Abstract-Based on the use of micro electro-mechanical system (MEMS) switches this paper presents a composite right/left-handed (CRLH) transmission line (TL) with a reconfigurable behaviour. The design strategy here adopted consists on the use of metal-insulatormetal (MIM) capacitors and short-circuited stubs resulting in a very compact and monolithic CRLH unit cell well suited for phase shifter applications.

We have investigated the macroscopic and microscopic properties of large sets of Ba0.7Sr0.3TiO3 thin films including several substitution rates of manganese. Thanks to a high degree of control of the processing parameters at each stage we have been able to find a link between the dc leakage current and the low and high frequency dielectric permittivity and losses. We supplemented these macroscopic observations with in depth investigations of the defect states through x-ray photoelectron spectroscopy. We found that both the leakage current and the extrinsic dielectric parameters arise from a large density of charged point defects related to oxygen vacancies. At the outer surfaces of the films, the density of such charged defects is so high that it can raise the Fermi level to close to the conduction band. Such degradation of the films' performance can be relieved by appropriate manganese substitution for the titanium host ions. Such doping is able to move back the Fermi level to close to the center of the bandgap thus changing the conduction process from interfacial Schottky to bulk Poole Frenkel and decreasing the extrinsic losses. This beneficial effect was already inferred in ceramics and thin films but we have established a clear link between the macroscopic parameters and the microscopic defect state. This model can be transferred to many high permittivity oxides.

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Based on advanced industrial fabrication processes and on specialized design strategies, a new class of ferroelectric metal-insulator-metal (MIM) capacitors with high tunability and high quality factor ( -factor) is here presented. Modeled by means of lumped element equivalent circuits and experimentally validated up to 67 GHz, a maximum tunability of 81% (0-20-V bias), and a -factor improvement up to 30% (at 0 V) could be demonstrated at 1 GHz. These varactors have been exploited in the design of reconfigurable filters, with a center frequency at around 1 GHz that can be tuned up to 112%, and a figure of merit (FoM) per applied bias better than 31.5 dB kV. Owing to their promising features, these materials have been exploited to design small-size capacitors suitable for millimeter-wave frequencies. The results demonstrate tunabilities and FoMs superior to the state-of-the-art. Based on this, two 60-GHz tunable phase shifters are proposed. They represent the first example of such devices based on MIM Ba,Sr TiO (BST) capacitors. In terms of insertion loss, size, FoM, and FoM per bias they show a remarkable improvement with respect to the state-of-the-art of ferroelectric-based devices, thus proving that the BST represents a promising candidate to operate into the millimeter frequency band.

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This paper proposes an electrical model of carbon-nanotube (CNT) networks, that can be patterned using inkjet transfer printing. The Double-Walled carbon Nanotubes (DWNTs) "inkjet"-able suspension was deposited in gaps of variable lengths cut out of the central line of the coplanar waveguide test structure. The proposed model was validated through measurements of the line input impedance and of the scattering parameters. The obtained results demonstrate that, by acting on the gap size and on the number of CNT ink layers, both the DC resistance and the resonance frequency of the test structure can be selected ad hoc (from tens of kΩ to tens of Ω and from few MHz to tens of MHz, respectively). Therefore, by exploiting the suggested equivalent circuit model, the CNT ink deposition process can be considered as a promising candidate for the design of microelectronic and microwave devices with customized behavior (i.e., variable resistors, matching load networks, filters, and resonators).

We show that assembled domains of magnetic iron-oxide nanoparticles (IONPs) are effective at increasing the dielectric permittivity of polydimethylsiloxane (PDMS) nanocomposites in the GHz frequency range. The assembly has been achieved by means of magnetophoretic transport and its efficacy, as well as the electromagnetic properties of the nanocomposite, has been found to depend on IONPs diameter. Remarkably, the dielectric permittivity increase has been obtained by keeping dielectric and magnetic losses very low, making us envision the suitability of nanocomposites based on aligned IONPs as substrates for radiofrequency applications.

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