扬声器热传递非线性模型

4．1 非线性电-力系统 电-力系统中的电学与力学状态变量决定了输入功率转换成热的量。图5中的等效电路考虑到了电动式扬声器主要的非线性机理,如：与音圈位移x有关的力因数BI@）,劲度Kms（x）以及电感Le（x）。     

扁线音圈

提到扁线音圈，大多数电声工程师会想到那是品质超群的高级扬声器的标志。一种最佳设计的扁线音圈将使换能器给出更宽的频率响应，相位响应更线性（因为电感量较小），并有较高的灵敏度。扬声器的灵敏度与许多因素有关，其中包括由音圈和磁路系统产生的力。由扬声器磁体产生的永久磁场是被音圈中电流产生的磁场调制的。当这个力耦合到振膜时就产生了声能。大多数传统扬声器用的音圈是由圆线绕制成的，由于圆线的性质决定了这类音圈的组成：导电体（铜、铝、铜包铝线等）、绝缘层和空气。当应用扁线时，绝缘层必须保留，而空气部分则消除了犤…     

感应式气流扬声器的设计原理

本文由气流扬声器的等效电路导出了直接决定感应式气流扬声器声学特性的输入阻抗和位移振幅频率响应。在忽略阻尼的条件下,进行了理论分析。分析表明它与普通的电动式气流扬声器的特性不同,感应式气流扬声器使用恒流源时在中频段具有平直的频率特性。这时,决定感应式气流扬声器中频段位移振幅的主要参量是扬声器的初次级线圈的互感量,磁感应强度与音圈的直径,而其高频特性下降的特点也与普通电动式气流扬声器不同。感应式气流扬声器的高频响应不决定于振动系统的机械共振频率而与音圈的质量和电感有关。在考虑阻尼影响的情况下,对感应式气流扬声器的频率响应进行了计算,并给出实验模型的测量结果。这些,可供气流扬声器研制、设计和使用人员参考。     

多媒体扬声器磁液应用技巧

说明了磁液在多媒体扬声器中的应用,将磁液应用在扬声器中,音圈工作温度会被降低,短期功率承受能力也被显著提高。并且,磁液可以给音圈提供均匀的径向的对中力,并在加强音圈对中的同时,在音圈碰芯的时候起到润滑的作用并减少刺耳的声音。介绍了用在多媒体和家庭影院中低音扬声器中的一种新的低成本的磁液。最近的磁液应用趋势是,充分利用磁液对中力将此也加注在一些小体积宽频带的扬声器（和全频扬声器）中。但在扬声器的设计上应有一些修改。     

扬声器振膜的振幅

最近发现一本介绍音箱的书籍中提到有关振幅的问题，原文如下：“扬声器工作在自由场或工作在密闭箱中，其锥盆的振幅(我想应该指位移振幅)会随着频率的降低而增大。”我认为它的意思是其位移振幅的最大值并非在单体的．fo附近(或音箱的f∞附近)，而是在最低频(1Hz)处，这与我用肉眼观测的相符。南大电声系教材《扬声器及其系统》一书中指出，扬声器的fo指使锥盆发生速度共振时的频率，其位移共振频率(即位移振幅最大值时的频率)在其fo附近，与上述观点不同，请问扬声器工作在自由场或工作在密闭箱中，其锥盆的位移振幅最大时的频率是在1Hz处还是在fo附近?另有一问题：若一扬声器为长音圈设计，则“Bl”当中的“l”是指音圈漆包线的总长，还是指处在均匀磁隙当中音圈漆包线的总长?有空的时候请帮我解答上述疑惑，谢谢!你的问题提得很好。我写的即将出版的《实用扬声器工艺手册》书中有一节关于“扬声器的振幅”，正好与你的问题对应。刊登出来供参考。     

新型高性能带式扬声器的结构及性能

WM带式扬声器与现有的等电动带式扬声器、铝带型带式扬声器等传统带式扬声器有本质的区别。现简述这几种带式扬声器的结构及性能特点。 （1）等电动带式扬声器 该扬声器是在一张很薄很轻的带状膜上用特殊方法附上特殊走向的箔状音圈,将带状薄膜置于平行强磁场中。给音圈通入音频电流时,音圈将带动薄膜做切割磁力线的音频振动从而使扬声器发声。由于音圈是均匀分布在薄膜的各个部位,因此薄膜的各个部位将受到相等的电驱动力。故该扬声器被称为等电动扬声器。该扬声器的振动系统很轻,因而高频响较好。但该扬声器的音膜较柔软,使得其在工…     

扬声器纸盆材料的静态扬氏模量测量

扬声器振动部件(包括音盆、定位支片、音圈、折环等)材料的弹性模量E'与损耗因数tan δ对扬声器的频响范围,频响曲线的平坦程度,音色的纯真及清晰度等都有密切的关系。特别是近年     

自粘线音圈实用价值探讨

80年代起,全国所有大中型扬声器厂家,基本上都引进国外音圈绕制自动线设备。自动线绕制音圈特点是提高生产效率,降低生产劳动强度,保证音圈有良好的一致性。自动线绕制音圈先决必要条件是具备自粘线和自粘纸带。本文着重对自粘线音圈粘接力与扬声器电功率、磁间隙温度变化,以及各扬声器厂家使用情况加以论述。     

大功率扬声器与功率有关的若干问题

在大功率扬声器设计中音圈线径设计是关键。从介绍音圈线径与功率的关系开始,谈到最大振幅(位移)及各注意要点,最后介绍了大功率扬声器用胶粘剂的一些使用问题。     

磁流体扬声器的性能分析

在电动式扬声器的磁路气隙中注入一种新颖的液态磁性材料——磁流体,就构成了磁流体扬声器。磁流体依靠气隙中的磁场定位,并与音圈,夹板和场芯保持密切的接触。当音圈运动时,磁流体紧随着音圈在一定范围内运动,从而加强了对音圈的热传导,并提供适当的阻尼,使音圈运动产生了一个定心作用。十多年前,国外已开始把磁流体应用于扬声器,并有实用的磁流体扬声器供应市场。     

Inductance formulas for circular and square coils

Some simple inductance formulas are given for a circular or square coil of any shape ratio. Each one represents a continuous transition between the extremes of a long coil and a short coil. A unique case is a cubic coil whose inductance is 2/3 the reference value based on area/length. For any shape, the relative error is very small and is stated. The theoretical formulas are given for comparison.     

新型平板扬声器的设计

针对传统扬声器的缺点,提出了一种平板扬声器的设计。扬声器由软磁材料、音圈、平板发声盘、环形导电线圈、偏磁线圈组成,并将音圈固定在以软磁材料形成的半闭合磁路上,音圈形成的电流通过导电环产生互感磁通而迫使发声盘振动,从而带动扬声器的振膜振动而发声。实践表明该扬声器具有频响宽、功率大、失真小、结构简单等特点,既能满足高保真音响和家庭影院系统需求,又能应用于多媒体音响系统的小型化要求,具有较好的应用前景。     

频率跟踪式谐振耦合电能无线传输系统研究

谐振耦合电能无线传输实际应用的瓶颈是谐振频率的失谐。本文基于谐振耦合电能无线传输机理和模型,分析了发射线圈与接收线圈的固有谐振频率变化对无线传输效率的影响和失谐机理,发现发射线圈电感变化是影响电能无线传输效率的主要因素之一,由此提出了发射功率源工作频率同步跟踪发射电路固有谐振频率的频率跟踪控制方法,从而保证了谐振耦合电能无线传输的谐振输电方式,避免了谐振频率的失谐,大幅度地提高了输电效率。文中制作了一个谐振频率为1MHZ的无线电能传输系统原理样机,验证了该方法的有效性。     

能量天平动圈位移的激光干涉测量研究

为精确测量普朗克常数h,实现能量天平法建立量子质量基准,提出了三轴双频激光外差干涉和折叠式Fabry-Perot(F-P)干涉绝对距离测量相结合的激光干涉测量方法,用于精密测量和定位能量天平装置中沿竖直方向在均匀磁场中运动的互感线圈位移。用三轴双频激光外差干涉精密测量运动线圈的质心位移和姿态,位移测量不确定度为10nm;进而将F-P腔干涉绝对距离测量与外差干涉测量结果进行比对和校准。仿真表明,采用本文方法,当位移测量范围约为30mm时,测量分辨率优于1nm。将该方法运用于真空中线圈位移测量,相对测量不确定度优于1.0×10-9。     

Tunable MEMS Spiral Inductors With Optimized RF Performance and Integrated Large-Displacement Electrothermal Actuators

We propose a tunable microelectromechanical systems integrated inductor with a large-displacement electrothermal actuator. Based on a transformer configuration, the inductance of a spiral inductor is tuned by controlling the relative position of a magnetically coupled short-circuited loop. The magnetic coupling between the inductors can be changed from 0.17 to 0.8 through an electrothermal actuator that can change their relative position by over 140 mum . For the first time, we investigate the impact of this tuning scheme on the inductance and quality factor and propose optimal designs. While a previous preliminary study has focused on keeping the ratio between the two coupled inductors close to one, we find that optimal performance is a weak function of this ratio. Instead, it primarily depends on the resistive loss of the short-circuited coil. Our theoretical studies are backed by a variety of fabricated and measured tunable inductors that show a ~2:1 inductance tuning ratio over a wide frequency range of approximately 25 GHz. In addition, the maximum and minimum quality factors of the tunable inductor are measured to be 26 and 10, respectively, which agree well with the theoretically expected values.     

A Copper/Polyimide Fabrication Process for Fabricating High-Inductance Microinductor

This paper reports on a technological process that combines copper as conductor, permalloy as magnetic core material, and polyimide as insulation material to complete a microinductor on glass with high inductance. The shape of the magnetic core scheme was rectangular, of which the width of the long side and short side were 1.4 and 0.6 mm, respectively. The dimensions of the inductor are 3.86 mm times 3.94 mm times 90 mum with coil width of 20 mum and space of 35 mum. The results show that the maximum inductance is 4 muH at 1 MHz, and the maximum quality factor (Q-factor) is 1.5 at 2 MHz.     

The effects of metals on a transcutaneous energy transmissionsystem

The effects of metal objects on the mutual inductance, self-inductance, and effective series resistance (ESR) of the coaxial coils of a transcutaneous energy transmission system (TETS) were investigated theoretically and experimentally. The theory considers a thin conducting sheet of infinite size aligned parallel to a current-carrying coil. Results of the theory indicate that coil parameters vary with the distance from the sheet to the coil. Changes in mutual and self inductance are independent of the conductivity and thickness of the sheet, with a larger percentage change for mutual inductance than for self inductance. Changes in ESR are proportional to the surface resistivity of the sheet. Experimental measurements using several aluminum sheets and a titanium alloy can in the presence of the TETS coils used for the Penn State artificial heart showed excellent agreement with the theory for inductance parameters and agreed within a factor of 2 for ESR measurements when skin effect was considered. It was generally observed that mutual inductance drops to 65% of its initial value as a metal sheet is moved to within 1-2 cm of the coil, while self-inductance drops to 80% of its initial value when the sheet is 2 cm from the coil. Measured changes in ESR tended to be higher than the calculated values with the discrepancy depending on distance to the metal object. Theory and measurements were extended to the case of lateral misalignment of the coils.     

Efficiency transition point for inductively loaded monopole

Whip or monopole antennas less than a quarter wavelength long can be significantly improved through series inductive loading in the antenna wire, provided that the coil losses are less than the improved radiation resistance. However, if the antenna is too short or the coil too lossy, the performance may degrade instead of improve. The combination of antenna length, radius, and coil Q factor for which the efficiency is 50% is an important design guide. This transition point varies with Q1/3 and even more slowly with length/radius ratio. For Q = 300, the transition point occurs for monopole lengths between 0.05 and 0.07 wavelengths.     

Inductance of a shielded coil

Models are developed for the inductance of a helical coil and a helical coil inside a conducting shield. Values of inductance are found from analysis. The dependence of inductance on the presence of the shield is assessed quantitatively and explained on the basis of physical principles, and the significance of skin and proximity effects in the wire coil is outlined. The inductance of an isolated, one-turn loop and a one-turn loop inside a conducting tube are measured and are found to be in excellent agreement with computed data. When the conducting shield and coil are very close, the inductance of the coil is found to be greatly diminished suggesting that one must account for the presence of shields when characterizing inductors, which might be used for loading and tuning of antennas. A nearby conducting shield must be accounted for in inductance calculations if reasonable accuracy is expected     

Inductance changes in annular discs near an infinite conducting plane

At high frequencies, the coupling with a conducting plane is greater for an annular disc than for a conventional coil of the same outside radius. Such discs therefore have benefits in certain inductance transducers, and it is shown that an optimum ratio of the inside to the outside radii exists.