal-to-mean ratio (SMR), and spatial displacement (SD) and compared to other common linear noncoherent imaging methods, such as migration and the standard wideband MUSIC (WB-MUSIC) which also works when the antenna is not accounted for. METHODS The data were acquired by scanning a synthetic oil-in-gelatin phantom that mimics the dielectric properties of breast tissues across the spectrum 1-3 GHz using a proprietary breast microwave multi-monostatic radar system. The phantom is a multilayer structure that includes skin, adipose, fibroconnective, fibroglandular, and tumor tissue with an adipose component accounting for 60% of the whole structure. The detected tumor has a diameter of 5 mm and is inserted inside a fibroglandular region with a permittivity contrast εr-tumor/εr-fibroglandular < 1.5 over the operating band. Three datasets were recorded corresponding to three antennas with different coupling mechanisms. This was done to assess the independence of the I-MUSIC method from antenna characterizations. The datasets were processed by using I-MUSIC, noncoherent migration, and wideband MUSIC under equivalent conditions (i.e., operative bandwidth, frequency samples, and scanning positions). SCR, SMR, and SD figures were measured from all reconstructed images. In order to benchmark experimental results, numerical simulations of equivalent scenarios were carried out by using CST Microwave Studio. The three numerical datasets were then processed following the same procedure that was designed for the experimental case. RESULTS Detection results are presented for both experimental and numerical phantoms, and higher performance of the I-MUSIC method in comparison with the WB-MUSIC and noncoherent migration is achieved. This finding is confirmed for the three different antennas in this study. Although a delocalization effect occurs, experimental datasets show that the signal-to-clutter ratio and the signal-to-mean performance with the I-MUSIC are at least 5 and 2.3 times better than the other methods, respectively. The numerical datasets calculated on an equivalent phantom for cross-testing confirm the improved performance of the I-MUSIC in terms of SCR and SMR. In numerical simulations, the delocalization effect is dramatically reduced up to an SD value of 1.61 achieved with the I-MUSIC in combination with the antipodal Vivaldi antenna. This shows that mechanical uncertainties are the main reason for the delocalization effect in the measurements. CONCLUSIONS Experimental results show that the I-MUSIC generates images with signal-to-clutter levels higher than 5.46 dB across all working conditions and it reaches 7.84 dB in combination with the antipodal Vivaldi antenna. Numerical simulations confirm this trend and due to ideal mechanical conditions return a signal-to-clutter level higher than 7.61 dB. The I-MUSIC largely outperforms the methods under comparison and is able to detect a 5-mm tumor with a permittivity contrast of 1.5.

A microstrip printed dipole solar antenna using polycrystalline silicon solar cells

A novel printed dipole solar antenna design with an integrated balun is proposed for the first time with high efficiency polycrystalline silicon solar cells is presented in this paper. The optimum orientation of the silver DC bus bars of the solar cell is determined in order to achieve best antenna performance. Good solar antenna performance similar to that of ordinary printed dipoles with PEC reflectors is achieved.

Detecting Point-Like Sources of Unknown Frequency Spectra

The problem of detecting point-like sources whose frequency spectrum is unknown is addressed. Limitations of single- frequency approaches are identifled by analytical as well as numerical arguments. To overcome these limits, difierent multifrequency approaches which combine frequency data incoherently are compared. In particular, a novel multifrequency MUSIC-like algorithm based on interferometric concepts is proposed. Results show that the algorithm outperforms other methods under comparison.

UWB breast cancer detection with numerical phantom and Vivaldi antenna

A detection algorithm is introduced for breast cancer diagnostics. A coaxial skin+breast tissue phantom has been used for numerical evaluations. The algorithm has been validated with both ideal and realistic sources. In particular, an antipodal Vivaldi antenna operating in the frequency range 1 – 2.5 GHz has been properly optimized for this application. A 5 mm thick tumor has been correctly detected in three different scenarios inside the breast tissue spanning from a subcutaneous to a deeper location.

A Compact Wide-Band Shorted Folded Antenna

Planar monopole antennas are easy to construct from a single metal plate and able to offer attractive performance in terms of impedance bandwidth and radiation properties [1]. However, the necessity of compactness has induced the research community to investigate folded radiation elements [2 and 3]. But, at the same time, by reducing the overall dimensions of planar monopole antennas distortions in the radiation pattern and drawbacks in the impedance bandwidth can be introduced. Special feeding techniques and particular grounding systems have to be designed in order to obtain an acceptable compromise between compact dimensions and interesting performance [4, 5 and 6]. The novel and compact wide-band shorted folded antenna presented in this paper offers a working bandwidth of 4.6GHz between 1.6GHz and 7.2GHz (IBR=4.5;1). Good radiation properties and acceptable omni-directionality are obtained throughout the operating bandwidth. The use of a vertical ground plane and a microstrip feeding system permit a dramatic reduction of dimensions when compared to a planar monopole antenna with same characteristics. In this paper, we present another promising bandwidth-enhancement technique, which consists of grounding the radiating element with the vertical ground plane. This solution is shown to only moderately disturb the radiation properties of the antenna. As a consequence of performance and reduced dimensions, this antenna represents a significant candidate for in-door, mobile and vehicular applications where the coverage of different communication protocols is required. Numerical simulation have been obtained by CST Microwave Studio and compared to experimental results of the constructed prototype. A good agreement is achieved.

Comparison of Noncoherent Linear Breast Cancer Detection Algorithms Applied to a 2-D Numerical Model

A comparative analysis of an imaging method based on a multifrequency Multiple Signal Classification (MUSIC) approach against two common linear detection algorithms based on noncoherent migration is made. The different techniques are tested using synthetic data generated through CST Microwave Studio and a phantom developed from MRI scans of a mostly fat breast. The multifrequency MUSIC approach shows an overall superior performance compared to the noncoherent techniques. This letter reports that this highly performing algorithm does not require any antenna calibration or phase response estimation and allows the use of efficient and complex antenna geometries without difficult algorithm redefinitions.