Harmonic and Intermodulation Performance of the Semiconductor Bolometer

A mathematical model for the temperature dependence of the bolometer semiconductor resistance is presented. The model, basically a sine-series function, can easily yield closed-form expressions for the harmonic and intermodulation performance of the acquired interferogram voltage with large-amplitude multisinusoidal variations in the incident radiation. The special case of two-tone equal-amplitude incident radiation is considered in detail. The results show that the intermodulation components are always higher than the harmonic components of the same order. The results also show that the second-order intermodulation is always dominant and is higher than the second-harmonic component by about 6 dB. Moreover, the results show that for relatively small incident amplitudes of the incident radiation the ratio between the second- and third-harmonic components is almost equal to the ratio between the second-harmonic component and the fundamental. The results also show that the ratio between the amplitudes of the second- and third-order intermodulation components is almost equal to the ratio between the amplitudes of the second-order intermodulation component and the fundamental.     

Harmonic and intermodulation performance of hearing aids under large sound pressure levels

A mathematical model for the input-output functions of the hearing aids is presented. The model, basically a sine-series function, can easily yield closed-form expressions for the amplitudes of the harmonic and intermodulation components of the output when the input is formed of multitone large sound pressure levels. The special case of two-tone equal-amplitude incident pressure level is considered in detail. The results show that the third-order intermodulation component is always higher than the third-harmonic component. The results also show that the input-output functions exhibiting peak clipping exhibit the worst harmonic and intermodulation performance for large sound pressure levels. The simple wide-dynamic range compression (WDRC) input-output function exhibits the best harmonic and intermodulation distortion performance under large sound pressure levels. These results are consistent with the previously reported observations and reveal that there is a correlation between intelligibility of high-level speech and the harmonic and intermodulation performance of the hearing aid under large sound pressure levels.     

Large Signal Analysis of the Michelson Interferometer with Gires-Tournois Interferometers in its Arms

A mathematical model for the transfer function of the Michelson interferometer with Gires-Tournois interferometers in its arms is presented. The model, basically a sine-series function, can easily yield closed-form expressions for the amplitudes of the harmonic and intermodulation components of the output when the input is formed of large-amplitude multisinusoidal voltage. The special case of two-tone equal-amplitude input voltage is considered in detail. The results show that the third-order intermodulation component is always higher than the third-harmonic component. The results also show that the linearity of the Michelson interferometer with Gires-Tournois interferometers in its arms improves with the increase of the front mirror reflectivity. Moreover, the results show that the third-order intermodulation exhibits a minimum for relatively large values of the front mirror reflectivity. Furthermore, compared with the traditional Mach-Zehnder interferometer, the results show that a reduction of 15 dB in the third-order intermodulation can be achieved even for relatively small values of the front mirror reflectivity.     

Harmonic and intermodulation performance of optical-fiber Mach–Zehnder microphone

In this paper, closed-form mathematical expressions are obtained for the amplitudes of the harmonic and intermodulation products of the fiber optic Mach–Zehnder microphone excited by a multitone acoustical perturbation. The results show the strong dependence of the harmonic and intermodulation performance on the amplitude of the acoustical perturbation tones and the phase shift produced by the DC bias voltage applied to the reference fiber of the Mach–Zehnder interferometer. The results also show that depending on the phase shift produced by the DC bias voltage, either the third-order or the second-order intermodulation will be dominant. Compared to previously published results for other types of microphones, it appears that the phase shift produced by the DC bias voltage plays an important role in deciding the order of the dominant intermodulation product.     

P波入射下固固界面的二阶谐波场特性

应用二阶势理论研究了P波入射到固-固界面情况下的二阶谐波场。运用变动参数法求解二阶非齐次势函数方程的边值问题,数值计算了二阶谐波位移与入射角的关系,结果表明当入射角到达某个角度时,二阶谐波场的位移会急剧增大。同时,当入射角度为θ_w时,特解位移趋近无限大的有关现象依然出现,关于边界面的影响也做了讨论。      

Improved analysis of the electrically manifested distortions of condenser microphones

An improved analysis for the electrically manifested nonlinear distortions in condenser microphones is presented. The analysis shows that in typical condenser microphones excited by multisinusoidal sound signals, the second-order intermodulation components of frequencies ω_r±ω_s will be dominant. This result suggests that, rather than using the total harmonic distortion (THD), the use of the standard two- or three-tone tests for measurement of the nonlinear performance of condenser microphones would be more reliable and sensible.     

Harmonic and intermodulation distortions and noise associated with two-tone modulation of high-speed semiconductor lasers

We present results of modeling and simulation of the harmonic and intermodulation distortions as well as the intensity noise of high-speed semiconductor lasers under two-tone modulation. Multiple quantum-well lasers are considered, which are characterized by large differential gain and a modulation bandwidth of about 25GHz. The study is based on the rate equation model of semiconductor lasers excited by injection current with two sinusoidal tones separated by a radio frequency. The modulated laser signal is modeled in both the time and frequency domains. The time domain characteristics include the fluctuating waveform, while the frequency domain characteristics include the frequency spectrum of the relative intensity noise (RIN), carrier-to-noise ratio, modulation response, harmonic distortion, and the second- and third-order intermodulation distortions (IMD2 and IMD3). The analysis is performed for three frequencies of 5, 15, and 24 GHz, which are, respectively, lower, comparable, and higher than the laser relaxation frequency. The range of the modulation depth covers the regimes of small and large-signal modulation. We show that both RIN and IMD3 of two-modulated laser are minimum when the modulation frequency is 5GHz, and maximum when the modulation frequency is 24 GHz. The second-order harmonic distortion, IMD2, and IMD3 values are larger in the vicinity of relaxation oscillations and increase with the modulation index, especially under large-signal modulation.     

相对论谐波辐射对激光参数与等离子体参数的依赖特性

分析了相对论谐波辐射对入射激光参数和等离子体参数的依赖特性.结果表明：入射激光强度、脉冲宽度、脉冲形状和等离子体密度等参数对相对论谐波辐射有重要的影响.所得结果为实验提供了参考和依据. 关键词：     

激光器非线性失真对SCM光波系统的影响

对于宽带副载波复用(SCM)的光波系统,研究并设法减小光源的非线性所引起的谐波失真和交调失真,是一个重要的理论课题。本文分析激光器的P—I曲线的非线性以及谐振腔里光子和电子相互耦合所引起的固有非线性及其对复用信道的影响。     

激光辐照碲镉汞红外焦平面探测器的热应力损伤研究

基于碲镉汞红外焦平面探测器的结构与其材料热力学相关特征,描述了激光辐照碲镉汞红外焦平面探测器造成的损伤机理。根据相关的辐照环境和条件,通过有限元分析法建立了三维仿真模型。基于COMSOL Multiphysics软件仿真了碲镉汞红外探测器受到波长10.6 μm的激光辐照时,探测器各部分的温度变化及应力变化情况;通过数值分析方法,比较了碲镉汞探测器在经过光斑面积相同。功率不同的激光辐照后,其表面径向及内部轴向的温度场变化及应力场变化情况。仿真结果表明:在经过106 W/cm2的连续激光辐照后碲镉汞探测器表面温度与应力快速升高,造成探测器表面损伤,同时探测器被辐照部位的温度变化也导致其内部局部应力值变化。将碲镉汞探测器的应力损伤阈值及变化趋势与文献中相关实验数据进行对比,发现二者结果基本一致,验证了模型的可行性。     

Second harmonic generation in scattering of intense beam of radiation by bound electrons near-resonance

Second harmonic generation in near-resonance scattering of intense beams of radiation by bound electrons is investigated by solving the equations of motion exactly to all orders in the intensity of the incident radiation. A two-level model for the atom and a one-mode classical field for the incident radiation is assumed and the rotating wave approximation is taken. It is shown that (i) the second harmonic radiation is an equally spaced triplet, (ii) the middle frequency in these is exactly two times the incident frequency and (iii) the splitting depends on the difference of incident frequency and resonance frequency and on the incident intensity. The counting rates for the three frequencies have been studied in the weak and the high intensity limits.     

红外光谱辐射计探测器高阶非线性响应校正方法

针对傅里叶变换红外光谱辐射计辐射定标需要黑体辐射面充满仪器视场的技术特点,分析了由于入射光子流较高导致红外探测器产生非线性响应误差的机理.通过仿真包含非线性误差的黑体辐射数据,研究了非线性误差对光谱产生的影响,并根据卷积和交叉迭代两种校正方法,提出了适合校正高阶非线性响应误差的迭代方法—梯度下降法.利用傅里叶变换红外光谱辐射计进行辐射定标实验,对比卷积、交叉迭代和梯度下降法三种校正方法的效果,结果显示三种校正方法均可有效减小非线性误差,分别使拟合优度提高了0.15%,0.29%和0.39%,梯度下降法校正后的光谱数据更为准确.     

Large signal performance of micromachined silicon inductive microphones

A mathematical model for the open-circuit output voltage of a micromachined silicon inductive microphone is presented. The model, basically a sine-series function, can easily yield closed-form expressions for the amplitudes of the output components resulting from a multisinusoidal input acoustic pressure. The special case of an equal-amplitude two-tone acoustic pressure input is considered in detail. The results show that, the microphone generates both even and odd-order harmonic and intermodulation products.     

Harmonic and Intermodulation Performance of Sagnac Fiber-Optic Interferometer

Abstract

In this article, closed-form expressions are obtained for the amplitudes of the harmonic and intermodulation products generated when driving the fiber-optic Sagnac interferometer by a DC bias voltage plus an equal-amplitude two-tone signal. The results clearly show the strong dependence of the harmonic and intermodulation performance on the DC bias voltage and/or the phase bias of the fiber-optic Sagnac interferometer. The results obtained suggest that the DC bias voltage and/or the phase bias play an important role in deciding the linearity of the fiber-optic Sagnac interferometer and, hence, its suitability for analog applications.     

Variations on the Kepler problem

The elliptical orbits resulting from Newtonian gravitation are generated with a multifaceted symmetry, mainly resulting from their conservation of both angular momentum and a vector fixing their orientation in space—the Laplace or Runge-Lenz vector. From the ancient formalisms of celestial mechanics, I show a rather counterintuitive behavior of the classical hydrogen atom, whose orbits respond in a direction perpendicular to a weak externally-applied electric field. I then show how the same results can be obtained more easily and directly from the intrinsic symmetry of the Kepler problem. If the atom is subjected to an oscillating electric field, it enjoys symmetry in the time domain as well, which is manifest by quasi-energy states defined only modulo ħω. Using the Runge-Lenz vector in place of the radius vector leads to an exactly-solvable model Hamiltonian for an atom in an oscillating electric field—embodying one of the few meaningful exact solutions in quantum mechanics, and a member of an even more exclusive set of exact solutions having a time-dependent Hamiltonian. I further show that, as long as the atom suffers no change in principal quantum number, incident radiation will produce harmonic radiation with polarization perpendicular to the incident radiation. This unusual polarization results from the perpendicular response of the wavefunction, and is distinguished from most usual harmonic radiation resulting from a scalar nonlinear susceptibility. Finally, I speculate on how this radiation might be observed.     

A cascaded second-order approach to computing third-order scattering of noncollinear acoustic beams

A theoretical development of the third-order nonlinear scattering of sound from two noncollinear ultrasonic beams produced by baffled piston sources is presented. The third-order intermodulation (IM3) frequency components are derived by exploiting cascaded second-order nonlinear effects where the quadratic nonlinear interaction of second-order frequency components with first-order (primary) frequency components is considered. It is shown that cascaded second-order interactions generate intermodulation frequency components that are equivalent to those generated by cubic nonlinear effects. Comparison of measured and modeled amplitude sweeps demonstrate the three-to-one gain in decibels of the amplitudes of the third-order intermodulation frequency components to that of the primary frequency components. Measurements are also presented for the farfield interaction of distantly spaced sources, which results in a highly focused ultrasonic parametric array. Also considered are the nearfield interaction of closely spaced sources, which results in scattering, with good agreement to the theory.     

The Reduction of Harmonic and Intermodulation Distortions with a Cascaded Mach-Zehnder Molulator

A cascaded two-stage Mach-Zehnder modulator is used to suppress the harmonic and intermodulation distortions simultaneously. The modulation electric fields are applied on the first and second stages in the y and z directions of z-cut lithium niobate crystal, respectively. Because of the inherent versatility of the adjustable modulation parameters, superior linear modulation response can be achieved. When —50 dB nonlinear suppression is required, the modulation depth of 7.5% can be obtained.     

Large signal performance of micromachined silicon condenser microphones

A mathematical model for the open-circuit output voltage of a micromachined silicon condenser microphone with a single deeply corrugated diaphragm as a function of the applied acoustic pressure is presented. The model, basically a sine-series function, can easily yield closed-form expressions for the amplitudes of the output components resulting from a multisinusoidal input acoustic pressure. The special case of an equal-amplitude two-tone acoustic pressure input is considered in detail. The results show that the microphone generates only odd-order harmonic and intermodulation products. The results also show that the amplitudes of these components are strongly dependent on the microphone parameters, the corrugation depth and the ratio between the half-length of the diaphragm and its thickness. Moreover, the results show that the acoustic pressure required to produce a pre-specified output open-circuit voltage is strongly dependent on these parameters.     

A New Way of Looking at Nuclear Resonant Scattering

A new model for nuclear-resonant scattering of gamma radiation from resonant matter has been developed and is summarized here. This “coherent-path” model has lead to closed-form, finite-sum solutions for radiation scattered in the forward direction. The solution provides a unified microscopic picture of nuclear-resonant scattering processes. The resonant absorber or scatterer is modeled as a one-dimensional chain of “effective” nuclei or “effective” planes. The solution is interpreted as showing that the resonant radiation undergoes sequential scattering from one absorber “nucleus” or “plane” to another before reaching the detector. For recoil-free processes the various “paths” to the detector contribute coherently. The solution for this case gives calculated results that are indistinguishable from those using the classical optical model approach, although the forms of the solutions are completely different. The coherent-path model shows that the “speed-up” and “dynamical beating” effects are primarily a consequence of the fact that the single “effective” nuclear scattering processes are 180° out of phase with the incident radiation while the double nuclear scattering processes are in phase with the incident radiation. All multiple scattering paths are, and must be, included. The model can also treat the incoherent processes, i.e., processes involving gamma emission with recoil or conversion-electron emission. The source of the resonant gamma radiation can be from a radioactive source or from synchrotron radiation: both cases are treated. The model is used to explain and understand the results when each of the following experimental procedures is applied: time-differential Mössbauer spectroscopy, time-differential synchrotron radiation spectroscopy, enhanced-resolution resonant-detector Mössbauer spectroscopy, and the “gamma echo”.     

A generalized time-domain model for nonlinear inter-satellite microwave photonics links under dual-tone modulation

A generalized time-domain model is presented for the evaluation of nonlinear distortion effects in inter-satellite microwave photonics links using a dual-drive Mach-Zehnder modulator (DD-MZM) under dual-tone modulation. The model results in simple exact expressions for any harmonic and inter-modulation components at the output of the detector which can be applied to almost all operating conditions of DD-MZM, providing useful information to select system parameters for the performance optimization. Two special cases, double sideband and single sideband modulation, are studied in detail. Numerical results for the third-order inter-modulation distortion ratio (IMR3) are well matched with the analysis ones.