首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
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.  相似文献   

2.
曹广军  刘光廷 《压电与声光》1993,15(6):49-52,67
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。  相似文献   

3.
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.  相似文献   

4.
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.  相似文献   

5.
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.  相似文献   

6.
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.  相似文献   

7.
Cho  Y. Yamanouchi  K. 《Electronics letters》1986,22(16):835-836
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.  相似文献   

8.
Acoustic surface wave filters   总被引:3,自引:0,他引:3  
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.  相似文献   

9.
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.  相似文献   

10.
Wait  J.R. 《Electronics letters》1967,3(9):396-397
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.  相似文献   

11.
Barlow  H.M. 《Electronics letters》1967,3(7):304-305
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.  相似文献   

12.
《Electronics letters》1967,3(10):450-451
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.  相似文献   

13.
《Electronics letters》1969,5(14):322-323
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.  相似文献   

14.
MEMS-IDT声表面波陀螺   总被引:4,自引:0,他引:4  
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。  相似文献   

15.
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.  相似文献   

16.
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.  相似文献   

17.
Hartemann  P. 《Electronics letters》1973,9(11):246-247
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.  相似文献   

18.
《Electronics letters》1969,5(21):540-541
The propagation characteristics of a magnetoelastic surface wave in ferrites are described using numerical calculations pertinent to gallium-y.i.g.  相似文献   

19.
张兰  吴雄斌  陈骁锋  李炎 《电波科学学报》2014,29(4):706-710+722
温度、压力和电导率是表征海水性能最主要的三个物理量,研究海水电导率的分布与变化,有助于人们深入研究海水电磁特性及化学组成. 文中建立了一种基于高频地波雷达的海水电导率反演机制,利用高频电磁波的海面衰减特性,通过分析高频地波雷达在海面不同雷达观测元间的附加衰减数据,结合区域验证过的电波衰减方程,建立海面电导率和地波Norton衰减因子之间的单调对应关系模型,进而获得沿岸海洋表面电导率的分布信息. 实验结果表明:利用高频地波雷达遥感海面电导率具有可行性.  相似文献   

20.
Stationary distribution of the efficient wave sources excited by interdigital transducers (IDT) of arbitrary configuration has been derived on the basis of reciprocity of the generation and reception of surface acoustic waves (SAW) in piezoelectrics. It was shown that these sources represent a linear combination of two stationary distributions on the surface S between the piezoelectric and IDT: the distribution of the normal component of SAW flux density formed in the mode of SAW reception by the short-circuit IDT and the field distribution of the SAW electric potential at the same surface S but in the absence of piezoelectric. The Y-parameter matrix of the device was obtained as an electric M×2-terminal network containing M IDT. It was shown that the SAW transfer admittances and SAW radiation admittances contained additional frequency-dependent multipliers. The characteristics take into account the smoothed diffraction, spatial dispersion in IDT, reflections from IDT, and electric loads of the device.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号