Calculation of the Differential Impedance of Tracks on FR4 substrates There is a discrepancy between calculated and measured values of impedance for differential TransmisSion lineson FR4. This is especially noticeable in the case of surface microstrip configurations. The anomaly is shown tobe due to the nature of the substrate material. This needs to be considered as a layered structure of epoxy resinand glass fibre. Calculations, using Boundary Element field methods, show that the distribution of the electricfield within this layered structure determines the apparent dielectric constant and therefore affects theimpedance. Thus FR4 cannot be considered to be uniform dielectric when calculating differential impedance.
上傳時間： 2014-12-24
上傳用戶：DE2542
阻抗匹配 阻抗匹配（Impedance matching）是微波電子學里的一部分，主要用于傳輸線上，來達至所有高頻的微波信號皆能傳至負載點的目的，不會有信號反射回來源點，從而提升能源效益。 大體上，阻抗匹配有兩種，一種是透過改變阻抗力（lumped-circuit matching），另一種則是調整傳輸線的波長（TransmisSion line matching）。 要匹配一組線路，首先把負載點的阻抗值，除以傳輸線的特性阻抗值來歸一化，然后把數值劃在史密夫圖表上。 把電容或電感與負載串聯起來，即可增加或減少負載的阻抗值，在圖表上的點會沿著代表實數電阻的圓圈走動。如果把電容或電感接地，首先圖表上的點會以圖中心旋轉180度，然后才沿電阻圈走動，再沿中心旋轉180度。重覆以上方法直至電阻值變成1，即可直接把阻抗力變為零完成匹配。 由負載點至來源點加長傳輸線，在圖表上的圓點會沿著圖中心以逆時針方向走動，直至走到電阻值為1的圓圈上，即可加電容或電感把阻抗力調整為零，完成匹配.........
標簽： 阻抗匹配
上傳時間： 2013-11-13
上傳用戶：ddddddos
Abstract: Impedance mismatches in a radio-frequency (RF) electrical TransmisSion line cause power loss andreflected energy. Voltage standing wave ratio (VSWR) is a way to measure TransmisSion line imperfections. Thistutorial defines VSWR and explains how it is calculated. Finally, an antenna VSWR monitoring system is shown.
上傳時間： 2013-10-19
上傳用戶：yuanwenjiao
為提高溫度測量效率，降低系統的成本，擴展傳輸距離，設計出一種新型溫度采集系統。單片機通過控制具有單總線方式的溫度傳感器DS18B20實現對溫度的測量，同時單片機通過控制具有單總線方式300～450MHz頻率范圍內的MAX7044與MAX7033無線發射與接收芯片實現溫度數據的無線傳輸。與傳統溫度采集系統相比，該系統利用單總線方式連接，采用無線傳輸方式實現遠距離通信，易于系統的集成與擴展。實驗結果表明，該系統結構簡單、方便移植，能夠同時實現多達上百點溫度的測量與500m范圍的傳輸。 Abstract: To improve the temperature measurement efficiency and reduce system cost,expansion of TransmisSion distance,a new type of temperature acquisition system is designed.Microcontroller controlled temperature sensor DS18B20which has a single-bus achieves temperature measurement,while microcontroller by controlled the MAX7044and MAX7033chip with a single-bus and having300~450MHz radiofrequency to achieve the wireless TransmisSion of temperature data.Compared with conventional temperature acquisition system,the system uses single-bus connected,and uses wireless TransmisSion means to achieve long-distance communications,easy-to-system integration and expansion.The experimental results show that the system is simple,convenient transplantation,and can be implemented in as many as a hundred-point temperature measure-ment and the TransmisSion range of500meters.
上傳時間： 2013-10-29
上傳用戶：515414293
介紹一種基于C8051單片機的動態心電監護系統。該系統由兩部分組成：以C8051F320單片機為核心的數據采集裝置和以PC機為平臺的分析處理系統。硬件電路功耗低，由單片機自帶的USB接口將數據傳送給PC機。軟件平臺采用LabVIEW可視化虛擬儀器系統開發平臺，將傳統儀器的功能模塊集成到計算機中，用戶可通過修改虛擬儀器的程序改變其功能。采用USB接口實時傳輸心電數據，并將數據采集模塊設計為計算機外設，使該系統高速快捷、小巧便攜。 Abstract: In this design，a low-cost ECG electrocardiogram monitoring system is introduced，which consists of two parts:data acquisition device based on C8051F320and PC terminal as the analysis and processing system.The system is low-power consumption，the data is transmitted to the PC terminal by USB interface of the C8051F320.By using the visible virtual instrument system developing platform LabVIEW，the traditional instruments function modules are integrated into the computer，so the user can modify virtual instrument software to change its function to meet their needs.Using USB in-terface to realize real-time ECG data TransmisSion，in addition，ECG data acquisition module is designed as the computer peripheral，which makes the syetem high-speed and portable.
上傳時間： 2013-11-13
上傳用戶：zhangzhenyu
提出一種基于C8051F040的炮塔方位角測試系統的設計方案，給出測試系統的各個模塊軟硬件設計。炮塔方位角測試系統集數據采集，數據傳輸和數據顯示等功能于一體，實現了炮塔方位角裝置的離線檢測。系統軟件采用C51編寫，對單片機進行有效電源管理，保證了系統的穩定性，可靠性。 Abstract: This paper puts forwards a design of artillery position system based on C8051F040，describes all modules hardware and software design of measurement system.The system has the function of information collection，TransmisSion，and display.It can measure artillery position system in offline.The system software using C51can manage the power of single chip microcomputer，guarantee the stability，reliability.
上傳時間： 2014-12-27
上傳用戶：7891
在汽車發動機起動時，若發動機起動后起動機不能及時斷電，將會燒毀起動機或損壞飛輪齒環；若變速器不在空檔位置起動，則起動機的瞬間動力將使汽車位移，還可能引起交通事故和人身安全。為此介紹一種利用NXP P89LPC901單片機控制的汽車起動保護控制器，通過檢測汽車起動開關、變速箱檔位、發動機轉速，實現對汽車發動機起動過程檢測和保護。起動保護控制器在發動機起動過程中通過采用逐個關閉打開負載系統，解決汽車發動機過程中因起動電流大而對汽車電源的沖擊影響,延長了電瓶壽命。 Abstract: When the automotive engine is started, the engine start motor and flywheel gear may be damaged， even traffic accidents and personal safeties may be caused by wrong operation or other factors.In order to ensure the automotive engine can be started normally and safely,it is necessary that the protecting measures and methods are considered in the automotive electrical control system.This paper introduces a kind of the automotive engine starting protect controller based on NXP P89LPC901 MCU.The controller can protect the engine starting process by detecting the starter key switch,TransmisSion stall and engine speed.Through the use of close and open load system,the controller can solve the impact on automotive power because of the high-current load in the process of the automobile engine starting, and extend battery life.
上傳時間： 2013-10-15
上傳用戶：mikesering
針對當前安檢力學試驗機所能完成的試驗種類單一、自動化程度低等問題，提出一種以ATmega128單片機為核心控制器的安檢力學試驗機的設計。詳細闡述了該安檢力學試驗機各個組成部分的設計原理和方案，并且給出了各部分的軟件設計思想和操作流程。經過大量測試試驗表明：設計的安檢力學試驗機可以完成多達十余種的力學安檢試驗，完全符合相關國家標準，并且具有數據采集精度高、傳輸速度快、操作安全簡便等特點，實現了安檢設備的多功能化、數字化和自動化。 Abstract: Currently， many mechanical security testing machines have only one function. The degree of automation of them is low. To solve those problems， a new kind of mechanical security testing machine， using ATmega128 micro-controller as its core controller， has been advanced. It describes the components of the machine. The principles and the scheme in the designing processes are presented in detail， and the software architecture and the operation processes of each part are given. After having done many testing， we have reached the following conclusions: the mechanical security testing machine presented can do over ten mechanical security tests complying with related national standards. It has high data acquisition accuracy and high TransmisSion speed. The operation of the machine is simple and safe. In general， this machine is a multi-functional， highly automatic， digitalized security testing device.
上傳時間： 2013-11-05
上傳用戶：a67818601
The SN65LBC170 and SN75LBC170 aremonolithic integrated circuits designed forbidirectional data communication on multipointbus-TransmisSion lines. Potential applicationsinclude serial or parallel data TransmisSion, cabledperipheral buses with twin axial, ribbon, ortwisted-pair cabling. These devices are suitablefor FAST-20 SCSI and can transmit or receivedata pulses as short as 25 ns, with skew lessthan 3 ns.These devices combine three 3-state differentialline drivers and three differential input linereceivers, all of which operate from a single 5-Vpower supply.The driver differential outputs and the receiverdifferential inputs are connected internally to formthree differential input/output (I/O) bus ports thatare designed to offer minimum loading to the buswhenever the driver is disabled or VCC = 0. Theseports feature a wide common-mode voltage rangemaking the device suitable for party-lineapplications over long cable runs.
上傳時間： 2013-10-13
上傳用戶：ytulpx
車輛行駛性能的好壞，不僅取決于發動機，而且在很大程度上還依賴于變速器及變速器與發動機的匹配。在汽車上使用的自動變速器大致有三類：液力自動變速器（Automatic TransmisSion，AT）、電子控制機械自動變速器（AutomaticMechanicalTransmisSion，AMT）和金屬帶式無級變速器（Continuously Variable TransmisSion，CVT）。前兩種變速器都是有級或分段無級自動變速，無級變速器CVT避免了齒輪傳動比不連續的缺點，具有傳動比連續、傳遞動力平穩、操縱方便、可使汽車行駛過程中經常處于良好的性能狀態、可改善汽車排放和降低燃油消耗等特點，真正實現了無級變速。我國的汽車工業與發達國家有較大的差距，通過研制無級變速（CVT）控制系統對縮小差距和世新紀發展我國民族汽車工業都具有十分重要的意義。
上傳時間： 2013-11-11
上傳用戶：qingzhuhu
