The design principle of circuit board

The design of the printed circuit board processing is based on the graph is based on circuit principle, realize the function of the circuit designer need. The design of the printed circuit board processing mainly refers to the layout design, need to consider the layout of the external connections. Optimize the layout of the internal electronic components. Metal wire and hole layout optimization. Electromagnetic protection. Various factors such as heat dissipation. Good landscape design can save production costs and achieve good circuit performance and heat dissipation performance. Simple layout design can be implemented by hand and complex layout design needs with the aid of computer aided design ( CAD) The implementation. In the design of high-speed, controllable impedance characteristics of the plate and the circuit impedance is one of the important and common problem. First look at the definition of a transmission line, transmission line is composed of two conductors of a certain length, a conductor used for sending signals, and the other is used to receive signals ( Remember that 'loop' to replace the concept of 'land') 。 In a multilayer board, every line is part of the transmission line, adjacent to the reference plane can be used as the second line or loop. A route as 'good performance' is the key to make it the characteristic impedance of a transmission line remained constant throughout the line. Circuit board become 'controllable impedance board' is the key to satisfy all line characteristic impedance of a specified value, usually between 25 ohms and 70 ohms. In multilayer PCB, good performance is the key to make it a transmission line characteristic impedance of the constant in the whole line. However, circuit board processing, characteristic impedance is what? Understand the characteristic impedance simple way is to look at the signal met what in transit. When along a cross section has the same transmission line moves, assuming that add 1 kv voltage staircase to the transmission lines, such as 1 volt battery connected to the front end of transmission line ( It is located in between transmitting circuits and circuit) Along the line, once connected, the voltage wave signal at the speed of light, its speed is usually about 6 inches/nanoseconds. Of course, this signal is sent to the line and circuit, the voltage difference between any part of it can be sent from the line and loop neighboring points to measure.