We successfully designed, fabricated, and tested our PCB. In the process we learned gained invaluable knowledge about PCBs, ICs, testing, and designing in general. Unfortunately, we did not have ample time to fully test and characterize the device. Therefore, we can only present our current analog and digital (see digital section) progress. For an in-depth analysis of the SNR and ENOBs of the system, see the final report.
Attenuation and Frequency Response
Oscilloscope screen captures show a test input to the system of approximately 216mV at 20KHz. After the input attenuation stage we were seeing only an attenuation of 16.6dB. This is not to our original specifications. By the time the signal has reached the VGA input, the attenuation has increased to 20.92dB. With the 10x attenuation seen at the VGA, our maximum input signal to the BNC without superseding our VGA’s max input level is 2.5V. To test the upper bandwidth specification for our system, we put in a 1MHz sine wave with 1V amplitude. At the input to the VGA, we were seeing an attenuation of 28.9dB. This shows that signal frequencies at the upper end of our bandwidth see a much greater attenuation factor. While we suspect that the power supply filtering is not adequate at high frequencies, more testing is required to prove this claim.
Operationally, as of April 28th, most aspects of the system are working. All of the user
inputs work, the video output appears to be clear, and configuring the FPGA is not a problem.
Our system can reliably put a waveform on the screen. However, as we’ve seen through
preliminary testing, our final output on the screen will have some error based on the large
amount of noise in the front-end and the non-uniform attenuation across our frequency range of interest. More testing will be required to get a better idea of our system’s overall performance.
Despite the fact the course will has ended, both of us will continue to work on this project purely for the academic and intellectual stimulation it provides. After all, you should never stop trying to improve. This design has made both of us become much better hardware engineers and helped secure us multiple interviews with companies like SpaceX (Alan) and The Spaceship Company (Neil).