剩余振幅调制对波长调制光谱信号线型的影响

在基于可调谐二极管激光吸收光谱技术的痕量气体检测中,波长直接调制时剩余振幅调制也会伴随发生,并对检测信号的线型和系统噪声产生严重影响。为了探讨剩余振幅调制对波长调制光谱二次谐波信号线型的影响,采用同时考虑振幅调制和波长调制两种影响因素的计算方法,理论分析出二次谐波信号的计算公式,与仅考虑波长调制的信号计算方式进行同条件线型计算比对,取得了二次谐波信号基线和正负峰值随剩余振幅调制的变化数据。结果表明,剩余振幅调制的大小对检测信号的线型和信号基线有直接影响,采用这种方法计算得出的二次谐波信号线型更贴近实际检测。     

温度和压强变化对二次谐波反演结果的影响

在气体质量流量测量系统中,波长调制光谱信号的谐波分量,特别是其二次谐波分量常被用作为检测对象,用于气体浓度、速度等信息的反演。基于波长调制原理,利用氧气(O2)分子在764.28nm附近的吸收谱线,分析了常见线型的半峰全宽,得出了不同温度、压强下洛伦兹线型的适用范围;研究了O2分子吸收谱线在不同温度、压强条件下的二次谐波峰值;对不同温度、压强下,采用二次谐波峰值反演气体浓度产生的误差进行了分析,并提出了误差修正方法;分析了实验过程中当最佳调制深度不能够随着温度、压强即时调整的情况下,最优调制系数在不同温度、压强变化下的适用范围,并给出了误差修正公式。     

用VHDL实现网格编码调制算法

网格编码调制（ＴｒｅｌｉｓＣｏｄｅｄＭｏｄｕｌａｔｉｏｎ，简称ＴＣＭ）是近几年发展起来的数字传输新技术。它利用集分割原理，将信号通过映射变成卷积码形式，使信号间具有最大的空间距离。与传统的ＰＳＫ、ＱＡＭ等数字调制方法相比，ＴＣＭ提高了传输率，降低了误码率。本文用ＶＨＤＬ语言对９６００ｂｐｓ和１４４００ｂｐｓＴＣＭ算法进行了电路描述，并利用Ｓｙｎｏｐｓｙｓ软件对电路进行了模拟和综合。     

用VHDL实现网络码调制算法

网格编码调制（Ｔｒｅｌｌｉｓ Ｃｏｄｅｄ Ｍｏｄｕｌａｔｉｏｎ，简称ＴＣＭ）是近几年发展起来的数字传输新技术。它利用集分割原理，将信号通过映射变成卷积码形式，使信号间具有最大的空间距离。与传统的ＰＳＫ、ＱＡＭ等数字调制方法相比，ＴＣＭ提高了传输率，降低了误码率。本文用ＶＨＤＬ语言对９６００ｂｐｓ和１４４０ｂｐｓＴＣＭ算法进行了电路描述，并利用Ｓｙｎｏｐｓｙｓ软件对电路进行了模拟和综合。     

调频SCA广播及一种新的接收电路

调频ＳＣＡ广播及一种新的接收电路电子工业部三所焦瑞萍，时申菊调频ＳＣＡ（ＳｕｂｓｉｄｉａｒｙＣｏｍｍｕｎｉｃａｔｉｏｎｓＡｕ－ｔｈｏｒｉｚａｔｉｏｎ）广播─—即辅助通信业务。无线电广播的调制方式有调幅和调频调相三种，调幅是用音频信号调制高频载波的振幅...     

调制域信号数字式差动放大电路研究

通过研究不满足Ｓｈａｎｏｎ采样定理的采样,发现当以低于Ｎｙｑｕｉｓｔ频率的采样频率对正弦周期信号采样时,能获得频率为该正弦周期信号频率与ｎ倍采样信号频率之差动放大。本文从频谱混叠的角度解释角调制信号差动放大的原理,给出了调制域中的差动公式和信号放大公式,并给出了适用于载波为方波的角调制信号的数字式差频放大电路的电路图,推导了该电路的误差和Ａｌｌａｎ方差公式,在文中给出了实验值。     

直接变频接收机性能分析

本文对直接变频接收机中正交矢量检测法进行了误差分析，讨论了由于接收机同相与正交两支路的增益差异、相位误差、本振泄漏及直流偏置导致其性能恶化的结果。为了实现ＧＭＳＫ信号解调，接收机中ＤＳＰ实现了调制信号的误差频谱估计、位同步恢复及译码。最后，用计算机模拟方法对该接收机性能进行了比较评价。     

自聚焦光纤列阵的动态测试原理及测试结果分析

本文采用调制传递函数来评价自聚焦透镜ＳｅｌｆｏｃＬｅｎｓＡｒｒａｙ（ＳＬＡ）像质，并在测试分析中得出一些有意义的结果。     

基于峰宽修正的玻璃药瓶内氧气残留浓度的检测研究

玻璃药瓶中的氧气残留对瓶中药品的无菌特性造成了严重的威胁。采用波长调制光谱（Wavelength Modulated Spectrum, WMS）技术解调得到的二次谐波信号峰高值作为氧浓度反演的基础。然而,在用二次谐波信号测量气体浓度时,由于调制深度的变化会导致二次谐波峰值的变化,这通常会给系统带来误差,进而降低浓度的反演精度。而调制深度受调制电流波动、温度和压强变化等因素的影响不能直接计算获得进而修正。针对这一问题,本文成功地将调制深度与二次谐波峰高的关系转换为二次谐波峰宽和峰高的关系。然后,利用峰宽校正后的谐波峰高对气体浓度进行反演。初步实验表明,利用峰宽校正后的谐波峰高对瓶内气体浓度进行预测的准确性提高了2.1%,且系统的整体鲁棒性也得以提升。本文提出的校正方法不需要系统参数信息与气体成分信息,可以直接从谐波信号本身出发对调制深度进行校正,十分适合于工业现场的在线氧气浓度预测。     

大信号设计GaAs MESFET功率合成

利用ＧａＡｓＭＥＳＦＥＴ功率特性的线性化模型，求出ＧａＡｓＭＥＳＦＥＴ近似最佳功率负载阻抗，为利用谐波平衡法计算提供初值。然后，使用自行研制的谐波平衡分析软件包，进行ＧａＡｓＭＥＳＦＥＴ大信号模型参数的提取和非线性电路模拟计算。将两只总栅宽为９．６ｍｍ的ＧａＡｓＭＥＳＦＥＴ管芯，利用内匹配功率合成技术，在Ｃ波段（５．５～５．８ＧＨＺ）制成１ｄＢ压缩功率大于８Ｗ，典型功率增益９ｄＢ的ＧａＡｓＭＥＳＦＥＴ内匹配功率管。     

Ti-LiNbO3 waveguide serrodyne modulator with ultrahighsideband suppression for fiber optic gyroscopes

The theoretical and experimental performance of guided-wave serrodyne phase modulators formed through indiffusion of Ti and LiNbO ₃ substrates is discussed. Basic serrodyne theory is reviewed and a modified model of the serrodyne modulator incorporating effects of polarization, light-source coherence, device response time, and device-related intensity modulation is developed. Sources of modulation errors and harmonic suppression limitations imposed by each are identified. Experimental results showing greater than 50-dB suppression to 200-kHz ramp frequency and correspondence to expected limitations are then presented. Good agreement between theory and experiment is found. The results indicate that very high suppression, greater than 60 dB, at frequencies to several hundred kilohertz are possible with Ti-LiNbO₃ waveguide devices     

退偏光纤陀螺刻度因数研究

首次在理论与实验两方面研究了闭环退偏干涉型光纤陀螺刻度因数的非线性误差,闭环锯齿波相位调制器对两个偏振光分量的不同调制深度是其非线性误差的原因之一。提出了降低闭环退偏干涉型光纤陀螺刻度因数非线性误差的方法。     

RF frequency shifting via optically switched dual-channel PZT fiber stretchers

We demonstrate a new technique for RF serrodyne frequency shifting with ultrahigh sideband suppression. This is accomplished using two parallel optically switched piezo fiber stretchers driven with two out-of-phase serrodyne modulations. We achieved sideband suppression of nearly 50 dB, an improvement of almost 30 dB compared to the standard fiber stretching approach. The frequency shifter is easily integrated into photonic and RF systems, is functional in certain broad-band applications, and allows for tunable translations.     

Resonator fiber optic gyro using digital serrodyne modulation

A resonator fiber optic gyro using digital serrodyne modulation for control the input lightwave frequency is proposed. In the system, phase modulators in an integrated waveguide circuit are used, instead of an acousto-optical modulator (AOM) frequency shifters with bulky shapes. With operating the signal digitally, it becomes easy to track the resonant frequency by the feedback with a higher accuracy. Errors due to nonideal digital serrodyne waveform are analyzed and are shown to be small enough. Performances of this system are experimentally demonstrated, under open-loop and closed-loop operation. The proposed scheme can implement the ways to reduce the noises without increasing the number of optical elements     

The DIGILATOR, a New Broadband Microwave Frequency Translator

Frequency translation of an RF wave can be accomplished by subjecting it to a constant rate of phase shift or by applying an ideal repetitive sawtooth phase function which snaps to zero at 360 degrees (serrodyne modulation). The DIGILATOR is a new type of frequeucy translator which employs a multibit latching ferrite phase shifter with a suitable digital switching driver to obtain a multiple-step approximation to the serrodyne phase function. This paper reviews the theory of an N-step DIGILATOR and describes the design of a 16-step, X-band device. Experiments showed that performance is independent of microwave frequency over the design frequency band of the phase shifter. The carrier and close-in sidebands were suppressed by 39 dB and predicted far-out sidebands were within 1 dB of theoretical amplitudes.     

Novel method for generating multiple wavelengths by pulsed serrodyne modulation

We propose a new scheme based on pulsed serrodyne modulation in an optical ring circuit designed to increase the number of wavelengths of optical pulses from a pulse-type multiwavelength light source. As the optical pulses circulate around the ring, the shift in the pulse wavelength increases as a result of the pulsed serrodyne modulation in the ring. By combining the shifted wavelengths of pulses with different round trips in the ring, we can produce a multiple wavelength output with a broad bandwidth. We calculated the spectral characteristics of the multiple wavelengths and confirmed the performance of the scheme experimentally.     

Serrodyne frequency translation of continuous optical signals using ultrawide-band electrical sawtooth waveforms

Serrodyne frequency translation of continuous optical signals by /spl plusmn/1.28 GHz is reported, significantly exceeding the highest previously published serrodyne shifts. To achieve these shifts, an ultrawide-band high-power electrical sawtooth created by spectral modulation of dispersed optical pulses was used. Its amplification involved a novel predistortion technique to compensate for the gain and phase ripple in the amplifier bandwidth.     

Serrodyne optical frequency translation using photonics-based waveforms

A new photonic method has been used to generate the sawtooth waveform in a serrodyne optical frequency translator. Experimental results demonstrate an overall sideband suppression of greater than 24.5 dB. The technique has wideband capability for realising higher optical frequency shifts and sideband suppression than electronic approaches.     

数字调制谐振式光纤陀螺中阶梯波复位误差的分析

谐振式光纤陀螺(R-FOG)是采用环形谐振腔来增强Sagnac效应的，其检测方案可以分为开环和闭环，在电路实现上，根据相位调制器控制信号的不同，又分为模拟调制和数字调制。相比而言，其数字闭环检测方案具有动态范围大、灵敏度高的特点。在数字调制的谐振式光纤陀螺中，其阶梯波的复位高度V2π是否精确，会对旋转角速度的测量和标度因数的线性度产生影响。从理论上分析了不精确的复位高度V2π对系统的影响，指出不精确的V2π将使谐振腔中的交叉耦合电场和直通耦合电场之间不会形成最佳相消干涉，从而产生误差。利用探测器输出总电场的表达式，以双频率调制的谐振式光纤陀螺为例，对引入的误差作了定量的数值计算，最后给出了克服误差的几种方法。     

Application of Multimode Laser Diodes in the Interrogation of Fiber Bragg Grating Sensors

The interrogation of fiber Bragg grating sensors with multimode laser diodes is theoretically and experimentally analyzed using two different approaches: serrodyne and dithering techniques. It is also demonstrated that by using several laser modes it is possible to enhance the measurement range without compromising sensitivity.