Results
Desired Device Specs | Our initial design specifications were as follows
- Minimum discernible signal less than 1 uV
- Image rejection over 48 kHz of band greater than 30 dB
- Tunable range of frequencies greater than 48 kHz
- Band frequency greater than 540 kHz
- Spurious signals below 10 uV
Achieved Device Specs | Our Results
- Minimum discernible signal determination - input signal of 500uV from digilent analog discovery II then attenuated by 60dB. So that we have a minimum discernable signal of 10^(-60/20)*0.0005 = 0.0000005 = 0.5uV
- Image rejection of a little over 30dB ~ 32dB. But we can adjust it in quisk so that the image is essentially entirely gone.
- Currently, the tunable range of frequencies is from 500kHz to 4MHz
- An our band frequency is indeed greater than 540kHz with most spurious signal (if not all) below 10uV
This image illustrates the image rejection capabilities of our radio. The delta signal/function on the right with the greater intensity is the desired signal, and the delta function on the left is the image we wish to remove.
A video of the radio working to look at actual AM frequencies is located here. I used a 19-inch magnetic mount (kindly supplied by my dad for this project) as the antenna to listen to the signals. Since I was located in a sort of valley surrounded by nearby hills, I believe the surroundings were hindering the strength of the received signals and thus they sounded a bit garbled. But they can clearly be identified as artificial - or human produced - signals.
What We Learned | It's not just about radios
Since the primary objective of the project was to serve as a learning opportunity for how to approach an electronics project, I believe we were able to attain that goal. In particular, we learned that datasheets are invaluable resources and that detailed bring-up procedures are crucial to eliminating haphazard errors. We also learned how to approach a problem from an engineering perspective. We were able to take provided design specifications and apply our knowledge of electronics, mathematics, and computers to create a design and prototype to verify that we met the desired specifications. We also have gained a large base knowledge of electronics and how they play a role in radio communication. A next step would be to study for and take the HAM radio test since the knowledge we learned in class heavily overlaps with the technical questions asked on the test. Lastly, we learned to have patience and perseverance when implementing a project. Things are bound to go wrong, and the best approach to the situation is to have a positive attitude that accepts that even when a project fails, the important part is that you learn something in the process.
Future Work | the sky is the limit
- edit quisk python code to be able to automatically select bandpass filters based on frequency (should be relatively simple to implement - unless we find a bug in the FST3253 multiplexer that was unnoticed before)
- noise analysis simulation followed by investigation of noise in the built circuit and the easiest ways to reduce the noise so that we can have a clearer signal come through
- Find components less expensive than the op-amps for small circuits such as creating the analog grounds, etc (minimizing cost of the project)
- construction of a case for the circuit board for a more polished look
- Investigate alternatives for our local oscillator that will allow us to listen to FM frequencies
- addition of a transmitter design that can work together with the receiver
page created by jordyn watkins | greenjacketgirl