Gain Deviation Research Articles

Planar Quasi-Isotropic Antenna and Its Implementation of Filtering Response

Two planar quasi-isotropic antennas are presented in this letter, and the filtering response is implemented on the second antenna. First, a printed shorted patch which can be equivalent to a magnetic dipole is utilized with a fan-shaped monopole serving as an electric dipole to achieve quasi-isotropic radiation. A lumped capacitor, a pair of near-field parasitic elements and a slot are introduced to improve the roundness. Ultimately, the gain deviation is reduced to 3.5 dB. Furthermore, a half-mode substrate integrated waveguide is applied to achieve the magnetic dipole for the second antenna. The filtering response is obtained by introducing a uniform impedance resonator. A radiation null is obtained above the operating band, whereas a quasi-isotropic radiation is achieved in band with a gain deviation of 7.3 dB.

Optical voltage sensor based on a piezoelectric thin film for grid applications.

Continuous monitoring of voltages ranging from tens to hundreds of kV over environmental conditions, such as temperature, is of great interest in power grid applications. This is typically done via instrument transformers. These transformers, although accurate and robust to environmental conditions, are bulky and expensive, limiting their use in microgrids and distributed sensing applications. Here, we present a millimeter-sized optical voltage sensor based on piezoelectric aluminum nitride (AlN) thin film for continuous measurements of AC voltages <350kVrms (via capacitive division) that avoids the drawbacks of existing voltage-sensing transformers. This sensor operated with 110μW incident optical power from a low-cost LED achieved a resolution of 170mVrms in a 5kHz bandwidth, 0.04% second harmonic distortion, and a gain deviation of +/-0.2% over the temperature range of ~20-60°C. The sensor has a breakdown voltage of 100V, and its lifetime can meet or exceed that of instrument transformers when operated at voltages <70kVrms with capacitive division. We believe that our sensor has the potential to reduce the cost of grid monitoring, providing a path towards more distributed sensing and control of the grid.

Recent Advancements in Quasi-Isotropic Antennas: A Review

Quasi-isotropic antennas are promising candidates due to their applications in modern communication systems, where full spatial coverage and/or uniform signal reception is required. In this work, an in-depth review of quasi-isotropic antennas is presented, with the aim of understanding the working principles of such antennas and presenting the recent advancements, challenges, and solutions offered by various researchers. First, different design techniques adopted to achieve quasi-isotropic patterns, such as the use of complementary dipoles, multiple monopoles or dipoles, and an array of discrete elements are discussed. Then, different types of quasi-isotropic antennas—for example, planar, electrically small, 3-D printed, dual-band/wideband, circularly polarized, metamaterial-inspired, and dielectric resonator-based quasi-isotropic antennas—are revisited. Their applications in various technologies, such as RFID, energy harvesting, wireless sensor networks, and the IoT, are briefly explained. Lastly, different key performance parameters, such as complexity of configuration, design approach, physical profile, far field and radiation characteristics, reflection coefficients, operating frequency and bandwidth, gain deviation, and fabrication process, are discussed and tabulated. This review not only provides a guideline but will also help antenna engineers in designing a quasi-isotropic antenna with desirable performance.

Fully digital background calibration of channel mismatches in time-interleaved ADCs using recursive least square algorithm

Time-interleaved analog-to-digital converters (TIADCs) have been considered as a very promising solution for high-speed direct sampling receivers. However, channel mismatches reduce the TIADC’s performance significantly. Therefore, calibration of these mismatches is emerging to maintain the performance of these TIADCs. This paper proposes a fully digital background calibration technique for multiple deviations including offset, gain, and timing mismatches. Offset and gain deviations in TIADCs are sequentially calibrated by taking the average value of the output samples, and calculating the ratios of power, respectively. Then, the timing mismatch is compensated by using the Hadamard matrix and the adaptive recursive least square (RLS) algorithm. The proposed calibration technique is proven through the simulation results for signal-to-noise-and-distortion (SNDR), spurious-free dynamic range (SFDR) and time convergence. As a result, the performance of TIADC is improved by 40.98 dB and 70.64 dB for SNDR and SFDR, respectively.

Prenatal exposure to air pollutants and early childhood growth trajectories: A population-based prospective birth cohort study

BackgroundAir pollution exposure during pregnancy has been documented to be associated with impaired fetal growth and adverse birth outcomes, but the evidence regarding the effects of air pollution on early childhood growth is still limited. ObjectiveWe aimed to explore the associations of exposure to air pollutants during pregnancy with childhood growth trajectories from birth to age of 6 years. MethodsA prospective cohort study based on the administrative registration system was conducted covering 62,540 births in Wuhan, China between January 1, 2011 and December 31, 2013 and followed for 6 years. Inverse distance weighted method was used to estimate the concentrations of air pollutants exposure for pregnant women. Group-based trajectory models (GBTM) were used to identify growth patterns of children: slow growth, normal growth, and rapid growth. Multinomial logistic regression models were used to examine the associations between prenatal exposure to air pollutants and childhood growth trajectories with adjustment for maternal age, educational status, pre-pregnancy BMI, residential areas, gestational diabetes, birth type, gender of infant, and breastfeeding duration. ResultsThe mean (SD) of prenatal exposure concentrations for PM10, SO2, NO2, CO, and O3 were 107.9 (30.4), 32.8(12.6), 55.8(13.1), 1081.2(293.1), and 81.6(31.0) μg/m3 respectively. Compared with normal growth trajectory, increased PM10 and CO exposure were significantly associated with higher risk of slow growth trajectory but lower risk of rapid growth trajectory. An increase in prenatal exposure to NO2 significantly increased both the risk of slow growth trajectory and rapid growth trajectory. Increased prenatal SO2 exposure was significantly associated with rapid growth trajectory and was not associated with low growth trajectory. With O3 exposure levels increased, risk to be rapid growth trajectory decreased. Prenatal air pollutants exposure had a greater impact on childhood growth of children who were girls, and those mothers lived in rural areas and were normal weight before pregnancy. ConclusionsHigh levels of air pollutants exposure during pregnancy were associated with the risk of being in a trajectory with the deviation of BMI gain from birth to 6 years old. These findings suggest that efforts to identify children at risk of growth deviation in early childhood should pay attention to environmental exposure during pregnancy for their mothers.

A 112-dB SFDR 89-dB SNDR VCO-Based Sensor Front-End Enabled by Background-Calibrated Differential Pulse Code Modulation

This article presents a high-dynamic-range (DR) voltage-controlled oscillator (VCO)-based front end for sensor readout applications. Unlike conventional VCO-based quantizers, which suffer from large voltage-to-frequency non-linearities, the proposed design leverages differential pulse-code modulation (DPCM) from compression theory to substantially reduce the amplitude of the signal incident to the VCO quantizer, thereby achieving an ultra-low total harmonic distortion (THD) of -112 dB. In addition, background digital gain calibration is employed to overcome gain deviation of the VCO, thus ensuring a robust design. Together with dynamic element matching (DEM), the techniques enable a high DR using only the first-order noise shaping inherent in VCO-based quantizers and a moderate 32× oversampling ratio. Fabricated in 65 nm, the sensor front end consumes 3.2- μW power and achieves an SNDR of 89 dB and a DR of 94 dB in 500 Hz of bandwidth. Together with a 1.18- μV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> integrated input-referred noise, it achieves a noise efficiency factor (NEF) of 4 and a Schreier FoM of 171 dB.

Efficient user pairing algorithm for enhancement of spectral efficiency and interference cancelation in downlink NOMA system

A new subcarrier-user allocation algorithm for the downlink non-orthogonal multiple access system is presented in this paper. The proposed algorithm aims to enhance the spectral efficiency of the system and the successive interference cancelation performance by guaranteeing a high difference in channel-gain between the paired users per subcarrier. To enhance the spectral efficiency, the proposed algorithm provides a higher priority to the subcarrier that has a higher best (maximum) channel gain value rather than that has a lower best channel gain value. Also, it pairs the strong user with the second minimum channel-gain user rather than the minimum channel gain user. Besides, the proposed algorithm divides the subcarriers into two groups according to the standard deviation of the channel gain of each subcarrier. Then, it gives the priority to the group with low standard deviation values during subcarrier-user allocation to guarantee a high difference in channel-gain between the paired users per subcarrier. Later, fractional transmit power allocation is applied to distribute the subcarrier power between the paired users. Simulation results prove that the proposed algorithm improves the spectral efficiency of the system, and guarantees a significantly higher difference in channel-gain between the paired users per subcarrier compared to the conventional algorithms.

Design and Verification of an Electrically Small, Extremely Thin Dual-Band Quasi-Isotropic Antenna

A novel design of an electrically small, dual-band quasi-isotropic antenna with a microstrip balun is presented in this letter. A quasi-isotropic radiation pattern is realized from the total current flow over the proposed structure at two different frequency bands. The electrical size ka of the antenna is 0.49 with an extremely thin profile of 0.0014λg. The antenna measurements reveal good uniformity of the radiation pattern with a maximum gain deviation of 5.83 dB at 942 MHz and 8.24 dB at 1.71 GHz with 57% and 95% radiation efficiency, respectively. The radiation performance of the antenna is also verified through wireless power receiving experiments in an office non-line-of-sight (NLOS) environment.

Causal graphical views of fixed effects and random effects models.

Despite the long-standing discussion on fixed effects (FE) and random effects (RE) models, how and under what conditions both methods can eliminate unmeasured confounding bias has not yet been widely understood in practice. Using a simple pretest-posttest design in a linear setting, this paper translates the conventional algebraic formalization of FE and RE models into causal graphs and provides intuitively accessible graphical explanations about their data-generating and bias-removing processes. The proposed causal graphs highlight that FE and RE models consider different data-generating models. RE models presume a data-generating model that is identical to a randomized controlled trial, while FE models allow for unobserved time-invariant treatment-outcome confounding. Augmenting regular causal graphs that describe data-generating processes by adding the computational structures of FE and RE estimators, the paper visualizes how FE estimators (gain score and deviation score estimators) and RE estimators (quasi-deviation score estimators) offset unmeasured confounding bias. In contrast to standard regression or matching estimators that reduce confounding bias by blocking non-causal paths via conditioning, FE and RE estimators offset confounding bias by deliberately creating new non-causal paths and associations of opposite sign. Though FE and RE estimators are similar in their bias-offsetting mechanisms, the augmented graphs reveal their subtle differences that can result in different biases in observational studies.

Design of an Electrically Small, Planar Quasi-Isotropic Antenna for Enhancement of Wireless Link Reliability under NLOS Channels

The performance of wireless networks can be greatly influenced by the radiation pattern and polarization of the antennas at the nodes, especially when they are under non-line-of-sight (NLOS) channel environments. In this study, we designed a planar quasi-isotropic antenna based on the combination of a meandered electric dipole and an electrically small loop at a frequency of 2.45 GHz. Its electrical size (ka) is 0.47 and shows a gain deviation of 3.01 dB with radiation efficiency of 82.6% per the simulation. The performance of a wireless link under the line-of-sight and NLOS channels in an indoor environment was measured using the proposed quasi-isotropic antenna as a receiving antenna after validating its radiation and impedance properties experimentally (the measured gain deviation: 5.2 dB, the measured radiation efficiency: 79.2%). This study demonstrates that better properties are achieved using the quasi-isotropic antenna. The quasi-isotropic antenna shows an improved packet delivery ratio (PDR) and received signal strength indicator (RSSI) compared to the results using omni-directional antennas as a transmitting and receiving pair in the NLOS channels. To the best of our knowledge, the experimental validation of the enhancement of wireless link reliability using a quasi-isotropic antenna has not been reported before, and was first carried out in this study.

Synthesis of contoured beam multifeed reflector antenna for optimum coverage

AbstractA synthesis procedure for realizing contoured beams in multifeed reflector antenna is proposed. The proposed procedure solves the synthesis problem so that the maximum gain and low ripple together with low cross polarization are achieved. To this end, first, the relation between the physical parameters of the antenna and the gain loss over the contour is investigated. Then, the maximum achievable gain is approximated, which is needed to study the next issue, that is the optimization procedure. A new optimization procedure is presented, through which the desired contoured beam is achieved. The synthesis procedure employs physical optic (PO) method, which is time‐consuming. To reduce the computational time, which is another focus of the analysis, we introduce an efficient method for computing the PO integral. Through this method, the 3D PO integral is mapped to a 2D integral. The procedure is applied to Brazil coverage. Results show that the cross‐polarization is below −20 dB and the gain deviation is less than 1 dB over the contour, which is suitable for satellite communications.

THE USE OF CHART ON STUDENTS’ ABILITY TO WRITE EXPLANATION TEXT

It is not doubt that writing has important role in real life. People can communicate, give information, and share their ideas through written way. Writing is classified as difficult skill because there are some components that should be considered, some kinds of text that should be understood, some steps that should be done, etc. Many students face difficulty to write explanation text, especially for generating the ideas. For that reason, chart is chosen as the media. The aim of this research is to find out the use of chart on students’ ability to write explanation text. It is conducted to the eleventh grade students of SMA Negeri 2 Jonggol. In this research, Pre Experimental method and Pre-test Post-test Group design are used. There are 36 students from class XI MIPA 1 taken as the sample by using random sampling. The data were taken from pre-test and post-test which were analyzed by using t-test formula after having the normal data. Based on the data calculation, the mean of gain is 20.04, and the total of deviation of gain is 9.46. Moreover, t-test value is 9.45. Meanwhile, t-table value is 2.03 at significant level 0.05 with the degree of freedom (df) is 35. In this case, the t-test value is higher than that of the t-table value (9.45 more than 2.03). It means that null hypothesis (Ho) is rejected. Therefore, the use of chart affects students’ ability to write explanation text.

Retinal Image Slip Must Pass the Threshold for Human Vestibulo-Ocular Reflex Adaptation.

We sought to determine whether repeated vestibulo-ocular reflex (VOR) adaptation training to increase the VOR gain (eye/head velocity) had a lasting effect in normal subjects and whether there was a retinal image slip tolerance threshold for VOR adaptation. We used the unilateral incremental VOR adaptation technique and horizontal active (self-generated, predictable) head impulses as the vestibular stimulus. Both active and passive (imposed, unpredictable) head impulse VOR gains were measured before and after unilateral incremental VOR adaptation training. The adapting side was pseudo-randomized for left or right. We tested ten normal subjects over one block (10 sessions over 12days) of VOR adaptation training and testing, immediately followed by a second block (5 sessions over 19days) of testing only without training. Our findings show robust short-term VOR adaptation of ~ 10% immediately after each 15-min training session, but that the daily pre-adaptation gain was most different on days 1 and 2, and for subsequent training days before saturating to ~ 5% greater than the pre-adaptation gain on day 1. This increase was partially retained for 19days after regular training stopped. The data suggest that stable vision in normal subjects is maintained when there is < 5% deviation in VOR gain from the original baseline, which corresponds to < 9°/s retinal image slip. Below this threshold, there is poor adaptive drive to return the gain to its original baseline value.

Изменение морфометрических показателей серого тюленя Halichoerusgrypusв условиях щенки и вскармливания .

In the study, morphometric indicators of female grey seals were measured to detect changes in their size characteristics during various physiological phases of ontogenesis, including molting, pregnancy, pup and feeding in conditions close to natural. It was found that the pup itself slightly affected the growth of a Mature female seal, while feeding was the most energy-consuming, causing further deviations in the weight gain.

To what extent does the composition of batches formed at the sorting facility influence the subsequent growth performance of young beef bulls? A French observational study

To meet the demands of the beef cattle sector in France, weaned beef calves are transported to sorting facilities and sorted into batches composed of animals of similar body weight (BW) before the beginning of the fattening period. This procedure aims to facilitate animal management. However, it leads to practices that affect animal welfare, health and performance, such as transporting weaned beef calves over long distances and mixing animals originating from different cow/calf farms. In contrast, other potentially beneficial practices, such as pre-weaning vaccination against bovine respiratory diseases (BRD), are seldom taken into consideration when batches are formed. This observational study, based on field data from 15,735 Charolais bulls, aimed to investigate which criteria should be favored for batch constitution by quantifying the effect of batch characteristics on the growth performance of young bulls during the fattening period. Clustering analysis was used to group young bulls exhibiting similar batch characteristics and define batch types. Associations between batch characteristics/batch types and individual growth performance/homogeneity of growth performance (mean and standard deviation (SD) of average daily gain (ADG) and fattening period duration) were studied using linear mixed models. The mean BW and the percentage of animals vaccinated against BRD before weaning were positively associated with ADG (+35 g/d for each additional 50 kg and +28 g/d for a high percentage of vaccinated animals, P < 0.05). In contrast, transportation distance was negatively associated with ADG (−12 g/d for each additional 120 km travelled). Mixing animals and BW homogeneity did not affect growth performance (P > 0.05). Only the mean BW and mixing animals negatively influenced the homogeneity of ADG (P < 0.01). The clustering analysis revealed that batches with the most BW heterogeneity, the least mixing, the shortest transportation distance and a high percentage of pre-weaning animals vaccinated against BRD had better growth performance compared to batches with the opposite characteristics (+61 g/d, P < 0.001). Our results suggest that major improvements of growth performance of fattening young bulls could be obtained by minimizing transportation distance, providing vaccination programs against BRD before weaning, and maintaining groups from the same cow/calf farm instead of constituting groups of animals with similar BW at the beginning of fattening.

Realization of Electrically Small, Low-Profile Quasi-Isotropic Antenna Using 3D Printing Technology

A 3D printed, low-profile, electrically small antenna with a quasi-isotropic radiation pattern is presented herein. It is composed of an electric meandered dipole antenna, and the extended arcs from the meander line mimicking the current flow of the loop antenna. A quasi-isotropic radiation pattern is achieved from the total current flow over the proposed structure. Modern stereolithographic 3D printing and nano-polycrystalline copper coating technologies are used to build a prototype. The measured antenna exhibits a good uniformity in terms of the radiation pattern with a maximum gain deviation of 4.5 dB at 959 MHz and a radiation efficiency of 81 %, close to the computed expectations. The electrical size of the antenna ka is 0.48, and its height is $\lambda _{0}$ /82.32.

High constant gain modified antipodal Vivaldi antenna incorporated with a phase compensation lens and a frequency selective surface

The aim of this study is to demonstrate the design of an antenna with a high gain as well as almost constant gain characteristics over 3.1–10.6 GHz. The modified antipodal Vivaldi MAVARW antenna initially developed in an earlier study is used as the basic antenna. Three different gain enhancement methods such as increasing antenna size, using a phase compensation lens (PCL), and using a frequency selective surface (FSS) are applied and investigated on a comparative basis for this aim. The final MAVARW antenna is composed of a two-cut square ring PCL, and an FSS. The final antenna has a minimum 12.24 gain level with a maximum 1.66 dB gain deviation over 3.1–10.6 GHz in simulations. The simulation results for the final antenna are validated experimentally with very good agreement. A minimum 12.2 dB gain level as well as a maximum 1.8 dB gain deviation is obtained in measurements.

An Additively Manufactured 3-D Antenna-in-Package With Quasi-Isotropic Radiation for Marine Animals Monitoring System

A low-cost and additively manufactured three-dimensional (3-D) antenna-in-package with quasi-isotropic radiation is proposed for a marine animals monitoring system. The antenna is based on a meandered dipole folded as a split-ring resonator structure, which can generate simultaneously a pair of orthogonal electric and magnetic dipoles, thus providing a quasi-isotropic radiation pattern. The antenna (integrated with a balun) has been inkjet-printed on a 3-D-printed buoyant cone structure, which acts also as the system package to house the electronics and the battery. The antenna designed at 2.4 GHz is electrically small, with a $ka\; = 0.49$ , and has a bandwidth of 70 MHz (2.9%). The measured gain deviation of the antenna (maximum to minimum) is near 3 dB in bandwidth, thus qualifying it as a quasi-isotropic antenna. Field tests of the antenna in the active state (integrated with the electronics) confirm a reliable communication range of 240 m in any direction in the azimuthal plane.

Lyapunov Control Method for Mismatched Uncertainty and Gain Variation Compensation in Switched Systems

Since the inherent nature of many applied high-technological systems and networks possesses switching behaviors, modeling, controlling, and stabilizing problems of the switching plants are becoming as the important research scenarios in the current literature. Moreover, consideration of the effects of mismatching uncertainties along with matching uncertain parts as well as unknown dynamics is a significant topic in the control engineering community. As a result, this paper is dedicated to the controlling problem of partially unknown nonlinear switched systems whose dynamics are perturbed by both matched and mismatched uncertainties. In addition, since the existence of gain deviations in real-world implementations of physical actuators can lessen the control act of the switching system, this paper handles the corresponding gain variations in the control inputs via some adaptation variables. In the design procedure, no limiting supposition is made for the switch signal of the switched plant. The proposed control algorithm is based on the variable structure control theory in which the selected sliding surface is able to deal with mismatching uncertainties and the deriving control law is robust against the lumped uncertain components. As a contribution, the Lyapunov functions are built such that not only to provide an asymptotic stable system but also to assure the global (practical) finite-time stability of the equilibrium state of the final closed-loop cascade switched plant. The robust performance of the developed control strategy is confirmed via two illustrative examples.

ANALYSIS OF NON-STATIONARY RADIOMETER GAIN VIA ENSEMBLE DETECTION.

Although considered as stationary and Gaussian in general, radiometer gain is usually a fluctuating signal with non-stationary properties. Analyses of such non-stationary features is challenging as the radiometer signal cannot be observed independently. On the other hand, time series of post-gain voltages constitute an ensemble set for the radiometer gain which can be used to characterize the radiometer gain. This paper presents a novel technique called "Ensemble Detection" which can analytically retrieve the standard deviation of stationary Gaussian radiometer gain or find an equivalent stationary Gaussian process which represents the non-stationary radiometer gain under different calibration schemes. It has been found that the equivalent Gaussian process for non-stationary radiometer gain heavily depends on the calibration structure and the observation times of the measurand and the calibration references.