一种新型的光谱自动测试系统

在研究了传统的光源和光探测器光谱特性测试技术的基础上,采用热释电探测器、单色仪及自动扫描器、锁相放大器和虚拟仪器技术同期怀 新型的光谱自动测试系统。该系统拓宽了光谱测试范围,提高了自动化程度和适用性。集成的ＬａｂＶＩＥＷ平台使系统具有很强的数据采集和处理功能,并使用户具有进一步优化系统的广阔空间。     

Controlled amplifier modelocked Er/sup 3+/ fibre ring laser

An erbium-doped fibre ring has been actively modelocked with an InGaAsP semiconductor amplifier employed as a modulator. Pulses having durations <4ps and peak powers of approximately 2 W around 1536 nm have been generated at a repetition frequency of 612 MHz by this new technique of controlled-amplifier modelocking (CAM).<>     

Demonstration of ultrafast all-optical wavelength conversion utilizing birefringence in semiconductor optical amplifiers

High-extinction-ratio wavelength conversion has been demonstrated in a semiconductor optical amplifier using a mixture of cross-gain and cross-phase modulation in a polarization rotation technique. 40-ps-wide pulses at 1311 nm have been generated using 47-ps, 5.7-mW peak-power input pulses at 1300 nm. Excellent agreement with experiment has been obtained using a computer model.     

ANALYSIS OF INTERNALLY GENERATED NOISE OF BIOELECTRIC AMPLIFIERS

This papenr deals with internally generated noise of bioelectric amplifiers that are usually used for processing of bioelectric events.The main purpose of this paper is to present a procedure for analysis of the effects of internal noise generated by the active circuits and to evaluate the output noise of the author‘s new designed bioelectric amplifier that caused by internal effects to the amplifier circuit itself in order to compare it with the noise generated by conventional amplifiers.The obtained analysis results of internally generated noise showed that the total output noise of bioelectric active circuits does not increase when some of their resitors have a larger value.This behavior is caused by the different transfer functions for the signal and the respective noise sources associated with these resistors.Moreover,the new designed bioelectric amplifier haws an output noise less than that for conventional amplifiers.The obtained analysis results were also experimentally verified and the final conclusions were drawn.     

Elimination of signal distortion and crosstalk from carrier densitychanges in the shared semiconductor amplifier of multifrequency signalsources

The signals from multifrequency sources that utilize a shared semiconductor optical amplifier often exhibit distortion and crosstalk due to carrier density changes in the shared amplifier. We propose a technique that eliminates the signal distortion and crosstalk by keeping the carrier density in the shared amplifier constant via feedforward of the electrical drive signals. We demonstrate the technique using a waveguide grating router multifrequency laser     

A genetic algorithm based method for source identification andfar-field radiated emissions prediction from near-field measurements forPCB characterization

A new method for predicting the far-field radiated emissions and for finding the radiation sources of a device from near-field measurements is presented. It is based on the substitution of the original device by an equivalent set of elemental dipoles, placed over the main radiating sources, which radiate the same near-field (and therefore, far-field). This equivalent set of elemental dipoles is generated using a genetic algorithm. From the position and type of the equivalent elemental dipoles, the position of the actual radiating sources is determined. Since the field produced by an elemental dipole is known, the far-field radiation of the actual radiating source can be calculated. The new method has been tested using synthetic data and real measurements from the radiation generated by a modem PCB demonstrating its viability and usefulness     

VHF频段宽带大功率LDMOS功放电路的设计与实现

介绍了一种VHF频段宽带大功率LDMOS功放的设计方法,使用ADS仿真软件对其大信号模型的阻抗参数进行了提取,通过宽带巴伦匹配技术实现了匹配电路的设计。利用谐波平衡法对功放电路的增益和效率指标进行仿真,并与实物测试数据对比,验证了设计方法的可行性。该功放电路在VHF频段100%相对带宽内,实现输出功率大于1000 W,效率高于70%,带内波动优于1 dB的指标。文中为VHF频段宽带大功率LDMOS功放电路的设计提供了一种可行的设计方法,可应用于同类型功放电路的设计中,具有广阔的工程应用前景。     

A novel wide-band noise-parameter measurement method and its cryogenic application

The concept of using a long mismatched transmission line to measure noise parameters has been known for some time. However, it has been limited to narrow-bandwidth applications, and a wide-band extension has never been reported. In order to measure the cryogenic noise parameters of a wide-band low-noise amplifier (LNA), a wide-band frequency-variation method is proposed. In this method, the four noise parameters at each frequency are derived numerically from a set of matched and mismatched noise temperatures measured within a surrounding frequency-sampling window. By scanning this frequency-sampling window, noise parameters over a wide frequency range can be obtained. Since this approach can be easily incorporated into existing noise measurement systems, a tuner is not required, and the technique can be applied to a cryogenic amplifier. This paper details the theory, implementation, and verification of this new method. The measured noise parameters of a cryogenic wide-band LNA are presented.     

Six-Port Interferometric Technique for Accurate $W$ -Band Phase-Noise Measurements

An innovative six-port (SP) phase-noise measurement technique for millimeter-wave high-power sources is proposed in this paper. Simulation results using a 94-GHz rectangular waveguide SP circuit model validates the measurement principle for both millimeter-wave oscillators and amplifiers. Phase-noise measurement results of a 100-W extended interaction Klystron amplifier are presented and discussed. Compared to conventional methods, this new method allows accurate low-cost phase-noise measurements.     

Fully Integrated CMOS Power Amplifier With Efficiency Enhancement at Power Back-Off

This paper presents a new approach for power amplifier design using deep submicron CMOS technologies. A transformer based voltage combiner is proposed to combine power generated from several low-voltage CMOS amplifiers. Unlike other voltage combining transformers, the architecture presented in this paper provides greater flexibility to access and control the individual amplifiers in a voltage combined amplifier. In this work, this voltage combining transformer has been utilized to control output power and improve average efficiency at power back-off. This technique does not degrade instantaneous efficiency at peak power and maintains voltage gain with power back-off. A 1.2 V, 2.4 GHz fully integrated CMOS power amplifier prototype was implemented with thin-oxide transistors in a 0.13 mum RF-CMOS process to demonstrate the concept. Neither off-chip components nor bondwires are used for output matching. The power amplifier transmits 24 dBm power with 25% drain efficiency at 1 dB compression point. When driven into saturation, it transmits 27 dBm peak power with 32% drain efficiency. At power back-off, efficiency is greatly improved in the prototype which employs average efficiency enhancement circuitry.     

Offset compensating bit-line sensing scheme for high density DRAM's

This paper describes a new bit-line sensing scheme that minimizes the sensitivity degradation caused by the electrical imbalance in a sense amplifier composed of scaled-down transistors. The new sensing scheme incorporates an offset compensating technique in a direct bit-line sensing scheme using a current-mirror differential amplifier. The compensation is performed by means of a simple negative feedback method that accomplishes cancellation of the total electrical imbalance in the sense amplifier with a short presetting time. The features of the circuit have been examined using simple DRAM test chips fabricated with a 0.5 μm CMOS process. Experimental results indicate that the magnitude of the imbalance of the sense amplifier is reduced to one-sixth by introducing the offset compensating scheme as compared to the conventional sensing scheme     

Compact Tunable Narrowband Terahertz-Wave Source Based on Difference Frequency Generation Pumped by Dual Fiber Lasers in MgO:LiNbO<Subscript>3</Subscript>

We demonstrate a high-average-power, single longitudinal-mode, and tunable terahertz (THz)-wave source based on difference frequency generation (DFG) in a MgO:LiNbO₃ (MgO:LN) crystal. The waves for DFG are generated using a pair of Yb-doped pulsed fiber lasers with a master oscillator power fiber amplifier configuration. The average power of the THz-wave output reaches 450 μW at 1.07 THz (280 μm) at a linewidth of 7.2 GHz, and the tunability ranges from 0.35 to 1.07 THz under the pulse repetition frequency of 500 kHz. A short burn-in test of the THz wave is also carried out, and the output power stability is within ± 5% of the averaged power without any active stabilizing technique. The combination of MgO:LN-DFG and stable and robust fiber laser sources is highly promising for the development of high-average-power THz-wave sources, particularly in the high transmission sub-THz region. This approach may enable new applications of THz-wave spectroscopy in imaging and remote sensing.     

Envelope-domain time series (ET) behavioral model of a Doherty RF power amplifier for system design

In this paper, we present an envelope-domain behavioral model of a high-power RF amplifier. In this modeling approach, we use the signal envelope information, and the behavioral model is generated using an established nonlinear time-series approach to create a time-domain model that operates in the envelope or signal domain. We have generated a model of a 200-W Doherty amplifier from measured IQ data taken using a wideband code-division multiple-access excitation; the amplifier was driven from the linear regime into saturation. The time-series model was created using a time-delay embedding identified from auto-mutual information analysis, and an artificial neural network was used to fit the multivariate transfer function. The model has been validated using measured and simulated data, and it has been used in the development of a system-level design of a digital pre-distorter.     

一种数字预失真功放输出动态提升技术

数字预失真功放的输出动态提升技术在现代功率放大器设计和研究中已成为一个重要的课题。本文基于数字预失真功放自身特征以及自适应信号处理技术,提出了一种全新的输出动态提升技术。理论分析和试验结果表明：采用该新型技术的数字预失真功放不仅输出动态得到了大幅度提升,而且线性也有一定程度改善。     

Integrated CMOS amplifier for ENG signal recording

The development and in vivo test of a fully integrated differential CMOS amplifier, implemented with standard 0.7-microm CMOS technology (one poly, two metals, self aligned twin-well CMOS process) intended to record extracellular neural signals is described. In order to minimize the flicker noise generated by the CMOS circuitry, a chopper technique has been chosen. The fabricated amplifier has a gain of 74 dB, a bandwidth of 3 kHz, an input noise of 6.6 nV/(Hz)0.5, a power dissipation of 1.3 mW, and the active area is 2.7 mm2. An ac coupling has been used to adapt the electrode to the amplifier circuitry for the in vivo testing. Compound muscle action potentials, motor unit action potentials, and compound nerve action potentials have been recorded in acute experiments with rats, in order to validate the amplifier.     

Full-band staggered-gain Gunn-effect amplification in Ka band

The feasibility of full-band low-noise instantaneous amplification in Ka band has been demonstrated using a staggered-gain amplifier technique. A simplified analysis of the overall gain variations in this two-stage amplifier is used to calculate the minimum isolation levels needed to meet a maximum allowable ripple. Using this technique, 10 ± 2.2-dB gain has been obtained from 26.6-39.4 GHz.     

Analysis of gain and saturation characteristics of a semiconductorlaser optical amplifier using transfer matrices

The transfer matrix method (TMM) has been applied to analyze the gain and saturation characteristics of semiconductor laser optical amplifiers. This method approximates the amplifier cavity by dividing it into M discrete subsections, and TMM has been applied to analyze the stepwise longitudinal field distribution at each subsection along the amplifier cavity. By incorporating also the carrier rate equations into the analysis, it has been shown that the approximation can accurately describe the carrier density and longitudinal field distribution along the amplifier cavity if M is sufficiently large (i.e., the size of each subsection is about an order of magnitude of one wavelength of the input signal). By assuming that the amplifier is biased below oscillation threshold such that the contribution of spontaneous emissions to the gain characteristics can be neglected, we have shown that our proposed method yields a fast and efficient algorithm in analyzing the gain and saturation characteristics of laser amplifiers. We have compared the results produced by our method to those analyzed using the average photon density (AVPD) approximation technique, as well as to experimental results on a 1.5-μm buried heterostructure semiconductor laser amplifier     

Optimization of input impedance and mechanism of noise suppressionin a DC SQUID RF amplifier

The optimal input impedance and noise of a DC SQUID RF amplifier at frequencies of the order of 1 GHz with a resonant input matching circuit have been studied analytically, numerically, and experimentally. A model for noise temperature and power gain has been developed for the practical resonant input tank circuit. A new effect of the output noise increasing or decreasing with changing the sign of voltage-to-flux transfer coefficient has been observed experimentally and explained analytically. The different values of noise temperature for the opposite dV/dΦ values have been interpreted using a model with partially correlated current and voltage noise sources. The equivalent layout for optimal input matching of a SQUID amplifier comprising series and parallel resonant circuits has been presented. Using such a matching circuit and SIS junction as a signal source the SQUID amplifier noise temperature about 1 K has been measured at 1.1 GHz     

InGaP/GaAs HBT功率放大器的键合线匹配技术

射频集成电路的性能很大程度受到封装的影响,与集成电路设计和制造工艺相比,封装技术并没有受到相应的关注.用一种新的键合线匹配功率放大器(PAM)的方法,利用封装寄生参数进行电路匹配设计,消除了封装的负面影响,并进行了试制验证;电路芯片采用InGaWGaAs HBT工艺制作并使用了16引脚微小引线框架(MLP)封装.无需芯片外表面贴装电容和电感,实现了功率放大器的低损耗输出阻抗匹配,节省了宝贵的线路板空间.电路测试指标很好地达到了设计要求,证明了该技术的可行性,为高性能、低成本射频功率放大器的开发提供了新的思路.     

Inter modulation distortion analysis of cascaded MESFET amplifiers using Volterra series representation

The third-order intermodulation distortion generated in a two-stage cascaded amplifier is derived analytically by means of the Volterra series expansion, for non-linear systems with memory. A unilateral transistor model is used, which takes into account the three major non-linearities, the gate capacitance, the trans-conductance and the output conductance, in each stage of the amplifier. The Volterra transfer functions are determined for this transistor model and closed-form expressions for the intermodulation distortion ratio are given, where the terms with a contribution less than 1% have been neglected. The equations identify the principal sources of the distortion in the amplifier circuit and the influence of the transistor parameters and load impedance is investigated. The analysis of the two-stage cascaded amplifier gives a new insight into the intermodulation distortion behaviour and is discussed in detail at the end of the paper. The results obtained here are compared with those received for single-stage amplifiers.