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Near-field scanning microwave microscopy is a technique with increasing popularity for the study of nanometer-scale electrical properties of samples. Here, we present an approach to quantify sample properties in images obtained with an inverted scanning microwave microscope (iSMM), recently introduced by our group. In particular, this study reports the analysis of the local electrical conductivity of a platinum diselenide sample and proves its semimetal behavior. The approach is validated by a full-wave numerical model, reproducing the complete iSMM operation as well as all steps of the calibration algorithms. To extract local sample properties, this article provides two calibration procedures, respectively, for transmission and reflection mode measurements, based on a two-port equivalent circuit of the iSMM. This enables the high-frequency quantitative characterization of a wide variety of samples and surfaces.

Near-field scanning microwave microscopy (SMM) employs microwave radiation to image and characterize samples down to the atomic scale, including soft biological structures or inorganic materials, such as ferroelectric films. However, SMM generally also senses sample topography; hypersensitivity to topography becomes problematic with additional parasitic contributions and may partially or completely mask nontopographic sample features in the data, such as contrast in electrical conductivity or permittivity. This work proposes a simple and effective procedure to remove unwanted parasitic effects from SMM images. Differently from existing procedures, the method is applicable either in postprocessing or in real time, i.e., during the scanning operation. This allows the immediate visualization of nontopographic sample features in the instrument screen. As a proof of concept, hafnium zirconium oxide (HfZrO) ferroelectric film with high surface roughness is studied; unwanted contributions were removed from SMM data, providing a clear map of the sample ferroelectric structure that was originally hidden.

In this contribution, the authors present guidelines for an effective design of an X-band 2D array of slotted waveguides for surveillance applications. The radiation pattern, with a narrow beam and cosec 2 profile, respectively, in azimuth and in elevation, is obtained by a beam forming network based on a hybrid architecture, in which the main corporate feed line feeds identical 11-element travelling wave slotted arrays. The latter produces a radiation pattern that is frequency-independent in azimuth and only slightly frequency-dependent in elevation. The fabricated antenna features a horizontal beam width (at -3 dB) of 1.16°, gain >31 dBi, and 30 dB sidelobe level in the 300 MHz operative band. The overall array is made up of three stacked layers: the first two for the corporate feed line and the third for the travelling wave radiating elements, resulting in remarkably compact external dimensions (170 cm × 25 cm × 2 cm) and relatively low weight (8 kg in total).

By exploiting a novel quantitative imaging technique based on Synthetic Optical Holography, we describe the dynamic behaviour of optical vortices in a speckle pattern generated by the interference of random scattered waves from the rough surface of a glass substrate. The system combines the advantages of digital holography and low-coherence interferometry to retrieve multiple holograms with sub-nanometric spectral resolution. The collection of multiple images of the complex scattered field allows to provide a statistical characterization of the phase singularities by changing the exciting wavelength.

We describe the implementation of quantitative phase imaging in a lens-free scanning system based on low-coherence synthetic optical holography. We show the imaging of rough scattering surfaces embedded in a microfluidic channel.

Polymer nanocomposites synergistically combine the good thermal properties of the hosting polymer matrix with the high mechanical performance of the fillers, providing a new class of materials with superior properties. The present study aims to evaluate in a multidisciplinary way the enhancement in mechanical and thermal-hygrometric properties of low and medium density nanophased polyurethane (PUR) foams with either randomly oriented or aligned nanofibers as compared to the neat ones. To this aim, 1% weight of carbon nanofibers (CNFs) were homogeneously dispersed into polyol of PUR foam by an ultrasonic cavitation method. In parallel, a small amount of CNFs was functionalized in advance by a co-precipitation method so as to align them into the polymer matrix through an external low intensity magnetic field. SEM analyses were used to compare the microstructure of the neat and nanophased samples. Results have shown that the addition of carbon nanofibers in the foams products a closer structure with a more uniform size and shape. Moreover, functionalized CNFs play a significant role in regulating cells shape as well as strengthening cells walls. Mechanical test results also demonstrated that CNFs increase both strength and stiffness of the samples. The alignment of carbon nanofibers within medium density nanophased foams determines the highest mechanical properties. However, the more noticeable improvement in samples performance occurred in low density nanophased foams. Finally, carbon nanoparticles decrease the thermal conductivity and increase the resistance against water adsorption.

When two filters are cascaded together, unwanted spikes appear in the rejection region. These spikes can have a strong impact on the rejection performance of the resulting filter. Therefore, it is desired to suppress or move them far away from the operational band, including part of the rejection band as well. This paper addresses a systematic evaluation of such phenomenon and proposes a simple yet effective method, called spike envelope curve, to have, in a single run and for any frequency, the worst possible case, without the need of repeating onerous analyses. It is also shown that a judicious choice of the length and losses of the line separating the filters can be exploited to mitigate considerably such a negative effect. The method is assessed by full-wave simulations and measurements.

Near-field scanning microwave microscopy (SMM) is a technique gaining popularity for the study of the electrical properties of both soft and hard matter on the nanometer scale. Despite the current focus on semiconductors, the applications of SMM on new two-dimensional materials such as platinum diselenide (PtSe2) are still in an initial stage. In this work, the imaging capabilities of an innovative SMM and the analysis of the electrical properties of PtSe2 are demonstrated.

Scanning Probe Microscopy (SPM) for Nano imaging includes different techniques, ranging from Atomic Force Microscopy (AFM) and Scanning Near-Field Optical Microscopy (able to acquire images beyond diffraction limit), up to Scanning Microwave Microscopy developed to achieve imaging and characterization of a sample at Microwaves. In the present work we describe a technique which implements the concept of "Synthetic Reference Wave", borrowed from Microwave Holography and already introduced in Synthetic Aperture Radars (SAR), to perform Nano scale quantitative imaging at infrared wavelengths. Although this approach was already combined in the past with AFM, in the following paper we proposed a different implementation, potentially suitable for wide-band imaging at Nano scale.

It is a popular opinion that the electromagnetic fields are only related to telecommunication systems as a carrier of the information. This is certainly true, but it is also in some way misleading because it excludes a lot of applications of paramount interest both from a research and a technological point of view. In this sense the research activity of the “Electromagnetic fields” group is exemplary. In fact, without disowning telecommunication applications, the research has been increasingly oriented towards new and original aspects, not strictly related to ICT. This new point of view led to deepening more and more topics related to physical aspects of the interaction between the electromagnetic fields and matter. As a consequence, models describing the behaviour of the electromagnetic fields in non-conventional environments were developed. For example, models combining Maxwell and Boltzmann equations to treat the non-linear effect of the plasma ignition were introduced; by the same token a multi-physical approach Maxwell-Schrodinger/Dirac to characterize the problem of the quantistic transport in nano-structured materials was developed. In the paper the most important research topics, their developments, applications and their evolution will be presented.

The present paper describes a novel implementation of the continuous phase shifting method (PSM), named heterodyne holography, in a scanning probe microscope configuration, able to retrieve the complex scattered field in on-axis configuration. This can be achieved by acquiring a continuous sequence of holograms at different wavelengths in just a single scan through the combination of scanning interference microscopy and a low-coherent signal acquired in the frequency domain. This method exploits the main advantages of the phase shifting technique and avoids some limits relative to off-axis holography in providing quantitative phase imaging.

This article presents a modular reciprocal multiplexer in which the number of channels can be reduced or expanded. The proposed configuration is based on reactive loads designed to substitute channel filters. This is at the same time easy to manufacture and easy to reconfigure as reactive loads are conceived, so as not to modify the characteristics of the active channels if a channel is added or removed. Additional filter tuning after a reconfiguration is not required. The proposed reciprocal design allows for both low costs and low losses since it does not require circulators or additional components, such as hybrid junctions, usually present in reconfigurable multiplexers, although maintaining a good degree of flexibility. A prototype of the proposed design has been fabricated and measured. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:538-546, 2016.

Recently, near-field scanning microwave microscope has become popular in the characterization of materials, in particular, semiconductors on the nanometer scale. However, its application to biological structures is still at the embryo stage due to challenges in probing wet and soft samples with little dielectric contrast. In this work, we used our homemade scanning microwave microscope to overcome some of the challenges to demonstrate the imaging and characterization of isolated mitochondria in the frequency range 28–33 GHz.

This paper presents an efficient segmentation method of a filter made up of side-coupled cavities that use a reduced complexity model. The model is built by using the reactance matrix of only three parallel waveguides, either coaxial or hollow, coupled via apertures among them. This allows building the databases necessary for fast and reliable analysis and optimization of very complex filters and multiplexers. The method was used to design a low-cost eight-channel coaxial-cavity input multiplexer.

Exosomes are nanovesicles known to mediate intercellular communication. Although it is established that zinc ions can act as intracellular signaling factors, the measurement of zinc in circulating nanovesicles has not yet been attempted. Providing evidence of the existence of this zinc fraction and methods for its measurement might be important to advance our knowledge of zinc status and its relevance in diseases. Exosomes from 0.5 ml of either fresh or frozen human plasma were isolated by differential centrifugation. A morphological and dimensional evaluation at the nanoscale level was performed by atomic force microscopy (AFM) and Transmission Electron Microscopy (TEM). Energy Dispersive X-Ray Microanalysis (EDX) revealed the elemental composition of exosomes and their respective total Zinc content on a quantitative basis. The zinc mole fraction (in at%) was correlated to the phosphorous mole fraction, which is indicative for exosomal membrane material. Both fresh (Zn/P 0.09 ± 0.01) and frozen exosomes (Zn/P 0.08 ± 0.02) had a significant zinc content, which increased up to 1.09 ± 0.12 for frozen exosomes when treated with increasing amounts of zinc (100-500 μM; each p 0.05). Interestingly, after zinc addition, the Calcium mole fractions decreased accordingly suggesting a possible exchange by zinc. In order to estimate the intra-exosomal labile zinc content, an Imaging Flow Cytometry approach was developed by using the specific membrane permeable zinc-probe Fluozin-3AM. A labile zinc content of 0.59 ± 0.27 nM was calculated but it is likely that the measurement may be affected by purification and isolation conditions. This study suggests that circulating nano-vesicular-zinc can represent a newly discovered zinc fraction in the blood plasma whose functional and biological properties will have to be further investigated in future studies.

In this work, Scanning Microwave Microscopy (SMM) is applied to breast cancer cells MCF-7 treated by fullerene (C60), in order to provide simultaneous topographic and electromagnetic characterization of sample surface. The exceptional properties of fullerene, like its lipophilicity and its ability to be functionalized with proteins and nucleic acids, make its use very promising for drug delivery and anticancer action. Moreover, it could be applied as a marker for cancer cells, or target for further treatment, as it is able to penetrate the cell membrane. Calibration of SMM data is necessary in order to isolate the probe-sample interaction, and to possibly disentangle the topography from the electromagnetic response of the sample. These aspects are discussed in the paper. Use of microwave microscopy could be crucial to investigate the effects of fullerene treatment, and could enable, in the future, deep imaging of its penetration inside the cells.

A Ka-band dual-polarization 3 dB directional coupler is designed for Beam Forming Network applications. The proposed solution is particularly suited for compact Nolen networks. Nolen architecture is attractive because it is planar and lossless. Two parallel square waveguides are coupled through an array of apertures, designed to get the desired coupling and high isolation between the two orthogonal polarizations.

The objective of this letter is to extend the use of the generalized thru-reflect-line measurement technique to the case of a radiating multimodal rectangular waveguide aperture. Although this radiating aperture has been carefully studied from a theoretical point of view, the relevant experimental characterization has been limited to the case where the feeding waveguide is monomodal. In addition to theory, we also present experimental results that agree quite well with full-wave simulations, thereby fully validating the measurement technique.

This article presents a methodology that allows the determination of the matrix representation of a package. The methodology is based on a set of calibration measurements, picked up at the external pins of the package, of a set of known integrated circuits. The representation of the package can be used both for a correct measurement of the embedded devices and to improve the design of integrated circuits. The effectiveness of the technique is demonstrated by the de-embedding of a packaged passive integrated inductor and the design of a low noise amplifier. The measurement sets were obtained through computer simulations. The effects of added noise on data, like measurement errors, are also investigated, and an approximate methodology, able to reduce these effects, is suggested. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:623-634, 2014.

This paper presents for the first time an innovative instrument called an inverted scanning microwave microscope (iSMM), which is capable of noninvasive and label-free imaging and characterization of intracellular structures of a live cell on the nanometer scale. In particular, the iSMM is sensitive to not only surface structures, but also ectromagnetic properties up to one micrometer below the surface. Conveniently, the iSMM can be constructed through straightforward conversion of any scanning probe microscope, such as the atomic force microscope or the scanning tunneling microscope, with a simple metal probe to outperform traditional SMM in terms of ruggedness, and width, sensitivity and dynamic range. By contrast, the application of the traditional SMM to date has been limited to mainly surface physics and semiconductor technology, because the traditional SMM requires a fragile and expensive probe and is incompatible with saline solution or live biological cells., 5 pages, 4 figures, published in Applied Physics Letters

In this paper, we report a novel approach based on a lensless Synthetic Optical Holography (SOH) that is aimed to recover the complex scattered field from buried surfaces at different wavelengths with sub-nanometric spectral resolution, without affecting the phase retrieval in depth. The proposed technique is applied to characterize and image the field scattered from a rough embedded surface of a microfluidic channel. The real and imaginary part of the random complex field revealed the presence of 2D optical vortices at each location in which a phase singularity is located. A statistical study of optical vortices is presented and the high spectral resolution is exploited to study the behavior of topological charges with the frequency shift.In this paper, we report a novel approach based on a lensless Synthetic Optical Holography (SOH) that is aimed to recover the complex scattered field from buried surfaces at different wavelengths with sub-nanometric spectral resolution, without affecting the phase retrieval in depth. The proposed technique is applied to characterize and image the field scattered from a rough embedded surface of a microfluidic channel. The real and imaginary part of the random complex field revealed the presence of 2D optical vortices at each location in which a phase singularity is located. A statistical study of optical vortices is presented and the high spectral resolution is exploited to study the behavior of topological charges with the frequency shift.

A technique is described to measure the generalized scattering matrix (GSM) of a waveguide device whose ports are multimodal. The device-under-test is placed in between suitable converters, thereby transforming multimodal ports into monomodal ports. The needed data are then measured using a standard vector network analyzer. A dedicated algorithm is finally used to recover the multimode GSM of the device. The experimental validation is reported in this paper for rectangular and square waveguides showing excellent agreement between theory and measured results.

In this work, we imaged exosomes with scanning tunneling microscopy (STM) and broadband scanning microwave microscopy (SMM) simultaneously, using exosomes prepared by a new salivary isolation method. By transforming the frequency-domain data to the time domain with optimum time gating, exosome images of higher contrast and resolution were obtained by using SMM than by using STM or atomic force microscopy (AFM).

Fullerene C60 is a nanoparticle being actively investigated for possible applications in biology and medicine since, owing to its lipophilicity, it should be able to be incorporated in or to permeate across a cellular membrane. Once exposing cells to such nanoparticles, the problem becomes how to assess the actual presence of fullerene in cells. Here we used a home-made broadband near-field scanning microwave microscope, in both time and frequency domains, and a commercial scanning capacitance microscope to investigate the ability of fullerene to permeate MCF-7 breast cancer cells. We found that, while the electromagnetic properties of the cell membrane are changed by fullerene exposure, surface roughness is a more reliable indicator of fullerene exposure.

A process for the fabrication of dielectricless rectangular waveguides (RWGs) integrated in the substrate is presented and experimentally validated. First, two complementary circuits are realized through milling the guide in a substrate and, then, are metallized with traditional additive processes used in printed-circuit board industry. Next, the circuits are joined together, and electric continuity is enforced through two additional rows of conductive holes along the guide sidewall, as it occurs in the substrate-integrated waveguide technology. A comparison between the propagative characteristics of a classic RWG and a waveguide with this methodology is reported. Finally, a slotted waveguide realized by this technology is fabricated and measured.

A substrate integrated waveguide Magic Tee with very compact size and operating over a wide band is proposed. The circuit is made of two stacked substrates connected by cutting a small aperture between them. This solution presents slightly higher complexity compared to a single substrate magic Tee but it avoids the radiation losses because the circuit is completely closed. A simple and effective procedure is used to design the circuit. A prototype is built and experimental results show a good agreement with simulations. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:932–936, 2016

Nanoparticles are receiving increasing attention as carriers of active drugs or biochemical signals. Among them, fullerene C 60 is particularly attractive since its cage structure helps it to carry other molecules and its lipophilicity helps it to penetrate through a cell membrane. This paper explores the potential of time-gated broadband near-field scanning microwave microscopy for detecting fullerene inside Michigan Cancer Foundation-7 breast cancer cells. It demonstrates measurement of relative variation of electromagnetic properties across the sample surface, while explaining the difficulty for measurement of absolute electromagnetic properties. The results are compared with scanning capacitance microscopy, atomic force microscopy, and scanning tunneling microscopy performed on the same samples.

The design procedure of a linear phase filter suited for radar applications in L-band is presented.It can manage more than 1 KW of peak power, although it is built in a compact case by using coaxial resonators instead of usual rectangular ones. The design is performed by using the adaptive method invented by the authors. The filter was built and measured, showing good agreement between simulations and experiments. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2717–2721, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26442

This paper illustrates the design guidelines and main features of a dual-channel rotary joint, operating in X- and Ka-bands. The core of the proposed solution is the double transducer between X and Ka rectangular waveguides and a nested coaxial waveguide, which shows very good performance in both bands.

This paper describes the use of the correlation maps in the Ground Penetrating Radar (GPR) for the detection of near surface objects. This method is based on the deflnition of bi-dimensional maps that describe the level and the nature of coherence between the received electromagnetic signals. The technique proposed provides the detection of objects, reducing the impact of the clutter and improving the image contrast by an appropriate combination of the information collected in the variance and time coherence of the received signals. The method has been tested in GPR developed by ourselves and described in detail. The implemented GPR system features a high dynamic vector network analyzer (VNA) and a mechanically scanned Vivaldi antenna; the scanning is bi-dimensional, so that A, B and C scans are available.

The aim of this paper is to discuss the effects of the exposure to Extremely Low Frequency ElectroMagnetic Fields (ELFEMFs) on nonand excitable cells using in vitro cell models, namely neuron-like cell line (PC12), glioblastoma-derived GL15 cells as glial model and C2C12 myocytes as muscle model, focusing our attention on standardized protocols for ELF-EMFs generation and exposure. A major issue in laboratory — and likely in nature — studies about possible biological effects of ELF waves is the difficulty in providing standard, reproducible environmental conditions. Hence, as part of the work we have developed an exposure system including a probing scanner, able to sample a given volume and to measure the timevarying magnetic field vector. The system allows detection, monitoring and removal of electromagnetic noise sources, as well as means to assess field homogeneity in terms of intensity and polarization.

An (N+1)-port junction endowed with complete rotational symmetry with respect to the first N ports is analyzed by a partial spectral decomposition of its S-matrix. This approach produces N/2 one-port boundary value problems, as well as a single two-port problem, which can be easily solved by means of standard full-wave simulators. The practical example of a coaxially fed 36-way power divider was easily analyzed by this method, and the results were nearly indistinguishable from those obtained by analyzing the device as a whole.

This paper introduces a general method for the analysis of the individual blocks forming a complex circuit by measurements or simulations carried out on the whole. This is useful in those situations where the analysis of the single blocks is difficult. Paradoxically, the analysis of more complex structures, which contain individual elements, as subcircuits is, in some circumstances, easier to perform or may even be the only way to acquire information about the individual elements. Under certain conditions, the elements can be combined to obtain different circuits according to classic segmentation technique. Owing to its formulation, the method is applicable to both simulation and measurement problems.

The filter prototype of side-coupled coaxial filters, which we recently proposed, has been modified to suit an arrangement in which the coupling apertures are placed on the side opposite the coaxial end gaps. In this situation, the modified prototype fits the physical counterpart better, resulting in a further design simplification. In addition, the feeds have also been modeled and included into the prototype, thus enhancing the correspondence between the prototype and physical structure. A practical design, concerning a WIMAX application, shows the reliability of this solution.

In this paper we discuss the application of a broadband Near-Field Scanning Microwave Microscope (SMM) to the imaging of biological samples, in particular mouse myotubes C2C12 and rabbit sarcomeres, highlighting the intriguing possibilities of the technique, and discussing the challenges in data interpretation. The system, developed by ourselves, exploits a Scanning Tunneling Microscope (STM) coupled to a Vector Network Analyzer, providing simultaneous STM/SMM images.

This paper presents an efficient segmentation of a filter made up of cylindrical multimodal cavities, coupled side by side, that leads to a reduced-complexity model. The latter is built by the combination of the Generalized Reactance Matrices of only two parallel cylindrical waveguides coupled through an aperture which the filter is segmented in. This allows to build the databases necessary for the optimization considering one coupling aperture at a time, thus reducing drastically the computation effort.

Time-Domain Reflectometry (TDR) is a well-well known technique, widely used in several fields, such as signal integrity and remote sensing. Here we show that TDR can be conveniently used in the Near-Field Scanning Microwave Microscopy, regardless the apparent mismatch between timescales involved at nanoscale and the period of a microwave signal. The technique is demonstrated on Highly Oriented Pyrolitic Graphite (HOPG) and CVD graphene.

We present a nano-patterning process for semiconducting polymeric composites that could potentially be utilized for the development of polymer-based data storage devices. Nano-patterning (writing) operates on the basis of the mechanical interaction between the electrically unbiased tip of an atomic force microscope and the surface of polymeric composite films. Via friction forces, the tip/sample interaction produces a local increase of molecular disorder in the polymer matrix, inducing a localized lowering in the conductivity of the organic semiconductor. Herein we suggest a figure of merit for quantifying the efficiency of pattern formation and we address the dependence of the writing process on the thermal annealing temperature of the composite film. Control experiments on composite films deposited on substrates with different roughness suggest that the writing effect is invariant to the roughness of the substrate. The potential storage density of the writing process depends on the tip curvature.

This contribution reevaluates the circuit prototype of tunable diplexers based on the ‘dual-manifold’ concept. The targeted application are diplexers whose channel center frequencies can be arbitrarily positioned, resulting in contiguous and non-contiguous channel spacing.

A substrate integrated waveguide six-port directional coupler is designed and characterized. The circuit exploits a very compact size and good reflection and transmission characteristics, as it exhibits both return loss and isolation higher than 15 dB over a 13% bandwidth. The device is made by connecting all ports to a single junction which mixes all signals. Some prototypes have been built and experimental results show a very good agreement with simulations. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2589–2592, 2015

This paper addresses the problem of deriving an actual coupled-line model from the "spot frequency" characteristics of transmission media derived by means of a numerical electromagnetic simulator. For a given set of coupled lines, possibly asymmetric and lossy, one of the main issues is to recover a model whose parameters are physically and practically meaningful. In order to satisfy the requirements, the model ought to basically yield a natural generalization of the well-known even/odd and c//spl pi/ modes for couples of lines, and collapse to a set of uncoupled lines when coupling is negligible. Hence, part of this study is devoted to discussing and evaluating models that satisfy such requirements. The end result is a Weissfloch-type equivalent circuit made up of uncoupled lines and input and output ideal transformers. The algorithm is then applied to the network parameters of coupled lines. The latter are evaluated by a full-wave method of moments approach, and a subsequent short-open calibration (SOC) procedure. Finally, a new algorithm is introduced that is able to evaluate and remove the contribution of the naked discontinuity due to ports, usually not directly available from the SOC routine.