Noise reduction in electron beams

Direct measurements were made of the electron-beam noise parameters using a modified Currie-type gun. The noise parameters were measured as a function of the electric field in the vicinity of the cathode. The S parameter was found to be strongly influenced by this field in the Currie-type gun, but the parameterpi/sis relatively unaffected.     

35-GHz transferred electron amplifiers

GaAs transferred electron amplifiers with 110-mW saturated power output at 35 GHz have been designed and fabricated. Small signal gain of 13 dB, 3-GHz bandwidth, and noise figures as low as 16.2 dB have been observed. Two basic amplifier designs which have been investigated are described.     

Triggering pulse durations in transferred electron devices

Pairs of 1.0 ps optical pulses, each focused onto a different region of a planar GaAs transferred electron device, were separated by a variable delay time ? to initiate and then inhibit dipole domain formation. The minimum pulse durations which could trigger domains were thus observed; the minimum value of ? which generated domains in the device studied was 7 ± 3 ps.     

Comment on noise in transferred electron amplifiers

The noise in transferred electron amplifiers is usually attributed to thermal noise of the carriers in the two valleys and intervalley scattering noise. The latter is here interpreted as being due to carrier density fluctuations in the two valleys (partition noise), which, because of the difference in mobility in the upper and lower valleys, shows up as current noise.     

Power reduction in liquid-crystal display modules

A method for driving a liquid-crystal display (LCD) which can reduce power consumption by up to 50 percent is described. While the drive method commonly used requires power-supply current both to charge and to discharge the display capacitance, the method described here allows the capacitance to be discharged by shorting the display electrodes momentarily.     

Electronic tuning of stable transferred electron oscillators

The problem of electronic tuning of microwave osciilator structures characterized by high energy storage and hence low noise is considered. The evolution of a wide-band varactor tuned J-band oscillator is described, and analytical criteria are presented which determine the position of the varactor diode and the theoretical maximum tuning range available including Varactor loss. Experimental results confirm the validity of the circuit model used for the proposed oscillator structures.     

Trigger sensitivity of transferred electron logic devices

An analysis of the Schottky-barrier gate transferred electron logic devices (TELD's) is developed which gives the trigger sensitivity in terms of the channel pinchoff voltage, normalized channel depletion width under the gate, device subthreshold transconductance, and the value of the external load resistor. The results presented show that the trigger sensitivity increases with increase in doping density, decrease in channel pinchoff voltage, and decrease in gate reverse bias. Furthermore, for the same material parameters (doping density, channel thickness, etc.) device subthreshold transconductance (gm) improves the trigger sensitivity by a factor (1 + gmRL). Device designs based on this analysis should result in improved device performance.     

An analysis of wide-band transferred electron devices

The trapping conditions of a high-field domain at the anode are studied by varying doping density, applied bias voltage, and doping notch depth and width near the cathode. It is shown that the frequency band of negative conductance of the trapped-domain mode depends significantly on the doping density, and a diode having the doping density of 3 × 10¹⁵/cm³exhibits the negative conductance over the wide range from 4 GHz to 42 GHz. The upper frequency limit of the negative conductance is due to the series resistance in the low-field region and the lower limit is determined by carrier transit-time effects in high-field region. The operation mode of a trapped-domain diode will change into a traveling dipole or accumulation mode from a trapped-domain mode depending on the doping density and the operation frequency for a large-signal operation.     

Dynamic cathode boundary fields and transferred electron oscillators

The evolution of a generalized time-dependent cathode boundary field model is discussed, and calculations are presented which demonstrate its applicability for explaining such diverse phenomena as 1) the appearance of anomalously high efficiency oscillations in InP and 2) the more moderate oscillatory behavior associated with GaAs.     

CW performance of vapor-grown GaAs transferred electron oscillators

The CW performance of GaAs transferred electron oscillators (TEO) is described. The TEO were fabricated from n⁺-n-n⁺epitaxial structures of GaAs grown from the vapor phase. The devices consisted of single mesas, 5-6 mil in diameter, on plated silver heat sinks. Fifteen devices were fabricated from three separate wafers and the results were very uniform. The dc to RF efficiency varied between 4 and 5.7 percent for the 15 devices packaged and tested. The best results were 350 and 390 mW of RF power with a conversion efficiency of 5.4 and 5.7 percent, respectively, at approximately 17.5 GHz from single 5.5-mil mesas. These data represent new highs in performance from single-mesa TEO at this frequency. The results indicate that vapor epitaxial growth procedures combined with a device fabrication scheme based on plated heat sink technology can yield reproducible TEO with RF powers greater than 250 mW at efficiencies greater than 5 percent. The results indicate also that the plated heat sink approach will be useful for other devices, such as IMPATTS, in which thermal considerations limit device performance.     

Operating modes of millimetre wave transferred electron oscillators

The harmonic content of both GaAs and InP millimetre wave transferred electron oscillators has been measured using a Michelson interferometer. The operating modes of these devices as a function of active length and frequency have thus been identified. Additionally, the higher frequency capabilities of InP as a millimetre wave oscillator material have been demonstrated.     

C波段高可靠星用介质振荡器、上下混频器一体化模块

在高可靠星用模块研究中 ,采用特殊工艺 ,将介质振荡器、上下混频器、微波放大器、中放等微波单元集成在尺寸为 1 0 0 mm× 40 mm× 45 mm模块中 ,大大减小了体积、降低了重量 ,从而应用更广泛 ,使用更灵活。     

Noise spectra of a CW silicon TRAPATT oscillator

Noise measurements on a double-sided silicon TRAPATT oscillator have been made and show that the noise is comparable to that of the silicon IMPATT oscillator.     

混沌测量中的噪声抑制

利用混沌系统的初值敏感性进行小信号测量是一种很好的有应用潜力的方法,可混沌系统也同样对干扰敏感,某一初值对应的混沌轨道会由于电路中的噪声产生偏离,从而造成测量误差.本文提出了一种减少测量噪声的方法.通过混沌电路的耦合使耦合轨道相互靠近,从而抑制噪声.实验研究表明该方法对混沌测量抑制噪声是有效的.     

Noise reduction in bulk negative-resistance amplifiers

The letter presents noise calculations for Gunn amplifiers with both uniform and nonuniform field distributions. The results indicate that amplifiers with an injection-limited cathode contact, and hence a uniform field distribution, exhibit significantly lower noise figures than those having an ohmic cathode contact, which yields a nonuniform field distribution. A further reduction of noise could be obtained by using materials with high negative mobility.     

High-efficiency GaAs transferred electron device operation and circuit design

In this paper it is shown that a GaAs transferred electron device is adequately described by a simple, static IV characteristic. This characteristic is used in a time domain computer simulation with the microwave circuit represented by transmission line equivalent circuit from which the voltage and current waveforms associated with the device are derived for a particular device IV characteristic and circuit. These data are analyzed for efficiency, frequency of oscillation, and starting transient and then are observed as various device and circuit parameters are changed in the simulation. From this study and parameter scan, the criterion for an efficient GaAs oscillator circuit and the maximum dc to RF conversion efficiency for device of a given quality, as specified by its current peak to valley ratio are found. Experimental observation of waveforms and efficiency and their dependence on the circuit and device parameters were then seen to be in good agreement, thus justifying the use of the phenomenological I-V characteristic. For a device with a current peak to valley ratio of 2, the theoretical and experimentally observed conversion efficiency limit appears to be slightly less than 20 percent. The use of the simple I- V characteristic is appropriate down to frequencies less than the "transit" frequency.     

Harmonic operation of GaAs millimetre wave transferred electron oscillators

Harmonic operation of GaAs millimetre wave transferred electron (TE) oscillators has been identified using a wideband waveguide system. The harmonic number was determined by precisely measuring the frequency as well as the frequency variations of the harmonic components when the oscillator was tuned mechanically or electrically. We find that GaAs TE oscillators at 94 GHz, matched to a waveguide circuit by means of a resonant disc, operate at the second or third harmonic frequency, depending on the length of the active GaAs region, which was between 1.8 and 2.6 ?m.     

Circuit considerations in the design of wide-band tunable transferred electron oscillators

Studies of the effects of the encapsulation on Gunn device performance have been carried out. Results are compared with those of Howes [1], and certain apparent discrepancies are explained.     

Detailed computer analysis of LSA operation in CW transferred electron devices

In the first part of the paper the importance of the microwave circuit parameters on the attainment of LSA oscillation in ideal uniform devices is investigated. It is shown to be desirable for the circuit to have high-dynamic impedance. In consequence stray capacity at the device, due to the device configuration or to the mounting arrangement, is to be avoided. The existence of a capacityCin parallel with the cold-device capacity C0effectively raises the lower limit for LSA operation ton/f > 2 times 10^{4}[(C+C_{0})/C_{0}]. In the second part of the paper devices with typical doping and mobility profiles are considered to operate in circuits with low-dynamic impedance as well as in circuits with high-dynamic impedance. The results presented show that the LSA operating efficiency can be very sensitive to certain inhomogeneities, notably doping ramps of order 12½ percent and high-resistivity regions at the cathode contact. The efficiency degradation is, however, very dependent on the circuit in which the device is operating. Finally it is shown that the efficiency of a CW device may be raised by several percent in some cases by compensating for the mobility profile with a suitable doping gradient.     

The transient behavior of high-field dipole domains in transferred electron devices

This paper provides an explanation for previously unexplained aspects of the transient experiments of Kuru, Robson, and Kino [1]. It is shown that in a transient experiment on a dipole domain in a transferred electron device, the ratio of change in charge at the domain to the charge transferred at the external terminals is strongly dependent on the magnitude of the bias step. For a small bias step the charge transferred at the external terminals is nearly equal to the change in domain charge, while for a quenching transient the charge transferred at the external terminals is about one-half the initial domain charge.