SIwave: Everything You Need to Know About the Resonant Mode Solver
SIwave is a tool for power integrity and signal integrity analysis. Today, we focus on the Resonant Mode Solver, which helps in computing resonant modes. The primary purpose of resonance calculations is to identify the optimal locations for placing coupling capacitors in power planes.
Key Concepts
- The size of the power plane is determined by the expected maximum current and the allowed maximum voltage drop.
- Even the best designs lack sufficient capacitance to maintain low impedance across a broadband spectrum.
- The power plane spectrum is derived from current pulses, necessitating decoupling capacitors to extend bandwidth.
File Import and Solver Selection
SIwave can import various CAD file types, including ODB, IPC, EDB, DXF, and GDSI. When a file is uploaded, it imports all relevant information such as material properties, stackup details, dimensions, and nets.
- Any process in SIwave starts by selecting the solver.
- Once a solver is selected, a dialog box appears, prompting the user to fill in missing information.
- For resonance mode analysis, enter the minimum and maximum frequencies to search for resonance.
Resonance Analysis
The resonance frequency is where impedance is very high, making the power plane behave like a perfect antenna. This frequency can cause the system to radiate energy and accept noise, which is undesirable.
Steps for Resonance Analysis
- Launch the solver and view the results, which list all resonances in the PCB within the band of interest.
- Analyze the Z11 plot to determine the severity of each resonance.
- Use the resonant mode solver to identify where to place decoupling capacitors.
Decoupling Capacitors
Decoupling capacitors are placed at identified resonance points to suppress unwanted resonances. The resonant mode solver helps determine the optimal locations for these capacitors.
Results and Interpretation
After adding decoupling capacitors, re-run the resonance analysis to observe changes. The Z11 plot will show reduced resonance peaks, indicating successful suppression.
Additional Considerations
- More resonances may appear after adding capacitors, but they are usually smaller and less significant.
- Always verify simulation properties, including minimum and maximum frequencies and the number of modes used.
Conclusion
The resonant mode solver in SIwave is a powerful tool for identifying and mitigating resonances in power planes. By strategically placing decoupling capacitors, you can maintain the integrity of your design and ensure optimal performance.
For further details, consult Ozen Engineering, Inc. for expert guidance and support.
SI Wave: Everything you need to know about the Resonant Mode solver (SD) SI Wave is a power integrity and signal integrity tool. Today, we'll focus on the Resonant Mode solver, which computes resonant modes.
The main reason for performing resonance calculations is to identify the best location to place decoupling caps in power planes. The size of the power plane is determined by the expected maximum current and allowed maximum voltage drop.
However, even the best design may not have enough capacitance to keep the impedance at low values for a broadband spectrum. The spectrum of the power plane is derived from the current pulses. Power planes need decoupling caps to extend their bandwidth beyond.
SI Wave can import various CAD files, such as ODB, IPC, EDB, DXF, and GDSI. When it uploads any file, it will import all kinds of information, including the material, stackup, dimensions, materials, and all the nets.
When using any process in SI Wave, such as DC, PI, or signal integrity, you must first select the solver. Once a solver has been selected, SI Wave generates a dialog box that looks like a form. The user needs to check the form and fill in the missing information.
For example, if you excite the computer as in the modes, you will get a simple dialog box where you need to enter the minimal frequency and the maximum frequency for which you are looking for resonance inside your design. You can also give the solver options and specify the accuracy.
Let's say you launch the solver. It will start solving, and you will get the results. From the results, you can determine the range of the bandwidth for which you want to solve. The definition of resonance is the frequency at which the impedance is very high.
Physically, this means that at this frequency, the power plane becomes like a perfect antenna, radiating lots of its energy out and accepting any signal or noise from outside the power plane. This is why we need to suppress this resonance. Once the solver is done, you can look at the results.
You will get a list of all the resonance in the PCB in the band of interest. The real part represents the resonant frequency, and the imaginary part stands for the losses or damping factor of the resonance. The wave number is simply the wavelength in free space at that frequency.
The q factor represents how sharp the resonance is. To determine where each resonance is, you can display the field between two layers. You have to select two layers, such as the VCC and ground, and click compute. You will get a list of plots, each representing one of the resonances.
By looking at the Z11 plot, you can see the resonant point and how bad it is. If it is very bad, you can add decoupling caps to suppress the resonance. After adding the decoupling caps, you can look at the results of the Z11 plot.
If you have suppressed the resonance, the Z11 value should be lower than before. In summary, the Resonant Mode solver allows you to display the field of each resonant, tell you which resonant you need to worry about, and, with the help of the Z11, tell if it is a good or bad resonant.
You can also look at the profile, which will tell you more information about how much time was spent and the mesh size.
Additionally, you can verify your simulation properties and see what the simulation properties are telling you about the minimum and maximum frequency, number of modes, and other information.
