Radio frequency fingerprint-based wireless device identification

The characteristics of pulse-modulated RF-driven atmospheric pressure argon (Ar) dielectric barrier discharge (DBD) have been investigated, on the basis of a 1-D coupled fluid model. Time-domain variations of the voltage and the charge density on the dielectric surface (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {k}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma $ </tex-math></inline-formula>) were obtained for different radio frequency (RF) voltage amplitudes (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {RF}}$ </tex-math></inline-formula>). Furthermore, the minimum voltage amplitudes of RF maintenance discharge (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {RF},\min }$ </tex-math></inline-formula>) changing with the pulse duty cycle (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D_{\text {R}}$ </tex-math></inline-formula>) and pulse modulated frequency (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\text {RF},\text {p}}$ </tex-math></inline-formula>) were discussed, and the variation of spatiotemporal average electron density with spatiotemporal average sheath voltage during the low-frequency period was studied for various <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D_{\text {R}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\text {RF},\text {p}}$ </tex-math></inline-formula>. It was found that <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {k}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma $ </tex-math></inline-formula> cannot reach a periodic steady state for smaller <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {RF}}$ </tex-math></inline-formula>. When it increases to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {RF},\min }$ </tex-math></inline-formula>, or even greater than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {RF},\min },V_{\text {k}} $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma $ </tex-math></inline-formula> reach the steady state and the time for both to reach the steady state is advanced. When <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {RF}}$ </tex-math></inline-formula> is 600 V, it is shortened to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.36\times 10^{-6}$ </tex-math></inline-formula> s (about 32 RF periods), comparing with that when <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {RF}}$ </tex-math></inline-formula> is 280 V. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {RF},\min }$ </tex-math></inline-formula> decreases as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D_{\text {R}}$ </tex-math></inline-formula> increasing from 20% to 100%. The discharge is only in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> mode for smaller <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D_{\text {R}}$ </tex-math></inline-formula> while it exists in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> modes for greater <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D_{\text {R}}$ </tex-math></inline-formula>. In addition, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {RF},\min }$ </tex-math></inline-formula> increases along with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\text {RF},\text {p}}$ </tex-math></inline-formula> growing from 0.01937 to 0.1356 MHz. When <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\text {RF},\text {p}}$ </tex-math></inline-formula> is higher, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> mode exists for discharge, while when it is lower, there are two modes: <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula>.

Autocorrelator, as a pulse measuring equipment, can effectively characterize pulse width and pulse waveform with high resolution. Limited by the refresh rate, conventional autocorrelator are incapable of capture the ultrafast processes of pulses, such as soliton transitions. In this paper, we proposed an ultrafast autocorrelator based on broadband radio frequency (RF) spectrum analyzer. The RF spectrum under test is firstly transformed to the continuous wave via the cross-phase modulation. Then the RF spectrum is mapped to the temporal domain through time stretch and finally measured by a real-time oscilloscope. The ultrafast autocorrelation trace is obtained from the inverse Fourier transform of the mapped RF spectrum. With the 60-GHz detected bandwidth of the photodetector adopted, the simulated ultrafast autocorrelator achieves the measurement rate of 50 MHz, the resolution of 300 fs, and the measuring window of 600 ps.

Radio frequency (RF) spectrum analysis is an essential technique for monitoring signal quality in ultrahigh-speed optical transmission, broad bandwidth photonic RF arbitrary waveform generation, and for characterization of high repetition rate optical pulse sources. Whereas the intrinsic bandwidth of electronics limits its use for RF spectrum measurement of high-speed signals, a photonic approach based on ultrafast Kerr nonlinear effects can readily measure the RF spectrum of optical signals having a bandwidth beyond 1 THz. The majority of fiber-based or integrated photonic RF spectrum analyzers reported to date can monitor only one channel at a time. We demonstrate how to harness mode-selective excitation of nonlinear optical effects to perform simultaneous multichannel RF spectrum analysis using a single integrated silicon photonic device. This approach, which can be scaled to a higher number of channels, opens up a new degree of freedom for realizing multichannel signal characterization using a single integrated photonic device.

In the unmanned aerial vehicle (UAV) based localization of slow-moving radio frequency (RF) sources with unknown transmitted strength of signal, such as a person with a cell phone in a search and rescue mission, the UAV navigation errors are significant sources of localization error. Although the use of a global positioning system (GPS) can reduce the UAV’s localization error significantly resulting in more accurate RF source localization, if the GPS signal is lost temporarily or permanently, the accuracy of the UAV-based localization decreases rapidly. In this paper, a simultaneous localization and mapping (SLAM)-inspired approach for simultaneous localization of UAV and RF sources (SLUS) is proposed. The proposed approach solves these two connected problems, i.e. the UAV localization and RF source localization, simultaneously to decrease the error of the UAV position estimation and the error of the RF source localization. In the proposed approach, beside the UAV position prediction, the RF source position prediction is also performed. Then the predicted states are augmented and the augmented predicted state information is corrected using range-ratio and bearing observations, i.e. RF source features, considering the unknown transmitted power. The proposed approach is simulated and the results show that the normal divergence of a target localization and the divergence of the UAV navigation in latitude and longitude channels have been eliminated using this approach. In other words, simultaneous localization of the UAV and RF sources uses the RF sources, as features in the environment, to aid the navigation system. Although the approach is similar to the mapping of RF sources in the environment, the created map would be useless after finding the RF sources. That is why SLUS has been used instead of SLAM. The main contributions of this work are: 1) performing simultaneous localization of a UAV and targets using RF signals, especially in a non-line of sight (NLOS) condition; 2) using difference of signal strength, i.e. differential received strength signal indicator (DRSSI), to eliminate the impact of unknown target signal power; and 3) simultaneous multi-target localization and tracking.

We report the radio frequency (RF) stress reliability response of 45-nm SOI RF nMOSFETs. The dependence of gate oxide degradation and off-state leakage (due to RF stress) on the contact spacing of the Source/Drain (S/D) terminals and the gate finger-to-gate finger spacing is investigated. The RF device performance trade-offs vs. RF stress reliability that result are investigated. Devices with “tight” S/D contact spacing have improved RF performance but worse RF reliability than devices with “loose” S/D contact spacing. Devices with “loose” gate-finger to gate-finger spacing have better RF performance and also better RF reliability. The net result of this investigation is that fundamental tradeoffs between RF performance and reliability exist at these advanced scaling nodes.

In mobile communications networks, if we can estimate the location of each user equipment (UE) with high accuracy, efficient cell planning and network optimization become possible. However, it is difficult for operators to estimate the location of most commercial UEs because they cannot feedback their location information directly to their serving base stations with the exception of UEs with Minimization of Drive Test (MDT) functions specified in LTE Release 10. Radio Frequency (RF) fingerprint method is known as an effective localization method, with which we can estimate the location of UEs with only RF signature and location information beforehand. In LTE, RF fingerprint database can be collected by conducting drive tests or using measurement data from UEs compatible with MDT. Although the estimation accuracy can be better with more RF signatures, the increase in the amount of RF signatures causes the increase in the feedback, which consumes the uplink capacity and UE battery. Furthermore, keeping all RF signatures in database is inefficient because some RF signatures do not have effect on improving estimation accuracy. Hence, it is important to clarify the effect of each RF signature and use only effective ones in the localization. In this paper, we conducted a field experiment to create an RF fingerprint database in dense urban area, and evaluated the effectiveness of each RF signature by making several localization models based on machine learning. Eventually, we clarified minimum RF signatures required to operate RF fingerprint localization in LTE network.

Establishing the health risks of exposure to radiofrequency fields requires multidisciplinary research

Objective: Exposure to Radio Frequency (RF) and Extremely Low Frequency (ELF) radiation is increasing steadily with the progress of technology and industrialization. The aim of this study was to investigate whether RF and ELF radiation are oxidative stress effects in the plasma and brain tissue of diabetic and non-diabetic rats. Methods: Experiment groups were designed as follows; C (control), S (sham), ELF (ELF radiation exposure), RF (RF radiation exposure), ELF+RF (ELF and RF radiation exposure), D-C (Diabetic Control), D-S (Diabetic Sham), D-ELF (Diabetic ELF), D-RF (Diabetic RF), D-ELF+RF (Diabetic ELF+RF). The experimental diabetes model was induced with a single dose of 65mg/kg streptozotocin (STZ). 2100 MHz RF and 50 Hz ELF radiation groups exposed for 1 month. Total nitric oxide (NOx), malondialdehyde (MDA) and total sulfhydryl groups (RSH) / glutathione (GSH) levels were measured in plasma and brain tissue. Results: RF + ELF radiation exposure caused an increase in NOx and MDA levels in plasma and brain tissue of diabetic and non-diabetic rats (p&amp;lt;0.05). Exposure to RF and RF + ELF radiation caused a decrease in plasma RSH / tissue GSH levels in non-diabetic rats (p&amp;lt;0.05). Conclusion: The most prominent effect was seen in the diabetic group with RF + ELF radiation exposure.

In this paper, we describe the whole process of designing and manufacturing an 83.2 MHz, three-stage radio frequency (RF) amplifier for a SKKUCY-9 cyclotron. It consisted of a preamplifier, intermediate power amplifier (IPA), and power amplifier (PA) stage. The maximum power value for each stage is 0.05 kW, 1.5 kW, then 20 kW RF power. Formula calculation, circuit design, and electromagnetic analysis were implemented in the RF amplifier design. Along with the power stage and anode power supply, an RF amplifier control system for the RF amplifier was developed. After design and manufacturing, we conducted impedance matching measurements with a network analyzer to achieve <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$50\Omega $</tex></formula> for the IPA and PA. Finally, we analyzed the RF amplifier characteristics by implementing RF testing with both a dummy load and a RF coupler. The expected and measured RF characteristics were in agreement, and a detailed analysis is described.

Photonic implementation of a highly reconfigurable wideband RF spectral shaper

Method for stabilizing beam intensity and energy in the SPring-8 linac

A wavelength-multiplexed fiber optic link architecture has been designed for transmitting wideband IF and LO signals at microwave frequencies over long distances. The architecture involves downconverting the input RF signal, directly amplitude modulating a laser diode, transmitting the resulting RF-modulated optical carrier through single mode fiber and subsequently upconverting the recovered RF signal to the original band. Wavelength division multiplexing and demultiplexing is used to transmit the local oscillation signal (required for down- and up-conversions) from the transmitter to the receiver through the same fiber. By using a frequency-divided LO signal in conjunction with frequency multipliers, we can down/up convert the wideband RF signal anywhere in the RF spectrum up to 100 GHz. A demonstration link has been implemented using this architecture and operates from 6.3 to 16 GHz. This link uses a 1.3 micrometers , 10 GHz RF bandwidth laser diode for IF transmission and a 1.55 micrometers , 1.5 GHz RF bandwidth laser diode for LO transmission.

A study is conducted on the influence of radio frequency (rf) waves upon interchange stability in HANBIT mirror plasmas. An emphasis is put on the interchange stability near the resonance region, ω0 ≃ Ωi, where ω0 (Ωi) is the angular frequency of the applied rf wave (ion cyclotron frequency). A strong nonlinear interaction between the rf wave and the interchange mode has been observed with the generation of sideband waves. A theory of rf-interchange mode interaction keeping effects of both the equilibrium ponderomotive force and the nonlinear sideband wave coupling is applied to interpret HANBIT experimental results, resulting in good agreement. Results have shown that the nonlinear coupling process is responsible for the rf stabilization of interchange modes near the resonance region.

In this paper an automatic direction system developed driven by AT89S51 microcontroller is proposed for outdoor wireless local area network (WLAN) antenna array. The system is intended to overcome the issue of direction lost of outdoor WLAN antenna array installed on a high spot caused by the wind and surrounding circumstances. The proposed system which is equipped with automatic radio frequency (RF) power level sensor will fix the direction of antenna to the proper orientation in azimuth direction by retrieving the received RF signal. In general the system consists of RF rectifier in the front-end to rectify the received RF signal and then convert it into a dc voltage. The output of RF rectifier is fed into operational amplifier (Op-Amp) to achieve the dc voltage level suitable for analog-to-digital converter (ADC) before being processed by microcontroller. From experimental characterization, it shows that the shifting of antenna array direction influences remarkably the received RF signal and is linear to the output voltage level of RF sensor in which for each 5dBm received RF signal produces 1mV output voltage level of RF sensor. Furthermore, the realized automatic direction system can handle the reflection angle of antenna array up to ±18° in azimuth direction.

Laser-based methods are known to be more efficient than traditional approaches for a range of tasks that include dismantling obsolete nuclear reactors, maintaining railroad tracks in good working condition, stimulating chemical reactions, and separating isotopes. Among the attractions of lasers are fewer byproducts, increased reactor cutting speed, enhanced lifetime and capacity of the railway, and the ability to deal with toxic agents without igniting them. Moreover, laser techniques are more effective than other methods in processing radioactive waste. Realizing these capabilities takes a high-power laser with superior optical quality. Acceptable cost and efficiency are additional requirements. High-power CO2 lasers are commercially available; however, they are expensive and inefficient, and suffer from deteriorating optical quality as power increases. Alternatives include so-called chemical oxygen-iodine lasers (COILs) and CO lasers. But the COIL, too, is expensive, and there is as yet no industrial prototype. And although NUPEC Corporation, in Tokyo, Japan, has impressively demonstrated a 20kW CO laser for cutting large arrays of steel pipes and plates,1 the system lacks an optical cable of transferring CO radiation. Furthermore, the laser requires cryogenic components, which adds to its cost. We propose a CO laser2 that dispenses with the need for an optical cable by installing the laser head on the manipulator. Our concept is based on the discharge of stable homogeneous radio frequency (RF) in a supersonic stream and the demonstration of laser generation in a small-scale experimental installation.3 We also devised a computational model for scaling the CO laser with RF discharge. Supersonic expansion makes it possible to obtain the required cryogenic temperatures, and the RF discharge enables us to get optimal parameters for vibrational excitation of CO molecules without an electronic gun. The reduced ratio of the electric field to gas density (E/N) in a column of gas is stated in the literature.4, 5 With our model, we can calculate the power parameters of the CO laser and optimize them to obtain high values of output power and efficiency. The cost of the laser is kept low through use of standard elements, for example, compressor, RF generator, and power station. Owing to the high density of the gas in front of the supersonic nozzle of the laser head and behind the supersonic diffuser, the closed contour serves as a pipeline that enables flexible positioning of the laser head, for example, on the manipulator. Consequently, no optical cable is needed to transfer laser radiation. A standard compressor can be used because values such as pressure and Mach number can be maintained in a stream that makes it possible to restore pressure upon an input in the compressor up to 1atm. Themodel consists of calculations of RF discharge parameters, vibrational kinetic equations, and dynamic gas equations that describe a supersonic stream in the RF discharge zone. We have considered low-current RF discharge with electron photoemission from the electrode surface and injection of electrons from electrode sheaths in a positive column. A low-current RF discharge is realized when the ratio of the time required for the ions to drift through the sheath and reach the electrode to the period of the RF field is much larger than unity.6, 7 Thus, the electrode sheaths have no time to break up and exist simultaneously at both electrodes. Plausible applications for the CO laser include dismantling obsolete nuclear reactors and hardening of the surfaces of railway rails. Our next step will be to test the laser in applications involving toxic agents, in processing radioactive waste by extracting ruthenium, and separating isotopes of heavy hydrogen and uranium. These applications can be extended substantially only once the laser is commercially available.