Milestone 4
Optimization
Upon receiving our radar PCB we set about to test its effectiveness and make sure that all of the electrical components were working correctly. Our sample test set up for the board can be found in the video below:
The oscilloscope is connected to test pins after our mixing and amplification stage. The associated waveform on the oscilloscope tells us that the PCB was manufactured correctly and that all of the electrical components seem to be working as intended. However, there seems to be several key issues with this waveform. For one, it seems that the waveform is clipping which is a problem as we lose on potential data points. The figure below shows some of the typical clipping which we observed:
After some research we discovered the root of the problem. Our amplification stage uses an amplifier which is being supplied 3.3V but also has an output voltage swing from rail of 1.3V. Essentially what this means is that the amplifier can never really amplify signals past 3.3V - 1.3V = 2.0V. Since we are also biasing around 1.8V this leaves us with millivolts of data that we can send to the ADC and then take the FFT of. Fortunately all of our chips can take both 3.3V as well as 5.0V which we also have access to on the board. By supplying 5.0V to both power planes we can increase our range before we actually begin to clip which partly solves our issue.
The antennas which we first tested with are also omnidirectional which is not great for detection purposes and can generate a lot of noise in and around the receiver. We decided to test with more directional antennas which can be seen below which garnered significantly better directional results:
White directional antenna can be found on the left compared to the omnidirectional patch antennas which can be seen on the right.
Delivery
Design Block Diagram:
Bare PCB:
Assembled PCB:
Portable Radar System (Battery Pack, Voltage Supply, STM Boards, PCB, Antennas):
Oscilloscope Demo:
Real-Time Spectrogram:
management
Overall management of the project was very successful. We stuck to our schedule and worked diligently to achieve our objectives and progress through the design, fabrication, and implementation of our project. The biggest delay came during the manufacturing process for the PCB which took significantly longer than expected largely due to manufacturing constraints and the different steps we needed to find an appropriate quote and supply them with the materials necessary to build our board. Despite this we worked well in our team and adjusted accordingly to deliver our final project.