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In this study, a reconfigurable, two-element, multiple-input multiple-output (MIMO) printed inverted-F antenna (PIFA) is presented with an enhanced isolation ability. The MIMO antenna system is designed using three different reconfiguration techniques that are based on positive-intrinsic-negative diodes, radio frequency micro-electromechanical switches and varactors. Their impact on the performance of the PIFA and the MIMO system is evaluated in terms of radiation characteristics, gain, power dissipated, radiation efficiency, linearity, biasing requirements and MIMO performance. Isolation between the two MIMO antenna elements is enhanced by integrating a reconfigurable band-reject filter within the ground plane between the radiating elements. The band-reject filter is reconfigured simultaneously with the radiating elements, hence resulting in less coupling and better isolation. The MIMO system along its various components is fabricated for the three different reconfiguration techniques and the comparison with predicted data shows great agreement.

This letter presents a new planar inverted-F antenna design that is dedicated for integration within mobile devices such as phones and tablets. The proposed antenna structure is based on nested capacitive slots in order to achieve a multiband behavior. The presented antenna is also reduced in size by 60%. The antenna is then reconfigured using positive-intrinsic-negative (p-i-n) diodes that are embedded within the antenna structure. Frequency reconfiguration is achieved to ensure that all the various commercial and required bands of interest are covered. Two prototypes are fabricated and measured where good agreement is noticed between the simulated and measured data.

In this article, we present a complete design for an optimized energy-efficient sensor for use in Internet of Things networks based on the concept of radio wake-up, with embedded addressing capability. Experimental and analytical results demonstrate the validity of the proposed design in terms of low power consumption and efficient functionality compared to existing solutions that are based on periodic wake-up patterns.

A novel methodology for the rapid preliminary design of deployable antennas for CubeSats is proposed in this article. It uses a graphical representation of antenna performance, consisting of a set of plots of different performance metrics against antenna geometry parameters. Coupled electromagnetic and structural design problems are addressed easily, enabling the rapid and direct comparison of different antenna concepts. This approach is demonstrated for a case study at ultrahigh frequency (UHF), comparing the performance of a dipole, a helix, a conical horn, and a conical log spiral (CLS), all based on dual-matrix composite deployable structures. The initial design space of antenna geometries is reduced by two orders of magnitude to a set of constraintsatisfying designs. A graphical user interface implementing the approach is presented, and the accuracy of the method is briefly addressed.

This paper presents an active 8-port feeding network that achieves a full range 360° phase coverage. The network is designed to only require a phase shift tuning of 180°. The performance of the proposed feeding network along its various active components can be achieved by necessitating less than 4 V of biasing voltage requirements. The feeding network is tested on an array of eight circularly polarized helical antenna elements where polarization reconfiguration in the radiated fields is achieved. The control of the phase shift between the feeding network ports allows the overall antenna array to change its polarization across the entire frequency band of interest between 1.7 GHz and 2.3 GHz.

This paper presents an overall review of the most recent electromagnetic (EM) based techniques that are employed for non-invasive, continuous glucose monitoring. The different types of EM based sensors are discussed and their challenges are addressed. Such sensors have proven to provide good sensitivity to glucose variation in blood. However, they exhibit some significant downfalls that must be addressed in the design of any future EM based device.

In today's wireless networks, interference serves as a harmful factor that can notably degrade the overall performance. Nevertheless, interference can also be beneficial when utilized as an additional power source for radio frequency (RF) based energy harvesting in order to charge Internet of Things (IoT) devices. In this paper, we quantify the positive impact of interference for energy harvesting using tools from stochastic geometry; in particular, we derive an expression for a suitable success probability metric and validate its accuracy using Monte-Carlo simulations as a function of various system parameters. Moreover, we design, implement and evaluate an experimental test bed for RF-based energy harvesting using WiFi access points (APs) in order to demonstrate the practical performance gains resulting from interference as a function of the number of access points, their relative locations, and the receivers antenna configuration. The obtained experimental measurement results corroborate the insights extracted from the analytical derivations.

The advancement in wireless communications requires the integration of multiple radios into a single platform to maximize connectivity. In this paper, the design process of reconfigurable antennas is discussed. Reconfigurable antennas are proposed to cover different wireless services that operate over a wide frequency range. They show significant promise in addressing new system requirements. They exhibit the ability to modify their geometries and behavior to adapt to changes in surrounding conditions. Reconfigurable antennas can deliver the same throughput as a multiantenna system. They use dynamically variable and adaptable single-antenna geometry without increasing the real estate required to accommodate multiple antennas. The optimization of reconfigurable antenna design and operation by removing unnecessary redundant switches to alleviate biasing issues and improve the system's performance is discussed. Controlling the antenna reconfiguration by software, using Field Programmable Gate Arrays (FPGAs) or microcontrollers is introduced herein. The use of Neural Networks and its integration with graph models on programmable platforms and its effect on the operation of reconfigurable antennas is presented. Finally, the applications of reconfigurable antennas for cognitive radio, Multiple Input Multiple Output (MIMO) channels, and space applications are highlighted.

International audience; In this paper, a reconfigurable patch antenna design operating at 868MHz for Low Power Wide Area Network (LoRa), 1.58 GHz for Global Positioning System (GPS) and 2.4 GHz for Bluetooth is presented. The design is reconfigurable thanks to the integration of a digitally tunable capacitor (DTC). The DTC capacitance changes according to a 5 bits' sequence command. A microcontroller is used to assign the required sequence, and thus leading to frequency reconfiguration. The antenna is a circular patch with a gain that varies from 0.2 dB to 6 dB based on the desired frequency of operation and the reconfiguration state. The antenna is designed for internet of things (IoT) applications.

This paper presents a new radio frequency (RF) rectifying design that is based on a tapered matching network. The rectifier operates over the Wi-Fi 802.11 b/g bands. The tapered matching network aims at transforming the Schottky diode's impedance into the input impedance of the circuit by resorting to dual transmission lines. Each line is designed with a different characteristic impedance. The rectifier topology is then integrated into a multiport RF energy harvesting system that relies on RF combining. The multi-port rectifier system shows excellent harvesting capabilities with an increased output DC voltage.

This paper proposes a new radio frequency (RF) energy harvesting system that operates over the Wi-Fi 802.11 b/g band at low input power levels. The system presented herein achieves good power conversion efficiencies (PCEs) over a power range that extends from (−20 dBm) to (3 dBm). A directive slot antenna is incorporated to drive the rectification process of the designed rectenna. The rectenna system is measured and tested, along with a power management circuitry, for design validation purposes. A good agreement between simulated and measured results is attained.

This paper focuses on enhancing multiband isolation between two antenna elements in a reconfigurable multiple input multiple output (MIMO) system. The antennas are reconfigurable printed inverted F antennas (PIFA) that resort to two PIN diodes each to achieve frequency reconfiguration. The isolation between the antenna elements is proposed to be improved through the use of multiple nested slots in the common ground plane between the elements. These slots collectively act as a multi-band reject filter and improve the isolation at the various operational frequencies of the antenna system. The reconfigurable MIMO antenna system is proposed for integration into mobile devices with an operation that covers mobile communication applications.

A new cognitive radio antenna system is presented and discussed in this study. The antenna system is composed of a wideband antenna that is used for channel sensing and a communicating antenna that is used for dynamic transmission over various frequencies. The communicating antenna is a software controlled reconfigurable antenna that can tune its frequency response by changing the height and angular position of its ground plane. This antenna is composed of a rectangular patch and three ground planes. Two ground planes are fixed while the third one moves and tilts based on the user's demand. The antenna's moving ground plane is controlled by an Arduino board and two linear actuators. The wideband sensing antenna is composed of a printed monopole patch that searches the spectrum for idle frequencies. A prototype of the complete antenna system is fabricated and tested. Both experimental and simulated results show good agreement.

In this paper cognitive radio is described, discussed and compared with software defined radio (SDR). The two types of cognitive radio are presented and examples on both spectrum interweave and spectrum underlay cognitive radio antenna systems are detailed. Reconfigurable filtennas are proposed as communicating antennas in a MIMO setting for both cases of cognitive radio. The benefits of resorting to filtennas as well as to MIMO configuration is shown and discussed herein. The various antenna examples are designed, tested and compared with each other. Conclusions are drawn based on the presented results.

This paper discusses the fundamental principles of a cognitive-radio RF system. The key points required to achieve a true cognitive-radio device are outlined. The operation of a cognitive-radio system is mainly divided into two tasks. In the first task, a cognitive-radio device searches and identifies any part of the spectrum that is not occupied. The second task consists of achieving an optimal mode of communication by allocating the appropriate channels to be used. In this paper, the RF requirements required to operate a cognitive-radio device are detailed. Such a device can adopt one of two scenarios of a cognitive-radio system: the ?interweave? or ?underlay? mode of operation. For both scenarios, a cognitive cycle is followed. This cycle consists of the following four steps: (1) observe, (2) decide, (3) act, and (4) learn. A cognitive-radio engine is responsible for managing and integrating these four functions together into a single cognitive-radio device. In this tutorial, the realization of the four functions of a cognitive-radio cycle are detailed for both types of cognitive radio, and various RF front-end examples are presented and discussed.

In this paper, frequency-tunable microstrip antennas, for cognitive radio applications, are proposed. The approach is based on electrically tuning the antenna's operating frequency by integrating reconflgurable band pass fllters into wideband antenna structures. The design of an open loop resonator (OLR)-based bandstop fllter, and its transformation to a bandpass fllter, are investigated flrst. Then, the incorporation of the bandpass fllter, with a wideband antenna, is detailed. The same methodology is employed to design cognitive radio pattern and polarization diversity tunable fllter-antennas. A good agreement between the simulated and measured results for the difierent fabricated prototypes is attained.

In this letter, we present a new technique to control reconfigurable and cognitive radio antenna systems. For both cases, the control is done by sensing a movement in the antenna surroundings. This surrounding awareness ability is achieved by incorporating an infrared (IR) motion detector with the antenna system. Once a movement is detected, the IR sensor generates a voltage that can be used to activate the biasing network of a reconfiguring element on an antenna structure. This concept is first tested on a varactor-based reconfigurable antenna. Then, a modified version of the circuit is used to control a cognitive radio antenna system that consists of a reconfigurable antenna and a wideband sensing antenna.

In this paper, a new reliable radio frequency (RF) rectifier topology with an enhanced operating power range is proposed. The presented RF harvester possesses an efficient RF to DC conversion ratio over an enhanced power range. A typical RF rectifier is initially optimized, and then the RF input is equally split into two branches. Splitting the input RF power improved the reliability and breakdown performance of the rectifier. This has the effect of increasing the power rectification range by approximately a factor of three. The design presented herein aims at avoiding any efficiency degradation in scenarios, where the RF power fed into a typical harvesting circuit varies. The proposed rectifier circuit is fabricated and the measured results show good agreement with simulated data.

In this paper, two compact multiband and reconfigurable planar inverted-F antenna (PIFA) designs operating at GPS, 3G, WiFi, GSM and 4G (UMTS and LTE) frequencies are presented. The multiband operation is accomplished by the multi-resonant slots while the reconfigurable PIFA operation is based on the appropriate integration of PIN diodes switches. Both antennas are proposed as suitable candidates for mobile devices' integration.

The implementation of a four sectorial reconfigurable MIMO antenna system is discussed in this paper. The proposed antenna system consists of two MIMO structures that operate at two different frequencies. The reconfigurability of the antenna system is software controlled through an arduino board and a mobile phone application. A prototype is fabricated and tested as a proof of concept.

This paper proposes a new RF rectifier with a dynamically extendable RF-DC power conversion (> 50%) range. Compared to typical rectifiers, the adopted power combining topology extends the dynamic efficient range by ∼ 3 dB, while maintaining acceptable performance at low powers. A 1.84 GHz rectifier with the proposed topology is designed. A prototype of the designed rectifier is fabricated and tested. It is shown that the proposed rectifier maintains acceptable conversion efficiency over a power range extending from 2 dBm to 11 dBm. The performance of such rectifier is to be assessed using different antenna configurations dedicated to harvest RF and/or solar energy to power battery-less devices.

In this paper, a reconfigurable cognitive radio receiver for autonomous spectrum sensing is presented. A reconfigurable antenna, low-noise amplifier, reconfigurable bandpass filter, single-ended balanced mixer, voltage-controlled oscillator (VCO), and variable gain amplifier (VGA) build up the chain of the proposed receiver. This receiver targets the WLAN IEEE 802.11WLAN IEEE 802.11 g commercial wireless standard. The receiver performance is demonstrated with a 20-MHz down-converted signal at its output.

A cognitive radio front end using an optically pumped reconfigurable antenna system (OPRAS) is investigated. The scheme consists of a ultrawideband antenna and a reconfigurable narrowband antenna in close proximity to one another. The narrowband reconfigurability is achieved by a integrating laser diodes within the antenna structure to control the switching state of photoconductive silicon switches. This scheme has the advantage of eliminating the use of optical fiber cables to guide light to the switches, and enables easier integration of the reconfigurable antenna in a complete communication system. The performance of the proposed technique is presented, and comparisons are made to other commonly used switching techniques for reconfigurable antennas, such as techniques based on PIN diodes and RF microlectromechanical systems integration. The application of this antenna design scheme serving as the receive channel in a cognitive radio communication link is also demonstrated.

This letter details a new reconfiguration technique for implementing frequency-tunable bandpass filters. This is achieved by changing the filter total capacitance via an integrated varactor within its structure. The reconfigurable bandpass filter is then incorporated within the feeding line of a printed antenna to form one structure. This combination allows the tuning of the antenna operating frequency without incorporating active components and biasing lines on the antenna radiating surface. The integrated antenna-filter combination, with filtering ability while preserving the radiation performance, is referred to as a “filtering antenna” or a filtenna. A prototype for the reconfigurable filter and the reconfigurable filtenna are fabricated and tested. A good agreement is found between the simulated and the measured data.

In this letter, a new conductive composite tape-spring is proposed for CubeSat deployable antennas that is constructed using a glass fiber reinforced epoxy with an embedded copper alloy conductor. The tape-spring is bistable enabling the antenna to be elastically stable in both the deployed and stowed states. A dipole antenna is designed, simulated, and tested to prove the viability of the electrical properties of this material.

In this letter, p-i-n diodes are used as switches to connect and disconnect four patch sections to a midsection of a planar antenna. The antenna system is connected to the field programmable gate array (FPGA) board controlling the activation of these switches. The antenna with the incorporated diodes is designed, installed, and measured. The methodology for using an FPGA to optimally control and produce the desired antenna frequency operation is presented and analyzed. The analogy between the measured and simulated results is found to be satisfactory. The proposed control methodology can be used with various antenna designs to obtain different possible states in an easy, fast, and low-cost manner.

This letter investigates a new reconfigurable antenna technique based on the rotation of a slot. The surface currents are redistributed for each slot position. The antenna is simulated, fabricated, and tested. The return loss frequency tuning matches the simulated data. The antenna radiation pattern remains unchanged for different slot positions. Finally, the process for automatic rotation and control of the slot is investigated using graph models.

This letter addresses the optimization and complexity reduction of switch-reconfigured antennas. A new optimization technique based on graph models is investigated. This technique is used to minimize the redundancy in a reconfigurable antenna structure and reduce its complexity. A graph modeling rule for switch-reconfigured antennas is proposed, and examples are presented.

This letter presents a new approach for the design of a multiresonant printed bowtie antenna. Several techniques were attempted to obtain one antenna which is operational in the 2, 3, and 5 GHz bands corresponding to many wireless applications. The idea of creating different slot configurations on different parts of a single antenna is the basic principle. A prototype of the final antenna design was fabricated tested and a good agreement was found between simulated and tested results.

Recent advances in reconfigurable RF components and systems have helped in the development of very complex reconfigurable antennas capable of radiating more than one pattern at different frequencies and polarizations. These types of antennas are becoming critical components in modern telecommunication systems from cognitive radio to cubesat communications.

This paper describes the implementation of an efficient transparent log spiral antenna for energy harvesting. The proposed antenna is a wide band antenna with circular polarization which is integrated with solar panels. The goal is to implement an efficient technique to collect RF energy without degrading the performance of the solar cell.

In this paper, a MIMO antenna structure composed of a set of directive printed dipoles is presented. The proposed MIMO antenna system is able to cover two different frequency bands. The directive property is achieved by designing an appropriate printed reflector within the antenna structure. A prototype antenna is fabricated and tested to validate the simulated performance.

The design of a reconfigurable cyclical printed antenna is discussed in this paper. The antenna's topology allows a wide bandwidth of operation and an ability for radiation pattern reconfiguration.. The antenna is designed at Ka-band, with different modes of radiation pattern characteristics. The different operational states reshape the radiation beam and redirect major radiation pattern lobes towards desired directions. The antenna is proposed for radar applications where such reconfigurable characteristic is desired.

In this paper a MIMO based meandered line antenna system is presented for mobile devices. First a non-uniform meandered line antenna with a topology of five turns is discussed. A p-i-n diode is used as a switch to connect and disconnect parts of this antenna, allowing it to tune its operating frequencies between 4G LTE and other wireless communication applications. Next, a two element MIMO configuration of this meandered line antenna is investigated. The size and position of the elements are optimized for integration in mobile devices.

This paper presents a reconfigurable antenna array that is made of four printed dipole elements. The change in the array operating frequency is achieved by feeding separately each array element via an external reconfigurable feeding network. The pattern diversity is achieved by incorporating a printed reflector between the array elements. A prototype antenna is fabricated and tested.

This paper presents a study on randomly distributed planar antenna array elements for adaptive beamforming. A comparison between uniformly and randomly spaced antenna arrays is detailed by using the adaptive least mean square algorithm. The study is based on varying the number of elements of the random planar antenna array to obtain an optimal performance.

This paper presents an agile tight feeding technique for use in highly integrated front-end architectures of mobile radios. This reconfigurable technique adjusts the operation of mounted antennas without installing switching components on their radiating surfaces. The proposed feeding technique is designed to feed two radiating structures on demand. The reconfiguration is achieved by resorting to two PIN diodes that are integrated within the feeding network whose operation ranges between 4 GHz and 6 GHz. A prototype is fabricated as a proof of concept. A good agreement is found between the simulated and measured results.

This paper discusses the merging of reconfigurable and deployable antennas for satellite and space communications. Reconfigurable antennas, normally proposed for terrestrial applications, allow deployable antennas to be more adaptive and more capable to perform additional functions. In this paper, various antenna concepts that can deploy and at the same time possess frequency tuning capability are proposed for space communications. The addition of tuning ability allows a more efficient, selective and cognitive communication schemes.

Frequency-tunable microstrip antennas, for cognitive radio applications, are proposed herein. The approach is based on tuning the operating frequency of a bandpass filter that is incorporated into a wideband antenna. The integration of an open loop resonator- (OLR-) based adjustable bandpass filter into a wideband antenna to transform it into a tunable filter-antenna is presented. The same technique is employed to design a cognitive radio pattern diversity tunable filter-antenna. A good agreement between the simulated and measured results for the fabricated prototypes is obtained. The radiation characteristics of each designed tunable filter-antenna are included herein.

In this paper a helical antenna that is deployed on a small satellite platform is presented. The antenna achieves reconfiguration in stages by deploying in and out of the satellite in a rotational matter to achieve frequency tuning. The antenna is circularly polarized with a wide bandwidth and a reasonable gain. The merging of deployable and reconfigurable antennas allows deployment on demand and adds more capabilities and adaptation ability to space communications.

This paper presents a reconfigurable printed two arms monopole antenna structure. The proposed antenna is able to change either its operating frequency or radiation pattern based on the activation of the integrated PIN diode switches. The purpose of the switches is to connect one of the two monopole arms or both to the antenna feeding line. A prototype antenna is simulated, built and tested. A good agreement is found between the simulated and measured data.

In this paper we present a new reconfigurable meander line antenna. The antenna is a non uniform meander line with five turns. A p-i-n diode is used as a switch to connect and disconnect parts of this antenna, allowing it to tune its operating frequencies between 4G LTE and other wireless communication applications. The position of the p-i-n diode is optimized to achieve tuning between various wireless communications applications of interest to mobile devices. The antenna with its compact size is designed, built and measured where analogy is found between the measured and calculated data.

This paper discusses an antenna design that achieves tuning of its frequency response by changing the height and angular position of its ground plane. The antenna is composed of a simple patch and three ground planes. Two ground planes are fixed while a third part moves and tilts based on the user's demand. The antenna's moving ground plane is controlled by an arduino board and two linear actuators. The antenna is simulated and measured. Good analogy is found between measured and simulated data.

This paper presents a new technique to correct switch failures in a frequency reconfigurable antenna array. The correction procedure requires at the beginning a detection of the failed switch. The detection process relies on integrating sensing lines within the array substrate to monitor the switch failure. The proposed correction technique is based on using Neural Network (NN) to overcome the failed switch. This is achieved by making the trained NN searches for other switch combinations that give the same array behavior.

This paper presents an antenna system dedicated for cognitive radio applications. The proposed antenna system consists of two sets of radiating structures. The first set is a two port frequency reconfigurable antenna and the second set is a two port sensing antenna. A prototype antenna is simulated, built and tested to prove the validity of a MIMO system for cognitive radio applications. A good agreement is found between the simulated and the measured data.

This paper presents a technique to reduce the cost and overcome the high processing power needed to analyze the signals received by wideband antennas. The idea is based on matching a wideband antenna to a reconfigurable filter. This will allow an easier processing for the received signal and the replacement of the bank of filters needed after the antenna by one reconfigurable filter element. Two prototypes are shown to prove the validity of the proposed technique.

This paper presents an antenna system suitable for cognitive radio applications. It consists of two pairs of antennas. The first one is a wide band antenna that monitors the channel in order to identify the idle parts of the spectrum. The second antenna has a frequency and radiation pattern tuning ability. This antenna communicates at different frequency bands as well as at different radiation directions. The directions of radiation depend on the locations of cognitive radio users. A prototype is fabricated, tested and compared with the simulated design where good analogy is found.

This paper presents an approach for embedding a reconfigurable band-pass and band-stop filters into an antenna structure. The band-pass filter is located in the feeding line of the antenna while the band-stop is included in the antenna ground plane. A prototype antenna is simulated, fabricated and tested to prove the validity of our new technique.

In this paper we discuss the detection of switch failures in reconfigurable antenna arrays. Changes in the antenna array's electromagnetic behavior due to a switch failure are detected by measuring the S parameters of sensing lines embedded into the array substrate. Several prototypes are designed, developed and measured to validate the proposed failure detection methodology.