Michele Borgese

Frequency-Reconfigurable Microstrip Antenna With Biasing Network Driven by a PIC Microcontroller

A low-profile microstrip patch antenna has been designed for tuning on a discrete set of instant frequencies. The frequency reconfigurability is obtained by resorting to electrically actuated switches operated via a software-controlled biasing network. A low-cost PIC microcontroller is employed to control the antenna operative condition among the available states. Measurements on a fabricated prototype show a good matching with simulations and prove the reliability of the proposed configuration.

An Inkjet Printed Chipless RFID Sensor for Wireless Humidity Monitoring

A novel chipless RFID humidity sensor based on a finite artificial impedance surface (AIS) is presented. The unit cell of the AIS is composed of three concentric loops thus obtaining three deep and high-Q nulls in the electromagnetic response of the tag. The wireless sensor is fabricated using the low-cost inkjet printing technology on a thin sheet of commercial coated paper. The patterned surface is placed on a metal-backed cardboard layer. The relative humidity information is encoded in the frequency shift of the resonance peaks. Varying the relative humidity level from 50% to 90%, the frequency shift has proved to be up to 270 MHz. The position of the resonance peaks has been correlated to the relative humidity level of the environment on the basis of a high number of measurements performed in a climatic chamber, specifically designed for RF measurements of the sensor. A very low error probability of the proposed sensor is demonstrated when the device is used with a 10% relative humidity level discrimination.

Frequency-reconfigurable antenna for software defined radio driven by PIC microcontroller

A microstrip patch antenna has been properly designed to operate at different instant frequencies within a predetermined set of discrete bands. This task is accomplished by recurring to p-i-n- diodes as switching elements among the various configurations proposed. A particular attention has been paid to the software-controlled biasing network obtained by employing a PIC microcontroller.

Enhanced chipless RFID tags for sensors design

Chipless technology is based on the modulation of the backscattered signal. The challenge in designing chipless RFID sensors is how to perform data encoding without the presence of a chip and adding the sensing capability. The aim of this work is to investigate chipless RFID design able to face these challenges.

Robust Reading Approach for Moving Chipless RFID Tags by Using ISAR Processing

A robust technique for reading moving chipless tags exploiting the inverse synthetic aperture radar data processing is presented. The procedure takes advantage from the known tag movement to improve the tag detection capability by integrating several received signals. The implicit advantage of the proposed detection scheme is that the background measurement, collected in the absence of the tag, can be easily performed before the tag passes in front of the reader antenna. The reading procedure allows for a significant increase of the interrogation distance and, more importantly, it greatly improves the detection probability in complex scenarios, where the tag is attached on arbitrary and highly scattering objects. A simplified model is used to demonstrate the capabilities of the presented procedure in detecting tags even in the presence of high clutter. Detection of tags with signal-to-noise ratio as low as −10 dB is experimentally demonstrated.

Permittivity measurement of thin dielectrics by using metamaterial absorbers inside a waveguide

A resonant method to determine the dielectric permittivity of thin films is presented. The method is based on a single reflection measurement and the unknown sample is used as a substrate of a ultra-thin metamaterial absorber transversally placed in a waveguide. The absorber is formed by a ground plane, the unknown sample and a multi-resonant frequency selective surface printed on a rigid known substrate. The real part of the dielectric permittivity of the unknown sample is estimated on the basis of the position of the resonant absorption peak whereas the imaginary part of the dielectric permittivity is a function of the absorption level. The main advantage of the proposed setup is the mechanical robustness (the sample is pressed between the FSS filter and the ground plane) which guarantees a high repeatability of the measurement.

Design of broadband reflecting metasurfaces for polarization conversion

A broadband linear polarization converter based on a reflecting metasurface is presented. The polarization converter is composed by a periodic arrangement of metallic particles, positioned in a square lattice with a periodicity T equal to 4.6mm. The metallic elements are printed on a metal-backed Rohacell HF31 layer with a thickness of 3mm. The unit cell topology is optimized by using a genetic algorithm. The polarization converter works from 7.3 GHz to 29.01 GHz. Since the genetic algorithm provides arbitrary cell geometries where surface currents are not excited, a refinement procedure is proposed for removing unnecessary pixels. The highest working frequency polarization converter obtained at the end of the refinement process is extended up to 32.88 GHz thus obtaining a relative bandwidth of 129.54%.

An Iterative Design Procedure for Multiband Single-Layer Reflectarrays: Design and Experimental Validation

A novel iterative procedure for designing multiband single-layer reflectarrays is presented. The multiband frequency behavior is achieved by simultaneously providing the desired phases at each operating frequency. A suitable reflectarray element shape formed by several concentric loops loaded with double stubs has been selected for achieving multiband operation. The problem of mutual coupling among the different self-similar resonating elements laying on the same substrate is analyzed and mitigated by employing an innovative iterative design approach. The proposed design approach is demonstrated by designing a tri-band single-layer reflectarray with widely spaced frequencies operating at 3.9 GHz (C-band), 7.5 GHz (X-band), and 12.5 GHz (Ku-band). The single-layer prototype is compact and lightweight as it has been fabricated on a thin Kapton film glued on to a Rohacell HF31 substrate. The overall thickness is approximately

Multi-frequency polarizarition converter with enhanced angular robustness

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Chipless RFID tag exploiting cross polarization for angular rotation sensing

/5 at the highest operative frequency. Measurements of the reflectarray radiation patterns agree with the estimated performance and prove the reliability of the proposed synthesis technique.