Low-noise wideband indium-phosphide transferred-electron amplifiers

X band pulsed, InP transferred-electron reflection amplifiers have been characterised by a study of the small-signal admittance, the large-signal dynamic conductance and the noise figure. These measurements have been made as functions of voltage, frequency and temperature on a number of different vapour epitaxial layers. The lowest observed noise figure was 8.8 dB at 10.0 GHz. An instantaneous bandwidth of more than 4 GHz at 7 dB gain has been obtained using a simple impedance-equalisation circuit.     

Low-noise room-temperature wideband parametric amplifiers

Two room-temperature parametric amplifiers are described which have gains of 26 dB. One has an excess noise temperature of between 74 and 85 K across the band 3.7?4.2 GHz, and the other has an excess noise temperature of between 85 and 99 K across the band 7.25?7.75 GHz.     

Nonlinearities of multicavity klystron amplifiers

The nonlinearities of a five-cavity klystron for wide-band operation are investigated by making use of the large signal analysis and experiments. The variations of frequency-response characteristics with respect to the input signal level, and the amplitude and phase nonlinearities are presented in detail for two typical tunings. It is shown that the nonlinearities are affected by the tuning of the intermediate cavity. The amplitude nonlinearity at saturation is about -3 to -6 dB within a frequency range of 80 MHz at the 14-GHz band. There exists some discrepancy between the calculated and measured phase nonlinearities. The nonlinear mechanisms are discussed to explain the results obtained by categorizing them into four parts. In the discussions, an emphasis is placed upon the velocity modulation of the beam by the intermediate cavity which introduces the frequency dependence into the nonlinearities.     

Low-noise amplifiers for WCDMA base-station receivers

This paper focuses on the design and measurements of low-noise amplifiers (LNA) targeted for WCDMA base-station applications. In addition, various gain control techniques and the accuracy in noise measurements have been analyzed. Two different LNA designs are presented. Both LNAs can be operated in two gain modes, which are optimized for different base-station configurations. Both designs are implemented using the same 0.25-μm SiGe BiCMOS process, and both designs achieve the NF of 1 dB and IIP3 of ?5 dBm in high gain mode.     

Low-noise two-wired buffer electrodes for bioelectric amplifiers

Active buffer electrodes are known to improve the immunity of bioelectric recordings against power line interferences. A survey of published work reveals that buffer electrodes are almost exclusively designed using operational amplifiers (opamps). In this paper, we discuss the advantage of utilizing a single transistor instead. This allows for a simple electrode, which is small and requires only two wires. In addition, a single transistor adds considerably less noise when compared to an opamp with the same power consumption. We then discuss output resistance and gain as well as their respective effect on the common mode rejection ratio (CMRR). Finally, we demonstrate the use of two-wired buffer electrodes for a bioelectric amplifier.     

Low-noise parametric amplifiers tunable over one full octave

Various possible ways of tuning low noise coolable parametric amplifiers through a full octave without adjusting the pump frequency are analyzed. Based upon this analysis, a novel and simple method is proposed and practically verified. In agreement with the theory, noise temperatures between 100/spl deg/K (at 4 GHz) and 240/spl deg/K (at 8 GHz) were achieved in a balance C-band amplifier.     

Three-dimensional evaluation of energy extraction in output cavities of klystron amplifiers

An accurate three-dimensional analysis of the performance of output gaps in klystron amplifiers was carried out. The parameters investigated were: beam radius, perveance, output gap angle, output gap peak voltage, RF phase, magnetic field, and beam interception. A new, accurate method for computing space-charge forces between axially and radially deformable rings was developed. Rigorous expressions for electric and magnetic fields in the tunnel and the gap were used. The highest computed efficiency for an optimally bunched beam was 80.3 percent with 6 percent "ideal" interception. An important conclusion is that efficiency decreases with increasing normalized tunned radiusbeta_{e}aforb/aconstant in the examined range0.4 and probably beyond. Excellent correlation in efficiency and interception between a model klystron developed by E. Lien of Varian and the authors' program was established.     

Low-noise and very high-efficiency four-wave mixing in 1.5-mm-long semiconductor optical amplifiers

Very high four-wave mixing (FWM) efficiency and signal-to-background ratio (SBR) are obtained in a 1.5-mm-long bulk semiconductor optical amplifier. The FWM efficiency is measured to be 5 dB at 1-THz pump-signal detuning, which is the highest value reported to date. With a pump power of -1.4 dBm, the SBR is in excess of 20 dB in a bandwidth of 12.5 GHz, for a pump-signal detuning range as large as 2 THz and the efficiency is under the same conditions larger than -1 dB for a pump-signal detuning range as large as 1 THz. These results make FWM an attractive method for practical wavelength conversion. Some low-detuning measurements show a maximum efficiency around 8 GHz.     

Low-noise amplifiers in wireless communications: state of the art,two new wideband all-active LNAs in SiGe-BiCMOS

The aim of this paper is three-fold. First, it introduces the low-noise amplifier, its relevance in modern wireless communications receivers and the performance expected of it. Then, it presents an exhaustive review of the existing topologies, presenting their advantages and shortcomings. And finally, it introduces a new class of LNAs, based on current conveyors, describing the founding principle and the performances of two new LNAs, one single-ended and the other differential. Both these new LNAs offer the following notable advantages over existent topologies: total absence of passive elements (and the smallest LNAs in their respective classes); wideband performance, with stable frequency responses from 0 to 3 GHz; easy gain control over wide ranges (0–20 dB). Comparisons with other topologies prove that the new class of LNA implementations greatly advances the state of the art. These amplifiers are ideally suited to today’s multi-band receivers.     

Optical klystron

A quantum effect in the interaction between a free electron beam and optical field has been considered. Velocity modulation on the electron beam is produced "classically" when the modulation-gap transit angle ωτ < 1.     

Low-noise photoparametric up-converter

An analysis is given for a photoparametric up-converter system. The up-converter consists of a single triplate line with one coaxial output connected to a circulator, through which the pump is applied and the signal extracted. The other end of the line is connected to the photo diode via a small coupling capacitor. The light is modulated at frequencies from a few hertz to some upper limit determined by the bandwidth of the triplate circuit. This arrangement is shown to give excellent results and the limit performance, as determined only by the diode parameters may be attained by following the up-converter with a degenerate parametric amplifier using the same pump plus a varactor doubler.     

The multiple-beam klystron

The multiple-beam klystron (MBK) is a device for extending klystron power generation capability at a given frequency by a factor of ten or more. The MBK utilizes a multiplicity of electron beams in conjunction with multiwavelength waveguide circuits. These circuits are periodically loaded and operate in thepi/2-mode. The efficiency, bandwidth, gain and stability of the MBK are equal to or better than that of the single-beam prototype klystron. Furthermore, the MBK permits generation of a given power level at an unusually low voltage, thus minimizing insulation, X-radiation, and modulator problems. An MBK utilizing ten external-circuit klystrons has been built for 750-Mc operation to demonstrate the principle of the device. A single main magnetic circuit is used to focus all beams simultaneously. An RF power output ten times that of one klystron was measured, corresponding to an efficiency of 44 per cent. Bandwidth and gain were identical with single-beam prototype operation. Individual beam drop-out tests were made which showed no disruption of operation in case of the failure of one or more beams. Limited tests tend to confirm the conclusion that the harmonic content of an MBK can be lower than that of a single-beam klystron.     

Low-noise HEMT using MOCVD

Low-noise HEMT AlGaAs/GaAs heterostructure devices have been developed using metal organic chemical vapor deposition (MOCVD). The HEMT's with 0.5-µm-long and 200-µm-wide gates have shown a minimum noise figure of 0.83 dB with an associated gain of 12.5 dB at 12 GHz at room temperature. Measurements have confirmed calculations on the effect of the number of gate bonding pads On the noise figure for different gate Widths. Substantial noise figure improvement was observed Under low-temperature operation, especially compared to conventional GaAs MESFET's. A two-stage amplifier designed for DBS reception using the HEMT in the first stage has displayed a noise figure under 2.0 dB from 11.7 to 12.2 GHz.     

高性能宽带低噪声放大器的研制

以薄膜混合集成电路为基础,采用AL2O3精细陶瓷做衬底和国际上较先进的共晶工艺,运用宽带内补偿网络和负反馈并用的设计方法,结合理论计算和仿真技术,实现了高指标C波段宽带低噪声放大器的设计,测试结果验证了设计的正确性,为高性能宽带低噪声放大器研制提供了新的设计依据和理论基础。     

Low-noise implanted-base microwave transistors

An improved small-signal bipolar microwave transistor utilizing ion-implantation has been developed. The structure comprises oxide isolation, arsenic-doped emitters and an ion-implanted base region. A noise figure of 3·9 dB at 8 GHz has been achieved. The variation of the device parameters with the implanted dose has been investigated and the results are interpreted in terms of a simplified model. Implanted emitters and diffused emitters have been evaluated and found to give similar results.     

Low-noise self-referenced CMOS oscillator

A new low-noise CMOS oscillator architecture is presented. The oscillator comprises of a loop formed by a switched capacitor integrator which sets the control voltage to a voltage controlled oscillator (VCO). The VCO output provides a clock for the integrator, thus closing the feedback loop. Phase noise reduction is obtained by suppressing the VCO noise by the feedback loop. Design considerations and simulation results supporting the architecture are presented.     

Millimeter-wave extended interaction klystron

The interaction of the HF fields in the distributed resonance system of a high-power millimeter-wave klystron with an electron beam is theoretically and experimentally studied under limitations imposed on the length of interaction space and moderate values of the beam perveance. A possibility of amplifying and generating extended interaction klystrons (EIKs) is demonstrated. The EIKs with the distributed extraction of energy exhibit relatively high efficiencies, output powers, and gains at an acceptable gain band. In the experimental prototypes of the four-cavity packaged EIK working in the mid-millimeter-wavelength range, the output pulse power is no less than 2.5–3 kW, the efficiency is 30%, the gain is 25–30 dB, and the gain band at a level of 3 dB is 0.25–0.35% at an anode voltage of 18 kV and a beam current of 0.5 A.     

Low-noise multistage avalanche photodetector

We propose a multistage compound semiconductor avalanche detector for low-noise amplification of photoelectronic signals. In this device, the junctions where amplification takes place are separated by heterojunctions, which act as traps for one species of charge carriers. We demonstrate by a calculation that such a structure will have a substantially improved signal/noise ratio.     

Low-noise amplifiers-then and now

The evolution in the performance of low-noise amplifiers (LNAs) has been dynamic over the past years. From the early LNAs that were complex, large, and heavy, to the present day InP high electron-mobility transistors that have virtually transformed the industry by their performance and extension into frequency bands that were not even considered in the past. This paper summarizes the transformation that has occurred in the LNA field, viewing where they were in the past, and where they are now