三点式LC振荡器振幅起振条件的简单推导方法

介绍一种物理概念明确，易于学生掌握的三点式振荡器振幅起振条件的简单推导方法。     

三角形耦合本振阵列天线波达方向估计

提出以对称三角形耦合振荡器阵列为本振阵列,分析了耦合本振振荡器的相位控制原理,给出耦合本振阵列相位控制方法,推导了耦合本振阵列锁相同步时,形成均匀的线性相位分布,且阵元间的相移只与边界上振荡器的振荡频率有关。利用耦合本振阵列形成均匀相位分布的这一属性,调整耦合本振阵列边界上的振荡器振荡频率,改变耦合本振相邻阵元的相移,实现波达方向估计。同时对三角形耦合阵列的稳定过程、波达方向估计进行了计算机仿真,验证了理论分析结果。     

二维矩形耦合本振阵列的波达方向估计

提出以矩形耦合振荡器阵列为本振阵列,分析了矩形耦合本振阵列的相位控制原理及方法,推导了耦合本振阵列稳定锁相同步时,本振阵列阵元间形成均匀的相位分布,且等相位差只与边界上振荡器的自由振荡频率有关。利用耦合本振阵列阵元间等相位差的这一属性,调节耦合本振阵列边界上的振荡器自由振荡频率,改变耦合本振相邻阵元的等相位差,实现波达方向估计。文中对波达估计算法进行了计算机仿真,验证了其理论分析结果,为注频锁相耦合振荡器阵列应用于天线接收技术提供有力的理论基础。     

基于OTA的文氏电桥振荡器

提出了基于OTA的文氏电桥振荡器，详细分析了该振荡器的原理，得出了起振条件和振荡频率。     

基于OTA的文氏电桥振荡器

提出了基于ＯＴＡ的文氏电桥振荡器，详细分析了该振荡器的原理，得出了起振条件和振荡频率。     

低相噪启钥式耦合微波光电振荡器研究北大核心

针对微波通信、雷达、电子战和导航等先进电子系统的应用发展需求,为了实现具有实用价值的极低相噪耦合微波光电振荡信号产生,提出了一种基于Sigma型光纤储能环腔架构的低相噪启钥式耦合微波光电振荡器。该方案通过Sigma型光纤储能技术消除了耦合微波光电振荡器中存在的偏振衰落问题,并且通过有源光纤环腔再生增益特性极大增强了振荡器品质因数,最终实现了10 GHz耦合微波光电振荡器的开机启钥稳定运行,起振信号在10 kHz频偏处的相位噪声达到-139.26 dBc/Hz。     

矩形耦合本振阵列接收波束形成

分析了耦合振荡器阵列的波束接收原理,以二维矩形耦合振荡器阵列为本振阵列,推导了产生均匀平面相位分布的控制方法,确定了波束形成的相位加权矢量,并通过仿真验证理论分析结果,为耦合振荡器阵列在天线接收技术的应用提供理论参考.     

LC反馈型和RC桥式振荡器起振条件的负阻分析

本文用等效负阻的方法,对RC桥式和LC反馈型振荡器起振条件作了推证,表明g_d>gL和A_(vo)F>1是统一的,并且在数量上建立了等效负阻和正反馈有关参量之间的关系。现在许多资料对LC反馈型和RC桥式振荡器起振条件的推证大都采用     

偶数级差分环形振荡器的稳定平衡态分析

与具有奇数增益级的差分环形振荡器不同,偶数级振荡器除了具有能够起振的非稳定平衡态,还有可能在起振前处于一种稳定平衡状态从而使电路锁定不能起振。该文主要分析了这种稳定平衡状态存在的原理,同时为了避免振荡器设计中的这种风险,提出了一种振荡器起振电路,使得电路在起振前处于接近非稳定平衡态的状态,从而能够快速起振。在0.13 m 1P8M 标准CMOS工艺下流片实现的4级差分环形压控振荡器(VCO)及其改进版本很好地验证了该文提出的理论和解决方法。经测试发现,第1款不带起振电路的4级VCO芯片锁定于稳定平衡态,不能起振;两种改进版本3级VCO和带起振电路的4级VCO都能够正常输出振荡信号。     

晶体管电流负反馈三点式振荡器

翻开有关三点式振荡器的书籍,可以清楚地查到三点式振荡器的起振条件: 式中h_(fe)为晶体管的电流放大系数。现在所谈的振荡器,其发射极串有电流负反馈电阻R_e(见图)。此振荡器的起振条件,是h_(FE)≥2X_1/X_2,正巧为原来无R_e时的二倍。根据振荡器振荡条件:Kβ=1,对于该振荡器,我们将e、c端视作输出端,b、e端视作输入端,则输入阻抗 (1)等效信号源内阻Z_3可以视为Z′_1与(Z_2+Z_3)的并联值:     

基于OrCAD/PSpice的波形发生电路设计仿真

对正弦波振荡器工作原理及振荡电路的起振条件进行了分析与研究。根据LC三点式振荡电路的组成原则设计并改进了电容三点式振荡器电路,在O rCAD/PSp ice仿真软件中对电路进行了时域及频域仿真分析,给出了振荡波形,测量了振荡频率。仿真结果表明通过对电路的改进改善了波形,所设计电路波形与理论值相接近。     

Identification of a class of two CFOA-based sinusoidal RC oscillators

Using a unified representation for a class of the two current-feedback operational amplifier (CFOA) sinusoidal oscillators, new circuits of this type can be systematically discovered. A catalogue of two circuit structures, each structure realizing 18 oscillator circuits, is presented. Moreover, using the RC:CR transformation, additional 18 oscillator circuits can be obtained from each structure. A third structure realizing additional two oscillator circuits is also presented. Some of the circuits enjoy one or more of the following attractive features: use of grounded capacitors, feasibility of absorbing the parasitic components of the CFOAs, availability of a buffered output voltage and orthogonal tuning of the frequency and the startup condition of oscillation. Moreover, it is shown that the use of the Barkhausen criterion for the determination of the startup condition of oscillation and the frequency of oscillation yields inaccurate results with relatively large errors depending on the selected component values. Furthermore, it is shown that using the roots of the characteristic equation of a specific oscillator structure will result in a startup condition that cannot be adjusted without disturbing the frequency of oscillation.     

Two-stage high swing fully integrated tunable quadrature sineoscillator

A new fully integrated two-stage operational transconductance amplifier-capacitor (OTA-C) sine oscillator circuit configuration using a 0.5 μm CMOS digital process is described. A simple linear impedance analysis is presented to predict the amplitude and distortion of oscillation. The accuracy of this approach is examined by comparing calculated, simulated and measured results. Transconductance tuning keeps the startup condition satisfied within the frequency range from 2 to 11 MHz     

通信电子电路中的LC并联谐振回路

LC并联谐振回路是通信电子电路中常用的单元电路。通过电路分析得出它的幅频特性与相频特性,认为它在通信电子电路中的应用主要有三种类型,即放大器的选频匹配网络、反馈式正弦波振荡器的选频反馈网络、调制与解调电路中的幅频变换及频相转换器件。     

A low frequency sine wave oscillator†

A now variable frequency oscillatory system is described. For certain system conditions the circuit produces a sine wave oscillation whose Frequency is varied over n wide range from ft very low to a high value simply by varying the gain of an amplifier rather than by changing the circuit time constant and accordingly no ganged condensers are used. Another important feature of the circuit is that the generation of a very low frequency oscillation is possible without incorporating a large value of the KC product. The oscillator utilizes an amplitude stabilizer operating on the controlled linear resistance of the initial region of the characteristic of a junction KET. The frequency relation is derived and the results are compared with experiment and found in agreement.     

基于电涡流的铜膜测厚研究

设计针对于PCB板的铜膜厚度进行测量。利用电磁感应的原理,以高频反射式电涡流传感器为基础,将LC电路产生的正弦电磁波辐射至铜膜。在铜膜上产生电涡流,从而引起辐射线圈电阻抗的变化,损耗增加,振荡信号幅值随之衰落。通过单片机对信号幅值进行A/D转换,数据处理,指示铜膜的厚度。所设计的装置体积小,携带方便,对铜膜检测的灵敏度较高,可以有效测量10～150μm的厚度,也可应用于其他金属镀层厚度的测量。     

New two CFOA-based sinusoidal RC oscillators with buffered outlet

Using a unified representation for a class of buffered-outlet two current-feedback operational amplifier (CFOAs)-based sinusoidal oscillators, new circuits of this type can be systematically discovered. A catalogue of four circuit structures, each structure realizing nine oscillator circuits, is presented. Moreover, using the RC:CR transformation, additional nine oscillator circuits can be obtained from each structure. While each circuit requires five passive elements, some of the circuits enjoy one or more of the following attractive features: use of grounded capacitors, feasibility of absorbing the parasitic components of the CFOAs and orthogonal tuning of the frequency and the startup condition of oscillation.     

Injection modulation in coupled laser oscillators

Injection modulation is the effect observed when laser oscillation is perturbed by an injected signal below the threshold of locking. In this regime the oscillation becomes a wave modulated in frequency as well as in amplitude. The modulation envelope has a characteristic waveform which depends on the amplitude and phase of the injected signal. Starting from the Lamb's equations for a dual-mode oscillator, we develop a theory of the injection modulation and calculate the waveforms in amplitude and frequency. The treatment applies both to the external injection into a laser and to the case of mutual coupling between two modes. Experimental results for a dual mode He-Ne laser are found to be in good agreement with the theory. It is pointed out how the injection modulation effects are appreciable even at very weak levels of injected amplitudes, e.g., down to 10^-5with respect to the oscillation field amplitude.     

An Inductive Conductivity Meter for Monitoring the Salinity of Dialysis Water

An inductive conductivity meter is described, especially adapted as a salinity monitor for dialysis water. Salinity are given. The principal problems of the inductive conductivity meter result from the low conductivity of electrolytes. The weak coupling due to the electrolyte means that stray coupling must be reduced to a very low level. This has been accomplished by means of a heavy copper eddy-current shield, which reduces the unwanted coupling to a level corresponding to a conductivity increment of the order of 10-8 ?-1. cm-1. The effect of parasitic impedances in the receiver core are minimized by designing this core as a current transformer, rather than a voltage transformer. The operating frequency is 5600 Hz. The circuits are described, including the oscillator, current-sensitive preamplifier, phase-sensitive detector, dc amplifiers, and alarm circuits. The phase-sensitive detector uses ordinary planar transistors and does not require a square wave reference signal.     

RC桥式振荡电路性能研究与仿真

针对RC桥式低频信号振荡器的性能和应用,对振荡电路的基本结构及性能指标进行探讨,分别从选频网络、稳幅环节及频率可调三个方面对电路性能进行改进,并结合仿真软件进行验证,得出性能完善,频率可在17 Hz~265.4 kHz之间连续可调的正弦波振荡器。