短波波段平衡／不平衡转换器的研制

文章对传输线变压器理论和平衡／不平衡转换器的基本电路进行了分析,并通过试验,总结出了制作符合技术要求的平衡／不平衡转换器的经验,最后介绍了实际制作过程中需要注意的问题。     

应用于电子乐器的不平衡——平衡转换器

利用公共交流电源为用电器供电是我们日常工作以及生活中必然的选择,由于不是完全各自独立的供电系统,这样用电器之间由于相互耦合的作用必然形成交流声和噪声环路。在此设计的这款＂不平衡——平衡转换器＂可以解决这个问题。该转换器电路中的省电电路系统也具有典型性。当然该转换器略加修改也可用于别的需要电气隔离的用电环境。     

150Ω同轴开关的巧妙测试方法

对于一款150Ω的同轴开关,输入输出接口都是外方内圆的结构,需要对其阻抗进行测试分析.由于手头无150Ω的差分电桥,也没有150Ω的同轴转接件,只有300Ω的差分电桥、标准电阻和相应的测试指数线,在此情况下,需要对被测系统进行分析,充分利用其特点和现有设备,把被测系统转换成更容易测试的系统,然后进行测试分析.     

一种新的IQ不平衡频域估计与补偿算法

针对正交频分复用（OFDM）系统中射频前端失真—同相/正交（IQ）不平衡影响系统性能的问题,提出了一种新型的IQ不平衡频域估计与补偿算法。通过同一个子载波上的两个不同导频信号,抵消信道的影响,以减小算法复杂度,便于实现。仿真结果表明,该算法既极大地降低了计算量,又取得了较好的估计与补偿性能,性能优于传统的算法。     

新型三相不平衡负载逆变器及控制策略研究

文中提出了一种新型三桥臂逆变器以综合补偿低压配电系统不平衡负载。该型逆变器仅使用单个电容充当直流链,并通过中性点电容连接负荷中性点和逆变器直流链负端。该型补偿器避免了因电容电压均衡而增加的控制电路,并可有效节省开关器件。文中详述了新型补偿器运行机理和数学模型,提出了适用于三相不平衡负荷补偿的控制策略。最后通过PSCAD仿真模型,验证了所提拓扑和控制策略的可行性。     

浅谈150KW短波发射机不平衡/平衡转换器调整的方法

本文以在维护过程中对不平衡/平衡转换器出现的问题进行分析,对该现象的处理方法及解决方案进行了说明,以便今后大家在维护该型号的发射机时处理类似现象提供了帮助。     

混合型动态三相不平衡补偿装置控制方法研究

本文基于低压配电系统多为三相四线制系统,由于单相负荷用电的随机性,三相不平衡问题越来越严重。过大的不平衡度降低了变压器带负载能力,增加了零线线损,从而加速绝缘老化,造成末端电压降低。为了解决这一问题并兼顾投资成本和补偿效果,本文提出了一种有源补偿加无源器件补偿的混合型补偿方案,分析了方案的配置,补偿优先级,对不平衡补偿采用有效值加瞬时值综合控制的策略,并且对三相不平衡各序分量控制,序分量限幅计算等关键问题进行深入研究,能够更好的指导相关研究和应用工作。     

地铁低压配电系统不平衡补偿研究

对于地铁低压配电系统中存在的三相电流不平衡情况,本文基于对称分量法补偿原理提出一种不平衡补偿方案,可有效实现负荷不平衡补偿,进而提高系统的安全稳定性.     

音频传输的平衡/不平衡方式及抗干扰

音频传输的平衡／不平衡概念,是对信号地而言,而不是对“工艺地”（机壳）的。双绞线是平衡式的,同轴线是非平衡式,但在同轴线的外屏蔽与机壳加有绝缘垫情况下,原来非平衡的同轴线对机壳来说又是平衡的。平衡接法一般有三条线：热端（“H”或“＋”）、冷端（“L”或“-”）以及屏蔽端。     

OFDM WLAN接收机IQ不平衡的时域补偿新方法

针对采用高阶调制的正交频分复用(OFDM)系统在前端模拟处理过程中易遭受到同相相位和正交相位(IQ)不平衡影响的问题,提出了一种新的OFDMWLAN系统接收机IQ不平衡估计和补偿方法。该方法利用较少的时域训练序列进行IQ不平衡参数的估计及补偿。仿真结果表明,该方法在降低了计算复杂度的同时,也获得了较好的估计性能。     

Uniform Transmission Line Equivalence of Cascaded Exponential Lines

The possibility of using cascaded sections of exponential transmission line in place of uniform transmission line is discussed. This makes it possible to reduce element lengths without changing the impedance level at the input and output terminals. Relevant design formulas are derived.     

传输线变压器相位补偿技术及其应用

传输线变压器是在短波和超短波频段使用广泛的重要器件,根据传输线变压器原理设计制造的器件具有结构紧凑、功率容量大、频带宽、损耗小等优点.该文研究了利用慢波线原理和相位补偿技术克服传输线变压器对于传输线电长度的限制,使其适用频率向s波段以上扩展的方法.文中给出了1:4阻抗变换器电路的传输损耗和高低端输入阻抗理论公式并对其进行了讨论.对所设计的S波段1:4阻抗变换器及功率合成器进行了仿真分析并设计制作了实物.仿真和实测结果表明,利用慢波线原理和相位补偿后的传输线变压器能够适用s波段及以上微波器件.     

铁氧体槽波导移相器的理论计算与实验研究

利用铁氧体矩形波导中的场方程,导出了铁氧体传输段的输入阻抗表达式,结合横向谐振技术和等效导纳概念,导出了铁氧体槽波导移相器计算模型的特征方程。在对计算模型进行了新的修正后,我们编程进行了计算,修正后的计算值与实验结果较吻合。     

双圆柱体结构天线阵列输入阻抗计算和阻抗匹配

该文介绍了一种由双圆柱体单元组成的全向天线输入阻抗的计算方法。文中将全向天线分解为馈电子系统和辐射子系统,同时将辐射子系统等效成一个N端口网络。首先根据传输线上电压、电流的传播关系,推导出网络的端口电压,端口电流和端口阻抗,然后由传输线上阻抗变换关系推导出天线的输入阻抗。从而可见,为实现该天线的阻抗匹配只须调节天线两端的短路活塞位置。同时,实测值验证了天线样品反射系数的计算结果。     

The Compensation of Step Discontinuities in TEM-Mode Transmission Lines

A method for the compensation of the effects due to discontinuities that arise when transmission lines of different characteristic impedance are joined is presented. The proposed method is not based calculating the equivalent circuit of the discontinuity but makes use of simple taper on the wider line at an impedance step to remove the effects of the discontinuity.     

Impedance boundary method of moments with extended boundaryconditions

An improved impedance boundary method of moments is proposed to accurately and efficiently determine the propagation characteristics of multilayer planar optical waveguides whose refractive index profiles contain large step index changes or a graded-index region combined with step index changes. Extended impedance boundary conditions are used in the impedance boundary method of moments to replace regions in the waveguide structure which have refractive index discontinuities. Two methods for determining the extended boundary conditions include the standard transfer matrix method and a procedure utilizing a cascaded transmission line representation with successive calculation of input impedances. Simulation results show significantly improved convergence rates in the determination of propagation constants     

Impedance Transformation Equations for Exponential, Cosine-Sqaared, and Parabolic Tapered Transmission Lines

Closed-form equations that give the value of an arbitrary complex impedance transformed through a length of dissipationless, nonuniform transmission line with exponential cosine-squared, and parabolic taper are presented. These equations are obtained by a second order nonlinear differential (Riccati) equation relating impedance, the nonuniform line impedance and the line length. The results presented should be useful in solving impedance matching problems.     

A lower bound for the length of nonuniform transmission line matching sections

A lower bound for the length of a nonuniform transmission line section needed to match a given load impedance to a given real input impedance is derived. The bound depends not only on the load and input impedances, but also on the maximum and minimum permissible values of characteristic impedance within the nonuniform line. Several specific cases are presented to illustrate the tightness of the bounds.     

Transmission-line amplifiers

A wideband thermionic vacuum-tube power amplifier in which an extended and continuous grid and cathode serve as an input transmission line that excites a corresponding traveling-wave signal on a similar transmission line between the screen grid and anode is analyzed. The usual gain-bandwidth product limitation is avoided by making the input and output capacitances part of the transmission lines. The gain mechanism is the same as that in the usual power tetrode in that bunched charges are delivered to the anode at the proper time and location along the anode transmission line to enhance the traveling-wave signal. If line attenuation losses are small, the power gain increases as the square of line length. Part of the backward wave can be made a forward wave by tapering the impedance of the output line. This type of amplifier could potentially use a field-emission cathode and thus avoid the high heater power and slow transit time of the thermionic emitter. Its disadvantages are low gain and low input impedance     

高温超导微带天线的谐振特性研究

传输线模型是分析微带天线的一种最简单的方法,但其未将导体的特性参数考虑到天线的分析中去,针对这一缺点,为研究超导体的表面阻抗对高温超导微带天线输入阻抗和谐振频率的影响,把导体特性对天线的影响看作一种微扰来处理,对传统的传输线模型进行了修正,并通过与谱域矩量法相比较,验证了修正后方法的有效性.进而利用修正后的方法计算分析了高温超导矩形微带贴片天线的输入阻抗和谐振频率,给出了关于高温超导微带天线输入阻抗和谐振频率的若干结论.