Photoconductivity study of semiconductors using the surface acoustic wave convolver

Photoconductivity study of a semiconductor using the SAW convolver is presented. The semiconductor is placed either on or a small distance above the SAW delay line. A fast rise time pulse of light is applied to the semiconductor surface through the piezoelectric substrate, and the resulting change in the semiconductor conductance is observed by the relaxation of the SAW propagation loss. This technique has the important advantage that no ohmic contact to the semiconductor is needed.     

MZOS结构界面特性的研究

分析了ＭＺＯＳ结构及其Ｓｉ－ＳｉＯ２子系统的Ｃ－Ｖ特性，发现ＺｎＯ中的氧空位和溅射工艺过程在Ｓｉ－ＳｉＯ２界面引入的界面电荷是影响ＭＺＯＳ结构界面特性的主要因素。研究还表明，低温热退火可以改善ＭＺＯＳ结构的界面特性。     

Efficiency of the surface-acoustic-wave diode convolver

The diode convolver performs signal processing, for example correlation, by mixing two input waveforms in an array of diodes, each diode being connected to a tap on a surface acoustic wave delay line. This paper gives the theory for the device efficiency, for a parallel circuit arrangement of taps and diodes. The effect of stray capacity is also analyzed. An experimental 31-tap device used hybrid circuitry in order to allow close spacing of the taps, giving a tap-to-tap propagation time of 90 ns. The efficiency agrees well with theory, showing that the bilinearity factor is maximized for an intermediate value of the bias current. The maximum bilinearity factor, relating external powers, was -34 dBm.     

Asynchronous operation of an analog convolver

A surface-acoustic-wave convolver can correlate a signal waveform by using an appropriate reference only if the signal arrives within a small time range related to the propagation delay in the device. It is shown here that the complete correlation function can be obtained for arbitrary signal timing if the reference waveform is made repetitive.     

Simple equivalent circuit for the nonlinear surface-wave convolver

A simple equivalent circuit for the centre-plate nonlinear acoustic-surface-wave convolver has been derived. This model has been tested experimentally and used to separate the magnitude of the nonlinear electromechanical coupling constant for the circuit response of the device.     

Optimization on configuration of surface conduction electron-emitters

In this work, a novel nanogap with inclined protrusion cathode in palladium strip fabricated by hydrogen absorption under high-pressure treatment is optimized for the surface conduction electron-emitter. Its field emission is sensitive to the geometry of surface conduction electron-emitters (SCE). For a specified emitter material, the SCE are further investigated by varying the thickness, tilted angle and gap of palladium (Pd). An optimal field emission efficiency with 80° tilted angle, 120 nm gap and 10 nm thickness of Pd is found for certain designed field emission efficiency. We further find that varying the emitter material work function of the emitter material from 5.12 eV to 3.9 eV will further improve the field emission property due to the increase of the emitted current.     

Theoretical and experimental study of transverse-horizontal convolver

The letter presents the results of theoretical and experimental studies for the transverse-horizontal convolver (THC) fabricated on LiNbO3. First, the definition of the figure of merit for the THC is proposed and, secondly, the existence of the crystal orientation and the direction of propagation with high efficiency and large electromechanical coupling coefficient for an LiNbO3 SAW THC is shown.     

Acoustic surface wave filters

Acoustic surface waves offer several advantages in the construction of delay lines and filters in the UHF range. In these devices the frequency response is determined by the finger spacing and overlap of the interdigital comb structures used as input and output transducers. Models are developed to describe these devices, and the predictions of these theories are compared with several experimental filters, including band-pass filters and dispersive delay lines.     

光栅辅助的表面波传感器研究

采用严格耦合波方法研究了普通棱镜耦合的表面波传感器与光栅辅助的表面波传感器的传感特性。设计了工作在1550nm处的一维光子晶体与光栅的材料参数与结构参数。光栅的深度为20nm,周期为524.6nm,占空比为0.5。模拟计算表明,光栅的引入导致双共振峰的出现,表面波的模式出现分裂。当外界折射率变化时,两个共振峰向相反的方向移动。利用双共振峰的这种特性进行传感,可以使光栅辅助的表面波传感器的角度灵敏度提高到普通棱镜结构的表面波传感器的3倍以上。     

Influence of surface metallisation on magnetoelastic surface wave

The surface-wave coupling which obtains between an elastic bulk shear wave and two magnetostatic modes (one of which is a bulk wave and the other a surface wave) is discussed in the context of a metallised semi-infinite ferrite geometry.     

光衍射法测量低频液体表面波衰减系数

为了对低频液体表面波的衰减系数进行测量,利用液体表面波的光衍射方法,得到了稳定、清晰的衍射图样,并发现了衍射条纹强度分布与光斑入射点位置有关。对此进行了理论分析,得到了衍射条纹强度分布与液体表面波振幅之间的解析关系式以及表面波振幅随距离变化的实验数据。结果表明,可以根据衍射条纹的强度分布来测量液体表面波的衰减系数,与经典流体力学理论相比较,符合较好。这一结果对测量液体的物理参量是有帮助的。     

Launching a surface wave over the Earth

It is pointed out that a recent proposal to launch a surface wave over a homogeneous surface has some fundamental drawbacks. However, it is possible that such a device may be useful as a launcher for trapped surface waves over a highly inductive surface.     

Launching a surface wave over the Earth

Proposals are made for a ferrite-loaded horn type of antenna capable of launching a 1.5 MHz surface wave over the Earth. The use of a ferrite coating on the conductor laid parallel with the ground, and forming one side of the horn, makes provision for a surface reactance which can be tapered up to reduce the size of the radiating aperture, and thence tapered down again to match the reactance of the ground.     

Experimental investigation of the hybrid TEM-dual surface wave

The conditions for minimum attenuation of this wave supported in one case by a coaxial guide and in another by a parallel-wire transmission line have been investigated experimentally and shown to comply with the earlier theoretical predictions. The best results are obtained by loading one or other of the two supporting surfaces and not both simultaneously.     

Magnetoelastic surface wave in ferrites

A magnetoelastic surface wave is shown to exist in an elastically isotropic ferrite, e.g. y.i.g. The wave exhibits a nonreciprocal behaviour, and is found to have no counterpart in a purely elastic medium.     

MEMS-IDT声表面波陀螺

声表面波陀螺的概念出现在70年代初期,发展为MEMS-IDT声表面波陀螺仅是最近几年的事情。MEMS-IDT声表面波陀螺仪是一种MEMS微机械振动陀螺,这种陀螺为单层平面结构,采用标准IC工艺就可完成加工,勿需悬浮的振动元件,有很强的抗冲击振动能力,可靠性高,可不用真空封装而保持较高的灵敏度。     

Practical surface acoustic wave devices

A tutorial discussion is presented on selected surface acoustic wave (SAW) devices for the use of engineers and electronic systems designers. Currently practical components for use in radar systems, communications systems, and as frequency domain filters are described. Emphasis is placed on nondispersive and dispersive delay lines, devices for generating and detecting various radar waveforms, devices for generating and detecting fixed and programmable biphase and multiphase codes, and broad-band and narrow-band filters. The device possibilities of several new approaches are described, including multistrip couplers, nonlinear convolvers, reflective structures, and overlay films. It is concluded that, while SAW devices have found many applications in large radar systems because of their size, cost effectiveness, and reliability, wide-scale applications, for example as frequency domain filters, will be needed to justify continued research in this field. Wide-scale applications will come as systems engineers realize the potential of these devices and confidently design them into their systems.     

Magnetostatic surface wave straight-edge resonators

The performance of the magnetostatic surface wave straight-edge resonator (MSSW-SER) is presented. The resonator uses a rectangular YIG film to propagate MSSWs where the straight edge serves as a reflector. Problems arising from coupling to width mode resonances and their effect on the main resonance are investigated. Through a careful choice of YIG and transducer parameters, the interference effects of the width mode resonances with the main resonance are minimized. As a result, highQ tunable microwave resonators with a tuning range from 2–20 GHz, insertion loss less than 10 dB, and spurious rejection better than 10 dB could be designed and fabricated. This MSSW resonator could be used to construct a tunable low-phase-noise feedback oscillator. However, the tuning range of this MSW feedback oscillator is limited by the phase change of the external amplifier circuit.     

Propagation characteristics of magnetoelastic surface wave

The propagation characteristics of a magnetoelastic surface wave in ferrites are described using numerical calculations pertinent to gallium-y.i.g.     

Frequency-selective scanning of acoustic surface wave

An acoustic-surface-wave point source is obtained when an interdigital transducer with concentric curved fingers is used. An array transducer composed of 80 point sources has been tested. The direction of propagation of the surface-wave beam emitted by this transducer depends on the frequency. A transmitting-array transducer and five receiving transducers are deposited on a quartz substrate. Each of these five outputs corresponds to a given frequency and delay prescribed by the positioning. At 12°, scanning was attained for a frequency variation of 7.6 MHz around a central frequency of about 60 MHz, corresponding to a delay variation of 18.2 ?s.