Gian Guido Gentili

Bio: Gian Guido Gentili is an academic researcher from Polytechnic University of Milan. The author has contributed to research in topics: Microstrip antenna & Radiation pattern. The author has an hindex of 14, co-authored 115 publications receiving 661 citations. Previous affiliations of Gian Guido Gentili include Instituto Politécnico Nacional & Leonardo.

Electromagnetic inversion in monostatic ground penetrating radar: TEM horn calibration and application

Abstract: A comprehensive analysis of electromagnetic (EM) inversion applied to pavement profiling by using a monostatic ground penetrating radar (GPR) is presented. Since in GPR systems using transfers EM (TEM) horns, the antenna is positioned close to the the investigated medium and a strong EM interaction occurs. This effect is taken into account by modeling the antenna with equivalent sources placed on the aperture section and by using an accurate EM modeling within the inversion loop in order to account for the contribution of near-field effects. Experimental results on the antenna modeling procedure and on a pavement profile estimation validate the feasibility of both the calibration and the inverse problem proposed.

Properties of TE-TM mode-matching techniques

Abstract: A line integral formulation of TE-TM mode-matching techniques for scattering problems in waveguides is described. The procedure is convenient from a computational point of view when the modes in the waveguides must be computed numerically. This reduction to line integrals has revealed an interesting property of mode-matching techniques: some coefficients representing coupling between TE and TM modes are always null, i.e., such modes are uncoupled. >

Design of Waveguide Filters With Cascaded Singlets Through a Synthesis-Based Approach

Abstract: In this article, we introduce a synthesis-based design approach for waveguide filters, including singlets. As is known, a singlet block comprises one resonator coupled to source and load plus an additional coupling between source and load. In this way, a pole–zero pair is produced, thus allowing the introduction of a transmission zero in the frequency response. Structure making that uses cascaded singlets (especially implemented in waveguide technology) has been successfully used to realize compact and quasi-in-line pseudoelliptic filters. The design of this configuration suffers, however, from a severe drawback; while an isolated singlet can be exactly synthesized, when these blocks are put in cascade, nonresonating nodes (NRNs) are required to allow the cascade connection. Consequently, the resulting topology includes both cross couplings and NRNs, for which no exact synthesis solution is till now available (all the design solutions proposed in the literature are based on optimization). The new design procedure here proposed overcomes this drawback, allowing the synthesis of the equivalent circuit of the cascaded-singlet topology. Once this circuit is obtained, the dimensioning of the singlets can be carried out by exploiting a full-wave simulator according to the procedure described in the article. The proposed design approach allows a very accurate initial dimensioning of the filter, which represents an excellent starting point for final adjustments/optimizations. A detailed design example is presented in the article showing how to practically implement the novel procedure. This new approach is also experimentally validated by a waveguide filter prototype, previously designed by optimization and fabricated. It is shown how this filter can be redesigned with the novel procedure, obtaining very similar physical dimensions in a noticeably shorter time.

Quasi-static analysis of shielded planar transmission lines with finite metallization thickness by a mixed spectral-space domain method

Abstract: A new method to analyze shielded planar transmission lines with finite metallization thickness is described It is based on a mixed spectral-space domain representation of the Green's function The method allows the accurate determination of the static parameters of the transmission line with great efficiency as compared to methods available in the literature Several numerical examples are shown on single and coupled planar transmission lines >

Low cost electronically steered antenna and receiver system for mobile satellite communications

Abstract: The design, construction, and basic characteristics of an electronically steered, adaptive phased array antenna for land mobile satellite communications are described here. The antenna system includes an array of six microstrip stacked patch antennas, each one connected to an RF channel, which include a monolithic microwave/millimeter wave integrated circuit (MMIC) low noise amplifier and a commercial silicon monolithic I-Q modulator. A six-way microstrip combiner adds the six channels so that the resulting signal is introduced in a global positioning system (GPS) receiver, constructed with two commercial application specific integrated circuits (ASICs). This receiver has a PC interface which include control boards, specifically designed for this application, that allow the setting of the amplitude and phase of each RF channel. Acquisition and tracking algorithms have been programmed in C-language for working in real time using as input data the signal levels provided by the receiver.

Ferrite devices and materials

Abstract: The development and current status of microwave ferrite technology is reviewed in this paper. An introduction to the physics and fundamentals of key ferrite devices is provided, followed by a historical account of the development of ferrimagnetic spinel and garnet (YIG) materials. Key ferrite components, i.e., circulators and isolators, phase shifters, tunable filters, and nonlinear devices are also discussed separately.

Modeling of ground-penetrating Radar for accurate characterization of subsurface electric properties

Abstract: The possibility to estimate accurately the subsurface electric properties from ground-penetrating radar (GPR) signals using inverse modeling is obstructed by the appropriateness of the forward model describing the GPR subsurface system. In this paper, we improved the recently developed approach of Lambot et al. whose success relies on a stepped-frequency continuous-wave (SFCW) radar combined with an off-ground monostatic transverse electromagnetic horn antenna. This radar configuration enables realistic and efficient forward modeling. We included in the initial model: 1) the multiple reflections occurring between the antenna and the soil surface using a positive feedback loop in the antenna block diagram and 2) the frequency dependence of the electric properties using a local linear approximation of the Debye model. The model was validated in laboratory conditions on a tank filled with a two-layered sand subject to different water contents. Results showed remarkable agreement between the measured and modeled Green's functions. Model inversion for the dielectric permittivity further demonstrated the accuracy of the method. Inversion for the electric conductivity led to less satisfactory results. However, a sensitivity analysis demonstrated the good stability properties of the inverse solution and put forward the necessity to reduce the remaining clutter by a factor 10. This may partly be achieved through a better characterization of the antenna transfer functions and by performing measurements in an environment without close extraneous scatterers.