How to Do a PCB Impedance Calculation Model
Using a Smith chart
The Smith chart is a useful tool when you want to determine the impedance of a circuit. It is a visual representation of the complex resistance versus frequency of an electrical circuit. It also shows the locus of impedance versus frequency, which is necessary for stability analysis and oscillation avoidance. Many PCs have the ability to display impedance values numerically, but the Smith chart helps you visualize the possibilities.
The Smith chart can be used to evaluate the signal path between a PC board’s contact pads and an electronic device. This device may be an IC, a transistor, or a passive component. It can also contain internal circuitry. By using this chart, you can determine the impedance of a circuit board and use it to design an electrical circuit.
The Smith chart can be used to identify the different types of impedance models encountered in pcb design. It has three shapes: bounded, unbounded, and inverted. A point in the center of a Smith chart represents an unbounded impedance model, whereas a point on the outer circle represents an inverted impedance model.
By using a Smith chart to calculate impedance, you can easily match the source and destination impedances. You can then calculate the size of your matching network. The size of the matching network depends on the amount of shift required between the source and the destination impedance. In addition, the series and parallel L and C values shift a point along the constant resistance and reactance curves. If the resistance decreases, you can add more R values to the end of the line.
Using a 3D field solver
PCB impedance calculation is a necessary step during the PCB design process. It involves calculating the transmission line or trace impedance on the PCB based on the design configuration. If the PCB is complex or contains multiple layers, the use of a 3D field solver can yield the most accurate impedance calculation.
Impedance calculation models usually assume that the cross-section is rectangular and that the current is perfectly returned. However, real cross-sections may be polygonal and can even cross gaps in the reference layer. This can cause significant distortions on the signals, especially in high-speed nets.
The solver supports two types of ports: wave ports and lumped ports. In both cases, you must explicitly define which type of port you want to use. You can either specify a plane for the wave port by using the geometry or define it manually by using the Wave Custom Size type.
Most 3D field solvers generate S-parameter behavioral models. These models are a simplified schematic representation of the actual device. As such, they require many iterations. For instance, you can create a simulation with many circuit models and compare their results.
PCB impedance calculations are essential for PCB design. It is important to model the regulated impedance of your PCB, so that you can avoid impedance mismatches. In addition, it is important to work closely with your PCB manufacturer. Your PCB manufacturer may have a dedicated CAM department that can provide appropriate indications for solving impedance-related design questions. However, it is important not to completely hand over control of impedance issues to an external party.