A novel substrate integrated coaxial line (SICL) is presented and experimentally verified in this paper. This structure exhibits unimodal operation over a wide frequency band, is shielded and not dispersive, can be fabricated by using simple, low-cost thin-film process, and can be easily integrated with active devices. Moreover, the same technology results particularly suitable to realize passive components for wideband applications. The design of a Lange coupler with operation bandwidth of 66%, to be used in a multi-port impulse radio for ultra wide band applications, is reported

This paper presents the design and implementation of a novel class of substrate-integrated waveguide (SIW) filters, based on partially air-filled cavity resonators. Removing the dielectric in a portion of the SIW cavity allows obtaining dual-mode cavities: such cavities represent a doublet, used as the building blocks in the design of filters. A thorough modal analysis of the air-filled resonant cavity based on transmission lines' representation and a detailed study of the doublet permit to demonstrate a full control of the operation frequency, pass bandwidth, spurious-free region, and position of the transmission zeros of the filter. This paper presents the design, fabrication, and measurement of several two-pole filters based on this concept, with the aim to show the capabilities of the proposed structure and of the design technique. A five-pole filter is also presented, to describe the extension of the proposed approach to higher order filters.

This article presents the implementation of a novel microfluidic sensor based on a resonant cavity. The cavity is based on the substrate integrated waveguide (SIW) technology and is fabricated by using stereolithographic 3-D printing, which guarantees fast prototyping and allows arbitrary geometry. The proposed sensor consists of a square cavity and an inner meander pipe provided with two openings, where the liquid under test is injected and extracted, and is fed by a coaxial probe, which represents the microwave port of the circuit. S-parameter measurement allows retrieving the electromagnetic properties of the liquid injected in the pipe. In particular, the loss tangent of the liquid is extracted from the variation of the cavity quality factor compared to air-filled pipe, after removing the actual losses of the structure. The dielectric permittivity of the liquid is retrieved from the shift of the cavity resonance frequency relative to the case of air-filled pipe, without any hypothesis of small losses. The performance of the sensor is discussed through the electromagnetic characterization of several fluids.

This letter presents an enhanced solution for low-cost sensors for the determination of the dielectric permittivity and the loss tangent of materials, based on substrate-integrated waveguide (SIW) cavities. The novelty consists in a slight, yet fundamental, modification of the standard sensor topology. The typical structure is based on an SIW resonant cavity with a hole in the middle and a pipe passing through, which contains the material under test. The modification consists in adding a metal sheath that partially covers the walls of the pipe. The metal sheath enhances the penetration of the electromagnetic field into the pipe, thus increasing the sensitivity of the device. Simulation and measurement results of various liquids demonstrate the advantage of the proposed structure.

This letter presents a voltage-controlled tunable phase shifter based on few-layer graphene. The phase shifter consists of a stub-loaded line, composed of a microstrip line with a stub attached to it through a taper and graphene pad. The bias voltage applied to the graphene pad determines a variation of graphene resistance, which eventually causes the phase change. Without any voltage bias, graphene exhibits high resistance, thus isolating the stub and leading to a low phase shift. As the bias voltage is increased, graphene resistance is lowered, the effect of the stub is more pronounced, and the phase shift is increased. A prototype operating in the frequency range from 5 to 6 GHz has been designed and tested. The measured maximum phase shift obtained is 40°, and the corresponding degradation of the insertion loss is 3 dB.

Objective: The potentialities of improving the penetration of millimeter waves for breast cancer imaging are here explored. Methods: A field focusing technique based on a convex optimization method is proposed, capable of increasing the field level inside a breast-emulating stratification. Results: The theoretical results are numerically validated via the design and simulation of two circularly polarized antennas. The experimental validation of the designed antennas, using tissue-mimicking phantoms, is provided, being in good agreement with the theoretical predictions. Conclusion: The possibility of focusing, within a lossy medium, the electromagnetic power at millimeter-wave frequencies is demonstrated. Significance: Field focusing can be a key for using millimeter waves for breast cancer detection.