Hello everyone! I'm a complete newbie to CST Studio Suite (using CST 2020 version). I've mastered basic 3D modeling of simple FSS (Frequency Selective Surface) and standalone RLC circuit building through tutorials. However, I'm totally stuck when it comes to field-circuit co-simulation of Energy Selective Surfaces (ESS) integrated with PIN diodes—especially how to accurately acquire incident and received energy data and generate comparison plots. I've tried three times without success, so I'm here to seek guidance from all the experts!
My core request is: a newbie-friendly, step-by-step guide for ESS field-circuit co-simulation, preferably using a basic case of "periodic ESS unit + PIN diode biasing circuit". The key focus should be the full process of "monitoring incident/received energy, extracting data, and creating comparison plots". Currently, I can independently complete ESS unit geometric modeling and simple diode circuit building, but I have no clue about three critical parts: field-circuit integration, nonlinear simulation settings, and energy data capture. Specifically, I need to figure out these questions:
1. Preparations: Project & Parameter Planning
- Which template should I choose when creating a new project? There are two options: "Microwave Studio (MWS)" and "Electromagnetic Studio (EMT)". My ESS targets the RF band (2-6GHz)—which is more suitable for nonlinear component simulation?
- What core parameters do I need to confirm in advance? For example, the unit period must satisfy "<λmin/2"—is λmin calculated based on the maximum simulation frequency? Do I need to predefine the diode's operating power range in parameters?
- How to choose between bidirectional and unidirectional coupling? ESS needs to simulate the switching characteristic of "transmitting low-power signals and reflecting high-power signals"—is bidirectional coupling mandatory to reflect the mutual influence between fields and circuits?
2. 3D Electromagnetic Model Building (ESS Core Part)
Periodic Unit Modeling Details:I want to build an ESS unit with a square patch + central PIN diode (period: 6cm×6cm). How to integrate the diode? There are two methods: "thin-line Lumped Network Element" and "thin-sheet Lumped Network Face Element"—which is easier for newbies? Do I need to separately model the anode/cathode metal structures of the diode?
Boundary & Port Settings:
How to configure periodic boundaries? For x/y directions using "Periodic BC", should the phase shift be set to 0 or calculated based on the incident angle? For the z-direction in open space, should I use PML (Perfectly Matched Layer) or "Add Space"?
Must Discrete Ports be used for field-circuit connection? Should ports be placed at both ends of the diode or at the feeder of the ESS unit? Should the impedance be set to 50Ω or matched to the circuit load? Do port names need to be strictly consistent with those in the circuit?
Energy Monitor Placement (My biggest confusion): How to accurately capture "incident energy" and "received energy"?
Incident energy: Should I add a "Power Flow Monitor" or "Electric Field Probe" near the excitation source? Do I need to limit the monitoring area (e.g., using the Subvolume function)?
Received energy: To monitor at the load side of the ESS, should I add a monitor corresponding to the incident side, or directly extract power data from the circuit load?
How to set the frequency range and sampling points for the monitor? For the 2-6GHz band, how many sampling points are needed to ensure a smooth comparison plot?
3. Circuit Model Building & Field-Circuit Connection
Nonlinear Components & Biasing Circuit:
How to import the PIN diode's SPICE model? After importing via "File→Import→SPICE Netlist", do I need to manually adjust parameters like forward voltage drop and reverse breakdown voltage?
How to design a biasing circuit that doesn't interfere with RF signals? I saw tutorials using "RF Choke + DC Block Capacitor"—how to select the inductance of the choke and capacitance of the capacitor? Does the DC bias voltage need to match the diode model (e.g., is 3V suitable for 1N4148)?
Field-Circuit Connection Operation:
How to associate the "External Port" in Design Studio (DS) with the ESS ports in MWS? Can I directly select the corresponding MWS project and port name in the port properties?
Do the two pins of the diode model need to be connected to the two Discrete Ports of the ESS separately? Will this cause a port count mismatch?
4. Simulation Parameter Settings & Execution
Solver & Excitation Selection: Must the Transient Solver be used for the nonlinear characteristics of ESS? Should the excitation source be a "Plane Wave" or "Pulse Voltage Source"? To simulate low-power/high-power switching, do I need to set a combined excitation of "low-power continuous wave + high-power pulse"?
Key Parameter Tuning:
What is the appropriate simulation time? I saw cases using 10μs to capture switching responses—does the 2-6GHz band require longer time? Is setting the time step to "≤1/100 fmax" feasible?
How to adjust iteration parameters to avoid non-convergence? Is setting the maximum number of iterations to 50 and target residual to 1e-6 suitable for newbies? Do I need to adjust the relaxation factor?
Mesh Setting Tips: Previously, overly coarse meshes led to distorted results when simulating standalone FSS. After adding diodes to ESS, do I need to locally refine the mesh around the diodes? Are there standards for the refinement range and mesh density (e.g., 20 lines per wavelength)?
5. Post-Processing: Creating Incident/Received Energy Comparison Plots
- Where to extract energy data after simulation? From "Field Monitors" in MWS or "Voltage/Current Probe" in DS?
- How to convert monitored field data into "energy"? For example, calculating incident power via power flow integration and received power via load voltage/current—what are the specific formulas and operation steps?
- Comparison plot creation: I want to generate "Transmission Efficiency vs. Frequency" curves (received energy/incident energy) and "Time-Domain Energy Variation" comparison plots. How to set templates in CST's "Post-Processing"? Do I need to export data to Excel for plotting?
6. My Failed Attempts (For Problem Localization)
- First attempt: Used an ideal diode instead of a SPICE model. The energy comparison plot showed no "high-power reflection" characteristic—does ESS simulation require a parameterized SPICE model?
- Second attempt: Only connected the input port of the ESS during field-circuit port association, with no circuit load at the output. As a result, received energy data was zero—do I need to build a complete loop of "excitation→ESS→load"?
- Third attempt: Only added a far-field monitor, which failed to extract near-field energy at the incident side—do I need to add near-field Power Flow Monitors at both the excitation and receiving ends?
I would be extremely grateful if any expert could break down the steps for these questions, attach screenshots of key operations (e.g., port association, monitor setup, post-processing plotting), or recommend ESS simulation case posts/videos suitable for newbies! I can provide my ESS unit model file and previous error screenshots to help locate the problem.
As a newcomer to ESS simulation, my questions may be basic—please bear with me! I hope to understand the core logic of ESS field-circuit co-simulation through this case, and then proceed to simulate ESS arrays. Thank you all in advance for your help!
