Design and Analysis of Antenna Feeding Networks Based on the Rotman Lens Using Interval Analysis (IA)

A new method for the design of antenna array feeding networks has been proposed in this work. In particular, the considered feeding networks are based on the Rotman lens. By knowing the maximum errors on the fabrication tolerances, the arithmetic of intervals and interval analysis (IA) are used for determining the lower and upper bounds of the antenna feeding network parameters of interest. Representative and preliminary numerical results are reported to show the potentialities of the proposed method. An experimental X-band Rotman lens prototype has been designed, fabricated, and assessed. The obtained results are quite good

A Reconfigurable Pseudohairpin Filter Based on MEMS Switches

This work presents a bandpass-reconfigurable planar pseudohairpin filter based on RF-MEMS switches. Hairpin-line structures are preferred to design microstrip filters because this class of filters offers a more compact size, and, in general, hairpin filters do not need ground connections for resonators. In this work, the U-shape resonators are arranged to obtain an interdigit capacitor to improve the coupling between the resonators. RF-MEMS switches modify the lengths of coupled resonators by adding microstrip segments to control the filter bandwidth, moving the center frequency and the return loss. An experimental hairpin tunable filter prototype based on RF-MEMS has been designed, fabricated, numerically and experimentally assessed, and compared concerning its tunability, quality factor, and capability with standard tunable filters based on PIN diodes. In conclusion, the tunable hairpin filter based on RF-MEMS switches offers the best performance in center frequency tuning range, compactness, and power consumption regarding reconfigurable filters based on standard PIN diodes switches. The obtained results are appealing and demonstrate the capabilities and potentialities of RF-MEMS to operate with the new communication standards that work at high microwave frequency bands

A COMPACT ULTRA-WIDE BAND PRINTED LOG-PERIODIC ANTENNA USING A BOW-TIE STRUCTURE

In this letter, an ultra-wideband compact printed log periodic dipole (LPD) array antenna is designed to operate between 500MHz and 6 GHz frequencies. The proposed LPD antenna structure consists of one bow-tie dipole and 15 regular dipole elements. The bow-tie element is introduced to improve the antenna's performance at the lowest frequencies below 1 GHz and at the same time to reduce the antenna size maintaining a good performance. An experimental antenna prototype has been designed, optimized, fabricated, numerically and experimentally assessed. The obtained results are very promising, and they demonstrated that the presented antenna prototype is able to operate in the range between 500MHz and 6 GHz with an average gain of 6 dBi and a very compact size

A Novel Detection Technique for a Chipless RFID System Using Quantile Regression

This work presents a novel approach for improving the detection capabilities of a chipless Radio Frequency Identification (RFID) system based on quantile regression. The main drawback of chipless RFID systems is the limited response of the tags due to the low-quality factor of the resonators, used to encode the information in the tag. The detection becomes very challenging especially for real-time data when noise is present. This work proposes the use of quantile regression to enhance the system performance. A chipless RFID system prototype has been fabricated (as a proof of concept) and experimentally assessed. The obtained results are quite satisfactory in the potentialities of the proposed methodology

A Survey of Resource Allocation Techniques for Cellular Network’s Operation in the Unlicensed Band

With an ever increasing demand for data, better and efficient spectrum operation has become crucial in cellular networks. In this paper, we present a detailed survey of various resource allocation schemes that have been considered for the cellular network’s operation in the unlicensed spectrum. The key channel access mechanisms for cellular network’s operation in the unlicensed bands are discussed. The various channel selection techniques are explored and their operation explained. The prime issue of fairness between cellular and Wi-Fi networks is discussed, along with suitable resource allocation techniques that help in achieving this fairness. We analyze the coverage, capacity, and impact of coordination in LTE-U systems. Furthermore, we study and discuss the impact and discussed the impact of various traffic type, environments, latency, handover, and scenarios on LTE-U’s performance. The new upcoming 5G New Radio and MulteFire is briefly described along with some of the critical aspects of LTE-U which require further research. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Development of Environmental Long Range RFID Sensors Based on the Modulated Scattering Technique

This work presents the development of a wireless sensor system for environmental monitoring based on the modulated scattering technique (MST). The MST sensor probes are based on the scattering properties of small passive antennas and radiate part of the impinging electromagnetic field generated by an interrogating antenna, which also acquires the backscattered signal as information. The MST probes are able to deliver data without radio frequency front end. They use a simple circuit that alternatively terminates the antenna probe on suitable loads to generate a low modulation signal on the backscattered electromagnetic wave. In this work, the MST sensor system for environmental monitoring has been proposed to obtain the best performance in communication range, load efficiency and power harvesting. The MST sensor has been fabricated and assessed in practical scenarios. The proposed prototype, able to operate in X band at 10 GHz and able to provide a communication range of about 15 m, serves as a proof-of-concept. The acquired measurements demonstrate that the prototype is able to measure accurately and send data without radio frequency front end or bulky wired connection with the same efficiency of standard wireless sensors such as radio frequency identifier (RFID) or wireless sensor networks (WSN)

Ultra-Wideband Antenna Array based on Orbital Angular Momentum

In this work, an antenna array able to generate orbital angular momentum (OAM) electromagnetic waves with ultra-wideband (UWB) characteristics is proposed. In particular the proposed array antenna is based on cavity back UWB antennas. In particular each array element is backed with a surface impedance waveguide SIW to improve the performances and reduce the single element dimensions. The array elements are a circularly arranged and the correct phase shift, mandatory to obtain a suitable OAM wave, have been obtained with reconfigurable reflection type phase shifters based on two quadrature hybrids and commercial pin diodes. The phase shifters are driven by mean of a suitable micro-controller. A proof of concept prototype has been designed fabricated and experimentally assessed. The obtained results were quite promising

Wearable non\u2010invasive blood glucose monitor system based on galvanic skin resistance measurement

This work proposes a wearable system for the non-invasive measurement of the blood glucose level. In particular, the blood glucose variations are related with the skin resistance measured with a suitable sensor. A micro-controller is aimed to measure, store and transmits on a wireless channel, the blood glucose level in a simple, non-invasive and unsupervised way. The system is particularly useful to monitoring the glucose level in diabetic patients, and to perform the oral glucose tolerance test (OGTT) useful to identify metabolic diseases and to diagnose diabetes mellitus in the early stage. The preliminary obtained results are quite promising and demonstrated the potentialities of the device as diagnostic and home care tool

Integration of Modulated Scattering Technique (MST) tags with IoT devices

Internet of things (IoT) has transformed numerous fields while providing better connectivity. In such scenario, the integration of various IoT devices have to be satisfied. The downside of commuting between cross platform IoT devices are difficult to achieve, because low power high range communication front end is mandatory. This paper proposes to utilize the Modulated Scattering Technique (MST) to integrate with IoT devices and to achieve the radio frequency communication capabilities. An MST system works similarly to an RFID, is highly miniaturized and exhibits good performances at microwave frequency bands without the necessity of radio frequency front-end. MST communication systems provide an high operative range with respect to standard RFID systems, and a very low consumption with respect to standard wireless radio frequency front ends, such as WiFi modules. This work proposes the integration of MST communication paradigms with an IoT system, in particular a prototype of air quality IoT sensor is presented and assessed

A Reconfigurable Pseudohairpin Filter Based on MEMS Switches

This work presents a bandpass-reconfigurable planar pseudohairpin filter based on RF-MEMS switches. Hairpin-line structures are preferred to design microstrip filters because this class of filters offers a more compact size, and, in general, hairpin filters do not need ground connections for resonators. In this work, the U-shape resonators are arranged to obtain an interdigit capacitor to improve the coupling between the resonators. RF-MEMS switches modify the lengths of coupled resonators by adding microstrip segments to control the filter bandwidth, moving the center frequency and the return loss. An experimental hairpin tunable filter prototype based on RF-MEMS has been designed, fabricated, numerically and experimentally assessed, and compared concerning its tunability, quality factor, and capability with standard tunable filters based on PIN diodes. In conclusion, the tunable hairpin filter based on RF-MEMS switches offers the best performance in center frequency tuning range, compactness, and power consumption regarding reconfigurable filters based on standard PIN diodes switches. The obtained results are appealing and demonstrate the capabilities and potentialities of RF-MEMS to operate with the new communication standards that work at high microwave frequency bands