Angular Modulation Research Articles

A cross layer protocol to mitigate effects of radio's linear impairments

The impact of signal-to-noise ratio (SNR) of an additive white Gaussian noise (AWGN) channel on bit error rate (BER) has been extensively studied in the literature through theoretical, simulation-based, and experimental results. However, it is too simplistic to assume that BER in a real-world communication system is influenced by AWGN alone. The system's radio, which contributes both linear and nonlinear impairments, also impacts BER. This paper studies the impact of linear impairments, namely quadrature skew and gain imbalance, on the BER of an angular digital modulation scheme, such as M-ary phase shift keying (M-PSK). It presents a mathematical derivation of a technique to measure these impairments. It implements this technique on an experimentation system and presents statistical properties of these measurements. A novel contribution of this paper is a cross layer protocol through which the receiver shares these measured values with the transmitter. The transmitter uses this information to combat the effects of radio's impairments on BER, thereby improving system performance. This paper also presents a cost benefit analysis which proves that the idea proposed in this paper is feasible and practical to implement on real-world systems.

LDPC coded lossy forwarding scheme for cooperative wireless networks

A new methodology for lossy forwarding based on a novel technique known as soft angular modulation is investigated. In this new relay (R) scheme, the soft symbols are embedded into phases at the R. This is more advantageous as to forward real values (under bandwidth constraints) via wireless channels is refrained. This makes the proposed scheme practically feasible. The proposed system provides a means of using distributed low-density parity-check coding. This also precludes the amplitudes of generated symbols descent to zero, as happens with most of the existing soft forwarding (or lossy) methods. Ordinarily, such schemes suffer from error propagation to the destination when the signal-to-noise ratio of the source (S)–R link is low; however, the system avoids this problem by regenerating soft versions of the S symbols at the R. Simulation results demonstrate that the proposed scheme can maintain very good performance.

Comparison of Radiation Dose and Image Quality with Various Computed-Tomography Scout Views: The Angular Modulation Technique Based on Information Calculated from Scout Views

Background: While using the automatic exposure control technique in computed tomography (CT), the scout view determines the radiation dose for the CT scan by taking anatomical morphology into consideration. Objectives: The goal of this study was to estimate radiation doses during scout scanning and to evaluate the hypothesis that the radiation dose during CT depends on the location and order of the X-ray tubes. Materials and Methods: A CT scanner (GE VCT 64-channel) with the X-ray tubes placed in the anteroposterior (AP), lateral, and posteroanterior (PA) positions was used to acquire the scout views. The effective doses were assessed using an anthropomorphic chest phantom (RSD Inc., Long Beach, CA), an AAPM CT performance phantom (CIRS model 610), and CT dose indices (CTDI) head phantom. Both single and two scout views were tested with the three views combined according to the order of scanning. The CTDIs obtained from the CT unit dose report were used to compare the chest CT radiation doses, while the image quality was evaluated based on the root-mean-square error values calculated using the Image program. Results: The results of this study indicate that single AP (0°) scout views obtained with the z-axis modulation technique (AutomA) during chest CT scanning resulted in CTDIs that were lower than those generated by using lateral (90°) or PA (180°) scout views. The analysis of two-scout views using AutomA alone revealed the lowest CTDI in the 90° - 0° scout views. However, based on the CT image noise analysis, a scout angle order of 0°-90° resulted in the optimal scout view combination with the minimal dose. Conclusion: Scout views may be useful in determining dose and image quality in CT scanning; however, it is necessary to first determine the most appropriate scout view for CT scans.

Enhancement of NO2 gas detection in hybrid silver nanoparticles-phthalocyanine thin films

Phthalocyanine-functionalized plasmonic sensing systems are typically based on Kretschmann configuration. Such scheme of detection utilizes spectral or angular modulation of reflected light, which is induced by surface plasmon's excitation in the metal film on prism. Phthalocyanine's layer plays a role of analyte adsorber. In present paper we offer another approach to phthalocyanine-plasmonic sensing, where both local surface plasmon resonance and optical absorption of phthalocyanines are simultaneously detected. Hybrid Ag nanoparticles (AgNps) - low symmetrical A3B zinc phthalocyanine (ZnPc) thin films were prepared, and their NO2 gas sensitive properties were examined. Since the plasmon resonance of AgNps was properly tuned to charge-transfer band of ZnPc-NO2 complex, we found out more than two-fold increase of the optical response to NO2 exposure in AgNps-ZnPc thin films compared to ZnPc films without AgNps.

Development of an Internet Web Application for the Study of Surface Plasmon Resonance Spectroscopy

An online web application was developed for the study of surface plasmon resonance (SPR) of different materials using angular and wavelength modulation. The present web application investigates the optical characteristics of the spectral and angular responses of a Kretschmann SPR sensor configuration that is widely applied for biological and chemical sensing by using the characteristic transmission matrix (CTM) method. The accuracy, efficiency, and reliability of the web application were validated by comparing the results generated by using the web application with other benchmark theoretical results and results of SPR experiments with standard samples.

The dynamics of combat module with nonlinear elastic support characteristics

The angular combat module oscillations are investigated. The combat module is situated in the combat vehicle platform using a nonlinear elastic characteristic support. The non autonomous and autonomous cases, the influence of resistance force are considered. The analytical methods for constructing solutions of appropriate models of combat module dynamics are presented by the using the Van der Pol and Ateb-periodic functions. The obtained results is the basis for evaluation of influence of angular oscillations on shooting accuracy on the move on rough terrain forming design solutions to reduce these vibrations.

Performance of surface plasmon resonance imaging system based on angular modulation and intensity measurement

This paper presents a surface plasmon resonance (SPR) imaging system based on angular modulation (AM) and intensity measurement (IM) together to avoid the mechanical errors of the angle scanning device. The SPR resonant angle was found by angular scanning method and then the light intensity changes were collected at a fixed incident angle. Glycerol gradient solution (0%, 1%, 2%, 3% (weight percentage) glycerol dissolved in water) experiments were conducted, which indicate that the best fixed angle location is the middle of the linear range of SPR absorption peak and the central area signals are more uniform than those of the border areas. The sensitivity differences of different areas of SPR images are studied, and an optimized algorithm is developed.

Macroscopic Degeneracy of Zero-Mode Rotating Surface States in 3D Dirac and Weyl Semimetals under Radiation.

We investigate the development of novel surface states when 3D Dirac or Weyl semimetals are placed under circularly polarized electromagnetic radiation. We find that the hybridization between inverted Floquet bands opens, in general, a gap, which closes at so-called exceptional points found for complex values of the momentum. This corresponds to the appearance of midgap surface states in the form of evanescent waves decaying from the surface exposed to the radiation. We observe a phenomenon reminiscent of Landau quantization by which the midgap surface states get a large degeneracy proportional to the radiation flux traversing the surface of the semimetal. We show that all of these surface states carry angular current, leading to an angular modulation of their charge that rotates with the same frequency of the radiation, which should manifest in the observation of a macroscopic chiral current in the irradiated surface.

Angular Modulation of Dual-Inverter Fed Open-End Motor for Electrical Vehicle Applications

In this paper, angular modulation index (AMI) implemented through a modified space vector modulation for the dual voltage source inverters (VSI) is proposed with the primarily aiming to reduce switching losses. The desired voltage across the load is synthesized by applying appropriate phase-angle displacement between space vector references. The proposed approach avoids the use of a dc/dc boost converter (which imposes loss and weight/price penalty to duplicate the dc-link voltage) and results to be particularly suitable for electrical/hybrid vehicle applications. Namely, the application of saving energy to keep driving has been identified as major concern. Hence, this work focuses on the strategy to enhance efficiency. The principles of the proposed controlling method and switching loss, which is reduced at least by 50%, are theoretically evaluated. This paper proposes a pioneering mathematical approach to correctly determine total harmonic distortion (THD) value of the voltage/current for the dual-VSI structure. Furthermore, simulation and experimental results prove that the proposed method insures benefits in terms of common-mode voltage, THD of the voltage, and switching loss reduction. The dual-VSI prototype supplying 1.5-kW induction motor is assembled in the laboratory to experimentally evaluate performance of the proposed method. Also, the simulation results carried out through MATLAB/Simulink environment are given to confirm performance of this easy-to-implement and high-efficient method.

Sensitivity in frequency dependent angular rotation of optical vortices.

This paper presents robust strategies to enhance the rotation sensitivity (and resolution) of a coherent superposition of optical vortices emerging from a single spiral phase plate (SPP) device when light's optical frequency (or wavelength) going into the SPP device is varied. The paper discusses the generation and measurement of ultrasmall rotation. Factors that affect the ability to perform precision rotation measurements include the linewidth and stability of the input light source, the number of photon counts making position rotation measurements on the CCD detector, SPP reflectivity, the length of SPP device, and the angular modulation frequency of the intensity pattern due to a coherent superposition of optical vortices in a single SPP device. This paper also discusses parameters to obtain a high-sensitivity single shot measurement and multiple measurements. Furthermore, it presents what I believe is a new scaling showing the enhancement in sensitivity (and resolution) in the standard quantum limit and Heisenberg limit. With experimentally realizable parameters, there is an enhancement of rotation sensitivity by at least one order of magnitude compared to previous rotation measurements with optical vortices. Understanding robust strategies to enhance the rotation sensitivity in an SPP device is important to metrology in general and for building compact SPP sensors such as gyroscopes, molecular sensors, and thermal sensors.

Impact of an Infant Transport Mattress on CT Dose and Image Quality

Neonates are at increased risk for cold stress and hypothermia in cool environments. An infant transport mattress (ITM) is commonly used to increase neonate temperature during transport and has been used during CT scanning. This study determined the impact of an ITM on radiation dose and image artifacts during CT scanning. CT images from a single clinical patient scanned with an ITM were reviewed, and observations of image artifacts were recorded. A phantom was scanned with and without the ITM while varying tube-current modulation, reconstruction method, slice thickness, metal reduction algorithm, tube voltage, and tube current. The effects of the ITM on computed tomography dose index (CTDIvol), mean Hounsfield unit (HU), and HU standard deviation were recorded. The clinical patient scan demonstrated significantly decreased mean HU and increased HU standard deviation. In the phantom, the ITM increased CTDIvol 27% and induced an artifact that decreased the mean HU by 3.5 HU and increased HU standard deviation by 4.6 HU. Angular tube-current modulation, strong iterative reconstruction, thick slices, metal artifact reduction, and high mA reduced the artifact. Using ITM during CT scanning is not recommended given the relatively brief scanning time, increased dose, and induced image artifacts. Based on our results, several acquisition parameters may be altered to mitigate the image artifact if an ITM is required during scanning.

Detecting compartmental non-Gaussian diffusion with symmetrized double-PFG MRI.

Diffusion in tissue and porous media is known to be non-Gaussian and has been used for clinical indications of stroke and other tissue pathologies. However, when conventional NMR techniques are applied to biological tissues and other heterogeneous materials, the presence of multiple compartments (pores) with different Gaussian diffusivities will also contribute to the measurement of non-Gaussian behavior. Here we present symmetrized double PFG (sd-PFG), which can separate these two contributions to non-Gaussian signal decay as having distinct angular modulation frequencies. In contrast to prior angular d-PFG methods, sd-PFG can unambiguously extract kurtosis as an oscillation from samples with isotropic or uniformly oriented anisotropic pores, and can generally extract a combination of compartmental anisotropy and kurtosis. The method further fixes its sensitivity with respect to the time dependence of the apparent diffusion coefficient. We experimentally demonstrate the measurement of the fourth cumulant (kurtosis) of diffusion and find it consistent with theoretical predictions. By enabling the unambiguous identification of contributions of compartmental kurtosis to the signal, sd-PFG has the potential to help identify the underlying micro-structural changes corresponding to current kurtosis based diagnostics, and act as a novel source of contrast to better resolve tissue micro-structure.

Propagation of structured light beams after multiple reflections in a spiral phase plate

This work presents propagation dynamics of structured light (complex light) containing optical vortices after it has undergone multiple reflections in a spiral phase plate (SPP) device having a nonzero surface reflection. In the calculations, the thick-plate approximation is assumed as it is expected to give a more accurate representation of the standard geometry of an SPP device from a low-surface reflection to a high-surface reflection. Calculations showing the propagation of counter-rotating optical vortices are presented, and the effect of the statistical nature of photons on the observation of the angular intensity modulation of the beam is discussed.

TU-F-CAMPUS-I-04: A Novel Phantom to Evaluate Longitudinal and Angular Automatic Tube Current Modulation (ATCM) in CT

Purpose: To manufacture a phantom specifically designed for the purpose of evaluating the performance of the longitudinal and angular automatic tube current modulation (ATCM) on modern CT scanners. Methods: In order to evaluate angular ATCM, the phantom has an elliptical cross section (aspect ratio 3:2). To evaluate longitudinal ATCM, the phantom consists of 3 sections, with different major axes (25 cm, 30 cm and 35 cm). Each section is 15 cm long in the longitudinal direction. Between each section is a smooth transition. The phantom was milled from a solid block of PMMA. ATCM performance is evaluated by 1) analyzing the applied tube current for each slice of the phantom and 2) analyzing the distribution of image noise (σ) along the scan direction at different positions in the phantom. A demonstration of the ATCM performance evaluation is given by investigating the effects of miscentering during a CT scan. Results: The developed phantom has proven useful for evaluating both the longitudinal and angular ATCM on modern CT scanners (spiral collimations ≥ 4 cm). Further benefits are the smooth transitions between the sections that prevent abnormal responses in the ATCM and the invariant sections that provide a means for investigating the stability of image noise. The homogeneity of the phantom makes image noise at different positions along the scan direction easy to quantify, which is crucial to understand how well the applied ATCM can produce a desired image quality. Conclusion: It is important to understand how the ATCM functions on CT scanners as it can directly affect dose and image quality. The phantom that has been developed is a most valuable tool to understand how different variables during a scan can affect the outcome of the longitudinal and angular ATCM.

Selection of modulation type in acousto-optic delay line with direct detection

This paper presents the physical and mathematical interpretation for the sequence of the response formation at the output of the acousto-optic delay line direct detection for various forms of connected to the terminals electro-acoustic transducer of high-frequency vibration. It has been shown that for the chosen design the intensity of light, which is incident on the photosensitive surface of the photodetector, varies only in the case of a change of acoustic power in the photoelastic medium. This eliminates the possibility of using the angular modulation for the transfer of video signal spectrum in the range of operating frequencies of the acousto-optic modulator in acousto-optic delay line with direct detection. In order to provide such a possibility it is recommended to install on the path of the deflected light a reference indicator, which converts the changes in the angle of diffraction into corresponding changes in the intensity of light, which is incident on the photosensitive surface of the photodetector. The proposed design is investigated for square and circular apertures of the light beam. It has been determined that best results are achieved in the case of the light beam with a square aperture and with a uniform distribution of power flow therein. We present the main results of experimental studies that confirm the effectiveness of the proposed design.

Defining the Observables for Quarks and Gluons Orbital Angular Momentum Distributions

We present a critical discussion of the observables that have been recently put forth to describe quarks and gluons orbital angular momentum distributions. Starting from a standard parameterization of the energy momentum tensor in QCD one can single out two forms of angular momentum, a so-called kinetic term, generally associated with the Ji decomposition, and a canonical term from the Jaffe Manohar decomposition. Orbital angular momentum has been connected to a Generalized Transverse Momentum Distribution (GTMD), for the canonical term, and to a twist three Generalized Parton Distribution for the kinetic term. We argue that while the latter appears as an azymuthal angular modulation in the longitudinal target spin asymmetry in deeply virtual Compton scattering, due to parity constraints, the GTMD associated with canonical angular momentum cannot be measured in a similar set of experiments.

Optical elements with extended depth of focus and arbitrary distribution of intensity along the focal segment obtained by angular modulation of the optical power

Light Sword Lens (LSL), i.e., an optical element with extended depth of focus (EDOF) characterized by angular modulation of the optical power in its conventional form is characterized by a linear relationship between the optical power and the angular coordinate of the corresponding angular lens sector. This dependence may be manipulated in function of the required design needs. In the present communicate this additional degree of freedom of design is used for elimination of the LSL shape discontinuity.

Angular Dependency of Hyperspectral Measurements over Wheat Characterized by a Novel UAV Based Goniometer

In this study we present a hyperspectral flying goniometer system, based on a rotary-wing unmanned aerial vehicle (UAV) equipped with a spectrometer mounted on an active gimbal. We show that this approach may be used to collect multiangular hyperspectral data over vegetated environments. The pointing and positioning accuracy are assessed using structure from motion and vary from σ = 1° to 8° in pointing and σ = 0.7 to 0.8 m in positioning. We use a wheat dataset to investigate the influence of angular effects on the NDVI, TCARI and REIP vegetation indices. Angular effects caused significant variations on the indices: NDVI = 0.83–0.95; TCARI = 0.04–0.116; REIP = 729–735 nm. Our analysis highlights the necessity to consider angular effects in optical sensors when observing vegetation. We compare the measurements of the UAV goniometer to the angular modules of the SCOPE radiative transfer model. Model and measurements are in high accordance (r2 = 0.88) in the infrared region at angles close to nadir; in contrast the comparison show discrepancies at low tilt angles (r2 = 0.25). This study demonstrates that the UAV goniometer is a promising approach for the fast and flexible assessment of angular effects.

Artificial Intelligence for Speech Recognition Based on Neural Networks

Speech recognition or speech to text includes capturing and digitizing the sound waves, transformation of basic linguistic units or phonemes, constructing words from phonemes and contextually analyzing the words to ensure the correct spelling of words that sounds the same. Approach: Studying the possibility of designing a software system using one of the techniques of artificial intelligence applications neuron networks where this system is able to distinguish the sound signals and neural networks of irregular users. Fixed weights are trained on those forms first and then the system gives the output match for each of these formats and high speed. The proposed neural network study is based on solutions of speech recognition tasks, detecting signals using angular modulation and detection of modulated techniques.

Observables for Quarks and Gluons Orbital Angular Momentum Distributions

We discuss the observables that have been recently put forth to describe quarks and gluons orbital angular momentum distributions. Starting from a standard parameterization of the energy momentum tensor in QCD one can single out two forms of angular momentum, a so-called kinetic term – Ji decomposition – or a canonical term – Jaffe-Manohar decomposition. Orbital angular momentum has been connected in each decomposition to a different observable, a Generalized Transverse Momentum Distribution (GTMD), for the canonical term, and a twist three Generalized Parton Distribution (GPD) for the kinetic term. While the latter appears as an azimuthal angular modulation in the longitudinal target spin asymmetry in deeply virtual Compton scattering, due to parity constraints, the GTMD associated with canonical angular momentum cannot be measured in a similar set of experiments.