Signal Phase Variations Research Articles

Wi-Rotate: An Instantaneous Angular Speed Measurement System Using WiFi Signals

We propose the design, implementation, and evaluation of an instantaneous angular speed (IAS) measurement system, namely Wi-Rotate, using commercial-off-the-shelf (COTS) WiFi hardware. Wi-Rotate exploits the Channel State Information (CSI) of WiFi signals to extract the physical characteristics of the rotation object to achieve accurate contact-free IAS measurements. Wi-Rotate contains three main components: Wi-Fresnel model, Wi-Phase model, and a combination model. Wi-Fresnel model explores the signal amplitude variation features when the rotating object cuts the Fresnel zone boundary to track target rotation. Wi-Phase model leverages signal phase variation and formalizes the problem of determining IAS as a linear programming problem. The combination model combines the IAS values obtained by Wi-Fresnel and Wi-Phase and utilizes a clustering method to further improve measurement accuracy. Comprehensive experiments are conducted to demonstrate the advantages of Wi-Rotate in terms of accuracy, sensing range, and system latency. Wi-Rotate is able to achieve real-time rotation measurements at an accuracy higher than 99% when the target is within 2 meters. Even when the target is 3 meters away, Wi-Rotate can still achieve an accuracy of 94%, demonstrating the long-range tracking capability which is critical for industrial applications.

Observations and modeling of D-region ionospheric response of Annular Solar Eclipse on December 26, 2019, using VLF signal amplitude and phase variation

Observations and modeling of D-region ionospheric response of Annular Solar Eclipse on December 26, 2019, using VLF signal amplitude and phase variation

Отклик ионосферы на прохождение тайфунов по наблюдениям методом СДВ-радиопросвечивания

The response of the lower ionosphere to the passage of several dozen typhoons has been studied using a regional network of VLF stations in the Russian Far East. The experimental data presented in all cases clearly demonstrates wavelike disturbances of the subionospheric VLF signal amplitude and phase during the active stage of typhoons crossing radio paths. With the exception of magnetoactive and seismoactive days, this means that the disturbances generated by a typhoon, when propagating into the upper ionosphere, pass through the lower ionosphere, causing corresponding disturbances in the amplitude and phase of the VLF signal. Spectral analysis shows that the range of the wave disturbances detected corresponds to the periods of atmospheric internal gravity waves (IGW). A mechanism of the action of IGWs on the lower ionosphere is proposed which allows us to interpret the VLF signal phase variations observed. According to this mechanism, the action of IGW on the lower ionosphere is caused by polarization fields arising during the wave motion of plasma in the lower part of the F layer. These fields projected along geomagnetic field lines into the lower ionosphere cause the upper wall of the Earth—ionosphere waveguide to rise or fall.

Ionospheric response to the passage of typhoons observed by subionospheric VLF radio signals

The response of the lower ionosphere to the passage of several dozen typhoons has been studied using a regional network of VLF stations in the Russian Far East. The experimental data presented in all cases clearly demonstrates wavelike disturbances of the subionospheric VLF signal amplitude and phase during the active stage of typhoons crossing radio paths. With the exception of magnetoactive and seismoactive days, this means that the disturbances generated by a typhoon, when propagating into the upper ionosphere, pass through the lower ionosphere, causing corresponding disturbances in the amplitude and phase of the VLF signal. Spectral analysis shows that the range of the wave disturbances detected corresponds to the periods of atmospheric internal gravity waves (IGW). A mechanism of the action of IGWs on the lower ionosphere is proposed which allows us to interpret the VLF signal phase variations observed. According to this mechanism, the action of IGW on the lower ionosphere is caused by polarization fields arising during the wave motion of plasma in the lower part of the F layer. These fields projected along geomagnetic field lines into the lower ionosphere cause the upper wall of the Earth—ionosphere waveguide to rise or fall.

Eddy-current flow meter response to spherical non-conductive inclusions travelling in a liquid metal

In this paper, we address the problem of characterizing the size and position of a spherical non-conductive inclusion in a conductive material. The characterization is done using an Eddy-Current Flow Meter (ECFM), a device usually used to measure the flow rate of liquid metals, but which is also sensitive to the second gaseous phase. ECFM responses to the passage of inclusions in a quiescent liquid metal are computed numerically. The signal amplitude and phase variations are analyzed for inclusions of different radii and radial positions travelling in the pipe. Two parameters are introduced to characterize these variations: the maximum amplitude of the ECFM signal and its corresponding phase. It is shown that a unique relation exists between these parameters and the size and position of the inclusion. The ECFM signal thus provides enough information to determine the size and position of the inclusions by means of an inverse method. This provides valuable information for low void fraction measurement in industrial liquid metal flows. Tables 2, Figs 5, Refs 10.

전자전 다중 위협 재밍을 위한 멀티빔 송수신장치용 광대역 고출력 송수신모듈 개발

An eight-channel transmit/receive module (TRM) was designed for a wideband electronic warfare multiple threat jamming transceiver. In the system, the TRM amplifies a multijamming signal from a multibeam transceiver module and a small radio frequency (RF) signal from an antenna. In TX mode, it has an output power of more than 43 dBm for a continuous wave. In RX mode, it has a gain of more than 10 dB and noise figure of less than 5 dB. The voltage standing wave ratio is less than 2:1, and the TX and RX path isolation is 50 dBc or more. The RF signal amplitude and phase variation are less than 2 dB and 10°, respectively. True time delay and a digital attenuator are used to compensate for the signal amplitude and phase for each channel.

A high efficiency BPSK receiver for short range wireless network

In this paper, a 910MHz high efficiency BPSK receiver is presented with Colpitts oscillator for short range wireless network. In this research, with injection-lock technique and using Colpitts oscillator, the efficiency of receiver has been improved. And also, behavior of an oscillator under injection of another signal has been investigated. Also, variation of output signal amplitude versus injected signal phase variation, the effect of varying the amplitude of injected signal and quality factor of the oscillator has been investigated. The designed receiver has 0.474 mW dc power and -60 dBm sensitivity. Data rate of receiver is 5 Mbps. The FOM of receiver is 94 pJ/bit. This receiver was designed and simulated in 0.18 μm RFCMOS technology. This proposed receiver can be used in short range wireless network for example, Wireless Body array network and wireless sensor network.

The Impact of Transformer Energization Levels on Powerline Communication Signal Integrity

There are advantages in implementing “through-transformer” powerline communication (PLC) on distribution grids. Research in distribution transformer characteristics has produced PLC strategies that take advantage of resonance phenomena due to shunt capacitive effects, which result in reduced high-frequency impedance at certain frequencies. However, the effects of phenomena associated with energized transformers on PLC signals has been largely overlooked. This paper outlines an experimental study of the PLC channel characteristics of two single-phase 11-kV/230-V transformers rated at 15 and 1 kVA, under various energization levels. Results show that distribution transformers can significantly influence the integrity of PLC signals impinging on their terminals by introducing noise, and signal amplitude and phase variation effects. This paper further identifies the phenomena behind these effects, and reveals how they can impact the quality of “through-transformer” PLC.

FBG wavelength demodulation based on a radio frequency optical true time delay method.

A new fiber Bragg grating (FBG) wavelength shift demodulation method based on optical true time delay microwave phase detection is proposed. We used a microwave photonic link (MPL) to transport a radio frequency (RF) signal over a dispersion compensation fiber (DCF). The wavelength shift of the FBG will cause the time delay change of the optical carrier that propagates in an optical fiber with chromatic dispersion, which will result in the variation of the RF signal phase. A long DCF was adopted to enlarge the RF signal phase variation. An IQ mixer was used to measure the RF phase variation of the RF signal propagating in the MPL, and the wavelength shift of the FBG can be obtained by the measured RF signal phase variation. The experimental results showed that the wavelength shift measurement resolution is 2pm when the group velocity dispersion of the DCF is 79.5ps/nm and the frequency of the RF signal is 18GHz. The demodulation time is as short as 0.1ms. The measurement resolution can be improved simply by using a higher frequency of the RF signal and a longer DCF or larger chromatic dispersion value of the DCF.

Double antinode excited quartz-enhanced photoacoustic spectrophone

A double antinode excited quartz-enhanced photoacoustic spectroscopy (DAE-QEPAS) spectrophone, employing a custom-made quartz tuning fork (QTF) and operating at the 1stt overtone resonance mode is reported. The signal phase variation along the QTF prong was investigated, and a piezoelectric transducer was introduced to compensate the phase shift between two QTF separated 1st overtone antinode points. Two sets of acoustic micro-resonators were optimized and assembled at two antinode points to improve the spectrophone performance. With the two antinodes excited by one laser source, the DAE-QEPAS spectrophone attained a sensitivity gain factor of ∼100 times and ∼3 times with respect to the 1st overtone resonances of a bare custom QTF and a standard on-beam QEPAS spectrophone, respectively. H2O was selected as the target analyte and a detection limit of ∼230 ppb was obtained by the DAE-QEPAS spectrophone for a 1 s integration time, corresponding to a normalized noise equivalent absorption coefficient of 1.73 × 10-9 cm−1·W·Hz−1/2.

Adaptive wavelet denoising unscented Kalman filter for BeiDou signal carrier tracking under ionospheric scintillation conditions

Ionospheric scintillation can cause BeiDou system (BDS) signal amplitude fading and phase variation as the radio frequency (RF) signals pass through the ionosphere. With the accidental, sudden, and regional characteristics of ionospheric scintillation, it is difficult to effectively mitigate the impacts of ionospheric scintillation from a system perspective. To overcome this problem, this work addresses the mitigation of scintillation for the BDS signal. We propose an adaptive wavelet denoising unscented Kalman filter (WDUKF)-based carrier tracking algorithm to mitigate the adverse impacts of ionospheric scintillation. First, as WD can better characterize the nonstationary of signal, the non-Gaussian noise caused by scintillation can be filtered by designing a sliding window-based online WD filter. Second, taking the denoised integrations as an input, we employ the phase lock indicator (PLI)-based adaptive UKF carrier phase estimator to reduce the linearization approximate error of conventional KF-based algorithms. Through adjusting the measurement vector of UKF with different scintillation scenarios adaptively, the divergence problem of UKF can be mitigated. Simulation and real data experimental results demonstrate the validity of the proposed method, especially in the case of 36 dB-Hz in moderate scintillation, the phase jitter and probability of loss-of-lock decrease about 6 deg (40%) and 71%, respectively.

Optical radio-photonic channel for transmission of a coherent narrowband analog signal

The channel of an optical transmission line of coherent narrowband analog signal consisting of a continuous-wave laser, an electro-optic modulator, and a vector phase rotator based on electrically controlled fiber-optical 1 × 2 splitter and fixed delay lines is analyzed. The scheme is constructed from commercially available components used in digital optical communication systems. The applicability of components for analog and small-signal circuits is determined. Variation of radio signal phase in the range from 0° to 170° for radio signal frequencies between 1 and 2 GHz is demonstrated experimentally. It is shown that phase variation is a linear function of frequency in this range.

Application of the locality principle to radio occultation studies of the Earth's atmosphere and ionosphere

Abstract. A new formulation of the previously introduced principle of locality is presented. The principle can be applied for modernization of the radio occultation (RO) remote sensing of the atmospheres and ionospheres of the Earth and other planets. The principle states that significant contributions to variations of the intensity and phase of the radio waves passing through a layered medium are connected with influence of the vicinities of tangential points where the refractivity gradient is perpendicular to the radio ray trajectory. The RO method assumes spherical symmetry of the investigated medium. In this case, if location of a tangent point relative to the spherical symmetry centre is known, the time derivatives of the RO signal phase and Doppler frequency variations can be recalculated into the refractive attenuation. Several important findings are consequences of the locality principle: (i) if position of the centre of symmetry is known, the total absorption along the ray path can be determined at a single frequency; (ii) in the case of low absorption the height, displacement from the radio ray perigee, and tilt of the inclined ionospheric (atmospheric) layers can be evaluated; (iii) the contributions of the layered and irregular structures in the RO signal can be separated and parameters of layers and turbulence can be measured at a single frequency using joint analysis of the intensity and phase variations. Specially for the Earth's troposphere, the altitude distributions of the weak total absorption (about of 1–4 db) of the radio waves at GPS frequencies corresponding to possible influence of the oxygen, water vapour, and hydrometeors can be measured with accuracy of about 0.1 db at a single frequency. In accordance with the locality principle, a new index of ionospheric activity is introduced. This index is measured from the phase variations of radio waves passing through the ionosphere. Its high correlation with the S4 scintillation index is established. This correlation indicates the significant influence of locally spherical symmetric ionospheric layers on variations of the phase and intensity of the RO signal passing through transionospheric communication links. Obtained results expand applicable domain of the RO method as a powerful remote sensing technique for geophysical and meteorological research.

GNSS Multipath Mitigation using Antenna Motion

A method is developed for characterizing and compensating specular GNSS multipath by considering signal amplitude and phase variations in response to antenna motion. This method seeks to improve multipath rejection capabilities. A known antenna motion profile is combined with a batch filter to estimate the code phase, carrier phase, and amplitude of the direct signal, the relative code phase, carrier phase, carrier Doppler shift, and amplitude of each significant multipath component, and the directions of arrival of the direct and multipath components. Hardware signal simulator results indicate accurate estimation of all multipath features, and experimental test results demonstrate measurable improvements in estimates of carrier amplitude in all cases, of direct-path carrier-phase in many cases, and of direct-path code phase in some cases. Anomalous results have also been obtained, including specular multipath component estimates that occur in doublets and that may represent attempts by the batch filter to approximate diffuse multipath. Copyright © 2015 Institute of Navigation.

A Large Signal Model to Improve Linearity of Rf Power Amplifier

Hetero-junction Bipolar Transistors (HBTs) have become very promising devices for power amplifier design in different communication applications. This paper proposes an analytical large signal model to predict nonlinear behavior of InGaP/GaAs HBT. The proposed model is directly fitted from linear model elements using Fourier transfer functions. As a consequence, the proposed large signal model shows good insight of circuit nonlinear behavior, and can be used to analysis large signal parameters of power amplifier. Based on the proposed large signal model, power gain and phase variation of an emitter follower amplify stage under different bias conditions have been analyzed. The calculated results show that: both gain and phase properties exhibit reverse deviation in saturation compared with that in forward amplify region, and can be used to maximize the linearity of power amplifier.

Automated Broadband Phase Correction of Fourier Transform Ion Cyclotron Resonance Mass Spectra

It has been known for 35 years that phase correction of FTICR data can in principle produce an absorption-mode spectrum with mass resolving power as much as a factor of 2 higher than conventional magnitude-mode display, an improvement otherwise requiring a (much more expensive) increase in magnetic field strength. However, temporally dispersed excitation followed by time-delayed detection results in steep quadratic variation of signal phase with frequency. Here, we present a robust, rapid, automated method to enable accurate broadband phase correction for all peaks in the mass spectrum. Low-pass digital filtering effectively eliminates the accompanying baseline roll. Experimental FTICR absorption-mode mass spectra exhibit at least 40% higher resolving power (and thus an increased number of resolved peaks) as well as higher mass accuracy relative to magnitude mode spectra, for more complete and more reliable elemental composition assignments for mixtures as complex as petroleum.

Analog automatic lock-in amplifier for very low gas concentration detection

A novel automatic analog lock-in amplifier for low quantity detection of gas is here presented. When compared to similar commercial apparatus in the literature, the proposed scheme shows the self-alignment of the relative phase between input and reference signals, both at power-on and for any variation of the input noisy signal phase and amplitude during the working time, so allowing to detect, in a continuous way, the mean value of the input signal (buried into noise). The circuit has been optimized to operate at a specified reference frequency (77 Hz), whose value is suitable for gas sensor application, avoiding any kind of interferences at 50 Hz net frequency and its harmonics. Experimental results have confirmed the correct functionality of the system, tested for 10, 20 and 30 ppm of CO concentrations. With respect to the simple resistive gas sensor interface implemented by a resistive voltage divider, the sensitivity improvement given by the proposed lock-in amplifier is of a factor of about 80, while the resolution, starting from about 5ppm, has been enhanced to a theoretical value of about 0.05ppm.

Effect of the ionosphere on defocusing of space‐based radars

Space‐based synthetic aperture radars can be detrimentally affected by electron density variations in the ionosphere, which cause signal phase variations resulting in image defocusing. In order to evaluate the significance of this problem, this paper determines how often the phase perturbations are large enough to cause defocusing. High cadence GPS TEC signals collected on Ascension Island during sunspot minimum and in Papua New Guinea over half a solar cycle have been analyzed. Both locations lie in the equatorial crest region. For a space‐based synthetic radar operating at 435 MHz, the average probability of defocusing varies from zero at quiet times, to around 1% between 18:00 and 24:00 at solar minimum, and to 45% between 18:00 and 24:00 at solar maximum. Corresponding values are given for radars operating at other frequencies. A method is developed to estimate such variations from the large database of S4 measurements.

On the relationship between sea state and the coherent-to-incoherent intensity ratio for high frequency, shallow water propagation

A 29-element source array and 32-element receiver array have been deployed in shallow water to investigate various aspects of the acoustic channel. Both arrays spanned much of the water column. Source-receiver range was 800 m, and 3.5 kHz pulses were transmitted using one source at a time and recorded on all elements. In this analysis, we compare the ratio of coherently to incoherently averaged intensities for each source-receiver pair, and averaged over all such pairs, to measure surface roughness. We find that the coherent-to-incoherent intensity ratio decreases with time after the direct path arrival, and that the slope becomes more negative as wind speed and thus surface roughness increases. A simple model for signal phase variation induced by surface scatter shows a direct relationship between the degree of phase variation and wind speed. The relationship between the slope of the coherent-to-incoherent intensity ratio and a physics-based model of incoherent sea surface forward scatter is also considered. [Work supported by ONR Code 321US.]

Broadband phase correction of FT-ICR mass spectra via simultaneous excitation and detection.

In typical Fourier transform ion cyclotron resonance (FT-ICR) mass spectra, temporally dispersed excitation and the delay between excitation and detection result in continuous variation of signal phase with frequency in the detected time-domain ion signal. The complex frequency-domain spectrum of such a signal is a linear combination of absorption- and dispersion-mode spectral components with corresponding asymmetric peaks. For this reason, magnitude-mode spectral display is usually employed to yield a phase-independent uniform and symmetrical peak shape at the expense of spectral resolution. In this work, we implement simultaneous excitation and detection to enable Fourier deconvolution to recover absorption-mode spectra for both low- and high-field FT-ICR instruments. These spectra yield resolving power improvement factors approaching the maximum theoretical limit of 2.0, as well as reduction in frequency assignment errors relative to conventional magnitude-mode spectra. The Fourier deconvolution procedure has the additional benefit of correcting for spectral variation resulting from nonuniform power distribution over the excitation bandwidth and the potential benefit of providing useful diagnostic information for interpretation of experimental performance.