Radio Frequency Bandwidth Research Articles

Hyperpolarized 13C Spectroscopy with Simple Slice-and-Frequency-Selective Excitation.

Hyperpolarized 13C nuclear magnetic resonance spectroscopy can characterize in vivo tissue metabolism, including preclinical models of cancer and inflammatory disease. Broad bandwidth radiofrequency excitation is often paired with free induction decay readout for spectral separation, but quantification of low-signal downstream metabolites using this method can be impeded by spectral peak overlap or when frequency separation of the detected peaks exceeds the excitation bandwidth. In this work, alternating frequency narrow bandwidth (250 Hz) slice-selective excitation was used for 13C spectroscopy at 7 T in a subcutaneous xenograft rat model of human pancreatic cancer (PSN1) to improve quantification while measuring the dynamics of injected hyperpolarized [1-13C]lactate and its metabolite [1-13C]pyruvate. This method does not require sophisticated pulse sequences or specialized radiofrequency and gradient pulses, but rather uses nominally spatially offset slices to produce alternating frequency excitation with simpler slice-selective radiofrequency pulses. Additionally, point-resolved spectroscopy was used to calibrate the 13C frequency from the thermal proton signal in the target region. This excitation scheme isolates the small [1-13C]pyruvate peak from the similar-magnitude tail of the much larger injected [1-13C]lactate peak, facilitates quantification of the [1-13C]pyruvate signal, simplifies data processing, and could be employed for other substrates and preclinical models.

Photonic RF and Microwave Fractional Differentiation, Integration, and Hilbert Transforms With Kerr Optical Micro-Combs

Integrated Kerr micro-combs are a powerful source of multiple wavelength channels for photonic radio frequency (RF) and microwave signal processing, particularly for transversal filter systems. They offer significant advantages featuring a compact device footprint, high versatility, large numbers of wavelengths, and wide Nyquist bands. We present our recent progress on photonic RF and microwave high bandwidth temporal signal processing based on Kerr micro-combs with comb spacings from 49GHz to 200GHz. We focus on integral and fractional Hilbert transforms, differentiators as well as integrators. The future potential of optical micro-combs for RF photonic applications in terms of functionality and ability to realize integrated solutions is also discussed.

Performance Analysis of Long Short-Term Memory-Based Markovian Spectrum Prediction

Dynamic Spectrum Access (DSA) solutions equipped with spectrum prediction can enable proactive spectrum management and tackle the increasing demand for radio frequency (RF) bandwidth. Among various prediction techniques, Long Short-Term Memory (LSTM) is a deep learning model that has demonstrated high performance in forecasting spectrum characteristics. Although well-performing, the theoretical characterization of LSTM prediction performance has not been well developed in the literature. Therefore, in this article, we examine an LSTM based temporal spectrum prediction model and characterize its prediction performance through theoretical analysis. To this end, we analyze the LSTM prediction outputs over simulated Markov-model-based spectrum data and spectrum measurements data. Our results suggest that the predicted scores of the LSTM based system model can be described using mixtures of truncated Gaussian distributions. We also estimate the performance metrics using the mixture model and compare the results with the observed prediction performance over simulated and measured datasets.

An Optimal Route Discovery using Biogeography based Optimization for Vehicular Ad Hoc Networks

Vehicular ad hoc network (VANET) is a subdivision of the mobile ad hoc networks which uses the moving vehicles as mobile nodes to form the mobile network. In conventional vehicular communications, the restricted radio frequency bandwidth affects the network performances. Therefore, Visible Light Communication (VLC) is integrated with the growing vehicular ad hoc network to obtain high data rate and less energy consumption during the communication. In this paper, vehicular communication is integrated with visible light communication to avoid the issues caused by the restricted radio frequency bandwidth. Moreover, the Routing using Biogeography Based Optimization (RBBO) is proposed to develop an optimal route between the source vehicles to the destination. This research performs two different communications such as vehicle to vehicle and vehicle to the infrastructure. The performance of the RBBOVLC-VANET method is analyzed by means of throughput, packet delivery ratio, delay and routing overhead as well as these performances are compared with the existing method namely ant colony optimization based routing protocol. The throughput of the routing using the biogeography based optimization method is 589.763 kbps for 500 nodes which is high when compared to the existing method.

LiFi-based smart systems for industrial monitoring

Light fidelity (Li-Fi) is an unfolding technology which can be used to transfer data through light. It is a complete transformation to the world of wireless data transfer. Harald Haas from the University of Edinburgh, UK termed and introduced light fidelity to world through the global talk show in which he demonstrated of a Li-Fi prototype at the TED Global Conference in Edinburgh on 12 July 2011. Challenging the pre-existing data transfer model namely the wireless fidelity (Wi-Fi) on various parameters such as speed, safety, reliability eco-friendliness and efficiency. The light emitting diode in a Li-Fi system is the source of data transfer utilising visible light as medium of communication. This can provide greater download capacity in comparison to the existing wired or wireless networks due to higher bandwidth of light. With such high potential every electronic day to day use commodity that has role of light over it can be thought of to be used as an internet accesses point. Since it cannot penetrate through walls, they have short range but are highly secure in the confinement of the surrounding in comparison to Wi-Fi and overcome the radio frequency bandwidth availability issues in the near future.

A WPT/NFC-Based Sensing Approach for Beverage Freshness Detection Using Supervised Machine Learning

The massive deployment of wireless sensors is a fundamental piece in the growing internet of things (IoT) industry. Therefore, it is imperative to use already existing hardware to realize new sensing functions with very few or no hardware added. As wireless power transfer (WPT) and near field communication (NFC) become standard features in smart phones, this article investigates beverage freshness sensing based on the WPT/NFC technology compatible with smart phones. A circuit model for the beverage-coil interaction was developed and the performance of features from different nature (e.g., magnitude, amplitude, phase) for classification was analyzed and tested. Accuracies up to 96.7% were achieved using supervised machine learning for milk freshness classification, when 5 different types of milk were used and up to 100% when just 2% fat milk was used for classification. Additionally, the radio frequency bandwidth needed for classification was reduced to 10 MHz using singular value decomposition (SVD) and boxplot analysis without affecting the classification accuracy for two different methods of feature extraction.

Demonstration of a wideband submillimeter-wave low-noise receiver with 4–21 GHz IF output digitized by a high-speed 32 GSps ADC

We report on a 275–500 GHz heterodyne receiver system in combination with a wideband intermediate-frequency (IF) backend to realize 17 GHz instantaneous bandwidth. The receiver frontend implements a heterodyne mixer module that integrates a superconductor-insulator-superconductor (SIS) mixer chip and a cryogenic low-noise preamplifier. The SIS mixer is developed based on high-current-density junction technologies to achieve a wideband radio frequency (RF) and IF bandwidth. The IF backend comprises an IF chain divided into two channels for 4.0–11.5 GHz and 11.3–21.0 GHz and an analog-to-digital converter (ADC) module that is capable of high-speed sampling at 32 Giga samples per second with 12.5 GHz bandwidth per channel and an effective number of bits of 6.5. The IF backend allows us to simultaneously cover the full 4–21 GHz IF range of the receiver frontend. The measured noise temperature of the receiver frontend was below three times the quantum noise (hf/kB) over the entire RF band. A dual-polarization sideband-separating receiver based on this technique could provide up to 64 GHz of instantaneous bandwidth, which demonstrates the possibility of future wideband radio astronomical observations with advanced submillimeter-wave heterodyne receivers.

A novel switch beam design method with extending switching radio-frequency bandwidth

In this paper, a new switching beam design method is proposed. By using a beam design method to design a beam, an ultra-wideband radio-frequency micro electromechanical system (RF MEMS) switch with a frequency band of 1–110 GHz is designed. With this design method, in addition to using the equivalent capacitance between the switch beam and the signal line, you can also make full use of the fringe field effect between them. Therefore, it can greatly increase the capacitance ratio between the two states of the switch up and down. Finally, it achieves the purpose of extending the working bandwidth of the switch. In the up state, the return loss is less than 20 dB and the bandwidth is greater than 100 GHz. The insertion loss is less than 0.2 dB. The bandwidth is greater than 100 GHz. In the down state, the isolation is less than 10 dB and the bandwidth is greater than 90 GHz.

Sub-nanosecond-speed frequency-reconfigurable photonic radio frequency switch using a silicon modulator

Radio frequency (RF) switches are essential for implementing routing of RF signals. However, the increasing demand for RF signal frequency and bandwidth is posing a challenge of switching speed to the conventional solutions, i.e., the capability of operating at a sub-nanosecond speed or faster. In addition, signal frequency reconfigurability is also a desirable feature to facilitate new innovations of flexible system functions. Utilizing microwave photonics as an alternative path, we present here a photonic implementation of an RF switch providing not only the capability of switching at a sub-nanosecond speed but also options of frequency doubling of the input RF signals, allowing for flexible output waveforms. The core device is a traveling-wave silicon modulator with a device size of 0.2 mm × 1.8 mm and a modulation bandwidth of 10 GHz. Using microwave frequencies, i.e., 15 GHz and 20 GHz, as two simultaneous RF input signals, we experimentally demonstrated their amplitude and frequency switching as well as that of the doubled frequencies, i.e., 30 GHz and 40 GHz, at a switching frequency of 5 GHz. The results of this work point to a solution for creating high-speed RF switches with high compactness and flexibility.

Broadly tunable and low power penalty radio frequency phase shifter using a coupled silicon microcavity.

We present a continuously tunable silicon photonics assisted radio frequency (RF) phase shifter using a coupled microring resonator. Using the coupled cavity, we demonstrate a sub-1 dB power penalty for a RF bandwidth of 34.5 GHz (9-43.5 GHz) and a phase shift of π over the reported frequency range. Rigorous optimization of the cavity design using the coupled-mode theory is carried out to realize ultranarrow resonance peaks with a low-extinction ratio and large phase shift. Thermal tuning of the cavity is used to tune the phase while all-optical tuning is exploited to achieve broadband operation. We present a detailed simulation and experimental study of the proposed configuration. The proposed device configuration exhibits a configurable resonance linewidth and extinction ratio that allows for a broad bandwidth and an extremely low power penalty microwave phase shifter. We believe the demonstration would allow better integration of the on-chip functional elements of integrated microwave photonics.

Wireless Network On-Chips History-Based Traffic Prediction for Token Flow Control and Allocation

Wireless network-on-chip (WiNoC) uses a wireless backbone on top of the traditional wired-based NoC which demonstrated high scalability. WiNoC introduces long-range single-hop link connecting distanced core and high bandwidth radio frequency interconnects that reduces multi-hop communication in conventional wired-based NoC. However, to ensure full benefits of WiNoC technology, there is a need for fair and efficient Medium Access Control (MAC) mechanism to enhance communication in the wireless Network-on-Chip. To adapt to the varying traffic demands from the applications running on a multicore environment, MAC mechanisms should dynamically adjust the transmission slots of the wireless interfaces (WIs), to ensure efficient utilization of the wireless medium in a WiNoC. This work presents a prediction model that improves MAC mechanism to predict the traffic demand of the WIs and respond accordingly by adjusting transmission slots of the WIs. This research aims to reduce token waiting time and inefficient decision making for radio hub-to-hub communication and congestion-aware routing in WiNoC to enhance end to end latency. Through system level simulation, we will show that the dynamic MAC using an History-based prediction mechanism can significantly improve the performance of a WiNoC in terms of latency and network throughput compared to the state-of-the-art dynamic MAC mechanisms.

Realization of Multitone Continuous Wave Lidar

We have developed a multitone modulated continuous wave (MTCW) Lidar system made of a CW laser with multiple fixed RF tones for a high precision range finding and velocimetry. In this paper, the MTCW Lidar system has been studied analytically and numerically. A proof-of-concept experiment by employing 1550-nm light source and multiple radio-frequency (RF) tone modulations ranging from 50 MHz to 6 GHz has been performed to demonstrate proof of principle for range finding with <1-cm range resolution. We also provide sine fitting algorithms on the measured RF tones to extract the range information in a single shot RF measurement and demonstrate the ways to improve the resolution beyond the actual RF bandwidth.

Underwater optical wireless communications, networking, and localization: A survey

Underwater wireless communications can be carried out through acoustic, radio frequency (RF), and optical waves. Compared to its bandwidth limited acoustic and RF counterparts, underwater optical wireless communications (UOWCs) can support higher data rates at low latency levels. However, the severe aquatic channel conditions (e.g., absorption, scattering, turbulence, etc.) pose great challenges for UOWCs and significantly reduce the attainable communication ranges, which necessitates efficient networking and localization solutions. Therefore, we provide a comprehensive survey on the challenges, advances, and prospects of underwater optical wireless networks (UOWNs) from a layer by layer perspective which includes: (1) Physical layer issues including propagation characteristics, channel modeling, and modulation techniques (2) Data link layer problems covering link configurations, link budgets, performance metrics, and multiple access schemes; (3) Network layer topics containing relaying techniques and potential routing algorithms; (4) Transport layer subjects such as connectivity, reliability, flow and congestion control; (5) Application layer goals, and (6) Localization and its impacts on UOWN layers. Finally, we outline the open research challenges and point out the prospective directions for underwater optical wireless communications, networking, and localization studies.

Single feed circularly polarized crescent-cut and extended corner square microstrip antennas for wireless biotelemetry

&lt;p&gt;In this paper, the development of two novel circularly polarized microstrip antennas is thoroughly explained. These antennas are fed by coaxial feeding technique. One of the primary objectives of the proposed work is to tune the antennas to work in ISM band. This frequency band refers to the internationally recognized radio frequency bandwidth which is to be used explicitly for Industrial, Scientific, and Medical applications. Therefore, these antennas would be suitable to use in the field of wireless biotelemetry. Two new antenna design techniques have been introduced to produce circular polarization, and details of these schemes are described. The proposed microstrip antennas are designed and simulated on Advanced Design System (ADS) software. The return loss of the proposed crescent-cut antenna is -19.3 dB at the operating frequency. The extended corner antenna has the return loss of -29.3 dB at the tuned frequency. The simulation results are also presented and discussed.&lt;/p&gt;

A 16-QAM 100-Gb/s 1-M Wireless Link With an EVM of 17% at 230 GHz in an SiGe Technology

This letter presents a 1-m wireless link established with a set of fundamentally operated Tx/Rx direct-conversion in-phase and quadrature (IQ) radio frequency (RF) front-end modules in a 0.13- $\mu \text{m}$ SiGe HBT technology featuring full chip-on-board packaging. Using a 16-quadrature amplitude modulation, data rates from 20 to 100 Gb/s with an error vector magnitude from 7% to 17% were achieved at a 1-m distance. Thanks to the new mixer-first Rx, the maximum data rate improved from 90 to 100 Gb/s compared with our previous work using the amplifier-first Rx. The peak performance was reached at 230 GHz. The Tx operates at a 3.5 dB backoff from $\text{P}_{\textbf {sat}}$ showing a 3-dB RF bandwidth (BW) of 28 GHz, a $\text{P}_{\textbf {out}}$ of 5 dBm, and an IQ imbalance below 0.7 dB. The Rx features a peak conversion gain of 8 dB, a single-sideband noise figure of 14 dB, a 3-dB RF BW of 26 GHz, and an IQ imbalance below 1 dB. This letter also provides an analysis of the RF front-end imperfections related to the large link BW.

Nash Bargaining Approach for Fair and Efficient LTE–WiFi Aggregation

As the demand for mobile traffic is growing, radio frequency bandwidths often become insufficient for guaranteeing specific performance. Utilizing unlicensed 5 GHz broadband bandwidths, the LWA system enables the synergistic use of LTE and WiFi systems based on link aggregation techniques, without critical deterioration of service quality. This provides considerable benefits to the mobile operators when they successfully operate two networks and maintain an optimal balance in managing network resources. This study addresses balancing and fairness for newly emerging LWA systems. In particular, we develop a two-stage LWA access framework based on the Nash bargaining game. The framework further improves fairness and efficiency in the LTE–WiFi resource utilization by incorporating user segmentations on the basis of user characteristics, such as service contract and usage patterns. Extensive experiments using a network simulator with an NS–3 unlicensed band produce good performance in terms of fairness and efficiency. The proposed scheme demonstrates better outcomes compared to the existing methods while concurrently using radio resources in the LWA system in a fair manner. Moreover, our approach presents a simple and fast decision-making process and requires simple user profiles—contract status and traffic generation history. Therefore, the proposed scheme is far lighter and more flexible than traditional approaches that require extensive information exchanges between heterogeneous networks.

Performance Evaluation of Centralized Reconfigurable Transmitting Power Scheme in Wireless Network-on-chip

Network-on-chip (NoC) is an on-chip communication network that allows parallel communication among all cores to improve inter-core performance. Wireless NoC (WiNoC) introduces long-range and high bandwidth radio frequency (RF) interconnects that can possibly reduce the multi-hop communication of the planar metal interconnects in conventional NoC platforms. In WiNoC, RF transceivers account for a significant power consumption, particularly its transmitter, out of its total communication energy. This paper evaluates the energy and latency performance of a closed loop power management mechanism which enables transmitting power reconfiguration in WiNoC based on number of erroneous received packets. The scheme achieves significant energy savings with limited performance degradation and insignificant impact on throughput.

Optical Multilevel Pulse Width Modulation for Analog Mobile Fronthaul

The evolution of radio access networks is towards a centralized architecture (C-RAN), with massive antenna deployments and large radio-frequency bandwidths. In the next future, traditional optical transport technologies based on digital radio over fiber will no longer be able to support the mobile fronthaul traffic connecting antennas hosted at remote radio units and centralized baseband units. Analog radio over fiber can be selected to support the mobile fronthaul (MFH) network and, in particular, pulse width modulation (PWM) is a viable alternative for analog signal transport. In order to increase the MFH spectral efficiency, we propose to exploit multilevel PWM (M-PWM) in a wavelength division multiplexing-passive optical network (WDM-PON) network, comparing its performance with a conventional 2-level PWM solution. Experimental results show successful transmission over 7.5-km standard single mode fiber (SSMF) of up to 16 aggregated LTE-like 20-MHz signals with 64-QAM on each subcarrier, while up to eight aggregated LTE-like 20-MHz signals with 256-QAM could be supported. M-PWM thus allows either using higher order modulation formats or aggregating a higher number of LTE channels.

Single-Shot Readout of Hole Spins in Ge.

The strong atomistic spin–orbit coupling of holes makes single-shot spin readout measurements difficult because it reduces the spin lifetimes. By integrating the charge sensor into a high bandwidth radio frequency reflectometry setup, we were able to demonstrate single-shot readout of a germanium quantum dot hole spin and measure the spin lifetime. Hole spin relaxation times of about 90 μs at 500 mT are reported, with a total readout visibility of about 70%. By analyzing separately the spin-to-charge conversion and charge readout fidelities, we have obtained insight into the processes limiting the visibilities of hole spins. The analyses suggest that high hole visibilities are feasible at realistic experimental conditions, underlying the potential of hole spins for the realization of viable qubit devices.

Non Wi-Fi Devices Interference Testing in a 2.4 GHz Wi-Fi Home

Abstract Operating in probably the most crowded radio frequency bandwidth, the 2.4 GHz Wi-Fi is still common in the majority of living environments. Besides having to face problems regarding co-channel and adjacent channel influence, Wi-Fi often coexists with other radio technologies operating in this bandwidth which makes it ideal for interference testing. In this article authors propose the use of freely available mobile applications to measure Wi-Fi signal spreading within a residential home as well as to quantify Wi-Fi performance in the presence of some commonly available interferers. A complete analysis of spectrum use is also provided by using a spectrum analyzer. We have found that Wi-Fi throughput degradation due to Bluetooth technology operated in the immediate vicinity of a mobile client is on average 26,5 % and decreases with distance from the Wi-Fi client. The presence of an active video baby monitor leads to a 7,5 % throughput degradation, but its functionality in heavy Wi-Fi traffic environment is however limited. The use of spectrograms in interference analysis is essential for a better understanding of the measured results.