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Showing papers on "Radio frequency published in 2017"


Journal ArticleDOI
TL;DR: In this article, a generalized hybrid architecture with a small number of radio frequency (RF) chains with full-resolution ADCs, or low-resolution ADC with a number of RF chains equal to the number of antennas is proposed.
Abstract: Hybrid analog/digital architectures and receivers with low-resolution analog-to-digital converters (ADCs) are two low power solutions for wireless systems with large antenna arrays, such as millimeter wave and massive multiple-input multiple-output systems. Most prior work represents two extreme cases in which either a small number of radio frequency (RF) chains with full-resolution ADCs, or low-resolution ADC with a number of RF chains equal to the number of antennas is assumed. In this paper, a generalized hybrid architecture with a small number of RF chains and a finite number of ADC bits is proposed. For this architecture, achievable rates with channel inversion and singular value decomposition-based transmission methods are derived. Results show that the achievable rate is comparable to that obtained by full-precision ADC receivers at low and medium SNRs. A trade-off between the achievable rate and power consumption for the different numbers of bits and RF chains is devised. This enables us to draw some conclusions on the number of ADC bits needed to maximize the system energy efficiency. Numerical simulations show that coarse ADC quantization is optimal under various system configurations. This means that hybrid combining with coarse quantization achieves better energy-rate trade-off compared with both hybrid combining with full-resolutions ADCs and 1-bit ADC combining.

219 citations


Journal ArticleDOI
TL;DR: This review article explains different lidar aspects and design choices, such as optical modulation and detection techniques, and point cloud generation by means of beam-steering or flashing an entire scene.
Abstract: 3D imaging technologies are applied in numerous areas, including self-driving cars, drones, and robots, and in advanced industrial, medical, scientific, and consumer applications. 3D imaging is usually accomplished by finding the distance to multiple points on an object or in a scene, and then creating a point cloud of those range measurements. Different methods can be used for the ranging. Some of these methods, such as stereovision, rely on processing 2D images. Other techniques estimate the distance more directly by measuring the round-trip delay of an ultrasonic or electromagnetic wave to the object. Ultrasonic waves suffer large losses in air and cannot reach distances beyond a few meters. Radars and lidars use electromagnetic waves in radio and optical spectra, respectively. The shorter wavelengths of the optical waves compared to the radio frequency waves translates into better resolution, and a more favorable choice for 3D imaging. The integration of lidars on electronic and photonic chips can lower their cost, size, and power consumption, making them affordable and accessible to all the abovementioned applications. This review article explains different lidar aspects and design choices, such as optical modulation and detection techniques, and point cloud generation by means of beam-steering or flashing an entire scene. Popular lidar architectures and circuits are presented, and the superiority of the FMCW lidar is discussed in terms of range resolution, receiver sensitivity, and compatibility with emerging technologies. At the end, an electronic-photonic integrated circuit for a micro-imaging FMCW lidar is presented as an example.

217 citations


Journal ArticleDOI
TL;DR: This work demonstrates significantly improved magneto-optical trapping of molecules using a very slow cryogenic beam source and either rf modulated or dc magnetic fields, and achieves a density orders of magnitude greater than previous molecular MOTs.
Abstract: We demonstrate significantly improved magneto-optical trapping of molecules using a very slow cryogenic beam source and either rf modulated or dc magnetic fields. The rf magneto-optical trap (MOT) confines 1.0(3)×10^5 CaF molecules at a density of 7(3)×10^6 cm^(−3), which is an order of magnitude greater than previous molecular MOTs. Near Doppler-limited temperatures of 340(20) μK are attained. The achieved density enables future work to directly load optical tweezers and create optical arrays for quantum simulation.

211 citations


Journal ArticleDOI
Clemens Ruppel1
TL;DR: This paper will try to focus on innovations leading to high volume applications of intermediate frequency (IF) and radio frequency (RF) acoustic filters, e.g., TV IF filters, IF filters for cellular phones, and SAW/BAW RF filters for the RF front-end of cellular phones.
Abstract: Today, acoustic filters are the filter technology to meet the requirements with respect to performance dictated by the cellular phone standards and their form factor. Around two billion cellular phones are sold every year, and smart phones are of a very high percentage of approximately two-thirds. Smart phones require a very high number of filter functions ranging from the low double-digit range up to almost triple digit numbers in the near future. In the frequency range up to 1 GHz, surface acoustic wave (SAW) filters are almost exclusively employed, while in the higher frequency range, bulk acoustic wave (BAW) and SAW filters are competing for their shares. Prerequisites for the success of acoustic filters were the availability of high-quality substrates, advanced and highly reproducible fabrication technologies, optimum filter techniques, precise simulation software, and advanced design tools that allow the fast and efficient design according to customer specifications. This paper will try to focus on innovations leading to high volume applications of intermediate frequency (IF) and radio frequency (RF) acoustic filters, e.g., TV IF filters, IF filters for cellular phones, and SAW/BAW RF filters for the RF front-end of cellular phones.

210 citations


Journal ArticleDOI
TL;DR: The system model based on OAM-MDM is mathematically analyzed and it is theoretically concluded that such system architecture can bring a vast reduction in receiver complexity without capacity penalty compared with conventional line-of-sight multiple-in-multiple-out systems under the same physical constraint.
Abstract: Mode division multiplexing (MDM) using orbital angular momentum (OAM) is a recently developed physical layer transmission technique, which has obtained intensive interest among optics, millimeter-wave, and radio frequency due to its capability to enhance communication capacity while retaining an ultra-low receiver complexity. In this paper, the system model based on OAM-MDM is mathematically analyzed and it is theoretically concluded that such system architecture can bring a vast reduction in receiver complexity without capacity penalty compared with conventional line-of-sight multiple-in-multiple-out systems under the same physical constraint. Furthermore, a $4\times 4$ OAM-MDM communication experiment adopting a pair of easily realized Cassegrain reflector antennas capable of multiplexing/demultiplexing four orthogonal OAM modes of $l = {-3}$ , −2, +2, and +3 is carried out at a microwave frequency of 10 GHz. The experimental results show high spectral efficiency as well as low receiver complexity.

208 citations


Patent
05 Sep 2017
TL;DR: In this paper, a communication device includes a dual-band antenna array configured to communicate RF signals in an RF band and to communicate MMW signals in a MMW frequency band with a remote device.
Abstract: In accordance with one or more embodiments, a communication device includes a dual-band antenna array configured to communicate RF signals in an RF band and to communicate MMW signals in a MMW frequency band with a remote device At least one transceiver is configured to generate the RF signals conveying a command to the remote device to transmit probe signals in the MMW frequency band, to receive the probe signals via the dual-band antenna in the MMW frequency band, and is initialized with first antenna beam steering parameters to facilitate a first antenna beam of the dual-band antenna array for the operation in the MMW frequency band A controller is configured to generate the first antenna beam steering parameters based on the probe signals and to generate the control signal to switch the dual-band antenna array to the operation in the MMW frequency band after transmission of the RF signals

207 citations


Journal ArticleDOI
TL;DR: Numerical results show that by incorporating such two techniques, the performance of the secondary system can be improved significantly compared with the case when the ST performs either harvest-then-transmit or ambient backscatter technique.
Abstract: This paper introduces a new solution to improve the performance for secondary systems in radio frequency (RF) powered cognitive radio networks (CRNs) In a conventional RF-powered CRN, the secondary system works based on the harvest-then-transmit protocol That is, the secondary transmitter (ST) harvests energy from primary signals and then uses the harvested energy to transmit data to its secondary receiver (SR) However, with this protocol, the performance of the secondary system is much dependent on the amount of harvested energy as well as the primary channel activity, eg, idle and busy periods Recently, ambient backscatter communication has been introduced, which enables the ST to transmit data to the SR by backscattering ambient signals Therefore, it is potential to be adopted in the RF-powered CRN We investigate the performance of RF-powered CRNs with ambient backscatter communication over two scenarios, ie, overlay and underlay CRNs For each scenario, we formulate and solve the optimization problem to maximize the overall transmission rate of the secondary system Numerical results show that by incorporating such two techniques, the performance of the secondary system can be improved significantly compared with the case when the ST performs either harvest-then-transmit or ambient backscatter technique

203 citations


Patent
19 Oct 2017
TL;DR: In this paper, a communication device includes a dual-band antenna array configured to transmit first radio frequency (RF) signals to a remote device in an RF band and transmit first millimeter wave (MMW) signals in a MMW frequency band.
Abstract: In accordance with one or more embodiments, a communication device includes a dual-band antenna array configured to transmit first radio frequency (RF) signals to a remote device in an RF band and to transmit first millimeter wave (MMW) signals to the remote device in a MMW frequency band, wherein the MMW frequency band is above the RF band A base transceiver station is configured to generate a consolidated steering matrix in accordance with the transmission of the first RF signals to the remote device in the RF band A remote radio head is configured to convert the consolidated steering matrix to a converted steering matrix that facilitates the transmission of the first MMW signals to the remote device in the MMW frequency band, and further configured to generate the first MMW signals in accordance with the converted steering matrix

180 citations


Patent
19 Oct 2017
TL;DR: In this article, a communication device includes a dual-band antenna array configured to transmit first radio frequency (RF) signals to a remote device in an RF band and transmit first millimeter wave (MMW) signals in a MMW frequency band.
Abstract: In accordance with one or more embodiments, a communication device includes a dual-band antenna array configured to transmit first radio frequency (RF) signals to a remote device in an RF band and to transmit first millimeter wave (MMW) signals to the remote device in a MMW frequency band, wherein the MMW frequency band is above the RF band. A base transceiver station is configured to generate a consolidated steering matrix in accordance with the transmission of the first RF signals to the remote device in the RF band. A remote radio head is configured to convert the consolidated steering matrix to a converted steering matrix that facilitates the transmission of the first MMW signals to the remote device in the MMW frequency band via the dual-band antenna array in accordance with an antenna beam pattern having at least one selected null direction, and further configured to generate the first MMW signals in accordance with the converted steering matrix.

178 citations


Journal ArticleDOI
TL;DR: In this article, a dual-port triple-band L-probe microstrip patch rectenna design for ambient RF energy harvesting using the GSM-900, GSM1800, and UMTS-2100 bands is described.
Abstract: A dual-port triple-band L-probe microstrip patch rectenna design for ambient RF energy harvesting using the GSM-900, GSM-1800, and UMTS-2100 bands is described. The compact dual-port L-probe patch antenna is implemented by stacking two single-port patch antennas back to back. Each port can independently harvest RF signal from a half-space with gain greater than 7 dBi, and together with both ports in a dc combining configuration, the antenna can acquire RF energy from nearly all directions. We also provide a design for a high-efficiency triple-band rectifier operating at GSM-900, GSM-1800, and UMTS-2100, which is replicated on each port and concatenated together to allow dc combining and near doubling of the output dc voltage. Measurement results show that our prototyped dual-port triple-band rectenna can receive RF power from nearly all directions with an efficiency of greater than 40% and an output voltage of more than 600 mV when the power density is greater than 500 $\mu \mathrm{W}/\mathrm{m}^{2}$ .

170 citations


Journal ArticleDOI
22 Sep 2017
TL;DR: In this article, a microwave photonic intensity differentiator based on a Kerr optical comb generated by a compact integrated micro-ring resonator (MRR) is proposed and experimentally demonstrated.
Abstract: We propose and experimentally demonstrate a microwave photonic intensity differentiator based on a Kerr optical comb generated by a compact integrated micro-ring resonator (MRR). The on-chip Kerr optical comb, containing a large number of comb lines, serves as a high-performance multi-wavelength source for implementing a transversal filter, which will greatly reduce the cost, size, and complexity of the system. Moreover, owing to the compactness of the integrated MRR, frequency spacings of up to 200-GHz can be achieved, enabling a potential operation bandwidth of over 100 GHz. By programming and shaping individual comb lines according to calculated tap weights, a reconfigurable intensity differentiator with variable differentiation orders can be realized. The operation principle is theoretically analyzed, and experimental demonstrations of the first-, second-, and third-order differentiation functions based on this principle are presented. The radio frequency amplitude and phase responses of multi-order intensity differentiations are characterized, and system demonstrations of real-time differentiations for a Gaussian input signal are also performed. The experimental results show good agreement with theory, confirming the effectiveness of our approach.

Journal ArticleDOI
TL;DR: This paper derives the analytical expressions for exact and asymptotic secrecy outage probability by using the stochastic geometry method and simulations are carried out to verify the proposed analytical models.
Abstract: In this paper, a hybrid visible light communication-radio frequency (RF) system, including a legitimate receiver (R) and an eavesdropper (E) is considered R can harvest energy from the light emitted by light emitting diodes (LEDs), which is used for the information transmission between R and the RF receiver which is close to the LED It is assumed that E tries to eavesdrop the information delivered from R to the RF receiver and R is with finite energy storage Considering the randomness of the locations of R and E, the statistical characteristics of the received signal-to-noise ratio at the RF receiver and E are characterized; then, we derive the analytical expressions for exact and asymptotic secrecy outage probability by using the stochastic geometry method Finally, simulations are carried out to verify our proposed analytical models

Journal ArticleDOI
TL;DR: In this paper, a dual-solar + electromagnetic energy harvesting powered communication system was designed for the 2.4 GHz ISM band, enabling the autonomous operation of a low power consumption power management circuit for a wireless sensor, while featuring a very good "cold start" capability.
Abstract: This paper discusses the design of a novel dual (solar + electromagnetic) energy harvesting powered communication system, which operates at 2.4 GHz ISM band, enabling the autonomous operation of a low power consumption power management circuit for a wireless sensor, while featuring a very good “cold start” capability. The proposed harvester consists of a dual port rectangular slot antenna, a 3-D printed package, a solar cell, an RF-dc converter, a power management unit (PMU), a microcontroller unit, and an RF transceiver. Each designed component was characterized through simulation and measurements. As a result, the antenna exhibited a performance satisfying the design goals in the frequency range of 2.4–2.5 GHz. Similarly, the designed miniaturized RF-dc conversion circuit generated a sufficient voltage and power to support the autonomous operation of the bq25504 PMU for RF input power levels as low as −12.6 and −15.6 dBm at the “cold start” and “hot start” condition, respectively. The experimental testing of the PMU utilizing the proposed hybrid energy harvester confirmed the reduction of the capacitor charging time by 40% and the reduction of the minimum required RF input power level by 50% compared with the one required for the individual RF and solar harvester under the room light irradiation condition of 334 lx.

Journal ArticleDOI
02 Jan 2017
TL;DR: The prospects originating from the application of all-metal 3D printing to the manufacturing of high-performance microwave waveguide devices are reported on.
Abstract: Additive manufacturing technologies are currently envisaged to boost the development of a next generation of microwave and millimeter-wave devices intended for, among others, satellite telecommunications, navigation, imaging, radio-astronomy, and cosmology. Due to their excellent electromagnetic and mechanical properties, all-metal waveguide components are key building blocks of several radio frequency (RF) systems used in these application domains. This article reports on the prospects originating from the application of all-metal 3D printing to the manufacturing of high-performance microwave waveguide devices. The technology investigated is the selective laser melting process, where a laser beam is used to fuse metal powder particles spread over a building platform. The complete parts are built by overlapping several constant-thickness layers. An overview on process parameters, material properties, and design rules is reported for this technology. The electromagnetic properties of test samples built in Al and Ti alloys have been experimentally characterized. A robust design of Ku/K-band filters aimed at satellite telecommunications has been implemented in several prototypes manufactured in Al. The corresponding measured performance confirm the applicability of the laser selective melting process to the intended applications.

Journal ArticleDOI
TL;DR: A model for time-averaged realistic maximum power levels for the assessment of radio frequency (RF) electromagnetic field (EMF) exposure for the fifth generation (5G) radio base stations (RBS) employing massive MIMO is presented.
Abstract: In this paper, a model for time-averaged realistic maximum power levels for the assessment of radio frequency (RF) electromagnetic field (EMF) exposure for the fifth generation (5G) radio base stations (RBS) employing massive MIMO is presented. The model is based on a statistical approach and developed to provide a realistic conservative RF exposure assessment for a significant proportion of all possible downlink exposure scenarios (95th percentile) in-line with requirements in a recently developed International Electrotechnical Commission standard for RF EMF exposure assessments of RBS. Factors, such as RBS utilization, time-division duplex, scheduling time, and spatial distribution of users within a cell are considered. The model is presented in terms of a closed-form equation. For an example scenario corresponding to an expected 5G RBS product, the largest realistic maximum power level was found to be less than 15% of the corresponding theoretical maximum. For far-field exposure scenarios, this corresponds to a reduction in RF EMF limit compliance distance with a factor of about 2.6. Results are given for antenna arrays of different sizes and for scenarios with beamforming in both azimuth and elevation.

Journal ArticleDOI
TL;DR: In this paper, a radio-frequency (RF) negative ion source based on the IPP Garching prototype source design was demonstrated in hydrogen and deuterium up to one hour with ITER relevant parameters.
Abstract: The ITER neutral beam system will be equipped with radio-frequency (RF) negative ion sources, based on the IPP Garching prototype source design. Up to 100 kW at 1 MHz is coupled to the RF driver, out of which the plasma expands into the main source chamber. Compared to arc driven sources, RF sources are maintenance free and without evaporation of tungsten. The modularity of the driver concept permits to supply large source volumes. The prototype source (one driver) demonstrated operation in hydrogen and deuterium up to one hour with ITER relevant parameters. The ELISE test facility is operating with a source of half the ITER size (four drivers) in order to validate the modular source concept and to gain early operational experience at ITER relevant dimensions. A large variety of diagnostics allows improving the understanding of the relevant physics and its link to the source performance. Most of the negative ions are produced on a caesiated surface by conversion of hydrogen atoms. Cs conditioning and distribution have been optimized in order to achieve high ion currents which are stable in time. A magnetic filter field is needed to reduce the electron temperature and co-extracted electron current. The influence of different field topologies and strengths on the source performance, plasma and beam properties is being investigated. The results achieved in short pulse operation are close to or even exceed the ITER requirements with respect to the extracted ion currents. However, the extracted negative ion current for long pulse operation (up to 1 h) is limited by the increase of the co-extracted electron current, especially in deuterium operation.

Journal ArticleDOI
TL;DR: In this article, a compact dual-comb source based on a monolithic optical crystalline MgF2 multi-resonator stack is presented. But the system is not suitable for coherent LIDAR applications.
Abstract: We present a novel compact dual-comb source based on a monolithic optical crystalline MgF2 multi-resonator stack. The coherent soliton combs generated in the two microresonators of the stack with the repetition rate of 12.1 GHz and difference of 1.62 MHz provided after heterodyning a 300 MHz wide radio frequency comb. An analogous system can be used for dual-comb spectroscopy, coherent LIDAR applications, and massively parallel optical communications.

Journal ArticleDOI
TL;DR: Preliminary results, conducted during field trial measurements, confirm the effectiveness of the proposed approach in terms of localization accuracy, and sensitivity/specificity to correctly detect a fall event from preimpact postures.
Abstract: Fall detection and localization of human operators inside a workspace are major issues in ensuring a safe working environment. Recent research has shown that the perturbations of the radio-frequency (RF) signals commonly adopted for wireless communications can also be used as sensing tools for device-free human motion detection. Device-free RF-based human sensing applications range from tag-less body localization to detection and monitoring of human well-being (e-Health). In this paper, we propose a real-time system for human body motion sensing with special focus on joint body localization and fall detection. The proposed system continuously monitors and processes the RF signals emitted by industry-compliant radio devices operating in the 2.4 GHz ISM band and supporting machine-to-machine communication functions. Human-induced diffraction and multipath phenomena that affect RF signal propagation are leveraged for body localization while for fall detection a hidden Markov model is applied to discern different postures of the operator and to detect safety-relevant events by tracking the received signal strength indicator footprints. Fall detection performances are corroborated by extensive experimental measurements in different settings. In addition, we propose also a sensor fusion tool that is able to integrate the device-free RF-based sensing system within an industrial image sensors framework. Preliminary results, conducted during field trial measurements, confirm the effectiveness of the proposed approach in terms of localization accuracy, and sensitivity/specificity to correctly detect a fall event from preimpact postures.

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate external broadening-free self-referencing of a soliton Kerr frequency comb using an optical spectrum spanning two-thirds of an octave.
Abstract: Self-referencing turns pulsed laser systems into self-referenced frequency combs. Such frequency combs allow counting of optical frequencies and have a wide range of applications. The required optical bandwidth to implement self-referencing is typically obtained via nonlinear broadening in optical fibers. Recent advances in the field of Kerr frequency combs have provided a path toward the development of compact frequency comb sources that provide broadband frequency combs, exhibit microwave repetition rates and are compatible with on-chip photonic integration. These devices have the potential to significantly expand the use of frequency combs. Yet to date, self-referencing of such Kerr frequency combs has only been attained by applying conventional, fiber-based broadening techniques. Here we demonstrate external broadening-free self-referencing of a Kerr frequency comb. An optical spectrum spanning two-thirds of an octave is directly synthesized from a continuous wave laser-driven silicon nitride microresonator using temporal dissipative Kerr soliton formation and soliton Cherenkov radiation. Using this coherent bandwidth and two continuous wave transfer lasers in a 2f-3f self-referencing scheme, we are able to detect the offset frequency of the soliton Kerr frequency comb. By stabilizing the repetition rate to a radio frequency reference, the self-referenced frequency comb is used to count and track the continuous wave pump laser's frequency. This work demonstrates the principal ability of soliton Kerr frequency combs to provide microwave-to-optical clockworks on a chip.

Journal ArticleDOI
TL;DR: The influence of strain on the RF performance of flexible GaN high-electron-mobility transistor (HEMT) devices is evaluated, demonstrating cutoff frequencies and maximum oscillation frequencies greater than 42 and 74 GHz, respectively, at up to 0.43% strain.
Abstract: Flexible gallium nitride (GaN) thin films can enable future strainable and conformal devices for transmission of radio-frequency (RF) signals over large distances for more efficient wireless communication. For the first time, strainable high-frequency RF GaN devices are demonstrated, whose exceptional performance is enabled by epitaxial growth on 2D boron nitride for chemical-free transfer to a soft, flexible substrate. The AlGaN/GaN heterostructures transferred to flexible substrates are uniaxially strained up to 0.85% and reveal near state-of-the-art values for electrical performance, with electron mobility exceeding 2000 cm2 V-1 s-1 and sheet carrier density above 1.07 × 1013 cm-2 . The influence of strain on the RF performance of flexible GaN high-electron-mobility transistor (HEMT) devices is evaluated, demonstrating cutoff frequencies and maximum oscillation frequencies greater than 42 and 74 GHz, respectively, at up to 0.43% strain, representing a significant advancement toward conformal, highly integrated electronic materials for RF applications.

Journal ArticleDOI
TL;DR: The role and effects of static and pulsed radio frequencies, millimetre waves, and terahertz radiation are reviewed to affect the activity in cell membranes, non-selective channels, transmembrane potentials and even the cell cycle.
Abstract: Since regular radio broadcasts started in the 1920s, the exposure to human-made electromagnetic fields has steadily increased. These days we are not only exposed to radio waves but also other frequencies from a variety of sources, mainly from communication and security devices. Considering that nearly all biological systems interact with electromagnetic fields, understanding the affects is essential for safety and technological progress. This paper systematically reviews the role and effects of static and pulsed radio frequencies (10 0 –10 9 Hz), millimetre waves (MMWs) or gigahertz (10 9 –10 11 Hz), and terahertz (10 11 –10 13 Hz) on various biomolecules, cells and tissues. Electromagnetic fields have been shown to affect the activity in cell membranes (sodium versus potassium ion conductivities) and non-selective channels, transmembrane potentials and even the cell cycle. Particular attention is given to millimetre and terahertz radiation due to their increasing utilization and, hence, increasing human exposure. MMWs are known to alter active transport across cell membranes, and it has been reported that terahertz radiation may interfere with DNA and cause genomic instabilities. These and other phenomena are discussed along with the discrepancies and controversies from published studies.

Journal ArticleDOI
TL;DR: This work demonstrates the synergy of direct ink writing and RF electronics for wireless applications by combining discrete transistors to fabricate GHz self-sustained oscillators and synchronized oscillator arrays that provide RF references, and wireless transmitters clocked by the oscillators.
Abstract: Radio-frequency (RF) electronics, which combine passive electromagnetic devices and active transistors to generate and process gigahertz (GHz) signals, provide a critical basis of ever-pervasive wireless networks. While transistors are best realized by top-down fabrication, relatively larger electromagnetic passives are within the reach of printing techniques. Here, direct writing of viscoelastic silver-nanoparticle inks is used to produce a broad array of RF passives operating up to 45 GHz. These include lumped devices such as inductors and capacitors, and wave-based devices such as transmission lines, their resonant networks, and antennas. Moreover, to demonstrate the utility of these printed RF passive structures in active RF electronic circuits, they are combined with discrete transistors to fabricate GHz self-sustained oscillators and synchronized oscillator arrays that provide RF references, and wireless transmitters clocked by the oscillators. This work demonstrates the synergy of direct ink writing and RF electronics for wireless applications.

Journal ArticleDOI
TL;DR: In this article, a CapsuleCASPER objective is to improve the capability to characterize the propagation of radio frequency (RF) signals through the marine atmosphere with coordinated efforts in data collection, data analyses, and modeling of the air-sea interaction processes, refractive environment, and RF propagation.
Abstract: CapsuleCASPER objective is to improve our capability to characterize the propagation of radio frequency (RF) signals through the marine atmosphere with coordinated efforts in data collection, data analyses, and modeling of the air-sea interaction processes, refractive environment, and RF propagation.

Journal ArticleDOI
TL;DR: In this article, a beamforming matrix and a dc power management network (PMN) are introduced to the hybrid power combining array, and the normalized dc output power of the proposed hybrid combining array is compared to the conventional power combining methods with regard to the incident wave angle.
Abstract: This paper discusses a new design approach that uses hybrid power combining rectenna array in radio frequency (RF) energy transfer systems to receive more energy in a wide incident angle range. A beam-forming matrix and a dc power management network (PMN) are introduced to the hybrid power combining. The normalized dc output power of the proposed hybrid power combining array is compared to the conventional power combining methods with regard to the incident wave angle, and the average received dc power is also calculated and compared. To experimentally verify the proposed hybrid combining array performance, four suspended patch antennas are attached to RF energy receiving architecture. A $4 \times 4$ Butler matrix and quadrature hybrids are used for the beam-forming matrix in a hybrid power combining rectenna array. A reconfigurable voltage doubler rectifier with a dc PMN is used to convert RF energy to dc energy and delivers proper voltage to the load. The measured results of each component are presented. Moreover, an experimental verification using fabricated components for RF energy transfer is presented and the measured received dc output power of conventional and proposed structures is presented and compared.

Journal ArticleDOI
TL;DR: Simulations and theoretical results provide insight on the cases, where a hybrid transceiver is the most energy efficient solution or not and for both single- and multi-carrier systems under the orthogonal frequency division multiplexing modulation.
Abstract: Hybrid analog-digital transceivers are employed with the view to reduce the hardware complexity and the energy consumption in millimeter wave/large antenna array systems by reducing the number of their radio frequency (RF) chains However, the analog processing network requires power for its operation and it further introduces power losses, dependent on the number of the transceiver antennas and RF chains that have to be compensated Thus, the reduction in the power consumption is usually much less than it is expected and given that the hybrid solutions present in general inferior spectral efficiency than a fully digital one, it is possible for the former to be less energy efficient than the latter in several cases Existing approaches propose hybrid solutions that maximize the spectral efficiency of the system without providing any insight on their energy requirements/efficiency To that end, in this paper, a novel algorithmic framework is developed based on which energy efficient hybrid transceiver designs are derived and their performance is examined with respect to the number of RF chains and antennas Solutions are proposed for fully and partially connected hybrid architectures and for both single- and multi-carrier systems under the orthogonal frequency division multiplexing modulation Simulations and theoretical results provide insight on the cases, where a hybrid transceiver is the most energy efficient solution or not

Journal ArticleDOI
Laurens Breyne1, Guy Torfs1, Xin Yin1, Piet Demeester1, Johan Bauwelinck1 
TL;DR: In this paper, a comparison between ARoF and sigma delta modulated signal over fiber (SDoF) is presented, which quantifies the improvement in linearity and error vector magnitude (EVM) of SDoF over AROF.
Abstract: With the continuously increasing demand of cost effective, broadband wireless access, radio-over-fiber (RoF) starts to gain more and more momentum. Various techniques already exist, using analog (ARoF) or digitized (DRoF) radio signals over fiber; each with their own advantages and disadvantages. By transmitting a sigma delta modulated signal over fiber (SDoF), a similar immunity to impairments as DRoF can be obtained while maintaining the low complexity of ARoF. This letter describes a detailed experimental comparison between ARoF and SDoF that quantifies the improvement in linearity and error vector magnitude (EVM) of SDoF over ARoF. The experiments were carried out using a 16-QAM constellation with a baudrate from 20 to 125 MBd modulated on a central carrier frequency of 1 GHz. The sigma delta modulator runs at 8 or 13.5 Gbps. A high-speed vertical-cavity surface-emitting laser (VCSEL) operating at 850 nm is used to transmit the signal over 200-m multimode fiber. The receiver amplifies the electrical signals and subsequently filters to recover the original RF signal. Compared with ARoF, improvements exceeding 40 dB were measured on the third order intermodulation products when SDoF was employed, the EVM improves between 2.4 and 7.1 dB.

Journal ArticleDOI
TL;DR: A germanium-tin (Ge0.9Sn0.1) multiple-quantum-well p-i-n photodiode on silicon (Si) substrate for 2 μm-wavelength light detection is demonstrated and a 3 dB bandwidth of around 1.2 GHz is achieved in Ge1-xSnx photodetectors operating at 2μm.
Abstract: We report the demonstration of a germanium-tin (Ge0.9Sn0.1) multiple-quantum-well p-i-n photodiode on silicon (Si) substrate for 2 μm-wavelength light detection. Characterization of the photodetector in both direct current (DC) and radio frequency (RF) regimes was performed. At the bias voltage of -1 V, a dark current density of 0.031 A/cm2 is realized at room-temperature, which is among the lowest reported values for Ge1-xSnx-on-Si p-i-n photodiodes. In addition, for the first time, a 3 dB bandwidth (f3dB) of around 1.2 GHz is achieved in Ge1-xSnx photodetectors operating at 2 μm. It is anticipated that further device optimization would extend the f3dB to above 10 GHz.

Journal ArticleDOI
TL;DR: Design examples of novel ultra-wideband energy harvesters are demonstrated with octave and decade bandwidths in the UHF and low microwave spectrum and the design challenges in terms of impedance matching based on the Bode-Fano theoretical limit, losses and miniaturization are highlighted.
Abstract: Ambient RF energy harvesting is a potential energy source for low-power and battery-less wireless sensors, enabling a range of applications from monitoring to security as part of the Internet-of-Things (IoT) scenario. One of the main challenges of ambient RF energy harvesting is the requirement of operation over a multitude of frequency bands of low ambient power densities resulting in a very wide aggregate operating bandwidth. In this paper, design examples of novel ultra-wideband energy harvesters are demonstrated with octave and decade bandwidths in the UHF and low microwave spectrum. The RF-dc conversion efficiency is maximized by tailoring the dimensions of a nonuniform transmission line used to provide broadband impedance matching. The design challenges in terms of impedance matching based on the Bode-Fano theoretical limit, losses and miniaturization are highlighted. Two prototypes are presented and their performance is evaluated. The octave band rectifier showed a measured RF-dc conversion efficiency of more than 60% over a frequency band of 470 to 860 MHz at 10-dBm input power. The decade band rectifier fabricated on Kapton substrate using inkjet printing featured a higher than 33% efficiency over a frequency band from 250 MHz to 3 GHz at 10-dBm input power.

Journal ArticleDOI
TL;DR: In this paper, the authors used frequency modulated spectroscopy with active control of residual amplitude modulation to improve the signal to noise ratio of the optical readout of Rydberg atom-based radio frequency electrometry.
Abstract: Rydberg atom-based electrometry enables traceable electric field measurements with high sensitivity over a large frequency range, from gigahertz to terahertz. Such measurements are particularly useful for the calibration of radio frequency and terahertz devices, as well as other applications like near field imaging of electric fields. We utilize frequency modulated spectroscopy with active control of residual amplitude modulation to improve the signal to noise ratio of the optical readout of Rydberg atom-based radio frequency electrometry. Matched filtering of the signal is also implemented. Although we have reached similarly, high sensitivity with other read-out methods, frequency modulated spectroscopy is advantageous because it is well-suited for building a compact, portable sensor. In the current experiment, ∼3 µV cm-1 Hz-1/2 sensitivity is achieved and is found to be photon shot noise limited.

Journal ArticleDOI
TL;DR: A novel wireless tag and RX system that utilizes broadcast frequency modulated (FM) signals for backscatter communication and a theoretical analysis of the error rate performance is provided and compared to bit-error-rate measurements on a fixed transmitter-tag-RX laboratory setup with good agreement.
Abstract: Nowadays, the explosive growth of Internet-of-Things-related applications has required the design of low-cost and low-power wireless sensors. Although backscatter radio communication is a mature technology used in radio frequency (RF) identification applications, ambient backscattering is a novel approach taking advantage of ambient signals to simplify wireless system topologies to just a sensor node and a receiver (RX) circuit eliminating the need for a dedicated carrier source. This paper introduces a novel wireless tag and RX system that utilizes broadcast frequency modulated (FM) signals for backscatter communication. The proposed proof-of-concept tag comprises of an ultralow-power microcontroller (MCU) and a RF front-end for wireless communication. The MCU can accumulate data from multiple sensors through an analog-to-digital converter, while it transmits the information back to the RX through the front-end by means of backscattering. The front-end uses ON–OFF keying modulation and FM0 encoding on ambient FM station signals. The RX consists of a commercial low-cost software-defined radio which downconverts the received signal to baseband and decodes it using a suitable signal processing algorithm. A theoretical analysis of the error rate performance of the system is provided and compared to bit-error-rate measurements on a fixed transmitter-tag-RX laboratory setup with good agreement. The prototype tag was also tested in a real-time indoor laboratory deployment. Operation over a 5-m tag-reader distance was demonstrated by backscattering information at 2.5 kb/s featuring an energy per packet of $36.9~\mu \text{J}$ .