Valentina Palazzi

Low-Power Frequency Doubler in Cellulose-Based Materials for Harmonic RFID Applications

This letter presents the design of a Schottky diode frequency doubler suitable for harmonic RFID tags. A microwave frequency doubler is implemented in a cellulose-based (paper) substrate, i.e., an ultra-low cost, recyclable and biodegradable material. The circuit exploits a distributed microstrip structure that is fabricated using a copper adhesive laminate to have low conductor losses. The measurements show a conversion loss of 13.4 dB at the output frequency of 2.08 GHz. This is achieved with an available input power of -10 dBm only. Finally a harmonic RFID experiment proves a reading range of 50 cm, obtained by transmitting 0 dBm and receiving a second harmonic of -60 dBm, i.e., well above the sensitivity of a typical microwave receiver.

Demonstration of a high dynamic range chipless RFID sensor in paper substrate based on the harmonic radar concept

This paper presents the design and implementation in paper substrate of a harmonic RFID chipless sensing tag. The proposed sensor is based on a Wheatstone bridge, where two of the four impedances change dynamically according to a physical parameter that has to be monitored. The passive tag is interrogated by a signal at f0 = 1.04 GHz and the signal transmitted back to the reader at 2f0 = 2.08 GHz is proportional to the magnitude of the parameter variation. A harmonic RFID experiment proves that this kind of architecture is capable of providing a dynamic range of more than 40 dB.

Scavenging for Energy: A Rectenna Design for Wireless Energy Harvesting in UHF Mobile Telephony Bands

The development of distributed and ubiquitous electronic devices is an achievement of modern technology that has the potential to revolutionize many aspects of human life. Such electronic devices are being employed not only in consumer areas like home automation, intelligent transportation systems, and personal entertainment but also for health-care applications, such as noninvasive biomedical parameter monitoring, as well as industrial and military applications. A novel WEH for commercial telephony frequencies in the UHF band has been presented. The system, being based on a broadband slot antenna and a thin flexible substrate, weighs fewer than 15 g, which is far below the competition requirements and makes the harvester particularly appealing for realistic scenarios. Thanks to the proper design of the rectifier and the matching network, an excellent performance has been verified over the whole band, with a rectenna conversion efficiency of up to 60% and an EFoM equal to 37.6 dB for 2 μW/cm2 of incident power density.

A novel compact harmonic RFID sensor in paper substrate based on a variable attenuator and nested antennas

This paper presents the design of a novel chipless harmonic RFID sensor in paper substrate based on a variable attenuator implemented as a π resistive network, which drives a single Schottky diode frequency doubler and a system of nested tapered annular slot antennas. The passive tag is interrogated by a signal at f0 = 1.2 GHz and the signal transmitted back to the reader is converted to 2f0 = 2.4 GHz in order for the system to be immune to clutter returns. The sensor information is encoded in the magnitude of the re-transmitted signal and a dynamic range around 20 dB is experimentally demonstrated.

A Novel Ultra-Lightweight Multiband Rectenna on Paper for RF Energy Harvesting in the Next Generation LTE Bands

This paper introduces a novel compact ultralightweight multiband RF energy harvester fabricated on a paper substrate. The proposed rectenna is designed to operate in all recently released LTE bands (range 0.79–0.96 GHz; 1.71–2.17 GHz; and 2.5–2.69 GHz). High compactness and ease of integration between antenna and rectifier are achieved by using a topology of nested annular slots. The proposed rectifier features an RF-to-dc conversion efficiency in the range of 5%–16% for an available input power of −20 dBm in all bands of interest, which increases up to 11%–30% at −15 dBm. The rectenna has been finally tested both in laboratory and in realistic scenarios featuring a superior performance to other state-of-the-art RF harvesters on flexible substrates.

Performance analysis of a ultra-compact low-power rectenna in paper substrate for RF energy harvesting

In this paper the experimental results of a compact low-power rectenna in paper substrate, designed to operate in the Wi-Fi band, are presented. The complete prototype, based on an annular slot antenna and a single-diode rectifier, features a weight of 1.5 grams and shows an RF-to-dc conversion efficiency in the design band of about 40 % for a −10 dBm available input power, of about 28 % at −15 dBm, and in the range [10, 22] % at −20 dBm, corresponding to an output DC voltage in the order of 320, 240 and 60 mV respectively. Additionally, the rectenna features an efficiency higher then 7 % in the whole band 1.8–2.7 dBm for a power density estimated around 3 µW/cm2.

Design of a ultra-compact low-power rectenna in paper substrate for energy harvesting in the Wi-Fi band

This paper presents the design of a novel rectenna based on a tapered annular slot and a single-diode rectifier, optimized to operate in the Wi-Fi band and in presence of low input power (Pavs=-15 dBm). In order to obtain a compact layout a double-layer architecture has been considered, according to which the interior metal surface of the annular slot is employed as ground plane for the rectifying circuit placed on the other side of the substrate. As a result, a rectenna with an active area of only 40 × 33 mm2 and an efficiency included between 26.5 and 28% has been obtained. The antenna has been fabricated in paper substrate and tested in the anechoic chamber. Then, the rectifier has been designed and optimized within the Advanced Design System suite. Finally, the rectenna performance has been discussed and compared to the State of the Art (SoA).

24-GHz CW radar front-ends on cellulose-based substrates: A new technology for low-cost applications

This paper presents, for the first time, a 24-GHz Continuous Wave (CW) radar front-end, entirely realized on a cellulose-based (i.e. paper) substrate. The front-end uses a microstrip circuitry that is fabricated using a copper adhesive laminate to have low conductor losses. A single dielectric layer is adopted to reduce complexity and, in perspective, costs. The radar exploits an external oscillator and transmits a power of about 2 mW. The antenna has a gain of 7 dBi and features an half-power beam width of 42 degrees. Its efficiency is 25%, including the feeding line. A singly-balanced diode mixer is adopted in the receiver chain. The mixer conversion loss is 11 dB with a local oscillator driving level of 0 dBm. In Doppler mode, the radar is able to detect a small fan (i.e. the movement of its rotor) at 1 m distance from the antenna. This contribution demonstrates that circuits on cellulose are capable to operate up to the boundary between microwave and millimeter-waves.

Design of a novel antenna system intended for harmonic RFID tags in paper substrate

This paper presents the design of a novel compact dual-layer harmonic tag in paper substrate, based on a system of nested annular slot antennas. The passive tag is interrogated by a signal at f0 = 1.2 GHz and the signal transmitted back to the reader is converted to 2f0 = 2.4 GHz in order for the system to be immune to clutter returns. The frequency conversion is performed by a single Schottky diode frequency doubler, which shows a theoretical conversion loss of 13 dB at the output frequency of 2.4 GHz for an available input power of only -10 dBm. Additionally, a tapered annular slot antenna has been proposed so as to increase the operational bandwidth.

Novel uniquely 3D printed intricate Voronoi and fractal 3D antennas

While 3D printing has enabled the rapid prototyping of numerous 3D structures, only very few designs have exploited this technology to create structures that are difficult or impossible to manufacture in any other way. In this paper, a novel surface modification technique is combined with high-resolution Stereo-lithography 3D printing to enable arbitrary 3D antenna designs that have never been demonstrated before including a Voronoi tessellation for light weight, low volume, and aerodynamic properties and 3D fractal geometries featuring similar physical advantages. Both antenna topologies utilize a novel metallization technique, electroless copper plating, to overcome the highly lossy properties of common 3D printed dielectric materials.