Marco Virili

A New Contactless Assembly Method for Paper Substrate Antennas and UHF RFID Chips

This paper deals with a low-cost method for the assembly of flexible substrate antennas and UHF RF identification silicon (Si) chips. Such a method exploits a magnetic coupling mechanism, thus not requiring for galvanic contacts between the Si chip and antenna itself. The magnetic coupling is established by a planar transformer, the primary and secondary windings of which are implemented on flexible substrate and Si chip, respectively. As a result, the Si chip can be assembled on the antenna with a mere placing and gluing process. First, the idea has been validated by theory. Electromagnetic simulations of a square heterogeneous transformer (1.0-mm side) show a maximum available power gain (MAG) of -0.4 dB at 868 MHz. In addition, the heterogeneous transformer is also quite tolerant with respect to misalignment between primary and secondary. An offset error of 150 μm reduces the MAG to - 0.5 dB. A sub-optimal matching strategy, exploiting a simple on-chip capacitor, is then developed for antennas with 50- Ω input impedances. Finally, the idea has been experimentally validated exploiting printed circuit board (PCB) prototypes. A PCB transformer (1.5-mm side) and a transformer rectifier (two-diode Dickson multiplier) have been fabricated and tested. Measurements indicates a MAG of -0.3 dB at 868 MHz for the transformer and the capability of the developed rectifier to supply a 220-kΩ load at 1.5 V with a - 2-dBm input power.

Microwave Circuits in Paper Substrates Exploiting Conductive Adhesive Tapes

In this work, a new technique to fabricate microwave circuits in paper substrates is proposed. This technique relies on a copper adhesive tape that is shaped by a photo-lithographic process and then transferred to the hosting substrate by means of a sacrificial layer. Microstrip lines in paper substrates have been electromagnetically characterized accounting also for the adhesive layers. Experimental results show an insertion loss better than 0.6 dB/cm at 10 GHz.

Smart Surfaces: Large Area Electronics Systems for Internet of Things Enabled by Energy Harvesting

Energy harvesting is well established as one of the prominent enabling technologies [along with radio-frequency identification (RFID), wireless power transfer, and green electronics] for the pervasive development of Internet of Things (IoT). This paper focuses on a particular, yet broad, class of systems that falls in the IoT category of large area electronics (LAE). This class is represented by “smart surfaces.” The paper, after an introductory overview about how smart surfaces are collocated in the IoT and LAE scenario, first deals with technologies and architectures involved, namely, materials, antennas, RFID systems, and chipless structures; then, some exemplifying solutions are illustrated to show the present development of these concurrent technologies in this area and to stimulate further solutions. Conclusions and future trends are then drawn.

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.

Wearable Textile Antenna Magnetically Coupled to Flexible Active Electronic Circuits

This letter proposes wearable electronic modules on textile, suitable for garment integration, based on antennas magnetically coupled to the active circuitry. The coupling mechanism is based on a heterogeneous transformer with the primary and secondary windings implemented in the antenna and in the circuitry substrate (hybrid or monolithic), respectively. The proposed coupling topology avoids galvanic contacts between the antenna and the active circuitry, allowing for interconnecting the antenna by a mere placing and gluing process. Bonding and soldering processes, often critical for textile materials, are thus avoided. The proposed innovation, mitigating the industrial realization constraints posed by textile implementation of active antennas and radio frequency identification (RFID) tags, should unsurprisingly enable and foster industrial developments of garment RFID, wearable electronics and body-centric communications systems. A patch antenna with transformer based on textile materials and operating in the frequency band 2.4-2.4835 GHz is designed, realized, and measured.

24 GHz Single-Balanced Diode Mixer Exploiting Cellulose-Based Materials

A 24 GHz single-balanced diode mixer in paper substrate is presented. The microstrip 180 degrees hybrid junction (rat-race) is fabricated exploiting a copper adhesive tape that is shaped by a photo-lithographic process and transferred to the hosting (paper) substrate using a sacrificial layer. Only three discrete devices are necessary for the mixer operation, namely: two low-barrier, Schottky diodes and a 0 Ω resistor, used as a jumper. The measurements show a conversion loss of about 10 dB at 24 GHz with a 50 MHz IF signal. At the same frequency the isolation between LO and RF ports is better than 35 dB. The record performance achieved demonstrates, for the first time, the feasibility of K-band mixers exploiting cellulose-based materials.

Review of the present technologies concurrently contributing to the implementation of the Internet of Things (IoT) paradigm: RFID, Green Electronics, WPT and Energy Harvesting

This paper summarizes the most important technologies, concurrently participating to build the technological platform needed for a realistic implementation of the Internet of Things (IoT) paradigm. At the present state of the evolution of IoT, these technologies are mostly: Radio Frequency IDentification (RFID), Green Electronics (GE), Wireless Power Transfer (WPT) and Energy Harvesting (EH). This contribution briefly explains the reason for that, and shows a collection of scientific contributions which can be seen as examples. The deep description of the proposed systems can be found in the relative referenced papers.

A 1.2 V, 0.9 mW UHF VCO Based on Hairpin Resonator in Paper Substrate and Cu Adhesive Tape

A 1.2 V, 0.9 mW, 998 MHz voltage controlled oscillator (VCO) adopting a distributed hairpin resonator in paper substrate is described. The microstrip resonator exploits a copper adhesive tape that is shaped by a photo-lithographic process and transferred to the hosting substrate using a sacrificial layer. To minimize the number of components, a cross-coupled differential VCO circuit is adopted. As a consequence only 3 external devices are necessary: a single-package BJT pair, a resistor and a by-pass capacitor. The measurements show a phase noise of -99 dBc/Hz at 100 KHz offset from the carrier. At 1.2 V the output power is -22 dBm, whereas the tuning sensitivity is about - 100 MHz/V. The proposed design shows the feasibility of low-power oscillators for autonomous wireless sensors based on green materials.

7.5–15 MHz organic frequency doubler made with pentacene-based diode and paper substrate

This work describes the realization of a fully organic “chip-less” tag, based on the harmonic RFID architecture, operating at 7.5 and 15 MHz. The tag is fabricated on paper substrate and includes an organic pentacene-based diode, as a non-linear component, to generate harmonics. The communication between reader and tag is provided by coupled resonators operating at the fundamental and harmonic frequencies. A measure campaign of the complete reader-tag system has been performed and the results are here reported.

WPT, RFID and energy harvesting: Concurrent technologies for the future networked society

The increasing attention of ICT community towards Internet of Things (IoT) is leading to the need of optimizing the management of an amount of information that grows with the addition of more objects connected to the internet. In this paper we will focus on the challenges that this scenario is inspiring and will dare suggest an holistic vision to look for solutions respectful of the environment.