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In underwater communications, reciprocal motion between transmitter and receiver has a significant impact on reception quality. In orthogonal broadband systems that provide high bit rates, this problem becomes more important, especially in the higher frequency range, where the absolute Doppler shift is the greatest. Due to the low propagation speed of acoustic wave underwater, a substantial difference exists between the Doppler shift for lower and upper frequencies of the utilized spectrum. Consequently, a frequency-independent Doppler shift factor is employed. One of the most popular methods for determining the Doppler shift is the use of pilots. The problem of selecting the number and determining the frequency of pilots in such a way as to obtain the lowest possible error rate was identified. Real-world testing was conducted in a multipath propagation environment with relative speeds of up to 1.5 m/s. The effectiveness of Doppler shift determination was evaluated by analyzing the bit error rate. The results of the conducted tests indicate that, based on the achieved error rate, it is sufficient to employ 7 pilots positioned at low frequencies.

Space-based opportunistic positioning is a crucial component of resilient positioning, navigation, and timing (PNT) systems, and it requires the acquisition of orbit information for non-cooperative low Earth orbit (LEO) satellites. Traditional methods for orbit determination (OD) of non-cooperative LEO satellites have difficulty in achieving a balance between reliability, hardware costs, and availability duration. To address these challenges, this study proposes a framework for single-station orbit determination of non-cooperative LEO satellites. By utilizing signals of opportunity (SOPs) captured by a single ground station, the system performs initial orbit determination (IOD), precise orbit determination (POD), and orbit prediction (OP), enabling the long-term determination of satellite positions and velocities. Under the proposed framework, the reliability and real-time performance are dependent on the initial orbit determination and the orbit calculation based on the dynamical model. To achieve initial orbit determination, a three-step algorithm is designed. (1) An improved search method is employed to estimate a coarse orbit using single-pass Doppler measurements. (2) Data association is conducted to obtain multi-pass Doppler observations. (3) The least squares (LS) is implemented to determine the initial orbit using the associated multi-pass Doppler measurements and the coarse orbit. Additionally, to enhance computational efficiency, two fast orbit calculation algorithms are devised. These algorithms leverage the numerical stability of the Runge–Kutta integrator to reduce computations and exploit the strong correlation among nearby time intervals of orbits with small eccentricities to minimize redundant calculations, thereby achieving orbit calculation efficiently. Finally, through positioning experiments, the determined orbits are demonstrated to have accuracy comparable to that of two-line elements (TLE) updated by the North American Aerospace Defense Command (NORAD). [ABSTRACT FROM AUTHOR]

Currently, it is more efficient to use LEO small spacecraft as radio control points to determine the compliance of the radiation parameters of electronic means with the relevant norms and conditions of permits for the use of the radio frequency spectrum. Such satellite radio monitoring systems make it possible to determine the parameters of signals and the location of radio-electronic means over a large area with a diverse terrain, which will increase the efficiency of radio monitoring systems. When performing such tasks, one of the most important parameters is the detection and isolation of a useful signal against the background of noise and interference. For such purposes, it is effective to use Kalman filters. It was found that the Kalman filter can detect and isolate useful signals against the background of noise and interference with very high accuracy. However, when solving such problems, problems arise related to the stability of the method to the choice of the initial state of the filter and the inevitable distortion of the frequency of the desired signal due to the presence of the Doppler effect. In the course of this study, it was found that the similarity coefficient depends on the noise level, but it does not actually depend on frequency distortion. It was also found that when the SNR ratio is greater than 0 dB, the radio signal at the input of the on-board measuring receiver will be received with a reliability of more than 90 %. Therefore, it can be concluded that the signal detection method for satellite radio monitoring based on the use of the Kalman filter is resistant to possible frequency distortions of the desired signal due to the Doppler effect and does not affect the correctness and speed of decisions made [ABSTRACT FROM AUTHOR]

Background/Aim: It has been reported that both the internal carotid artery (ICA) and the common carotid artery (CCA) are associated with hypoxia, also observed in late-onset fetal growth restriction (FGR). However, it has not yet been investigated whether these Doppler measurements differ in cases of late-onset FGR. This study evaluated the ICA and the CCA Doppler parameters in late-onset FGR fetuses and compared these measurements with those of healthy fetuses. Methods: This cross-sectional observational study comprised 75 singleton pregnancies diagnosed with late-onset FGR between the 32nd and 37th weeks of gestation, alongside 75 healthy fetuses paired 1:1 based on obstetric history and gestational age between June 2022 and May 2023. The Delphi consensus of 2016 was used for the definition of late-onset FGR. The exclusion criteria were congenital anomalies, presence of any additional disease, maternal body mass index over 35 kg/m², abdominal scars hindering ultrasound visualization, use of medications such as antenatal steroids, sympathomimetics, and indomethacin that affect vascular function, drug use, smoking during pregnancy, concurrent preeclampsia, and multiple pregnancies. Upon the patients' admission to the hospital, their demographic characteristics were documented, and ultrasonographic examinations and Doppler measurements were subsequently performed. The Doppler velocimetry of the umbilical artery (UA) encompassed measurements of the systolic to diastolic ratio (S/D), pulsatility index (PI), and peak systolic velocity (PSV). The carotid artery Doppler velocimetry of the middle cerebral artery (MCA), ICA, and CCA encompassed measurements of the PI, resistance index (RI), and PSV. We assessed the diagnostic performance of Doppler measurements for late-onset FGR through receiver operating characteristic (ROC) analysis. Results: In the late-onset FGR group, the mean UA-SD was higher (2.7 [0.6] vs. 2.5 [0.5], P=0.006), and the mean UA-PI (0.8 [0.2] vs. 0.9 [0.2], P=0.011) and mean PSV (35.6 [8.2] vs. 41.1 [7.1], P<0.001) were lower compared to the control group. In the late-onset FGR group, carotid Doppler measurements were more pronounced than UA Doppler measurements. Moreover, ICA Doppler measurements exhibited superior diagnostic performance in predicting late-onset FGR compared to other Doppler measurements (Area under the curve [AUC]=0.777, P<0.001 for ICA-PI; AUC=0.751, P<0.001 for ICA-RI; AUC=0.749, P<0.001 for ICA-PSV). Conclusion: In fetuses with late-onset FGR, UA Doppler measurements showed minimal differences compared to healthy fetuses, but differences in carotid Doppler measurements, especially in the ICA, were more pronounced. Therefore, in the management of fetuses suspected of having late-onset FGR, a more detailed Doppler examination might be required. [ABSTRACT FROM AUTHOR]

For a better understanding of atmospheric dynamics, it is very important to know the general condition (dynamics and chemistry) of the atmosphere. Planetary waves (PWs) are global scale waves, which are well-known as main drivers of the large-scale weather patterns in mid-latitudes on time scales from several days up to weeks in the troposphere. When PWs break, they often cut pressure cells off the jet stream. A specific example are so-called streamer events, which occur predominantly in the lower stratosphere at mid-and high latitudes. For streamer events we check, whether there are any changes of gravity wave (GW) or infrasound characteristics related to these events in ionospheric and surface measurements (continuous Doppler soundings, array of microbarometers) in the Czech Republic. First order signatures of streamer events were not identified in infrasound data at stations WBCI and PVCI. Supplementary ground-based measurements of GW using the WBCI array in the troposphere showed that GW propagation azimuths were more random during streamer and streamer-like events compared to those observed during calm conditions. GW propagation characteristics observed in the ionosphere by continuous Doppler soundings during streamer events did not differ from those expected for the given time period. [ABSTRACT FROM AUTHOR]

Background Malaria in pregnancy (MiP) has been associated with fetal growth restriction, the underlying pathogenic mechanisms of which remain poorly understood. Malaria in pregnancy is suspected to induce abnormalities in placental vascularization, leading to impaired placental development. Our study evaluated MIP's effect on uterine artery (UtA) and umbilical artery (UA) blood flow. Methods The analysis included 253 Beninese women followed throughout pregnancy and screened monthly for submicroscopic and microscopic malaria. Uterine artery Doppler measurement was performed once between 21 and 25 weeks' gestation (wg), and UA Doppler measurement was performed 1–3 times from 28 wg. Linear and logistic regression models were used to assess the effect of malaria infections on UtA Doppler indicators (pulsatility index and presence of a notch), whereas a logistic mixed model was used to assess the association between malaria infections and abnormal UA Doppler (defined as Z-score ≥2 standard deviation or absent/reversed UA end-diastolic flow). Results Primigravidae represented 7.5% of the study population; 42.3% of women had at least 1 microscopic infection during pregnancy, and 29.6% had at least 1 submicroscopic infection (and no microscopic infection). Both microscopic and submicroscopic infections before Doppler measurement were associated with the presence of a notch (adjusted odds ratio [aOR] 4.5, 95% confidence interval [CI] = 1.2–16.3 and aOR 3.3, 95% CI =.9–11.9, respectively). No associations were found between malaria before the Doppler measurement and abnormal UA Doppler. Conclusions Malaria infections in the first half of pregnancy impair placental blood flow. This highlights the need to prevent malaria from the very beginning of pregnancy. [ABSTRACT FROM AUTHOR]

Space-based opportunistic positioning is a crucial component of resilient positioning, navigation, and timing (PNT) systems, and it requires the acquisition of orbit information for non-cooperative low Earth orbit (LEO) satellites. Traditional methods for orbit determination (OD) of non-cooperative LEO satellites have difficulty in achieving a balance between reliability, hardware costs, and availability duration. To address these challenges, this study proposes a framework for single-station orbit determination of non-cooperative LEO satellites. By utilizing signals of opportunity (SOPs) captured by a single ground station, the system performs initial orbit determination (IOD), precise orbit determination (POD), and orbit prediction (OP), enabling the long-term determination of satellite positions and velocities. Under the proposed framework, the reliability and real-time performance are dependent on the initial orbit determination and the orbit calculation based on the dynamical model. To achieve initial orbit determination, a three-step algorithm is designed. (1) An improved search method is employed to estimate a coarse orbit using single-pass Doppler measurements. (2) Data association is conducted to obtain multi-pass Doppler observations. (3) The least squares (LS) is implemented to determine the initial orbit using the associated multi-pass Doppler measurements and the coarse orbit. Additionally, to enhance computational efficiency, two fast orbit calculation algorithms are devised. These algorithms leverage the numerical stability of the Runge–Kutta integrator to reduce computations and exploit the strong correlation among nearby time intervals of orbits with small eccentricities to minimize redundant calculations, thereby achieving orbit calculation efficiently. Finally, through positioning experiments, the determined orbits are demonstrated to have accuracy comparable to that of two-line elements (TLE) updated by the North American Aerospace Defense Command (NORAD).

Objectives: We aimed to evaluate a new ratio of amniotic fluid volume (AFV) to Doppler measurements, and compare its association with adverse perinatal outcomes (APOs) in fetal growth restriction (FGR). Methods: This prospective study included pregnant women with singleton fetal growth–restricted fetuses. Each participant underwent a detailed ultrasonographic examination. Uterine artery pulsatility index, umbilical artery pulsatility index (UA PI), middle cerebral artery pulsatility index (MCA PI), cerebroplacental ratio (CPR), and umbilical‐to‐cerebral ratio (UCR) were calculated, and the single deepest pocket (SDP) technique was used to estimate AFV. Amniotic‐umbilical‐to‐cerebral ratio (AUCR) was calculated as the ratio of SDP to UCR: AUCR = SDP / (UA PI/MCA PI). APO was defined as umbilical venous cord blood pH <7.10, 5‐minute APGAR score <7, and neonatal intensive care unit admission. Results: We compared the fetal ultrasonographic and demographic features between the APO and the non‐APO groups. The mean UA PI and UCR were significantly higher in the APO group. The mean SDP, CPR, and AUCR were significantly lower in the APO group. Receiver operating characteristic curve analyses demonstrated the highest area under the curve value (0.882; P < 0.001) for AUCR to APOs. Conclusion: The current study suggests that AUCR is the best predictor for APOs in FGR. Synopsis: The currrent study suggests that umbilical‐to‐cerebral ratio is superior to cerebroplacental ratio and the amniotic‐umbilical‐to‐cerebral ratio is the best predictor of adverse perinatal outcomes in fetal growth restriction. [ABSTRACT FROM AUTHOR]

A new method of high-precision positioning of mobile objects moving along program trajectories is proposed based on processing of satellite navigation measurements using robust filtering algorithms. The method is based both on the possibility of approximating (in particular, using electronic maps) the program trajectory of an object with a set of trajectory intervals with known analytical dependencies of navigation parameters and on the use of robust stochastic filtering methods that take into account the characteristic dynamics of the object and the uncertain nature of the type of interference distributions of Doppler and code satellite measurements. Electronic map information providing high accuracy of trajectory binding is integrated with algorithms of robust nonlinear filtering of satellite measurements that are optimal by the criterion of minimum nonlinear function of the measurement residual determined by the class of interference distributions of Doppler and code measurements. This makes it possible to significantly reduce computing costs while significantly improving the accuracy of positioning an object. The effectiveness of the proposed method is illustrated by a numerical example. [ABSTRACT FROM AUTHOR]

Abstract Smoothing process can effectively improve the accuracy of the Global Navigation Satellite System (GNSS) position estimation algorithm. In this study, a Doppler‐aided GNSS position estimation algorithm with a B‐spline smoothing strategy is proposed. B‐spline signal processing is used to smoothen the code measurements with Doppler measurements, which were selected because they are more robust and immune to cycle slips than carrier phase measurements. Next, the mathematical expressions of the smoothing process and position estimation are derived. The smoothing process is based on the structure of a digital filter, which is especially suitable for real‐time applications. The Cramer–Rao lower bound of the proposed algorithm is derived. Moreover, a complete implementation structure of the proposed algorithm is presented. The validity of the proposed algorithm is verified through scenario simulation in terms of static, kinematic, and adverse environments. The advantages of the proposed algorithm are demonstrated by comparison with existing algorithms.

Smoothing process can effectively improve the accuracy of the Global Navigation Satellite System (GNSS) position estimation algorithm. In this study, a Doppler‐aided GNSS position estimation algorithm with a B‐spline smoothing strategy is proposed. B‐spline signal processing is used to smoothen the code measurements with Doppler measurements, which were selected because they are more robust and immune to cycle slips than carrier phase measurements. Next, the mathematical expressions of the smoothing process and position estimation are derived. The smoothing process is based on the structure of a digital filter, which is especially suitable for real‐time applications. The Cramer–Rao lower bound of the proposed algorithm is derived. Moreover, a complete implementation structure of the proposed algorithm is presented. The validity of the proposed algorithm is verified through scenario simulation in terms of static, kinematic, and adverse environments. The advantages of the proposed algorithm are demonstrated by comparison with existing algorithms. [ABSTRACT FROM AUTHOR]

Parameter estimation of multiple sinusoids is one of the fundamental problems of signal processing having numerous application areas, including wireless communications and array signal processing. This article proposes an iterative, fast, and efficient algorithm to estimate the frequencies and amplitudes of multiple sinusoids in noisy environments. The proposed approach interpolates on the q-shifted DFT coefficients of multiple sinusoids. We theoretically demonstrate that the performance of the proposed algorithm depends on DFT-shift, number of iterations and minimum DFT frequency separation parameters. Further, mean square error of the proposed algorithm achieves the Cramér-Rao lower bound when these parameters are selected appropriately. We also propose solid bounds regarding how these parameters can be selected for optimum overall performance. The total computational cost of the proposed algorithm is in the order of O(K N log N), where K is the number of sinusoidal components and N is the signal length. We provide comprehensive numerical simulations that confirm the correctness of our theoretical deductions. [ABSTRACT FROM AUTHOR]

The present contribution deals with the estimation of haemodynamics Quantities of Interest by exploiting Ultrasound Doppler measurements. A fast method is proposed, based on the Parameterized Background Data‐Weak (PBDW) method. Several methodological contributions are described: a sub‐manifold partitioning is introduced to improve the reduced‐order approximation, two different ways to estimate the pressure drop are compared, and an error estimation is derived. A fully synthetic test‐case on a realistic common carotid geometry is presented, showing that the proposed approach is promising in view of realistic applications. [ABSTRACT FROM AUTHOR]

This paper presents a pulse radar system to detect drones based on a target fluctuation model, specifically the Swerling target model. Because drones are small atypical objects and are mainly composed of non‐conducting materials, their radar cross‐section value is low and fluctuating. Therefore, determining the target fluctuation model and applying a proper integration method are important. The proposed system is herein experimentally verified and the results are discussed. A prototype design of the pulse radar system is based on radar equations. It adopts three different pulse modes and a coherent pulse integration to ensure a high signal‐to‐noise ratio. Outdoor measurements are performed with a prototype radar system to detect Doppler frequencies from both the drone frame and blades. The results indicate that the drone frame and blades are detected within an instrumental maximum range. Additionally, the results show that the drone's frame and blades are close to the Swerling 3 and 4 target models, respectively. By the analysis of the Swerling target models, proper integration methods for detecting drones are verified and can thus contribute to increasing in detectability.

Attitude and heading estimation methods using the global navigation satellite system (GNSS) are generally based on multi-antenna deployment, where the installation space and system cost increase with the increase in the number of antennas. Since the single-antenna receiver is still the major choice of the mass market, we focus on precise and reliable heading and pitch estimation using a low-cost GNSS receiver. Carrier phase observations are precise but have an ambiguity problem. A single difference between consecutive epochs can eliminate ambiguity and reduce the measurement errors. In this work, a measurement model based on the time-differenced carrier phases (TDCPs) is utilized to estimate the precise delta position of the antenna between two consecutive epochs. Then, considering the motion constraint, the heading and pitch angles of a moving land vehicle can be determined by the components of the estimated receiver delta position. A threshold on the length of the delta position is selected to avoid large errors in static periods. To improve the reliability of the algorithm, the Doppler-aided cycle slip detection method is applied to exclude carrier phases with possible cycle slips. A real vehicular dynamic experiment using a low-cost, single-frequency GNSS receiver is conducted to evaluate the proposed algorithm. The experimental results show that the proposed algorithm is capable of providing precise vehicular heading and pitch estimates, with both the root mean square errors being better than 1.5°. This also indicates that the cycle slip exclusion is indispensable to avoid unexpected large errors.

The initial Gaussian mixture cardinality balanced multi-target multi-Bernoulli (GM-CBMeMBer) filter does not provide track information and assumes that the target birth intensity is known as a priori, but in reality the target may appear anywhere in the detection area. Therefore, the study proposes a labelled GM-CBMeMBer filter with adaptive track initiation. First, the filter introduces track label information and selects the measurements of newborn targets in the prediction process. In addition, it also makes full use of the Doppler information of the airborne Doppler radar. Then, the position estimate and velocity estimate of newborn targets are calculated by using position measurements converted and Doppler measurements, respectively. Further the label information in the prediction process is inherited during the update process, and the target states are updated sequentially with the Doppler measurements after having been updated by using position measurements. Monte–Carlo experiments show that the proposed filter can perform adaptive track initiation effectively, with good tracking performance, and provide target track information well.

Objective: To determine hemodynamic changes by Doppler ultrasound of the living fetus during 24 h after umbilical cord occlusion (UCO) in monochorionic diamniotic (MCDA) twin pregnancies.Method: We conducted a prospective observational study on fetuses undergoing UCO from 2015 to 2017. Doppler parameters peak systolic velocity (PSV) and umbilical pulsatility index (PI) were obtained in the middle cerebral artery (MCA), umbilical artery (UA) and ductus venosus (DV) before and right after UCO, and at 1, 3, 6, 12, and 24 h after. We used multiple of the median (MoM) to adjust for gestational age. Spaghetti plots visualized flow changes over time. Mixed model adjusting for paired longitudinal data compared the values at different time points.Results: A total of 16 women were included. MCA-PSV dropped within the first hour after surgery from 0.91 to 0.82 MoM (p = 0.08). MCA-PI and UA-PI increased in the first hour from 0.75 to 0.91 MoM (p = 0.02) and 0.94 to 0.98 MoM (p = 0.22), respectively. The DV-PIV increased to 1.14 MoM 3 h after surgery (p = 0.07). The spaghetti plots illustrated the small changes within the first hours and showed a stabilization of flow measurements near initial values 24 h after UCO.Conclusion: Within the first hours after UCO the circulation of the survivor twin undergoes small hemodynamic changes. [ABSTRACT FROM AUTHOR]

Acoustical Driving Forces (ADF), induced by propagating waves in a homogeneous and inhomogeneous lossy fluid (suspension), are determined and compared depending on the concentration of suspended particles. Using integral equations of the scattering theory, the single particle (inclusion) ADF was calculated as the integral of the flux of the momentum density tensor components over the heterogeneity surface. The possibility of negative ADF was indicated. Originally derived, the total ADF acting on inclusions only, stochastically distributed in ambient fluid, was determined as a function of its concentration. The formula for the relative increase in ADF, resulting from increased concentration was derived. Numerical ADF calculations are presented. In experiments the streaming velocities in a blood-mimicking starch suspension (2 μm radius) in water and Bracco BR14 contrast agent (SF6 gas capsules, 1 μm radius) were measured as the function of different inclusions concentration. The source of the streaming and ADF was a plane 2 mm diameter 20 MHz ultrasonic transducer. Velocity was estimated from the averaged Doppler spectrum obtained from originally developed pulsed Doppler flowmeter. Numerical calculations of the theoretically derived formula showed very good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

The initial Gaussian mixture cardinality balanced multi-target multi-Bernoulli (GM-CBMeMBer) filter does not provide track information and assumes that the target birth intensity is known as a priori, but in reality the target may appear anywhere in the detection area. Therefore, the study proposes a labelled GM-CBMeMBer filter with adaptive track initiation. First, the filter introduces track label information and selects the measurements of newborn targets in the prediction process. In addition, it also makes full use of the Doppler information of the airborne Doppler radar. Then, the position estimate and velocity estimate of newborn targets are calculated by using position measurements converted and Doppler measurements, respectively. Further the label information in the prediction process is inherited during the update process, and the target states are updated sequentially with the Doppler measurements after having been updated by using position measurements. Monte–Carlo experiments show that the proposed filter can perform adaptive track initiation effectively, with good tracking performance, and provide target track information well. [ABSTRACT FROM AUTHOR]

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract The aim of this study is to improve operational capabilities and range of the MIT-Coffee Can Doppler radar via aperture coupled Vivaldi type transmitter antenna, patch array receiver antenna, and an unequal power divider. Accordingly, a mechanical angular scanning feature for tracking multi-targets and the system integration of lightweight microstrip structures are realized for the radar. A narrow beamwidth in the receiver and a well impedance matching on the overall system to reduce return losses are achieved for the considered application. Good agreements between simulations and measurements for the fabricated antennas/divider and a successful integration of the antennas to the existing system for finding a moving target angular location is reported. It is shown that through wall identification and target velocity at scanned regions can be obtained with the proposed hardware configuration. Simulation results of antenna parameters for various number of array elements are listed which could be a useful tool for different engineering applications. [ABSTRACT FROM AUTHOR]

In this paper, Bragg and non-Bragg scattering mechanisms and frequency shifts from time-varying periodic water wave are studied from three aspects: wave tank measurements with an ultrahigh frequency radar, numerical simulation using the method of moments, and theoretical derivation applying the small perturbation method. The scattering field, radar cross section (RCS), and frequency shifts are discussed in both horizontal and vertical polarizations. The wave tank observations show that backscattering enhancement occurs when water wavelength is an integer multiple of Bragg wavelength, and there are several Doppler harmonics with frequency shifts of water-wave frequency and its integer multiples. Numerical simulations indicate that these Doppler harmonics except the one associated with the water-wave phase velocity are caused by the water surface edge effect. Moreover, theoretical analyses, numerical simulations, and wave tank experiments all show a clear exponential relationship between backscattering RCS and wave height. In addition, we further analyze the bistatic scattering and find that the scattering field is composed of plane waves propagating in the directions determined by water wavelength and radio wavelength, the bistatic frequency shift is the harmonic frequency of water wave, and the bistatic RCS also has an exponential relation with water-wave height. [ABSTRACT FROM AUTHOR]

A Doppler shift estimation system with relatively high dynamic range is conceived and demonstrated. The scheme is based on dual mixing the modulated radar echo and frequency to voltage mapping. Hence, it needs no radio frequency auxiliary part. This makes the system capable of becoming integrated into any photonic radar, which would positively affect the cost and size of such system. Since the mixing procedure is all-optical, the system is able to identify the Doppler frequency of a radar echo with carrier frequency as high as 40 GHz independent of its amplitude. The system dynamic range can be as high as 42 dB at 10-GHz radar carrier with an acceptable error of 5%. This dynamic range was achieved using lock-in amplification technique. [ABSTRACT FROM PUBLISHER]

This paper presents a pulse radar system to detect drones based on a target fluctuation model, specifically the Swerling target model. Because drones are small atypical objects and are mainly composed of non‐conducting materials, their radar cross‐section value is low and fluctuating. Therefore, determining the target fluctuation model and applying a proper integration method are important. The proposed system is herein experimentally verified and the results are discussed. A prototype design of the pulse radar system is based on radar equations. It adopts three different pulse modes and a coherent pulse integration to ensure a high signal‐to‐noise ratio. Outdoor measurements are performed with a prototype radar system to detect Doppler frequencies from both the drone frame and blades. The results indicate that the drone frame and blades are detected within an instrumental maximum range. Additionally, the results show that the drone's frame and blades are close to the Swerling 3 and 4 target models, respectively. By the analysis of the Swerling target models, proper integration methods for detecting drones are verified and can thus contribute to increasing in detectability. [ABSTRACT FROM AUTHOR]

Intrauterine growth restriction (IUGR) is a serious pregnancy complication with short- and long-term health consequences. The mechanisms underlying this condition are not well understood. Animal models are the basis for understanding the causes of IUGR and for developing useful therapeutic strategies. Here, we aimed to ascertain the in utero growth of fetuses from NK (natural killer cells)/MC (mast cells)-deficient mothers that give birth to growth-restricted pups and to determine the time point at which IUGR starts. We used high frequency ultrasound imaging to follow-up fetal and placenta size and employed Doppler measurements to document blood supply to the fetus in females that were deficient for NK cells and MCs. In mice lacking NKs and MCs, we observed significantly reduced implantation sizes from mid gestation onward, which was further associated with smaller placentas. Additionally, NK/MC-deficiency was associated with absent and reversed end diastolic flow in umbilical arteries of the fetuses and an increased systolic/ diastolic ratio as well as an elevated resistance index. Together, our results indicate that NKs/MCs promote blood flow, placental growth, and subsequent fetal development. The results of this study offer new insights as to how fetal growth is affected in vivo in NK/MC-deficient mice, whose pups are growth restricted at birth. The use of IUGR models and modern technologies enabling the in vivo follow-up of fetal development are important tools for understanding mechanisms behind pregnancy complications that in the future may lead to the development of effective therapies. [ABSTRACT FROM AUTHOR]

Results of a coastal measurement campaign called MediterraneAn Rfc and cLutter ENvironmental Experiment (MARLENE) are presented and studied. The campaign was held in spring 2014, on a DGA site in the Mediterranean Sea region of Toulon, France. Three coastal measurement radar systems, Millimeter wave Experimental Multifrequency Polarimetric High Resolution Interferometric System (Fraunhofer FHR), MARSIG (WTD 71), and MEDYCIS (ONERA), were deployed to simultaneously acquire sea clutter measurements. During the campaign, the in situ oceanic and meteorological conditions were characterized from the RV PLANET meteorological ship deployed by WTD 71 and by modeling from WAVEWATCH III and SWAN wave models. Radar measurements were performed at the C-, X-, Ku-, Ka-, and W-bands. The measurement results are presented in terms of reflectivity and mean Doppler spectrum according to low grazing angle and azimuth variations. Reflectivity variations are compared with the empirical GIT model and close results are obtained at the C- and Ka-bands. At the same frequency bands, mean Doppler Spectrum velocity is presented and analyzed according to grazing and azimuth angles. Physical interpretations of electromagnetic interaction with sea surface are discussed. [ABSTRACT FROM PUBLISHER]

Dead-reckoning (DR) algorithms, which use self-contained inertial sensors combined with gait analysis, have proven to be effective for pedestrian navigation purposes. In such DR systems, the primary error is often due to accumulated heading drifts. By tightly integrating global navigation satellite system (GNSS) Doppler measurements with DR, such accumulated heading errors can usually be accurately compensated. Under weak signal conditions, high sensitivity GNSS (HSGNSS) receivers with block processing techniques are often used, however, the Doppler quality of such receivers is relatively poor due to multipath, fading and signal attenuation. This often limits the benefits of integrating HSGNSS Doppler with DR. This paper investigates the benefits of using Doppler measurements from a novel direct vector HSGNSS receiver with pedestrian dead-reckoning (PDR) for indoor navigation. An indoor signal and multipath model is introduced which explains how conventional HSGNSS Doppler measurements are affected by indoor multipath. Velocity and Doppler estimated by using direct vector receivers are introduced and discussed. Real experimental data is processed and analyzed to assess the veracity of proposed method. It is shown when integrating HSGNSS Doppler with PDR algorithm, the proposed direct vector method are more helpful than conventional block processing method for the indoor environments considered herein.

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)