The Experts below are selected from a list of 94500 Experts worldwide ranked by ideXlab platform
Kazuo Hotate - One of the best experts on this subject based on the ideXlab platform.
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High-repetition-rate distributed Brillouin sensor based on optical correlation-domain analysis with Differential Frequency modulation
Optics Letters, 2011Co-Authors: Kwang Yong Song, Masato Kishi, Zuyuan He, Kazuo HotateAbstract:A kind of high-repetition-rate distributed Brillouin sensor is proposed and experimentally demonstrated based on optical correlation-domain analysis with Differential Frequency modulation, where the optical frequencies of the pump and the probe waves are modulated at slightly different RFs so that the temporal position of the measurement is continuously and repeatedly swept along a fiber under test. A distribution map of Brillouin Frequency variation along a 100 m optical fiber is acquired at a repetition rate of 20 Hz with an accuracy of ±2.5 MHz and a spatial resolution of about 80 cm.
Robert Meneghini - One of the best experts on this subject based on the ideXlab platform.
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on study of air space borne dual wavelength radar for estimates of rain profiles
2013Co-Authors: Liang Liao, Robert MeneghiniAbstract:In this study, a framework is given by which air/space-borne dual-wavelength radar data can be used to estimate the characteristic parameters of hydrometeors. The focus of the study is on the Global Precipitation Measurement (GPM) precipitation radar, a dual-wavelength radar that will operate in the Ku (13.6 GHz) and Ka (35 GHz) bands. A key aspect of the retrievals is the relationship between the Differential Frequency ratio (DFR) and the median volume diameter, D0, and its dependence on the phase state of the hydrometeors. It is shown that parametric plots of D0 and particle concentration in the plane of the DFR and the radar reflectivity factor in the Ku band can be used to reduce the ambiguities in deriving D0 from DFR. A self-consistent iterative algorithm, which does not require the use of an independent pathattenuation constraint, is examined by applying it to the apparent radar reflectivity profiles simulated from a drop size distribution (DSD) model. For light to moderate rain, the self-consistent rain profiling approach converges to the correct solution only if the same shape factor of the Gamma distributions is used both to generate and retrieve the rain profiles. On the other hand, if the shape factors differ, the iteration generally converges but not to the correct solution. To further examine the dual-wavelength techniques, the selfconsistent iterative algorithm, along with forward and backward rain profiling algorithms, are applied to measurements taken from the 2nd generation Precipitation Radar (PR-2) built by the Jet Propulsion Laboratory. Consistent with the model results, it is found that the estimated rain profiles are sensitive to the shape factor of the size distribution when the iterative, self-consistent approach is used but relatively insensitive to this parameter when the forward- and backward-constrained approaches are used.
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A Study on the Feasibility of Dual-Wavelength Radar for Identification of Hydrometeor Phases
Journal of Applied Meteorology and Climatology, 2011Co-Authors: Liang Liao, Robert MeneghiniAbstract:Abstract An important objective for the dual-wavelength Ku-/Ka-band precipitation radar (DPR) that will be on board the Global Precipitation Measurement (GPM) core satellite is to identify the phase state of hydrometeors along the range direction. To assess this, radar signatures are simulated in snow and rain to explore the relation between the Differential Frequency ratio (DFR), defined as the difference of radar reflectivity factors between Ku and Ka bands, and the radar reflectivity factor at Ku band ZKu for different hydrometeor types. Model simulations indicate that there is clear separation between snow and rain in the ZKu–DFR plane assuming that the snow follows the Gunn–Marshall size distribution and rain follows the Marshall–Palmer size distribution. In an effort to verify the simulated results, the data collected by the Airborne Second-Generation Precipitation Radar (APR-2) in the Wakasa Bay Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) campaign are employed. Using ...
A I Karsilayan - One of the best experts on this subject based on the ideXlab platform.
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a fully Differential low power divide by 8 injection locked Frequency divider up to 18 ghz
IEEE Journal of Solid-state Circuits, 2007Co-Authors: Shanfeng Cheng, Haitao Tong, J Silvamartinez, A I KarsilayanAbstract:A low power divide-by-8 injection-locked Frequency divider is presented. The Frequency divider consists of four current-mode logic (CML) D-latches connected in the form of a four-stage ring with the Differential input signal injected into the clock terminals of the latches. The output signals can be taken from the data terminals of any of the four latches. The proposed Frequency divider has higher operating Frequency and lower power dissipation compared with conventional static Frequency dividers. Compared with existing injection-locked Frequency dividers, the proposed fully Differential Frequency divider presents wider locking range with the center Frequency independent of injection amplitude. The Frequency divider is implemented in TSMC 0.18 mum CMOS technology. It consumes around 3.6 mW power with 1.8 V supply. The operating Frequency can be tuned from 4 GHz to 18 GHz. The ratio of the locking range over the center Frequency is up to 50% depending on the operating Frequency and biasing conditions.
Donghyun Baek - One of the best experts on this subject based on the ideXlab platform.
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76 81 ghz cmos transmitter with a phase locked loop based multichirp modulator for automotive radar
IEEE Transactions on Microwave Theory and Techniques, 2015Co-Authors: Joonhong Park, Hyuk Ryu, Jeonggeun Kim, Donghyun BaekAbstract:This paper presents the design of a linear Frequency-modulated continuous-wave (FMCW) radar transmitter (TX) for automotive radar applications. The TX has a wide operating range from 76 to 81 GHz by employing a Frequency-doubling architecture using an LC voltage-controlled oscillator operating at 38–40.5 GHz and a Differential Frequency doubler using a single transformer. A chirp generator is integrated into the TX, which provides various Frequency chirp profiles with programmable chirp slope and sweep duration. The proposed CMOS FMCW TX can be applied to various modulation algorithms for multiple target detection and the avoidance of ghost targets. The TX is implemented using 65-nm CMOS technology. The chip size is 1.48 $\,\times\,$ 1.85 mm $^{2}$ . The measurement results shows a 76–81-GHz Frequency range and 3-dBm output power while dissipating 320 mW. The phase-noise density of the TX is ${-}{\hbox{83.33}}$ dBm/Hz at an offset Frequency of 1 MHz when the output Frequency is 77 GHz.
Kwang Yong Song - One of the best experts on this subject based on the ideXlab platform.
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High-repetition-rate distributed Brillouin sensor based on optical correlation-domain analysis with Differential Frequency modulation
Optics Letters, 2011Co-Authors: Kwang Yong Song, Masato Kishi, Zuyuan He, Kazuo HotateAbstract:A kind of high-repetition-rate distributed Brillouin sensor is proposed and experimentally demonstrated based on optical correlation-domain analysis with Differential Frequency modulation, where the optical frequencies of the pump and the probe waves are modulated at slightly different RFs so that the temporal position of the measurement is continuously and repeatedly swept along a fiber under test. A distribution map of Brillouin Frequency variation along a 100 m optical fiber is acquired at a repetition rate of 20 Hz with an accuracy of ±2.5 MHz and a spatial resolution of about 80 cm.