Giuseppe Venanzoni

Calibration Protocol for Broadband Near-Field Microwave Microscopy

In this paper, we describe how to define and build a set of known loads to be used in near-field microwave microscopy. Such loads are necessary to set up a microwave calibration kit, enabling local quantitative measurements by the microscope. The proposed protocol is validated through the microscopy system we have recently developed that combines a scanning tunneling microscope and a 70-GHz vector network analyzer.

High Resolution Scanning Microwave Microscopy for Applications in Liquid Environment

In this work, we demonstrate a hybrid scanning tunneling microscope/near field scanning microwave microscope featuring nanometric resolution in liquid environment. The system performs an ultra-broadband microwave analysis, since the frequency is swept (up to 50 GHz) for each spatial point of the sample under measurement. A conversion in time-domain allows to disentangle near-field and far-field probe-sample interactions. Results are reported for highly oriented pyrolitic graphite immersed in water, and demonstrate microwave nanometric resolution in spite of the presence of the losses induced by the aqueous environment.

A new prototype for the design of side-coupled coaxial filters with close correspondence to the physical structure

This paper presents a new mixed lumped-distributed prototype for the design of coaxial filters, in which the cavities are coupled via their side-walls. The element values are explicitly given in terms of the well-known Cohns direct coupled cavity prototype. The main feature of the proposed model is its one-to-one correspondence to the physical structure, making a design feasible without additional optimizations or expensive tuning. The circuit has been employed in the design of several diplexers, obtaining excellent results.

Infrared Imaging of Fixed-Cells through Micro-Cavity Fiber Optic Scanning Microscopy

Noninvasive, lens-free microscopy methods helps biologists to measure quantitative contrast phase imaging without damaging the cells. An extrinsic scanning micro-cavity in optical fiber is proposed to achieve surface imaging at infrared wavelengths. The micro-cavity is realized by approaching a single mode fiber with a numerical aperture NA to a sample and it is fed by a low-coherence source. The measurement of the reflected optical intensity provides a map of the sample reflectivity, whereas from the analysis of the reflected spectrum in the time/spatial domain, we disentangle the topography and contrast phase information. The latter describes the contrast variation of the reflected spectrum from the cavity due to changes in topography and surface refractive index. The interference of diffracted waves defines the transverse field behavior of the electromagnetic field inside the micro-cavity, affecting in this way the transverse resolution, that is not defined by the numerical aperture NA of the fiber and consequently by the conventional Rayleigh limit (about 0.6λ/NA). The resolution in the normal direction is limited mainly by the source bandwidth and demodulation algorithm. The system shows a compact and simple architecture.

3-D-Printed Quasi-Elliptical Evanescent Mode Filter Using Mixed Electromagnetic Coupling

This letter presents an innovative topology of evanescent mode filters with mixed electromagnetic coupling finalized to take full advantage of additive manufacturing techniques. A four-pole filter with two transmission zeroes was designed starting from a suitable equivalent circuit. The filter was built using a 3-D printer and measured. The good experimental results show the usefulness of the solution when in-line topologies are required.

3D printing of X band waveguide resonators and filters

We present a novel approach to fabricate microwave passive components using very cheap SLA 3D printing technology associated with copper electroplating of the resulting 3D plastic structures. Some test structures are presented showing the excellent performance of the process.

Electromagnetic field modeling through the use of dirac matrices and geometric algebra

The basis for engineering electromagnetic computations still rely on Gibbs vector algebra. It is well known that Clifford algebra (geometric algebra) presents several enhancement on the latter. By taking advantage that in the three-dimensional space Clifford algebra is isomorphic to Pauli algebra it is possible to describe all the relevant vector operations occurring in electromagnetic theory in terms of Pauli matrices. In particular it is possible to write Maxwells equations in a form similar to the Dirac equation. In this way, instead of having six coupled equations from the curls operators, we can deal with just four linear equations. The latter can be further simplified to just two sets of two linear equations by the Weyl decomposition.

Additive manufacturing of microwave components: Different approaches and methodologies

In this paper, two different approaches for the additive manufacturing of microwave component are discussed. The first approach consists is the popular and cheap fused deposition modeling (FDM). In this paper it is shown that, by using different infill factor, FDM is suitable for the manufacturing of devices with controlled dielectric constant. The second approach is the Stereolithography (SLA). With this approach, better results can be obtained in terms of resolution. Furthermore a very easy way to copper plate the surface of microwave devices is shown and it effectiveness is demonstrated through the manufacturing and measurement of a two-pole filter with mushroom-shaped resonators.

Simple High-Performance Metal-Plating Procedure for Stereolithographically 3-D-Printed Waveguide Components

This letter presents a simple and cheap metal-plating procedure for plastic 3-D printed microwave components. The devices are built using a Stereolithographic printer and then metalized by a two-step process consisting in a silver-painted substrate followed by copper electrodeposition. The method achieves good adhesion of the metal to the plastic body and high conductivity. Resonators and <inline-formula> <tex-math notation=LaTeX>

Corrections to “Modified Adaptive Prototype Inclusive of the External Couplings for the Design of Coaxial Filters” [Sep 07 1905-1911]

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