In radio frequency and microwave design, all kinds of "powerful" commercial electromagnetic simulation software have all-encompassing functions. This "inner strength method" starts from the algorithm point of view and reminds everyone how to choose simulation software carefully.
Method 1: The distinction between "field" and "road"
There is no "road" in the world, and the "field" becomes a "road" if it is much more similar! In theory, all electrical problems can be solved by field theory, but after ignoring the phase difference caused by the "field" propagating on the "road" size, the "road" solidifies the electromagnetic parameters into the device characteristics and becomes a lumped parameter, which is The electrical characteristics can be solved using a method that is infinitely simpler than that of Mai Dashen (Mai's equation). Of course, the approximation of all this is due to the fact that the model size is much smaller than the wavelength of electromagnetic waves.
One-sentence summary: The component size is much smaller than the wavelength of electromagnetic waves (electrically small size), and the "road" (lumped parameter/quasi-static) simulation software is used.
Mind method 2: Selection of full-wave simulation algorithm
When the electrically small size cannot be satisfied, it is difficult to use lumped parameters to solve the problem, so field theory must be used! However, using Mai Dashen’s method is not as comfortable as Ji Dashen’s (Kirchhoff’s) solution, and all kinds of little gods look down on it. Based on Mai Dashen’s theory, numerical algorithms are used instead of mathematical analytical formulas, so that computer The human brain is liberated to solve the sufferings of the people. So, there are the method of moments (MoM), finite difference time domain (FDTD) method, finite element method (FEM), transmission line matrix method (TLM) and partial element equivalent circuit (PEEC) that we are not familiar with now. ) and other full-wave algorithms. The existing full-wave simulation commercial software does not run out of the circle of these algorithms, so after understanding the characteristics of these algorithms, you also know how to choose the appropriate commercial simulation software:
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MoM divides the conductor into electrically small-sized units, and by calculating the current (constant) on all conductor units, the electromagnetic field generated by all conductor current units is obtained as a whole;
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FDTD divides the spatial region corresponding to the simulated object into volume elements of small size, assuming that the field in each volume element is constant. Generally, pulses are used as the excitation function, and the model can obtain a broadband response;
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FEM divides air and all other materials into electrically small-sized units, assuming that the field inside each unit is constant, and uses variational techniques to solve Maxwell's equations;
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TLM divides the modeling object area into multiple electrically small-sized units, each unit corresponds to a three-dimensional transmission line node, and the transmission/reflection on each node can be obtained from the node impedance;
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PEEC replaces the field relationship between all changing units with the relationship of the circuit. The units are connected through local mutual inductance and mutual capacitance. The overall circuit is simulated, and then the solved current and voltage parameters are converted into fields.
A table summary
Now powerful full-wave software simulation tools emerge in endlessly, but if used improperly, the actual effect may differ from the simulation prediction by a thousand miles! Although the above-mentioned inner strength method is the foundation of electromagnetic simulation, it also reminds all kinds of supernatural powers to be able to hold when they are showing their simulation skills, and not to make low-level mistakes.
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