Behavioral models of the basic logic gates based on Verilog AMS.

In a new entry in the section "Verilog AMS Files", they are available for downloading the files that provide the possibility of simulate logic gates, the three basic ones, AND gate, OR gate and the inverter, from the behavioral point of view.

Mixed simulation is not implemented in QUCS Studio. Meaning that it is possible to work with logic circuits, but using the chronogram aproximation. One digital circuit in a QUCS Studio schematic can not be analyzed using transient analysis.

The logic gates coded in Verilog AMS and completed with some lumped elements offer the posibility of simulating using transient analysis with the advantange of the behavioral approximation. The same function for the logic gates implemented using the phisycal model (i. e. building the logic gates with the transistors that compose them physically) will take, on average, more time of analysis.

A Voltage Controlled Voltage Source with a Table defined dependency designed in Verilog AMS

As a second part of the post from a few days back, this time it is presented a voltage controlled voltage source with a table defined dependency. In many cases, there are SPICE models that include this type of controlled source as a part of the circuit, and this element, designed basically in Verilog AMS module, allows to cover this type of necesities.

Go and visit the "Verilog AMS Files" section of this site and you will find the links to the documentation and the files that are necessary to run in QUCS Studio this new controlled source.

A New Voltage Controlled Voltage Source with polynomial dependency for QUCS Studio

In QUCS Studio it is possible to find the basic controlled sources that are common in all the CAD tools. But there are other options for controlled sources that would be interesting for modelling devices and that it can be modeled in QUCS Studio using the Verilog AMS capabilities of the tool.

In the section "Verilog AMS Files" of this site it is now possible to find the description of the design process and the files necessaries to work with a new type of Voltage Controlled Voltage Source for QUCS Studio where the dependency is a polynomial expression of a determined independent voltage.

An improvement in the DCDC Model for QUCS Studio

In the previous DCDC spice model published in this site there were included two different aproximations that were rather inaccurate and could provoke convergence problems in transient analysis. After testing the first design, many of the failures in the transient analysis were resolved changing the independent voltage sources included in the model.

In this new model these inacurracies that are the existence of these independent voltage source have been resolved and the convergence problems explained before have been reduced significantly.

Until the number of tests are enough to declare the model free of convergence issues, this new approximation to the solution is definetly an improvement because It is better in terms of stability and it is more robust regarding the convergence problems.

To test the model, the previous test file can be used directly, replacing in the project folder the old model file for the new one.

Visit the "SPICE and Models" page and you will find the link for downloading the new DCDC model.

Note: It is still pending to include the characterization of several dynamic performances like the rise and the fall time, and some other parameters like the voltage levels in the output & input pinnes in all the situations. It is foreseen to include these parameters in the next issue of the model.

Improving convergence problems in the harmonic balance analysis

Convergence problems in harmonic balance analysis are a classic. I think every single human being involved in this stuff have struggled with them in many occasions. You will find plenty of technical papers talking about it. But most of them describe the issue in terms of the mathematical algorithm that is used to build the harmonic balance analysis in the CAD simulators. Not many of them help indeed to understand what can be done once the simulation has failed to converge.

Now, in a new entry in the section "Answering some Questions" it is available for downloading a brief studio regarding this problem, but focused in the case of QUCS Studio, using several examples of circuits and describing the problems that you will find when the convergence of the harmonic balance is an issue.

It is related to a question sent by email to the email address of this site.

Some Verilog AMS examples

Since this entry, some verilog AMS files examples are available in the site. (See the "Verilog AMS Files" menu) They are the following:
The first one, is a basic DCDC model. Similar to the one presented in the "SPICE and Models" menu of the site.
The second one is a voltage reference. This model allows to regulate positive values and also negatives ones. The test file is also included in the link for downloading.
The third one is a basic variagle gain amplifier. The test file is included also.

A few more FreeCAD models and similar stuff ...

They are already available several new models of component built in FreeCAD, in the FreeCAD electronic components section of this blog. This time, you will find the very common SOT23 package model along with its footprint, ready to be inserted in a new design. You will also find the SOC79 package, very common for diodes of many types, and the same than the SOT23 commented before, including the footprint.
In a separate FreeCAD file, you will find what can be considered as a portfolio of all the FreeCAD built packages included up to now in this blog.
Eventually, several different types of circuits are included to show what are the capabilities of FreeCAD as a high frequency  design tool.
Enjoy them !!!

FreeCAD 3D electronic component models available ...

High frequency circuits requires some level of accuracy in the designing phase. High frequency PCBs need to be designed taking into account the physical dimensions for each line included.

FreeCAD is a perfect solution for designing high frequency PCBs, but it needs 3D models of the electronic components used for these circuits.

In the section "FreeCAD electronic components", it can be found these 3D models, with other circuits designed and presented in this blog.

A DC-DC Converter model for QUCS Studio

The DC-DC converters are very common sub modules in many electronic systems. It is not a simple device so, in order to simulate in a complex electronic structure, it can be challenging to include every single component that comprise a DC-DC converter. It could be far more easy to consider all the DC-DC converter circuit as a single element in the simulation, and operate that way.

That is the idea beneath the DC-DC converter model that is presented in the document. You can access the model, and the document that presents the main features of it, in the "SPICE and Models" section.

How to design a L Band Oscillator with QUCS Studio and Free CAD

The same way that I described in a previous entry how to proceed to design a L band amplifier using as designing tool QUCS Studio, this time I will present a tutorial about designing a L band oscillator using the same environment. 

The most relevant part to make the difference compared to the previous mentioned tutorial is that, this time, non linear analysis are the essential part of the simulations.  

This time, in order to get an accurate analysis of the circuit response, another CAD tool is used to design the layout of the oscillator. This time, is Free CAD. The outcome is really cool. The 3D views of the circuit give to the design almost a professional touch.

The tutorial can be downloaded from here:

Designing a L Band Oscillator using QUCS Studio (Volume I)
Designing a L Band Oscillator using QUCS Studio (Volume II) 

And, as always in this site, if you find something wrong, something that you think could be easily improved, or something that you consider that would be interesting to add, please leave a comment in this entry or send an email to:

csc.rf.electronics@gmail.com

How to design a L Band amplifier with QUCS Studio

In this entry, it is presented the detailed process for designing a L Band amplifier using QUCS Studio.
The level of knowledge regarding QUCS Studio necessary to understand what is published in the file linked to this entry is almost none. In any case, if you start reading the file and you detect that you are lost, and you think that the problem is lack of knowledge of QUCS Studio, I recommend you to visit the Gunthard Kraus website and look for the tutorials that he published regarding the use of QUCS Studio.
This tutorials go from the basics of QUCS Studio, to really interesting stuff.

You can find them is this link:

Gunthard Kraus QUCS Studio tutorials

The files are also available in the QUCS Studio website, in the following link:

Tutorials from Gunthard Kraus in the QUCS Studio website

The tutorial can be consulted in the following link:

Design of a L Band Amplifier using QUCS Studio

And, as always in this site, if you find something wrong, something that you think could be easily improved, or something that you consider that would be interesting to add, please leave a comment in this entry or send an email to:

csc.rf.electronics@gmail.com

First time here ... Why another Blog? ... Was it necessary?

This is going to be the "Hello world" entry. I do not know if that is the right thing to do, but ... as far as I know, everybody do something like that. In any case I think It should be a little bit more useful than just that, so, I will take the opportunity to explain why another blog in the world.

The intention of this blog is to try to cooperate with those free software environments to analyze RF circuits that there are available. Some of them, at least, and a little.

What is the meaning of that? There are many people working really hard to offer to designers, beginners, experts and all kind of interested people, software to analyze and design electronic circuits.  They deserve all the credit, and all the support that they can find.

One of these people that are actively working in the same way that I pretend to do in this blog is Gunthard Kraus. Take a while and visit his website and you will see what I want to be when I grow up.

Gunthard Kraus website 

Even more important than sharing, the main idea underneath all of this is learning. There are many people that you can learn from, and, may be, I will be able to find some of them willing to share and even to correct if it is necessary the contents published in this blog.

My humble contribution is to share many years of experience designing RF circuits and other electronics but using as base their software. 

Most of the work that will be shown in this site, have been made using a couple of fantastic tools:

The first one. QUCS Studio. Really cool EDA tool, designed by Michael Margraf and a team that you should know.
The best way to learn about the project is to visit his web site and to download the latest version of QUCS Studio.

QUCS Studio website

The next one will be QUCS ... Yes QUCS ... Does it ring a bell? The story of why QUCS Studio and QUCS is complicated and it can be found if you look for it.
Sure it is better if you forget about sad tales and focus in using both programs and learning all you can from them.
QUCS, and a lot of information regarding the software and the people developing it, can be found here:

QUCS

Some other software, very interesting and well known indeed, that will be mentioned and used frequently will be:

Kicad EDA

GNU Octave

and

Free CAD 3D parametric modeler 

So, let's get start ..