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Tutorial: Setting Up a Workflow for RF Design with Open-Source Tools
Welcome to this tutorial on setting up a comprehensive workflow for RF design using open-source tools. In this chapter, we will guide you through the design process of a Medium Power Amplifier (MPA) operating at 50 GHz, covering key aspects and challenges encountered throughout the design and simulation stages.
Workflow Overview
1. DC Analysis with NGspice
We begin by setting up a simple DC analysis in Ngspice to evaluate the biasing operation of the MPA. This will allow us to determine the stability factor and ensure the amplifier operates within the desired parameters. Understanding the biasing conditions is crucial to ensure the amplifier functions efficiently at higher frequencies.
2. Input Matching with Qucs and NGspice
Next, we will focus on input matching using Qucs-s, still utilizing Ngspice for circuit simulation. Achieving proper impedance matching at the input is essential to maximize power transfer and minimize signal reflections, which is especially challenging at high frequencies like 50 GHz.
3. Output Matching and Non-Linear Behavior
For the output matching, we will explore the non-linear behavior of the MPA. As NGspice currently does not support non-linear analysis (as of April 2025), we will switch to using Xyce, a more advanced simulator capable of handling non-linear effects. This will allow us to simulate the amplifier's behavior under real-world conditions, including distortion and power saturation.
4. Data Extraction and Post-Processing
Once the simulations are complete, we will extract the simulation data from Qucs in CSV format and import it into Jupyter Lab for post-processing and plotting. Visualizing the data is essential for interpreting the amplifier's performance and making further design decisions.
5. EM Simulation with openEMS
As we extend the design, we will move on to the layout realization of the MPA. Here, we will perform electromagnetic (EM) simulations using openEMS, an open-source simulation tool for high-frequency circuits. We will use the Python interface developed by Volker Mühlhaus to set up and run the simulations (you can find more details on this in the provided tutorial). EM simulations help us understand the physical layout's impact on the amplifier's performance, including parasitic effects and signal integrity.
6. Final Remarks
Throughout this tutorial, we will cover the steps needed to create, simulate, and optimize a 50 GHz MPA using open-source tools
Let’s dive into the details of each step!