Piero Tognolatti

This paper proposes a novel method for feeding a half-turn quadrifilar helix antenna (QHA) operating in backfire mode. A self-phasing and self-supporting antenna is obtained using a specific method demonstrated numerically. Four straight parallel wires, by which a couple of short-circuited stubs are realized and connected in series with helix loops, constitute both the mast of the QHA and the feeding network. A prototype operating at 1 GHz is designed, realized, and measured. The results show a good axial ratio (measured cross-polar gain is about 25 dB below the co-polar one at the boresight) and good impedance matching over an adequately large frequency band.

This article introduces a passive reconfiguration strategy for RF networks based on radio frequency identification (RFID) integrated circuits (ICs) embedded within guided-wave structures. Each RFID IC is repurposed as a batteryless, addressable dc voltage source capable of biasing RF components, such as varactors and GaAs switches. Unlike conventional over-the-air (OTA) architectures, the proposed approach eliminates tag antennas by integrating the ICs directly into microwave transmission lines, where power, control, and signal share the same RF path. A dedicated multichip test platform is developed to experimentally characterize the IC behavior in this novel configuration, evaluating impedance variation, activation thresholds, and output stability. Measurements on a commercial RFID chip demonstrate reliable operation with only −15 dBm of incident RF power, and sufficient dc output to drive over 1000 GaAs SPST switches or 10 000 varactors. To validate the concept, a fully passive, four-element monopole array operating at 900 MHz is demonstrated, where each element is gated by an RFID-controlled SPST switch. The array performs beam steering through selective element activation, using a single RF feed to simultaneously energize the array, power the ICs, and transmit EPC Gen2 control commands.

A limitation to the practical use of chipless tags is due to the short reading distance, the small number of bits to be used for identification and the stability of the response. For sensor tag a further limitation is the sensitivity. In this work we present a design method and a model of a chipless sensor tag for crack mouth opening displacement that allow to improve these limitations. The sensor tag has been realized and measured confirming the design characteristics. It, based on the spectral signature, has 6 spectral lines (’bits’) for identification, 1 spectral line for the sensor with adjustable sensitivity. In the experimental measurements it resulted readable from a distance of around 40 cm, from a direction of ± 15° with respect to boresight and with a sensitivity of around 29MHz/mm.

Radio frequency identification (RFID) technology has gained significant attention in various industry sectors due to its potential for efficient inventory management, asset tracking, and object localization. Different RFID technologies are available; resorting to harmonic signals is currently less used but, recently, has gained interest in research activity. In this study, we present the design, prototype realization, and performance evaluation of a dual-band dual-polarized harmonic tag. The tag incorporates a dual-band matching circuit utilizing a zero-bias Schottky diode HSMS-2850 connected to a perturbed annular ring patch antenna. The antenna, in fact, is able to radiate in cross-polarization at the higher frequency. Through a comprehensive design methodology, including simulation optimization and prototype fabrication, we demonstrate the successful implementation of the tag. Measurements to validate the impedance matching properties, radiation patterns, and backscattering capability of the tag are also shown.

This paper presents the thermal validation of a Radio-Thermal Monitoring Sheet (R-TMS) designed for monitoring microwave hyperthermia treatments. The R-TMS consists of a grid of 77 passive Ultra High Frequency (UHF) Radio Frequency Identification (RFID) temperature sensors, which are wirelessly interrogated by an external reader integrated within the hyperthermia system, sharing the same antenna. The system was designed to ensure minimal interference with the therapeutic electromagnetic field while providing real-time feedback on skin temperature during the therapy. Laboratory assessments demonstrated the system's robustness against high-power electromagnetic fields, showing no significant self-heating or signal degradation. Pre-clinical tests confirmed that the R-TMS does not compromise treatment effectiveness or patient safety, with temperature monitoring results closely matching those obtained from conventional thermocouple-based methods. The proposed system offers a promising low-cost, wireless alternative for enhancing the safety and efficacy of superficial hyperthermia treatments.

The design and the characterization of a non-linear target to test an intermodulation radar was performed using the AWR design environment Version 22 by Cadence software. Two experimental setups for intermodulation measurements were realized in order to characterize connectorized or antenna-equipped devices. Both setups were modeled using the VSS software available inside AWR Version 22. The comparison between measurements and simulations on the designed target showed a very good agreement. Intermodulation measurements were performed on connectorized devices present inside electronic systems and on various transceiver available on the market. This experimental study evidenced that the non-linearities of devices such as amplifiers and mixers are visible at their access ports even when the device is switched off. Moreover, this study highlights the ability of an intermodulation radar to remotely detect the presence of a particular transceiver, even when the latter is switched off, thanks to the specific frequency response of its intermodulation products.

The roadmaps of satellite-based synthetic aperture radar (SAR) systems show a trend that requires a continuous improvement of the active antenna in terms of operating bandwidth, scanning angle capability, and swath width, thus leading to the demand for increased RF power and better power efficiency of the RF transmitter. Moreover, compact size and light weight are relevant objectives for making the overall SAR instrument appealing for future applications. The transmit/receive module (TRM) shown in this paper was developed while combining all these requirements in a cost-effective approach. A careful design of all relevant RF interconnects and passive devices was performed to ensure the largest output power from the last high-power amplifier of the transmitting chain, the lowest noise figure at the input of the receiving chain, and the calibration capability for appropriately tuning the TX and RX signal. The TRM was manufactured and experimentally tested to verify its performances. The measurement results show the superior performances of the proposed compact high-power large-bandwidth TRM. The achieved target objectives make the design of the proposed TRM readily applicable for the development of a compact, high-power, and highly integrated AESAs to be used for next-generation satellite constellations for Earth observation.

In this paper, we show a dual-polarized ultra-wideband aperture-coupled microstrip antennae (ACMA) to be used in space missions such as CubeSat Ka-band applications. We also report the specific developed design procedure, which is distinguished from other design procedures by minimizing the complexity of construction, since it utilizes a simple multilayer structure without interlayer interconnections or inclusions. This design procedure develops an architecture for ACMA with the main objective of minimizing costs in large-scale production. The design starts from assigned specifications in terms of fractional bandwidth constrained to be larger than 40%, return loss better than 10 dB, and polarization purity and polarization isolation better than 25 dB, using materials with adequate ohmic and dielectric losses. A frequency-scaled prototype has been also designed, realized, and measured. Good agreement between the simulation and measurement results has been obtained.

Many applications in communication systems require the development of dual band matching networks. A new method to design dual band matching networks was shown, which resorts to closed form equations based on transmission line theory, and has three particular characteristics: (i) it permits the minimum number of elements (two at most three) in the network; (ii) the topology of the network is not fixed but modular; and (iii) it is able to find multiple solutions within a predefined range of feasible characteristic impedances for the elements of the network. An extensive comparison with the results shown in the literature has been reported showing the improvements introduced by the proposed method. Numerical simulations and experimental results confirm the effectiveness of the method.