October 2023: Project Launch!
October has come and gone, and along with it all the fruit on the vines, so my hopes for field measurements this fall will need to wait until 2024. Fortunately, I came prepared with a Plan B: laboratory observations to make over the winter.
Since the project funding arrived, I have started to assemble the components of the imaging system. To start, here is the newly-acqured LibreVNA:
This is open source hardware designed by Jan Käberich (https://github.com/jankae), an embedded hardware/software engineer based in Germany. While the design files are open source and the bill of materials are published on the GitHub repository, I decided to purchase a pre-built unit to get a quicker start on capturing data.
To complement the LibreVNA, I will also be using a software-defined radio (SDR) unit I had laying around, the Nuand BladeRF 2.0. This caught my attention a few years ago based on its specs: it is a 2-channel multiple-input, multiple-output (MIMO) transceiver, with a 47MHz to 6GHz frequency range, similar to the LibreVNA but with the added benefit of a robust software ecosystem in the form of GNURadio, an open source, Python/C++-based software development toolkit.
This turns out to be right in the sweet spot for our experiments in microwave imaging. In this case, a single BladeRF unit would use four antennas (two for transmit, two for receive), allowing us to capture data along two different axes at the same time. I will report on the performance of both approaches in the months ahead.
I plan to start capturing data in the lab on a custom-built platform that will let me evaluate different materials and different spatial configurations. For example, comparing solid- with hollow-core materials, or the characteristics of different types of fruit. I am looking to build on work by Dr. Grace Okiror and several others, and am also exploring the possibility of working with a local aquaponics operation to measure plant growth. I will report the notes for our initial build and more detailed technical and measurement methods in my next update. Thanks for following!
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