Dielectric characterization by microwave cavity perturbation

A custom toolbox and example code to measure complex permittivity by microwave cavity perturbation

Please don't hesitate to email me if you have questions: nathan(dot)orloff(at)gmail.com.
Description of the purpose
This software package was developed to analyze microwave cavity perturbation data in order to determine material dielectric properties. Example software is provided to assist with data acquisition and organization. Specifically, it is de-signed to be used when measurements of the cavity response are made as a function of the degree of sample insertion into a microwave cavity.

Description of algorithms
cavity_analysis_toolbox is a MATLAB toolbox that contains a function to extract the complex permittivity.

cavity_measurement_toolbox is a MATLAB toolbox that contains example in-strument control functions to acquire data.

Statement of program tests
cavity_dataacquisition.m is example data acquisition code that acquires and or-ganizes the partial insertion data of the sample holder and sample.
cavity_exampleanalysis.m is example data analysis code used to process the acquired data following the data organization in cavity_dataacquisition.m.
cavity_exampledata.mat is a MATLAB data file that contains example data that can be loaded into cavity_exampleanalysis.m and processed. The test data is on quartz and yields a dielectric constant of 3.78 at 7.3 GHz.

Here is a link to the paper:
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=6862934&sortType%3Ddesc_p_Publication_Year%26queryText%3Dorloff

The code is written to be stepped through, rather than executed as a script.
To do this:
1) Download and unzip cavity_analysis_tollbox
2) Add the toolbox to your list of declared functions.
a. file>set path>add folder (or add with subfolders)> choose “cavity_analysis_toolbox”>save>close
3) Open cavity_exampleanalysis.m
4) Read through this m file.
a. It is annotated to let you know what to change.
b. Use the “Run and advance” Button in your matlab interface to step through the code, which is written in cell notation.
c. Once you change line 55 to your directory. It should do everything you need to.

The data is stored in cell arrays. “Sall” is a concatenation of all of the S-parameter data (Freq, S11, real,….,S22,imag). It is 9 columns by 401 points. Each of these S-parameter are stored in a cell. The column specifies the sample. The row specifies the insertion. If you use the variable editor it should be clear what you are looking at.

Once you step through the analysis, it will produce a structure. Like in c, which uses object, a structure has different fields specified by “.” You can toggle through the different fields by pressing “tab”.

Below is the structure tree. You can use the variable editor to navigate to any of the computed properties. All steps are record in the structure. My email client capitalized some of the letters in a strange way. To navigate to the real part of the permittivity, you would write “data.permittivity.reps” after running the code.