RF energy harvesters for wireless sensors, state of the art, future prospects and challenges: a review

The power consumption of portable gadgets, implantable medical devices (IMDs) and wireless sensor nodes (WSNs) has reduced significantly with the ongoing progression in low-power electronics and the swift advancement in nano and microfabrication. Energy harvesting techniques that extract and convert ambient energy into electrical power have been favored to operate such low-power devices as an alternative to batteries. Due to the expanded availability of radio frequency (RF) energy residue in the surroundings, radio frequency energy harvesters (RFEHs) for low-power devices have garnered notable attention in recent times. This work establishes a review study of RFEHs developed for the utilization of low-power devices. From the modest single band to the complex multiband circuitry, the work reviews state of the art of required circuitry for RFEH that contains a receiving antenna, impedance matching circuit, and an AC-DC rectifier. Furthermore, the advantages and disadvantages associated with various circuit architectures are comprehensively discussed. Moreover, the reported receiving antenna, impedance matching circuit, and an AC-DC rectifier are also compared to draw conclusions towards their implementations in RFEHs for sensors and biomedical devices applications

Wideband and UWB antennas for wireless applications. A comprehensive review

A comprehensive review concerning the geometry, the manufacturing technologies, the materials, and the numerical techniques, adopted for the analysis and design of wideband and ultrawideband (UWB) antennas for wireless applications, is presented. Planar, printed, dielectric, and wearable antennas, achievable on laminate (rigid and flexible), and textile dielectric substrates are taken into account. The performances of small, low-profile, and dielectric resonator antennas are illustrated paying particular attention to the application areas concerning portable devices (mobile phones, tablets, glasses, laptops, wearable computers, etc.) and radio base stations. This information provides a guidance to the selection of the different antenna geometries in terms of bandwidth, gain, field polarization, time-domain response, dimensions, and materials useful for their realization and integration in modern communication systems

Design of UWB microstrip patch antenna with variable band notched characteristics

Recently lower frequency band 4.5−5.5 GHz is proposed by the ASEAN countries for 5G cellular application and therefore, it is essential of designing an ultra-wideband (UWB) antenna for the particular band-notched characteristics. In this article, a compact tuning fork shape ultra-wideband (UWB) patch antenna with a variable band-notched characteristic has been proposed for 5G cellular application. The UWB antenna has been achieved by using a tuning fork shape with a simple partial ground plane. A pair of ring shape slits (RSS) on the ground plane has been added to achieve the band-notched characteristic. The proposed antenna has achieved a large −10 dB bandwidth of 7.8 GHz (2.9−11 GHz) and the VSWR value is less than 2 for the entire bandwidth excepted for notched frequency bands of lower 5G bands (4.5−5.5 GHz). Moreover, the antenna has a peak radiation efficiency of more than 87% for UWB and less than 27% for the notched frequency band. The notched-band is shifted with the change in the position of RSS’s within the vertical axis and thus, the variable band-notched characteristics have been achieved. Besides, the proposed antenna is compact with the dimension of 45×34 mm2 that makes it suitable for the lower band of 5G application

Design and Implementation of a Low‐Power Wireless Respiration Monitoring Sensor

Wireless devices for monitoring of respiration activities can play a major role in advancing modern home-based health care applications. Existing methods for respiration monitoring require special algorithms and high precision filters to eliminate noise and other motion artifacts. These necessitate additional power consuming circuitry for further signal conditioning. This dissertation is particularly focused on a novel approach of respiration monitoring based on a PVDF-based pyroelectric transducer. Low-power, low-noise, and fully integrated charge amplifiers are designed to serve as the front-end amplifier of the sensor to efficiently convert the charge generated by the transducer into a proportional voltage signal. To transmit the respiration data wirelessly, a lowpower transmitter design is crucial. This energy constraint motivates the exploration of the design of a duty-cycled transmitter, where the radio is designed to be turned off most of the time and turned on only for a short duration of time. Due to its inherent duty-cycled nature, impulse radio ultra-wideband (IR-UWB) transmitter is an ideal candidate for the implementation of a duty-cycled radio. To achieve better energy efficiency and longer battery lifetime a low-power low-complexity OOK (on-off keying) based impulse radio ultra-wideband (IR-UWB) transmitter is designed and implemented using standard CMOS process. Initial simulation and test results exhibit a promising advancement towards the development of an energy-efficient wireless sensor for monitoring of respiration activities

Optimization of Multi-Band Characteristics in Fan-Stub Shaped Patch Antenna for LTE (CBRS) and WLAN Bands

This study aims to optimize a fan-stub slot patch to get better suitability and performance for Citizens Broadband Radio Service (CBRS). The transition from the tedious configuration of slotted patch antenna in fan-stub shape is evaluated. Also, the impact of stub width W, stub length L, and its orientation are tested. Multiple simulation tests ensure the uniqueness in the type of slots or stubs that affect the multiband nature of patch. The optimization of basic fan-stub structure on return loss S11, Voltage Standing Wave Ratio (VSWR), and the operating band at the desired frequency is performed to accommodate the federal and non-federal use of the band. The simulation results show that the designed antenna is technically suitable to cover 4G LTE in CBRS (LTE-43 and LTE-48 band) as well as 5.5 GHz Wireless Local Area Network (WLAN) band of operation

Performance analysis of Ultra-wideband RF switch using discrete PIN diode in SC-79 package for medical application of microwave imaging

Microwave imaging is an emerging technology in the medical application which have similar functions as X-ray, Magnetic Resonance Imaging (MRI), and Computed Tomography scan (CT scan). In designing a microwave imaging system for medical application, it can use a monostatic radar approach by transmitting a Gaussian pulse (with an ultra-wideband (UWB) frequency). In this system, eight antennas are required with the support of RF switches. Thus, it is important to get the best performance of UWB RF switch in this application. Therefore, this paper presents the performance analysis of four different RF switch topologies (Design 1, 2, 3 and 4) using discrete PIN diode in SC-79 package. The design was based on single pole double throw (SPDT) switch. As result, Design 2 is the best topology after considering the tradeoff between isolation and return loss performances. Based on the three cascaded SPDT switches of Design 2, the insertion loss was less than -2 dB and return loss was more than -10 dB. Meanwhile, the isolation bandwidth (at the minimum isolation of -20 dB) was from 0.5 to 3.7 GHz (with 3.2 GHz bandwidth), hence, it could be used in the UWB frequency for medical application of microwave imaging

Rectenna Systems for RF Energy Harvesting and Wireless Power Transfer

With the rapid development of the wireless systems and demands of low-power integrated electronic circuits, various research trends have tended to study the feasibility of powering these circuits by harvesting free energy from ambient electromagnetic space or by using dedicated RF source. Wireless power transmission (WPT) technology was first pursued by Tesla over a century ago. However, it faced several challenges for deployment in real applications. Recently, energy harvesting and WPT technologies have received much attention as a clean and renewable power source. Rectenna (rectifying antenna) system can be used for remotely charging batteries in several sensor networks at internet of things (IoT) applications as commonly used in smart buildings, implanted medical devices and automotive applications. Rectenna, which is used to convert from RF energy to usable DC electrical energy, is mainly a combination between a receiving antenna and a rectifier circuit. This chapter will present several designs for single and multiband rectennas with different characteristics for energy harvesting applications. Single and multiband antennas as well as rectifier circuits with matching networks are introduced for complete successful rectenna circuit models. At the end of the chapter, a dual-band rectenna example is introduced with a detailed description for each section of the rectenna

CPW and microstrip line-fed compact fractal antenna for UWB-RFID applications

In this study, we present an implementation of Ultra Wide Band (UWB) Koch Snowflake antenna for Radio Frequency Identification (RFID) applications. The compact antenna, based on the Koch Snowflake shape, is fed by coplanar waveguide (CPW) and by microstrip line with an overall size of 31 × 27 × 1.6mm3. The simulation analysis is performed by CST Microwave Studio and compared with HFSS software. The antenna design exhibits a very wide operating bandwidth of 13GHz (3.4- 16.4GHz) and 11 GHz (3.5-14.577 GHz) with return loss better than 10 dB for microstrip line antenna and CPW antenna respectively. A prototype of CPW and microstrip antenna was fabricated on an FR4 substrate and measured. Simulated and measured results are in close agreement. The small size of the antenna and the obtained results show that the proposed antenna is an excellent candidate for UWB-RFID localization system applications

UWB Technology

Ultra Wide Band (UWB) technology has attracted increasing interest and there is a growing demand for UWB for several applications and scenarios. The unlicensed use of the UWB spectrum has been regulated by the Federal Communications Commission (FCC) since the early 2000s. The main concern in designing UWB circuits is to consider the assigned bandwidth and the low power permitted for transmission. This makes UWB circuit design a challenging mission in today's community. Various circuit designs and system implementations are published in this book to give the reader a glimpse of the state-of-the-art examples in this field. The book starts at the circuit level design of major UWB elements such as filters, antennas, and amplifiers; and ends with the complete system implementation using such modules

Compact Planar Ultrawideband Antennas with Continuously Tunable, Independent Band-Notched Filters

© 2016 IEEE. A compact planar ultrawideband antenna with continuously tunable, independent band notches for cognitive radio applications is presented. The antenna is fabricated using a copper-cladded substrate. A radiating patch with an inverted rectangular T-slot is etched on the top side of the substrate. A straight rectangular strip with a complete gap is embedded into the T-slot. By placing a single varactor diode across this gap, a frequency-agile band-notch function below 5 GHz is realized. On the bottom side of the substrate, a U-shaped parasitic element having an interdigitated-structure is placed beneath the radiating patch. The second narrow band notch is created by inserting a second varactor diode into the gap on one leg of the parasitic element. It has a frequency-agile performance above 5 GHz. The presence of the interdigitated structure suppresses higher order resonant modes and enhances the tunability of the notched bandwidth. Because these antenna structures naturally block dc, a very small number of lumped elements are required. The experimental results, which are in good agreement with their simulated values, demonstrate that both band notches can be independently controlled and the entire frequency-agile fractional bandwidth is as high as 74.5%, demonstrating a very wide notched frequency-agile coverage