Extracting the lumped elements model for the SMA connector in QUCS Studio

 

Many times, after a thorough and, some times, exhausting design process staring the simulator in the computer, it happens that the results obtained in the laboratory from the first bread boards manufactured are rather far from the theoretical analysis.

Almost of all the times, this miscorrelation of the results compared to the simulations are due to lack of accuracy in the models used.

One of the most significant details normally underestimated by the designers is the effect of connectors used for testing the PCBs.

SMA connectors are one of the most used connectors type in RF designs, because of the quality and its, general speaking, low cost.

But they are not transparent to the actual measurements once the are introduced in the testing PCB.

The effect is clear, even when the most simple structures are remarkable. In the present document it is presented a simple method to obtain the electrical model for SMA connectors that can improve the results of the circuits design.

Extracting the lumped elements model for the SMA connector in QUCS Studio

Simple way of getting S2P file from a simulation in QUCS Studio

 

The scattering parameters file is one of the most useful information the designer can handle, once it is involved in the analysis of a new RF circuit working in the small signal domain.

Normally the scattering parameter file is part of the inputs used for designing, but it is common to face the necessity of extracting S2P file for an intermediate simulation, to be later used in a following step of the design.

By the time of the publication of this document, QUCS Studio offers the option of exporting in a CSV file type one trace plotted in a diagram as a result of one simulation.

It is important to take note that the information contained in the CSV file is just the trace selected in the diagram. So, in order to get the 8 traces that compose the whole information archived in the S2P file as it is defined, this process should be repeated eight times.

In the document linked in this entry, it is presented a quite simple way of getting the whole S2P into one file in one single time. It is based on the usage of the OCTAVE capabilities included as nominal in QUCS Studio.

Simple way of getting S2P parameter file in QUCS Studio

OCTAVE Functions for Basic Signal Processing (II)

 

In the following entry of the blog, another OCTAVE function is included to the set published previously in this blog. In this case is the Root raised consine filter function, which allows to simulate one of the most used filter for pulse shaping purposes used in digital communications.

The filter is described in terms of its time equations, according to the following expression published by NASA:

"Root Raised Cosine Filters & Pulse Shaping in Communication Systems" by Erkin Cubukcu.

A brief description of the function performances is summarized in the document that is accessible in the following link:

OCTAVE Functions for Basic Signal Processing (II)

The files referred in the document can be downloaded in the following link:

OCTAVE Functions for Basic Signal Processing (II) FILES