光纤陀螺调制器的残余强度调制影响与消除

光纤陀螺(IFOG)用相位调制器的残余强度调制(RIM)直接影响标度因子稳定性.对Y波导调制器残余强度调制特性进行了实验测试,根据测试结果给出了残余强度调制特性的近似公式.对开环光纤陀螺,在调制器存在内静电压时,残余强度调制对标度因子稳定性影响的大小与调制器两分支残余强度调制系数的差和内静电压成正比;对数字闭环方式,残余强度调制不仅直接影响标度因子稳定性,也影响由2π复位环路确定的调制信号最高电压而间接影响标度因子稳定性,影响的大小与调制器两分支残余强度调制系数的差成正比,但与电光系数成反比.提出的三时隙解调方法不仅能消除残余强度调制的直接影响,也能消除通过2π复位环路的间接影响.     

微纳米PIN电光调制器的优化

在微纳米PIN电光调制器的基础上,分析了载流子浓度对其调制特性的影响。根据注入调制区载流子平均浓度随时间变化关系,采用在驱动信号中加入正反向预加重电压的调制电压方式,不仅可以提高注入载流子浓度,而且可以缩短反向抽取载流子所用的时间,从而有效提高电光调制器的调制速度;详细分析了PIN电光调制器结构中内脊高度H、外脊高度h,波导脊宽W以及重掺杂区到波导的距离Ws等参数对其调制特性的影响;最终根据数据的分析,给出了优化后的参数,制作了电光调制器并进行了测试,测试结果验证了文中数据分析的正确性。     

载频解调式脉冲调制器的研制

介绍了一种新型载频解调式栅极脉冲调制器.调制器由2只脉冲变压器、载频调制控制电路、解调与脉冲输出电路组成.调制器采用了内载频脉冲驱动模式,利用了MOSFET的极分布电容对信号的延时作用,通过二极管解调还原调制管触发脉冲,最终输出正负电压的调制脉冲.载频信号频率大于200 kHz,隔离变压器具有尺寸小,绕组匝数少的特点.采用这种模式的调制器,输出脉冲宽度宽、前后沿小、工作比高.详细介绍了基于载频解调式脉冲调制器的应用实例,并对其性能参数进行了测试.     

辐射正弦调制器设计

本文以用于红外探测器的基本特性探测率D参数测试的辐射正弦调制器的设计式作推导,给出五个正弦调制器设计数据表。一、物理概念红外探测器D参数测试系统均设选频放大器,选频放大器要求系统中的黑体辐射应经正弦调制,以让探测器的光电转换信号获得最大通过,这样的测量才精确。常用的圆光阑调制器不能满足辐射正弦调制的要求,因该调制器为非正弦调制器,其调制特性无法改变。文献在对圆光阑调制器的非正弦调制特性作分析时,作者均提到“理想的”正弦调     

基于电压补偿的弹光调制器稳定性控制方法研究

弹光调制器是由各向同性的弹光晶体和压电晶体组成的热机电耦合器件,其谐振频率随温度变化存在严重漂移,导致弹光调制器工作不稳定。为了实现弹光调制干涉信号的相位延迟量沿正弦规律变化,有必要对影响弹光调制干涉仪的稳定因素进行分析与控制。针对此问题,在建立弹光调制器振动模型和频率温漂模型的基础上,提出了基于数字锁相技术的驱动电压自调节方法。在该方法中,根据弹光调制干涉信号的四倍频与二倍频的比值,基于FPGA调节DDS输出方波信号的占空比以稳定弹光调制干涉信号的相位延迟量。实验结果表明,驱动电压自调节时的相位延迟量变化幅度为0.6%,电压一定时相位延迟量幅度下降了15.6%,证明该方法有效的稳定了相位延迟量,从而提高了弹光调制器的稳定性和调制效率。     

应用于TCXO的低功耗Sigma-Delta调制器的设计

采用CSMC 0.35μm混合工艺设计了一个用于温度补偿晶体振荡器(TCXO)的二阶低功耗Sigma-Delta调制器.为减小低频温度信号带宽内的1/ f噪声及失调对调制器精度的影响,采用斩波技术把1/ f噪声及失调调制到有用信号带宽之外.结合Cadence Spectre及Matlab仿真结果显示,该调制器在温度信号带宽范围内的信噪声比为93.6dB,精度达到15.26位.在3V电源电压下静态功耗小于80μW,满足了该TCXO系统对调制器的低功耗及14位精度的要求.     

一种宽脉冲高重频浮动板调制器的设计

浮动板调制器具有输出波形好、功率小、电压较低、波形变化灵活等特点,在中小功率控制极微波管中被广泛应用。介绍了一种采用功率MOSFET串联组成调制开关的应用于行波管发射机的40kHz/2kV固态浮动板调制器的设计,对调制器的电路拓扑进行了简要的概述,对调制器的关键器件即MOSFET开关管的选择、宽脉冲传输、开关管的驱动电路、调制器的保护电路及散热/绝缘设计等进行了较为详细的介绍。还就调制器抗打火设计进行了分析。最后给出了调制器的测试波形。     

相位型光寻址空间光调制器稳定性分析

基于光寻址空间光调制器的等效电路仿真及稳定性测试实验,对纯相位型光寻址空间光调制器的稳定性进行分析和优化。结果表明,光阀液晶层的电压脉冲波形会引起光寻址空间光调制器对读出光的相位调制波动,而驱动电压频率与写入光强度同时影响相位调制波动幅度及相位调制量。由实验测量得到的光寻址空间光调制器的相位改变量曲线可知:当驱动电压周期比响应时间小95%时,最大相位改变量对应的相位波动率减小为0.35%,但此时相位调制能力仅为0.8λ;通过优化光寻址空间光调制器驱动条件参数,可获得1λ的相位调制能力,同时最大相位改变量对应的相位波动率为1%。     

Y波导调制器残余强度调制的测量

为了便于分析Y波导调制器残余强度调制的产生机理,提出一种Y波导调制器残余强度调制的测试方法.系统采用Spartan-6系列的FPGA作为主控芯片,控制模数转换芯片ADS5560对经光电转换后的调制光信号进行采集,将采集到的数据打包后通过UART通信模式发送至PC机,获取Y波导调制器残余强度调制大小及波形信息.根据残余强度调制大小和波形信息分析模场改变引起的线性和杂散光与输出光的干涉两种机理产生的残余强度调制所占比例.测试结果表明,系统稳定性良好,对于Y波导调制器的开发有重要意义.     

高低频正弦调制器

红外探测器基本参数D~*标准化测量,测试系统中的黑体辐射应采用正弦调制器调制。正弦调制器可把辐射调制成真正的频率单一的正弦波,使其在系统中的传输不受电路频宽的影响,信号传输效率最高。这样测得的D~*参数才真实可靠。本文从调制器结构分析入手,引入传动比概念,照顾正弦光阑与调制盘的相配特性和电机的额定转速,设计为热释电探测器D~*测试所用的低频正弦调制器和PbS探测器时间常数测量所用的高频正弦调制器。给出了高低频正弦调制器的设计数据和结构图,以及PbS时间常数的测试结果。     

Large-signal theory of the effect of dispersive propagation on theintensity modulation response of semiconductor lasers

We have derived an exact large-signal theory of propagation in a dispersive fiber of an optical wave with sinusoidal amplitude and frequency modulation. This has been applied to the study of large-signal direct-modulation of semiconductor lasers. It is shown that the large-signal response can significantly deviate from the predictions of the small-signal theory. In particular, the improvement in modulation response caused by frequency-to-intensity modulation conversion in propagation that occurs with small-signal modulation is no longer achieved with large-signal modulation, which could affect systems such as dispersion supported transmission. Experimental results confirm our theory     

Lyapunov-based control for three-phase PWM AC/DC voltage-sourceconverters

The three-phase pulsewidth modulation (PWM) AC/DC voltage-source converter with the control laws proposed so far is not only unstable against large-signal disturbances, but also has the problem that its stability depends on the circuit parameters such as the DC-output capacitance. This paper describes a new control law based on Lyapunov's stability theory. It is shown that the converter can be stabilized globally for handling large-signal disturbances. The resulting closed-loop system not only guarantees a sufficient stability region (independent of the circuit parameters) in the state space, but also exhibits good transient response both in the rectifying and regenerating modes. Also, a new simulation technique is introduced which increases the speed of the simulation process considerably. Computer simulations are presented to confirm the effectiveness of the proposed control strategy and the validity of the simulation technique. Experimental results are also presented to verify the theoretical and simulation studies     

A transfer matrix method based large-signal dynamic model formultielectrode DFB lasers

A large-signal dynamic model capable of modeling the transient behavior of the output power and wavelength of multielectrode DFB lasers is described here. The key feature of the model is the use of a modified form of the transfer matrix method resulting in a time-dependent implementation of this technique. Other features are the inclusion of longitudinal spatial hole burning and nonlinear gain in the model. The versatility of the model is demonstrated in an analysis of the response of a two-electrode DFB laser under large-signal direct current modulation which illustrates the important role played by longitudinal spatial hole burning. The limited use of wavelength tunability in controlling chirp is also demonstrated. However, a scheme to improve the damping mechanism through nonuniform excitation called backbiasing is proposed. Finally, wavelength switching is demonstrated using the model     

Analysis of an experimental technique for determining Van der Polparameters of a transistor oscillator

The Van der Pol (VDP) model of a transistor oscillator describes the behaviour of the oscillator with three parameters. When operating in steady state, only two parameters can be determined by spectrum analysis, these being the oscillation frequency and amplitude of oscillation. In this paper, a technique for measuring the other VDP parameter is examined. In this approach, a periodically modulated voltage is added to the bias of the oscillator to perturb the operational state. A theoretical derivation shows that the power spectrum of the perturbed oscillator contains additional information for determination of the other VDP parameter. A simple analytical perturbation formula predicts the oscillator's response to the ramped bias. Our experimental results agree with the analytical perturbation solution and therefore, this allows one to read off the other VDP parameter from the experimental data. The VDP model allows one to predict the behaviour of coupled transistor oscillators more accurately and simply than does the traditional large-signal model of the transistor. This VDP model will simplify oscillator array design since the number of parameters needed to describe each oscillator is reduced from that which would be required using a large-signal circuit model     

Modeling and Performance Analysis of the DC/DC Series–Parallel Resonant Converter Operating With Discrete Self-Sustained Phase-Shift Modulation Technique

A dynamic study of the dc/dc series–parallel resonant converter operating with a discrete self-sustained phase-shift modulation technique is presented. The study includes the synthesis of a suitable averaged large-signal dynamic model and the design of a nonlinear feedback controller based in the input–output linearization approach. The proposed controller and modulation type provide some outstanding features: zero-voltage switching operation for the whole load range, narrowed frequency variation range, fast transient response, and robustness in relation to external parameter variations. Experimental and simulation results are reported to validate the theoretical predictions and confirm the superior performance of the nonlinear controller when it is compared with a conventional linear controller.      

High-speed modulation of semiconductor lasers

An overview is given of the direct modulation performance of high-speed semiconductor lasers, The high-speed response characteristics are described using a cascaded two-port model of the laser. This model separates the electrical parasitics from the intrinsic laser and enables these subsections to be considered separately. The presentation concentrates on the small-signal intensity modulation and frequency modulation responses, and the large-signal switching transients and chirping. Device-dependent limitations on high-speed performance are explored and circuit modeling techniques are briefly reviewed.     

Chirp reduction using push-pull modulation of three-contact lasers

Low-chirp modulation of three-contact distributed-feedback (DFB) lasers is experimentally demonstrated, using a push-pull modulation scheme. When the laser was modulated with a 2.0-Gb/s pseudorandom bit sequence, the -20-dB linewidth was measured to be 0.055 nm after deconvolving the measurement equipment's response. The results are simulated using a large-signal time-domain model that illustrates the mechanisms responsible for the low chirp. The grating structure is shown to have a significant effect on the performance of the device under push-pull modulation     

High-speed modulation of semiconductor lasers

An overview is given of the direct modulation performance of high-speed semiconductor lasers. The high-speed response characteristics are described using a cascaded two-port model of the laser. This model separates the electrical parasitics from the intrinsic laser and enables these subsections to be considered separately. The presentation concentrates on the small-signal intensity modulation and frequency modulation responses, and the large-signal switching transients and chirping. Device-dependent limitations on high-speed performance are explored and circuit modeling techniques are briefly reviewed.     

Nonlinearity and cross modulation in field-effect transistors

It is shown that present large-signal models are inadequate for cross modulation in field-effect transistors, but the cross-modulation performance can be accurately predicted from a power-series approximation to the measured l.f. transfer characteristic of the device. The cross modulation for typical field- effect transistors is essentially independent of frequency up to about 100 MHz. A large-signal h.f. model of the field-effect transistor is proposed for the prediction of cross modulation and related phenomena at very high frequencies. Computer predictions of cross modulation based on this model agree well with experimental measurements.     

Effect of junction temperature on the large-signal properties of a 94 GHz silicon based double-drift region impact avalanche transit time device

The authors have developed a large-signal simulation technique extending an in-house small-signal simulation code for analyzing a 94 GHz double-drift region impact avalanche transit time device based on silicon with a non-sinusoidal voltage excitation and studied the effect of junction temperature between 300 and 550 K on the large-signal characteristics of the device for both continuous wave(CW) and pulsed modes of operation.Results show that the large-signal RF power output of the device in both CW and pulsed modes increases with the increase of voltage modulation factor up to 60%,but decreases sharply with further increase of voltage modulation factor for a particular junction temperature;while the same parameter increases with the increase of junction temperature for a particular voltage modulation factor.Heat sinks made of copper and type-IIA diamond are designed to carry out the steady-state and transient thermal analysis of the device operating in CW and pulsed modes respectively. Authors have adopted Olson’s method to carry out the transient analysis of the device,which clearly establishes the superiority of type-IIA diamond over copper as the heat sink material of the device from the standpoint of the undesirable effect of frequency chirping due to thermal transients in the pulsed mode.