An experimental investigation of dielectric-coated antennas

The characteristics of a monopole antenna embedded in a cylinder of low-loss dielectric have been measured. A cylinder of infinite length was approximated by extending the length of a finite cylinder until the admittance did not change. Admittance and current distribution data are represented as a function of antenna length for various diameters and dielectric constants of the cylinders. The results compare well with a theoretical analysis by Ting. The effect of the cylinder is to increase the electrical length of the antenna and decrease the bandwidth.     

源搅拌混响室的仿真分析与实验研究

根据谐振腔理论,分析了理想情况下影响源搅拌混响室性能的主要因素,通过数值计算对其进行仿真验证,确定了影响混响室场均匀性的主要因素有激励天线的极化方向,摆放位置以及激励源的位置数等;在此基础上提出了一种可行的源搅拌方案,通过实验的方法,在满足一定采样数情况下,实现了混响室较好的场均匀性;同时借助K-S拟合对源搅拌混响室测量场值的统计特性进行了分析,结果表明:源搅拌混响室的一维场分布服从瑞利分布。     

An experimental investigation of the microstrip step discontinuity

A simple, inexpensive technique for performing wideband (multidecade) validation measurements is introduced. The authors emphasize scaling the desired validation frequencies and dimensions so that both the measurement and the fabrication can be performed accurately and inexpensively. The utility of a composite structure (rather than a single discontinuity) is also demonstrated, and the sensitivity of the structure to changes in the discontinuity is checked. The technique allows an inexpensive validation to be performed which previously could be realized only with large scatter, if at all     

An experimental investigation of conventional and efficientimportance sampling

Importance sampling is a technique that can significantly reduce computer run-time in the estimation of bit error rate (BER). However, in the conventional implementation (CIS), the improvement reduces markedly for systems with long memory. An approach to recover the full improvement for such systems has been previously suggested, and is called `efficient' important sampling (EIS). A report is presented on an extensive series of simulation-based experiments with CIS and EIS, both to compare theoretical predictions to experimental observations, as well as to gain insight into the conditions of applicability, especially for EIS     

Model analysis and experimental investigation of the friction torque during the CMP process

A model for calculating friction torque during the chemical mechanical polishing(CMP) process is presented,and the friction force and torque detection experiments during the CMP process are carried out to verify the model.The results show that the model can well describe the feature of friction torque during CMP processing. The research results provide a theoretical foundation for the CMP endpoint detection method based on the change of the torque of the polishing head rotational spindle.     

化学机械抛光过程中扭矩的模型分析与试验研究

提出了一个计算化学机械抛光（Chemical Mechanical Polishing,CMP）过程中硅片所受扭矩的模型,并通过CMP过程中摩擦力和扭矩的在线检测试验进行了验证。试验结果表明该扭矩计算模型可以较好地描述CMP过程中硅片所受扭矩的特征。该研究可以为基于抛光头旋转轴扭矩变化的CMP终点检测方法提供理论依据。     

An experimental investigation of electrically thick rectangular microstrip antennas

The electromagnetic properties of electrically thick rectangular microstrip antennas were investigated experimentally. Antennas were fabricated with different patch sizes and with electrical thicknesses ranging from 0.03 to 0.23 wavelengths in the dielectric substrate. The resonant frequencies were measured and compared to existing formulas. The bandwidth was calculated as a function of electrical thickness and the antenna radiation patterns were measured.     

Angular acceleration estimation and feedback control: An experimental investigation

Angular acceleration estimation and its application in acceleration feedback control are investigated experimentally in the paper. In combination of Newton Predictor (NP) with Kalman Filter (KF), a new predictive estimator for angular acceleration, called Newton Predictor Enhanced Kalman Filter (NPEKF) is proposed. This estimator provides a wide bandwidth and a small phase lag of the estimated acceleration while attenuating noises. Based on the estimated acceleration an acceleration feedback control (AFC) is presented for multiple degree-of-freedom (DOF) mechatronic system. The design of AFC is specified in terms of its stability and ability in suppressing dynamic disturbances. Experiments are conducted on a 2-DOF direct-drive manipulator. The frequency responses of the acceleration estimated by NP, KF and NPEKF are compared with those of the measured acceleration via linear accelerometer. The performance of AFC using the estimated acceleration is assessed against that using the measured acceleration. This study has shown that the proposed NPEKF estimator is able to supply the AFC with reliable required acceleration.     

An experimental investigation on the nature of reverse current of silicon power pn-junctions

At this time, little importance is given to the surface component of reverse leakage current of silicon pn-junctions although reliability issues reveal device blocking weakness when performing at high voltage and temperature. Junctions which have almost the same perimeter but different area have been realized and their reverse current has been measured at room temperature and high temperature both for standard recovery and fast recovery (gold-doped or electron irradiated) pn-junctions. It is shown that for standard recovery junctions the surface component of the reverse current is the primary component from room temperature up to above 150/spl deg/C and has influence on reaching high permissible working voltages. For gold-doped or electron irradiated junctions, the bulk component is dominant at high junction temperature, but it is shown that a comparatively negligible surface component can impose lower reverse working voltages or lower junction operation temperature. The surface component may be a cause of limitation on the operation of power silicon diodes at high reverse voltage above 175-200/spl deg/C junction temperature.     

An experimental investigation of the off-diagonal Seebeck effect on textured YBCO high-Tc superconductor

The off-diagonal Seebeck effect was investigated on a melt-textured YBa₂Cu₃O_7−δ (YBCO) high-T_c superconductor. It was found that the transverse voltage V_x was proportional to the longitudinal temperature difference Δ T_z, measured directly with a pair of differential thermocouples, for textured samples with their c-axes tilted with respect to the surface’s normal. This supported the idea that the off-diagonal thermoelectric effect accounts for the anomalously high laser-induced transverse voltage on the oriented YBCO superconducting thin films. The variation of the V_x against the sample’s thickness d, at a given Δ T_z, deviated from the inversely proportional relationship when the sample was too thin. The deviation was discussed qualitatively in terms of deteriorated surface layers. The data of V_x(d) was fitted to obtain a reasonably reliable ∣ S_c−S_ab∣ value of 12 μ V K⁻¹.     

An experimental and theoretical analysis of double-diffused MOS transistors

An experimental and theoretical study of double-diffused MOS transistors (DMOST's) has been made. A simple, analytic two-transistor model gives insight into DMOS device physics as well as predicting DMOST characteristics. Both the model and experimental results show that three distinct regions of operation exist: short-channel control, long-channel control, and carrier velocity saturation control. Quantitative criteria are established for judging the region of operation as a function of device parameters and terminal voltages. A DMOST may be optimized to have the same d.c. characteristics as its short-channel component transistor over most of its operating range. A two-transistor model suitable for Computer-Aided Circuit Design (CAD) is also presented.     

有机分子激光喇曼光谱偏振特性的实验研究

激光偏振喇曼光谱在确定分子振动模的对称性和红外光谱结构分析方面具有重要作用,本文报道了利用532nm激光从实验上测定了丙酮、甲醇、乙二醇和甲酰胺分子的激光偏振喇曼光谱,确定了各喇曼谱线对应的喇曼频移。测定了丙酮、甲醇、乙二醇和甲酰胺分子各喇曼频移对应的退偏比,并对各条谱线所属正则振动模的对称性进行了初步分析。     

An experimental investigation of the end-hat effects in acrossed-field amplifier via three-dimensional electron densitymeasurements

In situ three-dimensional electron density profile measurements have been made for the first time to study the end-hat space-charge region in a crossed-field amplifier. It has been found that a separated electron population exists in that region and is detached from the main beam when the end-hats are biased positively with respect to the sole. An investigation into the vacuum electric field profile and the overall device performance versus end-hat bias has suggested that such an electron population may be caused by a redistribution of the beam electrons by the axial and radial end-hat electric field     

An experimental investigation of high permittivity dielectric resonators for millimeter-wave microstrip components

This paper proposes a new type of high permittivity whispering gallery mode cylindrical dielectric resonators with a geometry which is very suitable for use in microstrip type integrated circuits. These “oversized” resonators, together with high Q factors and ease of fabrication, are potentially interesting for millimeter wave integrated filters and oscillators. In this paper, we report an experimental investigation of such resonators carried out in Ka band (26.5–40 GHz). Measured results including resonant frequencies and loaded quality factors will be presented. Application to millimeter wave filters will also be demonstrated.     

An analysis and experimental approach to MOS controlled diodesbehavior

The metal oxide semiconductor (MOS)-controlled diode (MCD) is a new class of power semiconductor diode that can achieve ideal diode performance. In this paper, experimental verification of the MCD key concept is presented for the first time by using commercially available power metal oxide semiconductor field effect transistors (MOSFETs) operating as MCDs. Measurements of the reverse recovery currents and reverse recovery charges of these “MCDs” are obtained and compared with the body diodes of the MOSFETs. These measurements suggest that MCDs can reduce the reverse recovery current, storage charge, and switching loss significantly. Optimized MCD performances at 1.2 kV, 2.4 kV, and 4.5 kV are also predicted based on numerical simulations. Ideal performance of the MCD close to that predicted by the device simulation should be obtained once an optimized MCD is developed     

An investigation of ARQ and hybrid FEC-ARQ on an experimental highlatitude meteor burst channel

A computer investigation of error-control-coding techniques and bit error patterns recorded on an experimental Northern latitude meteor burst link is presented. Automatic repeat request (ARQ) and hybrid forward error correction (FEC) with ARC are examined from the standpoint of probability of message delivery and encountered message delivery delays. It is demonstrated that FEC will yield substantial improvement in the number of messages deliverable within a specified time constraint. Potential gains in extending the usable time duration of a meteor burst channel are on the order of factors of four with successful message delivery percentages increased by factors of 50     

An experimental investigation of the active-idle pattern of speech over land mobile radio telephone channels

Two methods of speech detection at the syllabic level of voice traffic over land mobile radio telephone channels are presented. Both methods are based on the periodic comparison of the audio signal level with a threshold and provide an ON-OFF pattern of active-idle periods on the channel at a rate equal to 100 to 200 samples per second. One method is entirely digital whereas the other method uses an analog detector followed by digital processing. Results of the analysis show that during a conversation more than 50 percent of the time the channel is idle, with an average duration of the silences larger than 300 ms. These results and those concerning other parameters of interest indicate that even during a conversation many useful idle periods do occur. These silences could indeed be exploited by making them available to additional users and hence improve both the efficiency of the channels and their congestion.     

Theoretical and experimental investigation of the ellipticalannular ring antenna

Analysis of a confocal elliptical annular ring microstrip antenna is carried out using the generalized transmission line model. It is found that a circularly polarized wave can be obtained over a wider frequency range than for conventional structures. It is also found that unlike the elliptical patch the resonant frequency for the odd mode is lower than that of the even mode. Therefore, for a left-handed circularly polarized wave, the feed is to be placed at an angle of -45° with the major axes of the ellipses instead of +45° as in the elliptical patch. An elliptical ring is fabricated, and its input impedance and the radiation patterns are tested. Very good agreement between the theory and the experiment is obtained. Experimental radiation patterns show an excellent circularly polarized wave with an axial ratio less than 1 dB in the broadside direction     

Design and experimental investigation of the asymptotic conicaldipole antenna

The paper describes the application of the “equivalent charge distribution method” for designing the geometry of a special type of dipole antenna used for the faithful reproduction of electromagnetic pulse type waveforms. Using this method, the design equation of the surfaces of an asymptotic conical dipole antenna (ACD) has been derived. The surface of the asymptotic conical dipole antenna, obtained by this method, is compared with those computed by the method of Baum (1969). The response of an ACD antenna, fabricated using design data computed from the design equations derived in the paper, is measured and presented