Friday, August 13, 2010

progress with octave model

Greetings MEP!

Due to a block of uninterrupted time, I managed to hack and slash my way through beginnersville in Octave. I conquered plotting today. Right now, I have an RF and an LO signal attractively plotted in a png (attached). 

The goal is to model the five-port device in Octave, then build it in VHDL. If  you have MATLAB, you should be able to load up the Octave model (attached as well)

If you are wondering what a five-port device is, please know you are not alone. If you have access to IEEE Communications June 2010 issue, then there is an article in there that describes them, including some built and tested examples. 

Here's a snippet from an optical article in wikipedia that refers to the superset of the five-port, which is named six-port. In the IEEE article, the sixth port is described by a dependent equation if you assume that you know the local oscillator power. Since the designer should know this, the design can be simplified down to a five port device. Five ports is as simple as you can get, and has almost all the performance of a six port device. 

"In principle, the six-port device consists of linear dividers and combiners
interconnected in such a way that four different vectorial additions of a
reference signal (LO) and the signal to be detected are obtained. The levels of
the four output signals are detected by balanced receivers. By applying suitable
base-band signal processing algorithms, the amplitude and phase of the unknown
signal can be determined."

I asked the author of the article for the design files used, and hope to hear a response. Having gerbers of a working five-port device that just happens to work on our bands would be a big step forward for this line of research. 

If you've worked on, with, or near six/five port devices, I'd love to hear about it. 

More soon!
 -Michelle W5NYV

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