Matchable Loads from S-Parameters Defined Matching Networks

This post compares two different ways for finding the matchable loads \(Z_L^{'}\) that provide the desired impedance \(Z_G^{*}\) to the generator.

I will show the difference between two approaches, one rigorous and the other approximate, by using a set of S-parameters obtained by a black box network. The only requirement is that the black-box is linear, as the S-parameters requires linearity. For the curious, they are obtained from a binary weighted sweep of a lossy \(LL\) network composed of 1024 states in total from SimSmith.

STM32CubeIDE programmer and ST-LINK GDB server on Linux

This article discusses how to create a minimal set-up for running a gdb server on Linux using ST tools.

ST provides the STM32CubeIDE, which is an IDE based on Eclipse and designed to include the entire STM32 workflow. I am not super fan of all this super complex and bloated IDEs, as they tend force a fixed development strategy on the user. I therefore tried to look for alternatives.

Tandem Directional Coupler: Circuit Theory Approach

This document discusses the analysis of an ideal “tandem” directional coupler using lumped element circuit theory.

A directional coupler is a four port device that is used to sample the forward and reflected wave in a transmission line. It is a key component of a VNA and can be used to measure power flowing in a transmission line, but it can have countless possible uses. Generally they are built using distributed elements structures, but there are also versions built using lumped elements.

The tandem directional coupler, or also tandem bridge, is one of those directional couplers that is built using a lumped element approach. This kind of directional coupler, famous for radio-hams, has inherently large bandwidth and can handle a lot of power. It is also well suited for low frequency scenarios, down to the kHz range. It is composed of two current transformers, or two transformers with a high turn ratio, and two termination resistors with the desired characteristic impedance \(Z_0\), which can be arbitrary but usually 50\(\Omega\).

Coupled coils and coupling coefficient: from fraction of total flux to inductance definition

It is possible to relate the coupling coefficient \(k\) to both the total (\(\phi_{1}\) or \(\phi_{2}\)) and shared flux (\(\phi_{12}\) or \(\phi_{21}\)) or to the self (\(L_{1}\) and \(L_{2}\)) and mutual (\(M\)) inductances: \[ k = \frac{M}{\sqrt{L_{1} L_{2}}} = \frac{\phi_{12}}{\phi_{1}} = \frac{\phi_{21}}{\phi_{2}} \]

Simple proof:

Appunti Laurea Magistrale e Triennale, Ingegneria Elettronica, Università di Bologna, Cesena

A volte le vacanze natalizie sono utili per riordinare un po’ e così, per liberare spazio, ho deciso di digitalizzare gli appunti. In realtà solo quelli più decenti, quindi non sono tutti i corsi ma solo alcuni.

Meglio sempre prendere il contenuto con senso critico, non dovrebbero esserci errori, ma nel caso lasciare un commento 🤓. Se pensate vi siano stati utili, accetto ben volentieri una birra! 🍻

Load- and Position-Independent Moving MHz WPT System Based on GaN-Distributed Current Sources

This paper describes the modelling, analysis, and design of a complete (dc-to-dc) inductive wireless power transfer (WPT) system for industrial moving applications. The system operates at 6.78 MHz and delivers up to 150 W to a load moving along a linear path, providing a quasi-constant dc output voltage and maintaining a zero voltage switching operation, regardless of position and load, without any retuning or feedback.

The inductive link consists of an array of stationary transmitting coils and a moving receiving coil whose length is optimized to achieve a constant coupling coefficient along the path. Each Tx coil is individually driven by a constant amplitude and phase sinusoidal current that is generated from a GaN-based coupled load-independent Class EF inverter. Two adjacent transmitters are activated at a given time depending on the receiver’s position; this effectively creates a virtual series connection between the two transmitting coils. The Rx coil is connected to a passive Class E rectifier that is designed to maintain a constant dc output voltage independent of its load and position.

Extensive experimental results are presented to show the performance over different loading conditions and positions. A peak dc-to-dc efficiency of 80% is achieved at 100 W of dc output power and a dc output voltage variation of less than 5% is measured over a load range from 30 to 500 Ω.

The work in this paper is foreseen as a design solution for a high-efficient, maintenance-free, and reliable WPT system for powering sliders and mass movers in industrial automation plants.

This paper is published with Open Access on IEEE Xplore:

A. Pacini, A. Costanzo, S. Aldhaher and P. D. Mitcheson, “Load- and Position-Independent Moving MHz WPT System Based on GaN-Distributed Current Sources,” in IEEE Transactions on Microwave Theory and Techniques, vol. PP, no. 99, pp. 1-10. doi: 10.1109/TMTT.2017.2768031

PhD Tutorial: Position and Load Independent DC to DC Wireless Power Transfer System for Moving Applications

In order to pass to the third year of the PhD at the University of Bologna, it is required to give a 40 minutes presentation to first introduce your field, in the form of a tutorial, and then briefly show your research.

The presentation is organized as follows

• Tutorial
  • Introduction to Wireless Power Transfer (WPT)
  • Inductive Power Transfer (IPT)
  • Class E Resonant Inverter
  • Advantages of Wide Bandgap Semiconductors (WBG)
• Research Contribution
  • Geometry Optimization of Sliding Inductive Links for Position-Independent Wireless Power Transfer
  • Design of a Position-Independent End-to-End Inductive WPT Link for Industrial Dynamic Systems

Introduction to Wide BandGap Semiconductors and Class E rectifier

As an assignment to achieve the PhD credits for the Summer School of Information Engineering, it was requested to write a short report. This is a very simple introduction to Wide BandGap Semiconductors and Class E rectifier.

International Morse Code

This is a nerdy post, just to share a cheat-sheet which contains the International Morse Code along with the NATO Phonetic alphabet. I created this, using various resources online, just to lose some time…

Import a RF design (and logos) from svg, png or Gerber files into Kicad

KiCad is a wonderful software for PCB designing, it is open-source and can handle the complete workflow from the schematic to the final layout.

Unfortunately, it is not (yet) intended for RF circuit and antenna design. In these cases, a suitable program should be used, which could be ADS, CST, HFSS, or others. These are expensive but, unfortunately, the open-source tools are still not complete enough. I generally use multiple open-source tools depending of the requirements and quite often compare the results to evaluate the correctness.

Long story short, I was facing with the need to create a PCB by incorporating some custom Inductive Power Transfer coils, which I could export to a Gerber file from CST and some patch antennas and matching circuits, from ADS. The idea was to import the different parts from the Gerbers into different footprints, which are then assigned to schematics blocks and placed on the PCB.

There are no ways (yet) to get it simply by using some pre-baked functions, but some tricks are needed.

This post is a walk-through different options that can be used. I try to compare the options and outline the strengths of each one.

Notice that the same methods can be used to produce custom logos or any custom shape.

Theory of Information - Matlab Code Snippets

That is a collection of some snippets in Octave (Matlab) I created during the course "[TIC] TEORIA DELL'INFORMAZIONE E CODICI LM" for the MS in Electronic and Telecommunication Engineering.

As always, they are open-sourced on GitHub, so any suggestion is welcomed. The best way is by fork & pull.

Appunti del corso "Equazioni Differenziali LM"

Durante il corso di "Equazioni Differenziali LM" nell'ambito del corso di laurea in "Ingegneria Elettronica e Telecomunicazioni per lo Sviluppo Sostenibile" ho scritto una versione \( LaTeX \) degli appunti e delle dispense fornite dal docente Prof. Massimo Cicognani.
Sono disponibili su GitHub.
Nel caso si trovassero errori o typos vari, la cosa migliore sarebbe fare una fork del repository, fare i fix vari e pull request a seguire. Per i meno scaltri, anche aprire una issue potrebbe essere sufficiente e provvederò successivamente io al fix.