= Plant Doctor: Harnessing Backscatter Radio Sensors for Agriculture =
**WINLAB Summer Internship 2024**\\
**Group Members:** Sam-Fone Cheung, Shriya Das, Aly Mustafa, Xiang Meng\\
**Advisor:** Aggelos Bletsas


== Project Objective 
Backscatter radio, or reflection radio, offers a low-cost and low-power alternative to conventional radio sensor networks. This is crucial for modern agriculture which requires continual monitoring of environmental conditions such as soil moisture or temperature. Prior research using capacitance sensors to measure soil moisture has shown promising results using backscatter radio, despite the limited range.

Our group expanded this work to use temperature sensors on a plants which will transmit information using a network of RFID (radio frequency identification) tags. These sensors should be battery-less and low-cost as they will harvest ambient radio frequency (RF) energy. 

Over the summer, our team split into two groups to build the transmitter and receiver, ultimately converging. 


== Weekly Progress
==== WEEK ONE ====
[https://docs.google.com/presentation/d/176HsRDAxeJxmf1tP5aNRFMfCJ6p95QO6EIxRgzuDiPA/edit?usp=share_link Weekly Presentation]\\

Receiver: Read prior art about [https://ieeexplore.ieee.org/document/8454387 backscatter radio], RFID tags, and [https://ieeexplore.ieee.org/document/8454387 capacitance sensors]. 
Transmitter: Started learning the TI Launchpad microcontroller, read the documentation, and spoke to Dr. Rich Howard.||


==== WEEK TWO ====
[https://docs.google.com/presentation/d/1bY_nNpxIUeusqLehttZEXWjmkHdcylSNkebI1xsyuZM/edit?usp=sharing Weekly Presentation]\\

Receiver: Used RTL-SDR's to explore software-defined radios (SDR) and tune into local FM stations. \\Also familiarized ourselves with [https://www.gnuradio.org GNURadio] and its tutorials.
Transmitter: Learned how to use TI Launchpad MCU MSP-EXP430G2ET. \\Implemented an adjustable 200kHz-300kHz 50% duty cycle square wave output. Also implemented user input through digital input using the I/O pins. \\Attempted potentiometer user input, but did not successfully complete it. ||


==== WEEK THREE ====
[https://docs.google.com/presentation/d/15bAzRQfZHG3FM4fyjsaUbeUBmcJpEHqheeM7rIhx3_g/edit?usp=sharing Weekly Presentation]\\

//Progress: //Continued using GNURadio to implement [https://wiki.gnuradio.org/index.php?title=Simulation_example:_FSK frequency shift keying (FSK)] and [https://www.mathworks.com/help/signal/ref/periodogram.html periodograms] (maximum likelihood estimators). We also used MATLAB/Octave to compare our results from GNURadio using the SDR.
[[Image(unnamed.png, align=center)]]


==== WEEK FOUR ====
[https://docs.google.com/presentation/d/1tVhHWkjkA914yFxDjfUT3V-OctOSd3-dtMAMtxsk6sg/edit?usp=sharing Weekly Presentation]\\

//Progress: //Explored the accuracy of the receiver while changing the power transmission, frequency, and distance between the SDR and signal generator. Learned about matched filters and how to [https://www.telecom.tuc.gr/~aggelos/files/TCOM2014.pdf implement them into the receiver]. Despite a frequency measurement error, we implemented logging into GNURadio using a file sink.  

\\Using the TI Launchpad Microcontroller we were able to implement FSK. also created a block diagram to illustrate how both the transmitter and receiver should work together to send information about a plant's temperature.\\
[[Image(unnamed.2.png, 520px, align=center)]]


==== WEEK FIVE ====
[https://docs.google.com/presentation/d/1IVHxp37dLoeeXByd_AVcU_r4t5fZpaF5VpObRvP3WJ0/edit?usp=share_link Weekly Presentation]\\

//Progress: //This week, we received three different kinds of thermistors. We were able to implement a backscattered signal that encoded the information from the ADC (using a potentiometer). We are now investigating ways of measuring values from the thermistors, mainly considering a Wheatstone bridge.


==== WEEK SIX ====
[https://docs.google.com/presentation/d/1IVHxp37dLoeeXByd_AVcU_r4t5fZpaF5VpObRvP3WJ0/edit?usp=sharing Weekly Presentation]\\

//Progress: //We moved the bench to on top of an antistatic mat. We also implemented twisted pair cables and an external DC power supply. All of these changes were made to get cleaner signals and avoid accidental antennas. We also made major progress on our work, being able to measure voltage across a Wheatstone bridge (see below) and encode it as a backscattered signal between 100kHz and 200kHz.
[[Image(wheatstone.png, 300px, align=center)]]