Integrator circuit with bipolar transistor for Gbit/s applications

A novel continuous time integrator circuit suitable for Gbit/s signal processing is presented. It takes advantage of the inherent low impedance characteristic of broadband transistors. Instead of charging a capacitor from a high impedance current source, basically an inductance is used which is driven by a low impedance voltage source.<>     

一种基于FDTD的简单有效的天线阻抗计算方法

本文从有源区的软激励时Yee差分方程出发,推导了一种适用于理想的间隙激励(δ-gap source)和探针激励的天线输入阻抗新的计算公式,该方法简洁、有效,公式物理意义明确,能够有效地消除硬激励(hard source).计算天线阻抗时,在频率很低接近零时阻抗值的严重失真,使得应用时域有限差分法计算天线输入阻抗变得更加快捷适用.最后,本文应用该方法分别计算了一个单极子天线和同轴馈电的微带天线,单极子天线的计算结果和前人的计算结果吻合得很好,并且消除了频率接近零时以前计算结果的严重失真,微带天线和已有软件的计算结果进行了比较,得到了满意的结果.     

一种新型传输零点可控的微带带通滤波器

提出了一种新型的传输零点可控的微带带通滤波器结构,它由一段低阻抗线和与之相连的平行耦合线构成。通过调节低阻抗线与平行耦合线的偶模阻抗比,可以改变谐振器的2个模式之间的距离,从而灵活的调节滤波器的带宽;而通过调节平行耦合线的间距,则可以方便的调节传输零点的位置。仿真与实测结果都表明该滤波器具有良好的性能：低插损,结构紧凑,可以灵活的调节带宽和传输零点的位置。     

升压变压器低阻抗保护的原理及测试方法

升压变低阻抗保护主要作为发电机—变压器组相间短路的后备保护,逻辑判据中包含相间阻抗、相电流及负序电流三个变量参数,在测试过程中有一定的难度。通过对国电南京自动化股份有限公司生产的GDGT801型数字式发变组保护A柜变压器低阻抗保护的调试和检测,总结出该保护的调试技巧及测试方法,对有类似微机保护装置的发电厂、变电站、电力职业院校及电力培训中心也有一定借鉴意义。     

Noise-cancelling microphone using a piezoelectric plastics transducing element

A noise-cancelling communication microphone using a piezoelectric plastic as the transducer element has been developed. The bimorph structure adopted in conjunction with an impedance matching preamplifier circuit and suitable acoustic design provides an adequate, stable output at low impedance, with an acceptable frequency response. The susceptibility of the microphone to electromagnetic fields is low.     

Low-loss micromachined inverted overlay CPW lines with wideimpedance ranges and inherent airbridge connection capability

A new type of overlay coplanar waveguide (CPW) structure, “inverted overlay CPW (IOCPW)” is developed using micromachining techniques to provide easy means of airbridge connection between the ground planes, as well as to achieve low losses over wide impedance ranges. Measured IOCPW showed less than 1 dB/cm loss at 50 GHz over a wide impedance range from 25 to 80 Ω. It also offered low effective dielectric constant, and insensitivity to the substrate losses. Wide impedance ranges and simple process steps make IOCPW a promising uniplanar transmission line medium for mm-wave monolithic applications     

A modified current mirror with level shifting capability and low input impedance

A current mirror with DC level shifting capability and low input impedance is described. The input impedance can be varied over a limited range without significantly altering the current gain of the circuit, and lateral p-n-p transistors can be used to provide reasonable performance up to a few megahertz.     

Current-controlled translinear impedance converter

A current-controlled impedance converter is described which is implemented using two translinear active devices: a current conveyor with unity gain and an adjustable differential current-mode amplifier. It has low parasitic input impedance and useful properties when the amplifier gain is near unity. To characterize the circuit, SPICE simulation results are given and discussed.     

Miller long-duration sweep generator

A Miller-integrator circuit using a simple amplifier with positive feedback has been analysed. The circuit has the high input impedance inherent with insulated-gate field-effect transistors and the low output impedance characteristic of emitter followers. Owing to these properties and the high voltage gain, it is possible to obtain long-duration sweeps of good linearity. A sweep of about 2 h duration and of a linearity error of 0.05% has been obtained. The ratio of the dynamic range of the output voltage to the supply voltage is greater than 60%, and the output impedance is less than 10?.     

Simple ultra-lowpass filter (diode brake)

A circuit is described that uses two point-contact diodes and a capacitor to remove frequency content down to 0.1 Hz or lower, while transferring d.c. signal levels at low impedance and without loss. To operate, the filter requires a moderately high load impedance and input-signal amplitude variations of at least 100mV.     

A low impedance receiver for power efficient current mode signalling across on-chip global interconnects

In this work we propose a low impedance receiver for on-chip high speed current-mode signalling over global interconnect. The receiver provides a very low input impedance even with a low quiescent power. The low input impedance helps to get high link bandwidth without any passive terminator. Moreover, the receiver has high transimpedance gain over a large bandwidth. This facilitates in reducing the signalling current by 6.7 times compared to a passive termination. A test chip has been fabricated in 0.18 μm CMOS process to test the topology with a prototype global interconnect having a length of 10 mm. Power consumption of the transceiver for a data rate of 2.5 Gbps data is 2 mW. This gives an energy efficiency of 0.8 pJ/b.     

AB类功率放大器的设计与仿真研究

在比较A类、B类、C类和介于A类、B类中间的AB类四类功放电路各自优缺点的基础上,提出功率放大器工作点的选取以及通过阻抗匹配来实现高效率的方法。讨论了放大器输入回路阻抗变换电路、晶体管放大电路以及输出回路阻抗变换电路的设计思想,运用电报方程从理论上推导出用于信号源和晶体管之间阻抗变换的传输线变压器输入输出阻抗计算公式,由此设计出模拟信号处理电路中非常重要的AB类高功率放大器。仿真和实验结果表明,放大器在1MHz～50MHz的范围内,输入0．1w时输出为1w,其增益达到10dB,并且失真率非常低。     

Analyze and Design High-Speed Power Delivery Networks Using New Multiinput Impedances in Printed Circuit Boards

In this paper, a new input impedance, the multiinput impedance, which includes all information of the full impedance matrix, is proposed to accurately analyze and design planar power delivery networks (PDNs) in high-speed printed circuit boards and packages. The multiinput impedance includes all of the potential impacts of the other operating active power ports in both low and high frequencies. A systematical power-delivery-network analysis and design method using the multiinput impedance is developed. The global and local characteristics of the decoupled PDN are well demonstrated by the multiinput impedance, which make the analysis and design of the modern decoupled PDNs more accurate and reliable. Numerical and measured results show that the proposed multiinput impedance can characterize both the global and local characteristics of the planar PDNs with high accuracy.      

Very low Q-factor impedance measurements using a lock-in amplifier technique†

A technique for very low Q-factor impedance measurements, based on a lock-in amplifier as a vector voltmeter, is presented. Some practical details are discussed. The accuracy of the measurements has been studied by comparison, using a bridge method. As an application, the forward bias impedance of a variety of p-n junction is presented.     

A 90-100 GHz double-folded slot antenna

A double-folded slot antenna (DFS) has been designed, fabricated, and tested at 90-100 GHz. The antenna shows a very wideband impedance around 20 Ω from 85 to 110 GHz. The low impedance is compatible with superconductor-insulator-superconductor (SIS) junctions, Schottky diodes or high electron mobility transistor (HEMT) amplifiers, which require a low impedance at millimeter wave frequencies. The antenna is placed on a dielectric lens to synthesize a semi-infinite substrate and realize high-directivity patterns. The measured radiation patterns agree very well with theoretical calculations and demonstrate symmetric main beams and sidelobe levels below -15 db over a 10% bandwidth. The double folded slot antenna is an attractive candidate for low-cost wideband millimeter-wave monolithic microwave integrated circuits (MMIC) front ends     

An inexpensive detector-cable matching device

A simple, inexpensive, and effective means of impedance matching between detector and connecting cable is described. This device utilizes a low capacitance transistor that has recently become widely available at low cost.     

Synthesizing Microstrip Branch-Line Couplers With Predetermined Compact Size and Bandwidth

A new method for designing the microstrip branch- line couplers with predetermined compact size and bandwidth is proposed in this paper. With the proposed approach, the size of the quarter-wavelength transmission line in the branch-line coupler can be reduced greatly. In addition, the proposed couplers can be easily fabricated on the printed circuit board without any lumped element. A chart concludes the relationship between bandwidth and size reduction rate. It shows that open stubs with low impedance perform better than those with high impedance; moreover, the more open stubs with low impedance utilized, the broader the bandwidth will be. Furthermore, the measured frequency responses show good agreement with the theoretical results.     

A new electronically tunable current mode universal filter using MO-CCCII

A new electronically tunable universal current mode biquad filter structure employing three multiple output current controlled conveyors (MOCCCII) and two grounded capacitors is presented. The proposed filter offers the following advantageous features: low input impedance and high output impedance—a desirable property of current mode filters; realization of low pass, band pass, high pass, notch, and all pass; no matching constraint; low sensitivity performance and use of grounded capacitors suitable for integration. The practical design problems due to nonlinearities of MOCCCIIs have also been addressed. The feasibility of the design is confirmed via SPICE simulations.     

Hybrid stimulator for chronic experiments

A hybrid stimulator is described which combines constant current and constant voltage characteristics. Pulses are delivered with high output impedance to assure the passage of a predetermined amount of current. During the quiescent periods between pulses, the output changes to low impedance, diminishing the post-pulse charge. Electrode erosion and tissue damage are thus minimized, permitting safe, long term excitation.     

The fields due to a small loaded loop in free space

A theoretical analysis of a resistively loaded, electrically small loop is presented which shows the variations of the transverse-wave impedance close to the loop as the resistive loading is altered. The theoretical results are compared with those obtained from a numerical simulation using Numerical Electromagnetics Code (NEC). Depending upon the loading, the loop exhibits electric (high wave impedance) or magnetic (low wave impedance) dipole properties, or intermediate wave impedances. These changes in wave impedance are closely related to variations in the far-field radiation pattern, and simulations are used to demonstrate this. Measured results are used to demonstrate that the variations predicted in wave impedance actually occur in practice. These results have bearing on the interpretation of emission measurements and on the design of circuits to minimize interference to other neighboring circuits