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A highly sensitive, large throughput and wide dynamic range (in the aspect of size and material type) broadband tunable microwave interferometer based rectangular waveguide wear debris detection system is presented. Passing of (non)ferrous and (non)conductive particles through the sensor, which causes inductance and/or capacitance changes, are detected as transmission signal variations of the system. We first demonstrate the sensing principle with the aluminum particle of 800 μm and epoxy resin particle of 1 mm3 at 6 GHz. Then, the effects of particle size and flow speed are tested with aluminum particles ranging from 200 μm to 1.8 mm. The measurement results show that the system is able to measure particle sizes with known material and differentiate nonconductive particles from conductive ones. With the proposed data processing techniques, this system is capable of detecting as small as 76 μm particles within an 8 mm outer diameter tube. And with future improvements on sensitivity and particle material characterization, the proposed system has the potential to differentiate (non)ferrous and (non)conductive particles and measure their sizes as a real-time wear debris sensing devices for rotating and reciprocating machines.

In this work, we present a tunable 24-GHz antenna array based on a CMOS-compatible 110-nm-thick nanocrystalline graphite film grown by plasma enhanced chemical vapor deposition. The film has a nominal bulk conductivity exceeding 16000 S/m (hence, greater than any graphene monolayer or industrially available graphene multilayer) but still able to show an outstanding modulation of its charge carrier density in the upper microwave spectrum. The manufactured layer was used to design, simulate, fabricate, and test a 24-GHz patch antenna array, with each radiating element having overall dimensions of just $\lambda _{0}/8\times \lambda _{0}$ /7. The fabricated array exhibits a measured maximum gain of about 3 dBi around 24 GHz (unbiased state), with a half-power beam width of only 14.5° (suitable in wireless links where a high directivity is envisaged). Spanning the dc bias voltage between -25 V and 25 V at 24 GHz, the gain can be tuned continuously between -1.5 dBi and 4 dBi, whereas the resonance frequency undergoes a maximum shift of 166 MHz. This voltage-dependent tuning of the gain represents a first step in developing carbon-based applications to control amplitude and phase simultaneously and independently. These results (never reported) demonstrate the big potential of nanocrystalline graphite for high-performance microwave components that are CMOS compatible (a highly desirable characteristic for high fabrication yield and large-scale production), with unprecedented tunability for next-generation high-capacity communications.

The design of a Ku-band reconfigurable reflectarray antenna for emergency satellite communications is presented. Bidirectional high data rate satellite links are needed in emergency conditions where other telecommunication infrastructures are not available. In order to operate in this type of scenario, an antenna should be deployable, transportable, and easily repointable. The need of an automatic and fast satellite location and pointing system leads to a completely electronic reconfigurable antenna. The operative bandwidth is from 10.7 to 12.5 GHz for reception and from 14 up to 14.5 GHz for transmission (30% of relative bandwidth). The selected antenna architecture is based on a dual reflectarray system comprising a passive subreflectarray and an active main reflectarray made of reconfigurable 1-bit elementary cells based on PIN diodes.

This paper presents recent advances on reconfigurable reflectarrays at the University of Perugia. In particular, the activities carried out in the framework of the FP7 project ARASCOM (“MEMS and Liquid Crystal based” Agile Reflectarray Antennas for Security and COMmunication). As for ARASCOM outcomes, the purpose of the project is the design of a very large reconfigurable reflectarray controlled with micro-electro-mechanical systems (MEMS) for mm-wave imaging system at 76.5 GHz. A system with sufficient resolution to detect concealed weapons impose challenging requirements on the antenna, which shall be made of hundreds of thousands elements. The problem has been addressed by exploiting some innovative solutions and architectures that will be described in this document. In particular, the dimensioning of the reflectarray, the proposed 1-bit geometry of elementary cell, and the innovative biasing control architecture are reported together with the MEMS design and fabrication and the experimental results of a demonstrating board that validated the adopted procedure.

The problem of very large reconfigurable reflectarray (RA) antennas based on RF MEMS technology is addressed in connection with a 77 GHz RA for imaging application being developed within the European FP7 project called ARASCOM. Since thousands of reconfigurable elementary cells are employed, reducing the number of tuneable components is of paramount importance for the practical realization of the reflectarray. A dramatic reduction of the number of tuneable devices is shown to be achievable without performance degradation by a proper architecture based on 1-bit digital phase shifting and on the separable illumination of the RA. The elementary cell design, the fabrication technology and the control network architecture are illustrated in some detail showing the feasibility of the approach proposed.

This paper proposes a novel version of folded reflectarray antenna that allows a full electronic reconfigurability of the radiation pattern. The reconfigurability is obtained adopting an elementary cell on the main reflector able to provide at the same time the required phase-shift to the incident field and the necessary twist of the incident polarization. Since in many applications an antenna with dual-polarization operation is required, the proposed design allows the reflectarray to manage at the same time two orthogonal linear polarizations in two adjacent frequency bands. This achievement is obtained by replacing the polarizing grid, as typically adopted, with a dualband and dual-polarized FSS. As a proof of concept, two test antennas have been designed, manufactured and tested.