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Two, Cadende spb software Cadende spb This is Cadence software, the current version of the Cadence SPB 16.5 ORCAD schematic design which is the international standard which PCB design, simulation, very full, with up complex than protel, mainly requirements, set up complex but do the requirements for the design, so the design together with less than protel obviously powerful. įirst, the domestic use of the relatively large number of protel, protel 99se, protel DXP, Altium, which is a development of the company, escalating software Altium Designer 9.1 is the current version of relatively simple design is more casual, but do these complex pcb software is not very good. Negative current actually flowing into the circuit and a positive current flowing out of the same, but just in front of the wave alternating current signal through the upper and lower lines form a capacitor, the end of the cycle. Advancing 0.01 per nanosecond, you get some of the charges (± Q) from the battery in a constant time interval (± t) flowing from the battery within a constant power (± Q) is a constant current. Charge from the front end of the battery cable, when moving along this line, give a continuous portion of the transmission line charging, thus forming the loop between the transmission line and the voltage difference of one volt. Every 0.01 nanoseconds, the transmission line must be charged another paragraph, and then propagate the signal to start along this section. Every move 0.06 inches, must put more charge moves to the transmission line, and the more negative charge added to the circuit. Ġ.01 in the next nanosecond, but also the period of 0.06 inches voltage transmission line from 0 to 1 volt adjustment, which must be added a number of positive charges to the transmission line, and add some negative charge to the receiving line. The first 0.01 ns 0.06 inches forward, when the transmission line has a positive excess charge and the loop has excess negative charge, the charge difference between the two is maintained at 1 volt difference between the two conductors, and two conductors which form a capacitor. Zen method is to " generating a signal", then 6 inches / nanosecond propagation velocity along the transmission lines. Figure 2 is a schematic diagram of the voltage signal transmission. Of course, this is really the signal transmission line and the voltage difference between the loops, which can be any point from the adjacent points of the transmission line and the circuit to be measured. Assumed that the distal end of the stepped wave and a voltage V to this transmission line, such as the one volt battery is connected to the transmission line ( which is located between the transmission line and the loop ), once connected, the signal voltage wave along the line speed of light spread, its speed is usually about 6 inches / nanosecond. When the microwave along a transmission having the same cross-section as shown in a transmission line is moved, which is similar to FIG. However, what is the characteristic impedance ? Understand the characteristic impedance of the easiest ways is to look at the signal transmission encountered something. In the multi-layer circuit boards, the good performance of the transmission line characteristic impedance of the key is that it remains constant in the entire line. Ĭircuit boards become critical " controlled impedance board" is to make all the characteristic impedance of the line to meet a specified value, usually between 25 ohms and 70 ohms. A line a " good" is the key to make the transmission line characteristic impedance is maintained constant throughout the line. In a multilayer board, the lines are each part of a transmission line, as a reference plane adjacent to the second line or loop. First, look at the definition of the transmission line : transmission line consists of two conductors composed of a certain length, a conductor used to send a signal, and the other for receiving signals ( remember " loop " instead of "ground " concept ). In high-speed design, controlled impedance characteristic impedance circuit board and is one of the most important and widespread problem. Simple layout can be achieved by hand, complex layout needs the computer-aided design (CAD) implementation. Excellent layout can reduce production costs, to achieve good performance of the circuit and thermal performance. Optimize the layout of metal wires and vias. Optimize the layout of the internal electronic components. Printed circuit board layout design mainly refers to the need to consider the layout of the external connections. Printed circuit board design is based on the schematics, circuit designers to achieve the required functionality.