F.E.T. oscillation frequency domain solution

A new approach is used to determine when the necessary condition for oscillation, Re (Za)<0, holds in a microwave oscillator. Here Za is the Schottky GaAs f.e.t. active network impedance. This analysis has been used to develop a computer program that calculates the frequencies at which the above condition holds. The computer program also provides inband impedances and reflection coefficients and has been utilised to study Ku-band y.i.g.-tuned oscillators. Bandwidth and initial frequency of oscillation curves as functions of f.e.t.-model lumped elements are generated from the computer program.     

Nonlinear J.F.E.T. model for computer-aided circuit analysis

A simplified circuit model is proposed to represent the nonlinear d.c. and low-frequency small-signal operation of j.f.e.t.s. This model is particularly useful for computer-aided circuit analysis programs, such as the iterative nodal analysis program BIAS-3. Operation in the off, resistance, and pinch-off regions of the j.f.e.t. is included.     

C.C.F.E.T.: an active charge-coupled device

A charge-coupled device is described in which an amplified measure of the charge can be obtained nondestructively at each element. Features of the device include high charge gain (?105) and the facility to reset the device and introduce charge packets into the c.c.d. by the `punchthrough? effect.     

F.E.T. mixer with the drain l.o. injection

Performance of a 6/4 GHz frequency convertor showed conversion gains up to 4.7 dB with 3.9 dB noise figure. On cooling to 200 K, a gain increase of 2.4 dB and a noise-figure decrease of 1.8 dB were measured.     

J.F.E.T. bucket-brigade circuit: some recent experimental results

A bucket-brigade circuit implementation with junction field-effect transistors (j.f.e.t.) offers a significant improvement in maximum data rates for digital operation, and in maximum bandwidth for analogue operation. Some 10-stage monolithic j.f.e.t. brigades have recently been built and successfully operated at data rates of 50 MHz. In the Letter, the j.f.e.t. structure is briefly described and some experimental results are presented.     

高效率E类放大器

E类放大器是一种新型高效率功率放大器,理论效率接近100％,有很好的发展前景,本文介绍了E类放大器当前发展概况、电路结构、工作原理、技术特性;给出了理论分析、设计方法以及微波频段E类放大器出现的新问题,最后给出集中参数电路和微带电路的E类放大器实例。     

Perturbation theory for multistrip acoustoelectric surface-wave amplifier

The `multistrip perturbation theory? of the coupler has been extended to the multistrip amplifier. A study of the acoustoelectric gain shows that, if the number of strips per wavelength is very large, the gain becomes that predicted by Adler, but the number of strips per wavelength required to reach this condition increases drastically with the conductivity of the semiconductor; it also shows that the width of the strips on the semiconductor should be as large a fraction as possible of their period, and that, if the conductivity of the semiconductor is low and the number of strips per wavelength is small, gain can be obtained from electrons drifting at a velocity less than the sound velocity in the opposite direction to the surface wave, and, in some cases, even in the same direction.     

Three dimensional nonlinear theory of the gyropeniotron amplifier

The saturation regime of gyropeniotron interaction in a cylindrical waveguide with slotted wall (magnetron type) is studied by developing a three-dimensional nonlinear theory for the amplifier. The wave amplitude is calculated self-consistently in the presence of the RF current modulation by solving a set of coupled nonlinear differential equations. Extremely high efficiency of about 75% is calculated for interaction between the n-mode and the second cyclotron harmonic of a 70kV, 3·5 A beam with v_⊥=/v_z2 under ideal conditions of zero velocity spread and on-axis guiding centre location. The effects of spread in beam velocity and guiding centre position are also calculated. An efficiency of about 38% is obtained for a beam with 5% velocity spread and 10% guiding centre spread. The performance characteristics of the amplifier are shown for cyclotron harmonics up to order s = 8. The efficiency drops to 22% at s equals; 8.     

E类功率放大器研究与应用

分析了E类功率放大器的工作原理,并基于此设计出一种高效高频E类功放,作为无线电能传输系统中发射级的前端驱动电路。运用LTspice仿真软件,对其基本原理电路进行实验分析。为进一步提升输出功率和传输效率,电路还加入了阻抗匹配。仿真结果表明,此电路可实现在6.78 MHz下以85%左右的高效率进行10~30W的功率传输,整体电路结构简单,有实用价值。     

Piezoelectric coupling coefficient of interdigital Rayleigh-wave transducers

The letter describes the theoretical dependence of the piezoelectric coupling coefficient and capacitance of an interdigital Rayleigh-wave transducer on the ratio electrode-width/gap-between-electrodes.     

Class E tuned power amplifier with shunt inductor

The `class E tuned power amplifier with a shunt inductor' is presented. It offers a DC-to-RF power conversion efficiency approaching 100 percent. The proposed circuit of the amplifier uses a shunt inductor instead of a shunt capacitor. The conditions for optimum operation are formulated and discussed. The following are determined: the waveforms, the fundamental-frequency components, the peak values of the collector current and voltage, the output power, and the values of the load network elements. Experimental results are also presented. The proposed amplifier circuit minimizes the power dissipated during the on-to-off transition, even if the switching time is an appreciable fraction of the signal period.     

The New Search for E.T.

A new telescope has been especially designed and constructed at the Oak Ridge Observatory to detect pulses of visible light that a far-off civilization could be sending toward Earth. Unlike a regular imaging telescope, the new telescope has no lens, nor is it designed to pluck pristine images of celestial bodies orbiting overhead. It uses a 1.8 m diameter mirror and a 0.9 m secondary mirror to scoop up raw photons from the sky. Called photon buckets, they are less expensive to build and operate than imaging telescopes. A key feature is its use of multipixel photomultiplier tubes that allows more star systems to be observed at a time     

The early days of E.A.T

Experiments in Art and Technology seems a commonplace collection of words. Yet, when E.A.T. was founded in 1960, the notion of combining art and technology was a radical one-decades before its time. The article gives a brief historical review of E.A.T     

Phase-correcting feedback system for class E power amplifier

A phase-correcting feedback system which reduces the AM-to-PM distortion of Class E power amplifiers for wireless communication is presented in this paper. It comprises a novel limiting amplifier, a phase detector, and a phase shifter all operating at 835 MHz. The phase-correcting feedback together with a Class E power amplifier were fabricated in a 0.8-μm GaAs MESFET process. The limiting amplifier has a phase error less than 2.5°. The phase detector and phase shifter have a sensitivity of 10 mV/degree and 80°/V, respectively. The Class E power amplifier delivers 26.5 dBm to the load with a power added efficiency of 67%. The phase correcting feedback system reduces the 30° phase distortion of the Class E amplifier down to 4°, and its total power dissipation is 21.5 mW     

New type of Rayleigh-wave transducer on piezoelectric ceramics

An interdigital transducer on a piezoelectric ceramic with the polarisation directed from one comb to the other is described. The efficiency is determined by complex-admittance measurements.     

ViewSonic E70F

这款由优派国际推出的E70F显示器,是一款17英寸通用型显示器,其最高分辨率为1280×1024.在安规方面,这一款显示器通过MPRⅡ等多个国家的安规标准,这些安规对产品本身的电磁波有一定的限制,可更好保障人身安全.     

A normal mode theory for the Rayleigh wave amplifier

A Rayleigh acoustic wave traveling on the surface of a semi-infinite piezoelectric medium may be amplified by interaction with drifting carriers in an adjacent semiconductor. The gain and frequency response of this interaction is determined here by using a normal mode expansion of the Rayleigh wave piezoelectric fields. The configuration which uses a thin semiconductor film supported by a semi-infinite dielectric and separated from the piezoelectric by a small air gap is described in detail and the results are expressed in a form that clearly shows the effect of piezoelectric, air gap, and semiconductor parameters. Comparisons with experimental data for the lithium niobate-silicon film configuration show that acoustic gains on the order of 100 dB/cm can be obtained in the frequency range above 0.1 GHz.