高饱和电流光电探测器在低噪声系数和高增益RoF光链路中的应用

研究了光载无线通信(RoF)链路中掺Er3+光纤放大器(EDFA)对链路噪声系数(NF)和增益的影响,同时采用自制的具有高响应度、高饱和功率特性单载子传输光电探测器(UTC-PD)作为链路光电转换器件,在不以NF为代价的同时使得链路增益性能获得大幅提升。实验表明,对于由LD、马赫-曾德调制器(MZM)、EDFA、光滤波器(OBPF)和UTC-PD组成的RoF光链路,在LD输出功率为17dBm、UTC-PD的输出平均光电流为60mA时得到最低链路NF为30.3dB,相比不含EDFA的基本链路在LD输出光功率同为17dBm时的NF略小0.4dB;同时链路增益高达15.5dB,相比基本链路大幅提升了41.3dB。     

掺铒光纤放大器增益和噪声研究

文章首先介绍了掺铒光纤放大器(EDFA)的结构和工作原理,然后运用能级理论和激光原理,深入全面地分析了影响EDFA增益和噪声的主要因素,得出了EDFA增益和噪声与泵浦功率、泵浦方式、输入信号光功率和掺铒光纤长度等关系的一些重要结论,并且通过实验进一步验证了这些结论;提出了提高EDFA增益,减小噪声系数的方法;最后根据文中得出的结论,设计了一种高增益低噪声的C波段EDFA光路,该光路已经应用于工程实践中.     

Evaluation method of device noise figure and gain through noise measurements

A new method of evaluating the noise figure and available gain of a linear two-port device only from noise measurements is proposed. In this method, there is no need for tuning at the output port of a device under test (DUT) by the use of an excess noise injection through a circulator to the device output port. Hence it gives a much simplified procedure and an improvement of accuracy.     

Optimal noise figure of microwave GaAs MESFET's

The optimal value of the minimum noise figure Foof GaAs MESFET's is expressed in terms of either representative equivalent circuit elements or geometrical and material parameters in simple analytical forms. These expressions are derived on a semiempirical basis. The predicted values of Fofor sample GaAs MESFET's using these expressions are in good agreement with the measured values at microwave frequencies. The expressions are then applied to show design optimization for low-noise devices. This exercise indicates that shortening the gate length and minimizing the parasitic gate and source resistances are essential to lower Fo. Moreover, a simple shortening of the gate length may not bring an improved Founless the unit gate width is accordingly narrowed. The maximum value of the unit gate width is defined as the width above which the gate metallization resistance becomes greater than the source series resistance. Short-gate GaAs MESFET's with optimized designs promise a superior noise performance at microwave frequencies throughKband. The predicted values of Foat 20 GHz, for example, for a half-micrometer gate device and a quarter-micrometer gate device are 3 and 2 dB, respectively. These devices could be fabricated with the current technology.     

Experimental gain and noise figure performance of distributed MESFET amplifiers

The noise figure and gain characteristics of lossless and lossy MESFET distributed amplifiers have been theoretically investigated by various workers. In the letter, in order to support previously reported theoretical results, the experimentally measured noise figure and power gain performance of two-stage and five-stage hybrid microwave distributed amplifiers employing MESFETs are presented. The measured results are compared to theoretically obtained values and found to be in reasonable agreement over most of the band.     

Sub-mA single ended CMOS low noise amplifier with 2.41 dB noise figure

This paper presents a single ended low noise amplifier (LNA) using 0.18 μm CMOS process packed and tested on a printed circuit board. The LNA is powered at 1.0 V supply and drains 0.95 mA only. The LNA provides a forward gain of 11.91 dB with a noise figure of only 2.41 dB operating in the 0.9 GHz band. The measured value of IIP3 is 0.7 dBm and of P1dB is −12 dBm. Zhang Liang is currently with Cyrips, Singapore. Ram Singh Rana was born in Delhi (India). Having primary education in Bijepur, Dwarahat(India), he received the B.Tech. (hons.) degree in Computer Engineering from G.B. Pant University, Pantnagar, India in 1988 and the Ph.D degree from the Indian Institute of Techonology (IIT), Delhi, India in 1996. He worked for his Ph.D in the Centre for Applied Research in Electronics, IIT Delhi in close interaction with the Semiconductor Complex Limited, Mohali, India. He was with ESPL, Mohali(India) in 1988 for a very short period and then served IIT Delhi as Senior Research Associate (88-90) and Senior Scientific Officer (90-95) where his main contributions were on CMOS analog IC design in subthreshold operation. He was a Lecturer in the Kumaon Engg. College, Dwarahat (India) before serving the IIT Roorkee (Formerly Univ. of Roorkee) in 1998 as assistant Professor. In 1999, he was a Manager (Engineering), Semiconductor Product Sector of the Motorola, Noida, India. Since joining the Institute of Microelectronics, Singapore in 2000, he worked mostly on RFICs, Fractional-N PLLs, ADCs. During 2001-2004, he worked there as IC Design Research and Training Program Manager. Currently, he is serving the institute as Senior Research Engineer in CMOS IC design (below 1V) for biomedical and bio-sensors. His current interests include design and consultancy for CMOS ICs/systems for the biomedical and high speed communication applications. Dr. Rana received Young Teacher Career Award from the All India Council for Technical Education in 1997. He was an Adjunct Asstt. Professor with the National University of Singapore (NUS), Singapore in 2004. He is sole inventor of two US granted patents and has filed several other patents. He has authored/co-authored about 40 publications. He has been reviewer for several IEEE journals and conference papers. Dr Rana is a senior member of IEEE and a member of Graduate Program in BioEngineering, NUS Singapore. He has chaired /co-chaired sessions in many international conferences. Zhang Liang was born in China in June 1978. He received the Bachelor degree and the Master degree in Electrical Engineering from the Xi’an JiaoTong University, Xi’an, China, in 2000 and 2003 respectively. Since 2003, he has been a postgraduate student in the Electrical and Computer Engineering department, National University of Singapore(NUS), Singapore and has successfully completed M.Engg degree program of the NUS. He is currently working on RFICs as a design engineer in Cyrips, Singapore. His design and research interests include integrated circuit design for communications. He has authored/co-authored several publications of international standard. Hari K Garg obtained his BTech degree in EE from IITDelhi in 1981. Subsequently, he obtained his MEng & PhD degrees from Concordia University in 1983 & 1985, and MBA from Syracuse University in 1985. He was a faculty member at Syracuse University from 1985 till 1995. He has been with the National University of Singapore since 1995 till present with the exception of 1998-1999 when he was with Philips. Hari’s research interests are in the area of digital signal/image processing, wireless communications, coding theory and digital watermarking. He has published extensively on these and related topics. He is also founder of several companies in the space of mobile telephony. In his spare time, Hari enjoys singing and a good game of Squash.     

Expression for the optimum noise figure of microwave MESFETs

An analytical expression for the optimum noise figure, F₀, of GaAs microwave MESFETs has been calculated. The generator impedance needed for an optimum noise figure is also derived. Predictions based on this theory compare well with reported measurements. Finally, with the aid of computer graphics, the results are displayed in a universal nomograph which can be used to determine F₀.     

Direct parameter-extraction method for MOSFET noise model from microwave noise figure measurement

A new method for the determination of the four noise parameters of the metal oxide semiconductor field effect transistors (MOSFETs) based on the noise figure measurement system without microwave tuner is presented. The noise parameters are determined based on a set of analytical expressions of noise parameters by fitting the measured noise figure of the active device. These expressions are derived from an accurate small signal and noise equivalent circuit model, which takes into account the substrate parasitics, pad capacitances, and series inductances. On-wafer experimental verification is presented and a comparison with tuner based method is given. Good agreement is obtained between simulated and measured results for 0.5 × 5 × 16 μm, 0.35 × 5 × 16 μm and 0.18 × 5 × 16 μm (gate length × number of gate fingers × unit gate width) MOSFETs.     

Signal-induced noise in fiber-optic links using directly modulatedFabry-Perot and distributed-feedback laser diodes

A quantitative comparison has been made, both theoretically and experimentally, of signal-induced noise in high-frequency, single-mode fiber-optic links using directly modulated multimode (Fabry-Perot) and single-frequency (distributed-feedback, DFB) lasers. It is shown that the common procedure of evaluating the signal-to-noise (S/N) performance in a typical fiber-optic link by treating the various sources of noise as additive quantities that are independent of the modulation signal is inadequate. This is due to the presence of signal-induced noise, which concentrates at low frequencies, so that a casual observation might lead to the erroneous conclusion that it is of no relevance to high-frequency transmission systems. It is shown that, for Fabry-Perot lasers, signal-induced noise arising from translation of low-frequency noise to high frequencies causes significant degradation in S/N performance in transmission of 6-GHz signals over only 1 km of single-mode fiber. With DFB lasers, signal-induced noise due to interferometric phase arrow intensity conversion is present, but does not become significant even for transmission at 10 GHz up to 20 km     

Interferometric noise reduction in fiber-optic links bysuperposition of high frequency modulation

The reduction of interferometric noise by superposition of high frequency modulation is analyzed. It is shown that the nature of this reduction is due to a redistribution of noise energy from baseband to higher frequencies where it can be discarded by low-pass filtering. Detailed analysis revealed the dependence of the noise reduction factor on the product f_0τ, and the modulation index of the high frequency superimposed modulation. The proper choice of parameters can lead to complete elimination of the converted phase noise from the system     

Fast state-space decimator with very low round-off noise

A method for the efficient realization of high-order Infinite Impulse Response (IIR) output-decimating State-Space Digital Filters (SSDF) is presented. By applying the state decimation and block processing to the nth-order narrow-band SSDFs, computational efficiency as well as low round-off noise levels are achieved. Further, the favorable behavior of certain SSDF forms with respect to the overflow limit cycles is retained. Such Fast State-Space IIR Decimators (FSSD) are simple to design, have multiplication rates comparable to Finite Impulse Response (FIR) decimators, have a highly parallel processing algorithm, and are very easy to implement on programmable signal processors. In the digital filter applications which do not require the linear-phase response, the FSSD may be considered as an alternative to a single-stage FIR decimator for moderate decimation factors.     

A technique for improving gain and noise figure of common-gate wideband LNAs

This paper presents a novel compensation design for regulators, i.e., modified NMCF (nested Miller compensation with feedforward Gm stage), resulting in a linear LDO (low dropout) regulator whose performance is independent of the off-chip capacitor and its ESR (equivalent series resistor). The proposed compensation method ensures the stability of the feedback loop and the sufficient phase margin of the LDO regulator. Besides, the transient response become faster. The analysis of the stability is derived to solidify the proposed design. The proposed design is implemented using TSMC 0.35 μm 2P4M CMOS process. The results verify the performance and the stability on silicon. The power supply rejection ratio is 25 dB @ [200 Hz, 3 MHz], [50 Ω, 500 Ω] provided that the input voltage varies from 4 to 5 V.     

Optimum source admittance for minimum noise figure of microwave transistors

Noise measurements of microwave transistors have shown that the optimum source admittance with respect to the minimum noise figure approaches the conjugate complex value of the transistor input admittance with increasing frequency. This fact is explained using the noise equivalent circuit of a microwave transistor.     

Quantum limited noise figure operation of high gain erbium dopedfiber amplifiers

Performance improvements obtained by using an isolator as an amplified-spontaneous-emission-suppressing component within erbium-doped fibers are evaluated. Simultaneous high-gain and near-quantum-limited noise figures can be obtained by such a scheme. The noise figure improves for input signal powers below -5 dBm, and an improvement of 2.0 dB with a simultaneous gain increase of 4.1 dB is measured relative to a gain-optimized fiber. The optimum isolator location is evaluated for different pump and signal wavelengths in both an Al/Er-doped and a Ge/Er-doped fiber, for pump and signal power variations and different pump configurations. In all cases the optimum isolator position lies within 10-37% of the total fiber length for small signal operation     

Measuring gain and noise figure of erbium-doped fiber amplifiers using a broad-band source and a transmission filter

We report a unique low-cost technique for measuring gain and noise figure (NF) in erbium-doped fiber amplifiers using a broad-band amplified spontaneous emission source and a transmission filter, by extracting the slope and intercept of output power spectral density versus input power spectral density at filter edges. The required filter depth is 30 dB. Discrepancies of /spl les/0.3 dB are found between gain or NF obtained from this technique and those measured using conventional spectral-interpolation technique employing multiple lasers at 100-GHz spacing across the C-band.     

Damage effects on low noise amplifiers with microwave pulses

The damage effect experiment is carried out to the low noise amplifiers (LNAs) based on Bipolar Junction Transistor (BJT) and Pseudomorphic High Electronic Mobility Transistor (PHEMT) by microwave pulse injection experiment platform. The essence of the LNA damage with microwave pulses is the damage to the core semiconductor device. The influence rule upon the damage power of the LNA by different microwave pulse widths and pulse numbers is obtained. The injection, reflection and output waveforms are measured by high frequency oscilloscope and the typical damage waveforms of the LNA are analyzed. Inspection is made on the damaged semiconductor device by a scanning electron microscope (SEM) and the microscopic damage images of the semiconductor devices with different pulse widths and pulse numbers are analyzed in comparison.     

微波光链路和光电探测器残余相位噪声的测量

提出了一种测量长光纤微波光链路以及链路中某一器件残余相位噪声的方法。与以前传统的残余相位噪声测量方法相比,新提出的基于互相关的双音法抑制了不相关噪声源引入的噪声,而保留了待测器件的噪声。通过这种方法,测量了外调制长光纤微波光链路的残余相位噪声,一个6 km微波光纤链路的残余相位噪声在1 kHz频偏处被测得为-130 dBc/Hz,在10 kHz频偏处被测得为-140 dBc/Hz,相较于光纤长度为1 m的短微波光链路,残余相位噪声恶化了接近10 dB。另外,为了找出光电探测器的残余相位噪声与其非线性引起的射频功率压缩度之间的关系,还用这种方法测量了工作在不同条件下的光电探测器的残余相位噪声,实验结果表明:光电探测器的非线性会恶化它的残余相位噪声。     

Improvement of gain and noise figure in double-pass L-band EDFA by incorporating a fiber Bragg grating

An obvious improvement on both the gain and noise figure (NF) is demonstrated in the new double-pass L-band erbium-doped fiber amplifier (EDFA) with incorporating a fiber Bragg grating (FBG). Compared with the conventional L-band EDFAs, the gain is improved by about 6 dB in the new configuration for a 1580-nm signal with an input power of -30 dBm at 60 mW of 980-nm pump power. It is important that the NF is greatly reduced in the new configuration, as the FBG greatly compresses the backward amplified spontaneous emission. For the economical utility of pump power and erbium-doped fiber length, such a configuration may be a very competitive candidate in the practical applications of L-band EDFAs.     

A new CMOS wideband low noise amplifier with gain control

In this paper, a new CMOS wideband low noise amplifier (LNA) is proposed that is operated within a range of 470 MHz-3 GHz with current reuse, mirror bias and a source inductive degeneration technique. A two-stage topology is adopted to implement the LNA based on the TSMC 0.18-μm RF CMOS process. Traditional wideband LNAs suffer from a fundamental trade-off in noise figure (NF), gain and source impedance matching. Therefore, we propose a new LNA which obtains good NF and gain flatness performance by integrating two kinds of wideband matching techniques and a two-stage topology. The new LNA can also achieve a tunable gain at different power consumption conditions. The measurement results at the maximum power consumption mode show that the gain is between 11.3 and 13.6 dB, the NF is less than 2.5 dB, and the third-order intercept point (IIP3) is about −3.5 dBm. The LNA consumes maximum power at about 27 mW with a 1.8 V power supply. The core area is 0.55×0.95 mm².