uSimmics, formerly QucsStudio, is a powerful free circuit simulator for learning analog circuits, RF circuits, transmission lines, filters, signal integrity, EMC, and noise reduction techniques.
This page organizes the articles on this site so that you can learn circuit simulation step by step, from the basics to practical engineering applications.
This blog is operated by an engineer with more than 20 years of experience in high-frequency circuit design, EMC, and signal integrity design.
The articles explain practical topics based on real hardware development issues, including impedance matching, ringing, crosstalk, ferrite beads, PCB transmission lines, and S-parameter analysis.
The purpose of this site is not simply to explain how to operate a simulation tool.
The focus is on understanding why circuits behave the way they do and gaining knowledge that can be applied to real design work and noise-related problems.
Free engineering tools such as uSimmics continue to evolve year by year, and AI tools such as ChatGPT are also becoming useful for organizing and understanding technical knowledge.
This site aims to make RF design and circuit simulation easier to learn by combining practical engineering experience with modern learning tools.
Overview and Comparison Articles to Read First
Before you start learning uSimmics, formerly QucsStudio, it is helpful to understand how this tool is positioned and how it differs from other circuit simulators.
This section summarizes articles about the name change from QucsStudio to uSimmics, the difference between LTspice and uSimmics, and the relationship with Qucs-S.
- What Is uSimmics? Summary of Changes from QucsStudio
- Differences and Comparison Between LTspice and uSimmics
- What Is Qucs-S?
Learning Routes by Purpose
If you are new to circuit simulation, start with installation and basic operation.
If you are already involved in RF circuits, PCB design, or EMC countermeasures, you can also start from topics such as S-parameters, transmission lines, impedance matching, and noise analysis.
A. First Steps: Installation to Your First Simulation
- What Is uSimmics? Summary of Changes from QucsStudio
- How to Install uSimmics
- Initial Settings and Workspace Setup
- Basic Operation of the Circuit Editor
- Tutorial: DC Analysis
B. S-Parameters, Smith Charts, and Impedance Matching
Learn about S-parameters, Smith charts, VSWR, and impedance matching, which are important topics in high-frequency circuit design.
- Importing S-Parameter Files
- How to Read a Smith Chart
- Evaluating Circuits with VSWR
- Creating a Matching Circuit
- Trying Automatic Matching
C. Transmission Lines and PCB Trace Design: Microstrip / Stripline
Understand why PCB traces behave as transmission lines, and learn practical impedance calculations for microstrip and stripline structures.
- Transmission Line Calculator
- Microstrip Calculation Procedure
- Stripline Calculation Procedure
- PCB Structures with Different Dielectric Constants
- Effects of Etching on Real PCBs
D. Filter Design: LPF
Learn how to design low-pass filters, handle real component models, optimize circuits, and evaluate variations.
- LPF Design
- Filter Synthesis
- LPF Optimization Using Real Components
- Basics of Optimization
- Monte Carlo Analysis
E. Variation and Monte Carlo Analysis
In real circuits, component tolerances and variations can greatly affect performance.
This section explains Monte Carlo analysis, the tol function, parametric analysis, and related topics.
- Monte Carlo Analysis
- tol Function and Distribution Settings
- Variation Models for Real Components
- Parametric Analysis
F. Noise Design / EMC: From Causes to Countermeasures
Problems such as ringing, reflection, crosstalk, and unstable ground are very common in high-speed circuits.
This section helps you understand the physical mechanisms of EMC and signal integrity using actual simulation waveforms.
- Introduction to Noise Countermeasures
- What Is Reflection in High-Speed Signals?
- Understanding Ringing
- Why Ferrite Beads Work
- What Is Crosstalk?
Who This Roadmap Is For
- Students and beginners who want to learn circuit simulation
- PCB designers struggling with signal integrity or EMC issues
- Engineers who want to understand S-parameters and transmission lines
- People looking for a free RF circuit simulator
- People who want to understand real noise problems from a physical viewpoint
Recommended Starting Points
- If you want to install the tool first → How to Install uSimmics
- If you want to understand S-parameters → Importing S-Parameter Files
- If you want to design matching circuits → Creating a Matching Circuit
- If you want to calculate PCB impedance → Transmission Line Calculator
- If you want to evaluate variations → Monte Carlo Analysis
- If you want to understand noise countermeasures → Introduction to Noise Countermeasures
Tip: Bookmark this page so you can come back to it anytime as an entry point for learning RF design, EMC, transmission lines, and circuit simulation.