Orthogonal Channel Coding for Simultaneous Co- and Cross-Polarization Measurements

2009 ◽  
Vol 26 (1) ◽  
pp. 45-56 ◽  
Author(s):  
V. Chandrasekar ◽  
Nitin Bharadwaj
Keyword(s):  
Channel Coding ◽  
Electromagnetic Waves ◽  
Polarization State ◽  
Dual Polarization ◽  
Colorado State University ◽  
Weather Radars ◽  
Current Implementation ◽  
Polarization States ◽  
Linear Depolarization Ratio ◽  
Orthogonal Phase

Abstract Dual-polarization weather radars typically measure the radar reflectivity at more than one polarization state for transmission and reception. Historically, dual-polarization radars have been operated at copolar and cross-polar states defined with respect to the transmit polarization states. Recently, based on the improved understanding of the propagation properties of electromagnetic waves in precipitation media, the simultaneous transmit and receive (STAR) mode has become common to simplify the hardware. In the STAR mode of operation, horizontal and vertical polarization states are transmitted simultaneously and samples of both horizontal and vertical copolar returns are obtained. A drawback of the current implementation of STAR mode is its inability to measure parameters obtained from cross-polar signals such as linear depolarization ratio (LDR). In this paper, a technique to obtain cross-polar signals with STAR mode waveform is presented. In this technique, the horizontally and vertically polarized transmit waveforms are coded with orthogonal phase sequences. The performance of the phase-coded waveform is determined by the properties of the phase codes. This orthogonal phase coding technique is implemented in the Colorado State University–University of Chicago–Illinois State Water Survey (CSU–CHILL) radar. This paper outlines the methodology and presents the performance of the cross-polar and copolar parameter estimation based on the simulation as well as data collected from the CSU–CHILL radar.

scholarly journals SEA-POL Goes to Sea

2019 ◽  
Vol 100 (11) ◽  
pp. 2285-2301 ◽  
Author(s):  
Steven A. Rutledge ◽  
V. Chandrasekar ◽  
Brody Fuchs ◽  
Jim George ◽  
Francesc Junyent ◽  
...  
Keyword(s):  
Doppler Radar ◽  
The United States ◽  
Upper Ocean ◽  
State University ◽  
Dual Polarization ◽  
Regional Study ◽  
Ocean Turbulence ◽  
Colorado State University ◽  
Weather Radars ◽  
Microphysical Processes

AbstractA new, advanced radar has been developed at Colorado State University (CSU). The Sea-Going Polarimetric (SEA-POL) radar is a C-band, polarimetric Doppler radar specifically designed to deploy on research ships. SEA-POL is the first such weather radar developed in the United States. Ship-based weather radars have a long history, dating back to GATE in 1974. The GATE radars measured only reflectivity. After GATE, ship radars also provided Doppler measurements. SEA-POL represents the next advancement by adding dual-polarization technology, the ability to transmit and receive both horizontal and vertical polarizations. This configuration provides information about hydrometeor size, shape, and phase. As a result, superior rain-rate estimates are afforded by the dual-polarization technology, along with hydrometeor identification and overall improved data quality. SEA-POL made its first deployment as part of the Salinity Processes in the Upper Ocean Regional Study, second field phase (SPURS-2) fall 2017 cruise to the eastern tropical Pacific, sailing on the R/V Roger Revelle. SPURS-2 was a field project to investigate the fate of freshwater deposited on the ocean’s surface. Oceanographers are keenly interested in how fast these freshwater patches mix out by wind and upper-ocean turbulence, as the less dense rainfall sitting atop the salty ocean inhibits mixing through increased stability. To this end, during SPURS-2, SEA-POL produced rain maps identifying the location of freshwater lenses on the ocean’s surface thereby providing context for measurements of SST and salinity. Examples of SEA-POL polarization measurements are also discussed to assess microphysical processes within oceanic convection. Future ocean-based field campaigns will now benefit from SEA-POL’s advanced dual-polarization technology.

scholarly journals Gaussian Model Adaptive Processing in Time Domain (GMAP-TD) for Weather Radars

2013 ◽  
Vol 30 (11) ◽  
pp. 2571-2584 ◽  
Author(s):  
Cuong M. Nguyen ◽  
V. Chandrasekar
Keyword(s):  
Time Domain ◽  
Gaussian Model ◽  
Radar Data ◽  
Adaptive Processing ◽  
Colorado State University ◽  
Weather Radars ◽  
Ground Clutter ◽  
Moment Estimation ◽  
Interpolation Procedure ◽  
The Time Domain

Abstract The Gaussian model adaptive processing in the time domain (GMAP-TD) method for ground clutter suppression and signal spectral moment estimation for weather radars is presented. The technique transforms the clutter component of a weather radar return signal to noise. Additionally, an interpolation procedure has been developed to recover the portion of weather echoes that overlap clutter. It is shown that GMAP-TD improves the performance over the GMAP algorithm that operates in the frequency domain using both signal simulations and experimental observations. Furthermore, GMAP-TD can be directly extended for use with a staggered pulse repetition time (PRT) waveform. A detailed evaluation of GMAP-TD performance and comparison against the GMAP are done using simulated radar data and observations from the Colorado State University–University of Chicago–Illinois State Water Survey (CSU–CHILL) radar using uniform and staggered PRT waveform schemes.

Design and Performance Analysis of 2D OCDMA System with Polarization States

2016 ◽  
Vol 37 (4) ◽  
Author(s):  
Manisha Bharti ◽  
Ajay K. Sharma ◽  
Manoj Kumar
Keyword(s):  
Phase Shift ◽  
Polarization State ◽  
Phase Shift Keying ◽  
Modulation Formats ◽  
Differential Phase Shift ◽  
Differential Phase ◽  
Differential Phase Shift Keying ◽  
Shift Keying ◽  
Polarization States ◽  
Code Division Multiple

AbstractThis paper focuses on increasing the number of subscribers in optical code-division multiple access (OCDMA) system by using one of the features of light signal that it can be propagated in two polarization states. The performance of two-dimensional (2D) OCDMA system based on wavelength-time coding scheme by adding polarization state is investigated at varying data rates from 1 GHz to 6 GHz and for various modulation formats. It is reported that with increase in data rate of system, the performance of the system deteriorates due to polarization mode dispersion. Non-return to-zero (RZ), return to-zero (RZ), carrier suppressed return-to-zero (CSRZ) and differential phase shift keying (DPSK) modulation formats are simulated for a single user system with polarization. Investigations reveal that differential phase shift keying (DPSK) modulation format suits best to the proposed system and exhibit the potential to improve the flexibility of system for more number of users. The investigations are reported in terms of Q-factor, BER, received optical power (ROP) and eye diagrams.

Investigation of Polarization State Generation with Ergodicity of Polarization States Based on the Quaternion Approach

2014 ◽  
Vol 34 (3) ◽  
pp. 0306002 ◽  
Author(s):  
刘岚岚 Liu Lanlan ◽  
吴重庆 Wu Chongqing ◽  
李政勇 Li Zhengyong
Keyword(s):  
Polarization State ◽  
State Generation ◽  
Polarization States

scholarly journals Classification of Hydrometeors Using Measurements of the Ka-Band Cloud Radar Installed at the Milešovka Mountain (Central Europe)

2018 ◽  
Vol 10 (11) ◽  
pp. 1674 ◽  
Author(s):  
Zbyněk Sokol ◽  
Jana Minářová ◽  
Petr Novák
Keyword(s):  
Central Europe ◽  
Terminal Velocity ◽  
Small Particles ◽  
Cloud Droplets ◽  
Vertical Temperature Profile ◽  
Ka Band ◽  
Cloud Radar ◽  
Weather Radars ◽  
Cloud Particles ◽  
Linear Depolarization Ratio

In radar meteorology, greater interest is dedicated to weather radars and precipitation analyses. However, cloud radars provide us with detailed information on cloud particles from which the precipitation consists of. Motivated by research on the cloud particles, a vertical Ka-band cloud radar (35 GHz) was installed at the Milešovka observatory in Central Europe and was operationally measuring since June 2018. This study presents algorithms that we use to retrieve vertical air velocity (Vair) and hydrometeors. The algorithm calculating Vair is based on small-particle tracers, which considers the terminal velocity of small particles negligible and, thereby, Vair corresponds to the velocity of the small particles. The algorithm classifying hydrometeors consists of calculating the terminal velocity of hydrometeors and the vertical temperature profile. It identifies six hydrometeor types (cloud droplets, ice, and four precipitating particles: rain, graupel, snow, and hail) based on the calculated terminal velocity of hydrometeors, temperature, Vair, and Linear Depolarization Ratio. The results of both the Vair and the distribution of hydrometeors were found to be realistic for a thunderstorm associated with significant lightning activity on 1 June 2018.

scholarly journals Design and experimental analysis of dual-band polarization converting metasurface for microwave applications

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Bilawal Khan ◽  
Babar Kamal ◽  
Sadiq Ullah ◽  
Imran Khan ◽  
Jawad Ali Shah ◽  
...  
Keyword(s):  
Electromagnetic Waves ◽  
Polarization State ◽  
Plane Waves ◽  
Microwave Frequency ◽  
Dual Band ◽  
Orthogonal Polarization ◽  
Frequency Bands ◽  
Practical Applications ◽  
Sensor Applications ◽  
Polarized Waves

Abstract The manipulation of polarization state of electromagnetic waves is of great importance in many practical applications. In this paper, the reflection characteristics of a thin and dual-band metasurface are examined in the microwave frequency regime. The metasurface consists of a 22 × 22 element array of periodic unit cells. The geometry of the unit cell consists of three layers, including a 45° inclined dipole shape metal patch on top, which is backed by a 1.6 mm thick FR-4 substrate in the middle, and a fully reflective metallic mirror at the bottom. The proposed surface is exposed to horizontally (x) or vertically (y) polarized plane waves and the co and cross polarization reflection coefficients of the reflected waves are investigated experimentally in the 6–26 GHz frequency range. The metasurface is designed to convert incident waves of known polarization state (horizontal or vertical) to orthogonal polarization state (vertical and horizontal) in two distinct frequency bands, i.e. 7.1–8 GHz and 13.3–25.8 GHz. In these two frequency bands the simulated and experimental results are in good agreement. The polarization conversion ratio (PCR) of the surface is greater than 95% in the targeted frequency bands. A detailed parametric analysis of the metasurface is also discussed in this work and it has been estimated that the surface has the additional ability to convert linearly polarized waves to circularly polarized waves at several distinct frequencies. The proposed metasurface can be utilized in sensor applications, stealth technology, electromagnetic measurements, and antennas design.

scholarly journals A Thermal Tuning Meta-Duplex-Lens (MDL): Design and Characterization

Nanomaterials ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 1135 ◽  
Author(s):  
Ning Xu ◽  
Yaoyao Liang ◽  
Yuan Hao ◽  
Min Mao ◽  
Jianping Guo ◽  
...  
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Electromagnetic Waves ◽  
Incident Light ◽  
Polarization State ◽  
Transmission Efficiency ◽  
Metallic State ◽  
Phase Gradient ◽  
Storage Devices ◽  
Change Material

Multifunctional metasurfaces play an important role in the development of integrated optical paths. However, some of the realizations of current multifunctional metasurface devices depend on polarization selectivity, and others change the polarization state of the outgoing light. Here, based on vanadium dioxide (VO2) phase change material, a strategy to design a meta-duplex-lens (MDL) is proposed and numerical simulation calculations demonstrate that at low temperature (about 300 K), VO2 behaves as a dielectric so that the MDL can act as a transmission lens (transmission efficiency of 87.6%). Conversely, when VO2 enters the metallic state (about 355 K), the MDL has the ability to reflect and polymerize electromagnetic waves and works as a reflection lens (reflection efficiency of 85.1%). The dielectric waveguide and gap-surface plasmon (GSP) theories are used in transmission and reflection directions, respectively. In order to satisfy the coverage of the phase gradient in the range of 2π in both cases, we set the antenna as a nanopillar with a high aspect ratio. It is notable that, via symmetrical antennas acting in concert with VO2 phase change material, the polarization states of both the incident light and the outgoing light are not changed. This reversible tuning will play a significant role in the fields of imaging, optical storage devices, communication, sensors, etc.

scholarly journals Macrophage Polarization and Osteoporosis: A Review

Nutrients ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2999
Author(s):  
Joseph Muñoz ◽  
Neda S. Akhavan ◽  
Amy P. Mullins ◽  
Bahram H. Arjmandi
Keyword(s):  
Bone Resorption ◽  
Bone Mineralization ◽  
Macrophage Polarization ◽  
Polarization State ◽  
M2 Macrophages ◽  
Cytokines And Chemokines ◽  
Polarization States ◽  
Classically Activated Macrophages ◽  
Cost Efficient ◽  
Alternatively Activated

Over 200 million people suffer from osteoporosis worldwide. Individuals with osteoporosis have increased rates of bone resorption while simultaneously having impaired osteogenesis. Most current treatments for osteoporosis focus on anti-resorptive methods to prevent further bone loss. However, it is important to identify safe and cost-efficient treatments that not only inhibit bone resorption, but also stimulate anabolic mechanisms to upregulate osteogenesis. Recent data suggest that macrophage polarization may contribute to osteoblast differentiation and increased osteogenesis as well as bone mineralization. Macrophages exist in two major polarization states, classically activated macrophages (M1) and alternatively activated macrophage (M2) macrophages. The polarization state of macrophages is dependent on molecules in the microenvironment including several cytokines and chemokines. Mechanistically, M2 macrophages secrete osteogenic factors that stimulate the differentiation and activation of pre-osteoblastic cells, such as mesenchymal stem cells (MSC’s), and subsequently increase bone mineralization. In this review, we cover the mechanisms by which M2 macrophages contribute to osteogenesis and postulate the hypothesis that regulating macrophage polarization states may be a potential treatment for the treatment of osteoporosis.

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