Fundamentally , electromagnetic compatibility testing in a dark room for an existing model is validated test . These tests are not only expensive but also time-consuming . Application early in the design process simulation software is used to reduce the cost of testing has a lot of methods. However , EMC is a complex subject , in order to realize the complexity of the current board full 3D simulation is very difficult . Because of these difficulties , the experts can focus on key areas of the board of the simulation , such as power and ground network system or a single key , to determine the electromagnetic radiation ( emission ) and irradiated (sensitivity ) reasons. Knowledge of these analyzes will be applied to obtain the PCB design principles of the designers .
In the latest development of the simulation software , the user can see the entire layout design from the most popular PCB layout tools. Review feature checks all wiring boards , network or various design principles trace. The software can import the following data cabling routing tool provider : Altium, Cadence, Mentor, OrCAD and Zuken. The software was developed by renowned experts and professionals from IT industry giants simulation software company jointly developed . The former provides the interface to a variety of PCB layout tools, while the latter focuses on the number of years to build and validate EMC / SI rule-based expert systems. Over the years , the company's experts with flexible measurement techniques studied many EMC design issues , the eventual establishment of a variety of effective design rules. These rules are based on the design of the key check , the results verified by testing . Eventually, the different functions can be combined to form a common recognition of the major sources of electromagnetic disturbance software tools .
This general -purpose software does not require specialist EMC aspects , it allows the designer to check the PCB design meets the EMC rules. Secondly , wiring design software to provide a detailed description and a possible solution to the problem of EM . Integrated browser can display EMC design rules violate the exact location . In fact the main purpose , the development of this package is to make no background knowledge related to EMC user earlier in the design can be more easily pinpoint where EMC problems occur , thereby minimizing the cost of measurement and redesign .
Rule-based checks
Emission or by certain geometric coupling is caused by inconsistent rules . For example , consider the current return paths , each signal has a good signal to the track preset path , but in the power supply layer and the ground circuit layer often occurs . Loop current always choose the path of least resistance ; while at high frequencies , choose the path of least resistance . The new software may determine which of the return path is not continuous. For example , the path may be due to the separation plane interrupted . If the loop is not in a position to follow the geometry of the signal path, the loop current is a different path to use. The loop current is dependent on the size of the surrounding area , there will be an antenna radiating or receiving interference signals , resulting in EMC compliance failures or possible design faults. This software tool to identify supply in such a discontinuous layer of copper on higher frequencies by one or more capacitors are linked ( Figure 1 ) . Those capacitors will form one pair of loop current path has a low impedance , thus avoiding undesirable loops.
EMC problems due to the capacitance signal is too far away so you can not connect as a result of faults in Figure 1
Another rule is to search for those changes in signal layers and the reference plane of the loop current network . If the signal trace is changed to just below the top reference plane , the resulting radiation is very small . In this case, the loop current can continue to flow in the same plane . If the signal level while varying the reference plane , the return path must be assured (see Figure 2 ) . In the vicinity of vias using capacitors must avoid loop current paths and loops do not want. This software allows the design rules must be identified and changes in the layer below the apertured region of BGA , as reflux , but not through the capacitor through BGA. If this principle is violated , the layer change occurs where vias are highlighted by the software came out .
Figure 2 if the signal and the reference plane layer change at the same time, the need to guarantee the return path.
At higher signal frequencies , the need to reduce the length of the outer layer of wire , check maximum permitted length of the cable , and contrary to the place will be noted .
Another rule checks blocking capacitor is connected to the supply voltage pin to the maximum distance . Because the effective radius of the blocking capacitor is small, not more than to the decoupling pin allowed distance. Otherwise , no action of the capacitor can be ignored. Violation of this rule will be the distance between each capacitor to be listed along to . A final important rule is to not leave traces too close to the edge of the reference plane layer . In this case , the line impedance will change , and may cause signal reflections in the impedance discontinuities .
With this package , you can check the specific rules to guide the user through a list of errors , and then display the key area of wiring. In the early design stage to change the position of components, you can create a routing path to prevent electromagnetic compatibility problems , it does not require additional shielding or filters , thus saving valuable board space and component cost .
Conclusion
With the circuit board designs become more complex, electromagnetic compatibility to more strictly regulate the development of the survivors in the early design phase will seek a solution is necessary . Software simulation packages , especially when it relates to the wiring tool widely used effectively together using the interface , there are quite significant in the product development process .
