Preliminary Design

The note that we were assigned to filter was the note A with a frequency of 110 Hz. Therefore, our designed filter had to accept only this note and not the notes E (82.41 Hz) and D (146.83Hz). In addition, our filter likely needed to allow a little leeway around the 110Hz mark since the given guitar would likely not be perfectly in tune.

Initially, some research was conducted in order to find a more efficient band pass filter design than the basic two stage RC one explored in lab (EE 222). We found the following article provided from Texas Instruments that proved very helpful:

From this document, the following narrow band pass filter was designed for a frequency of 110Hz. The steps for the design are laid out clearly in the document linked above. Experimentation with this circuit would be necessary in order to determine if it fit our purpose and if it performed better than the two stage RC filter explored in lab. It is also possible that the filter would need to be repeated in order to get a good enough final filter quality for our purpose (excluding the adjacent notes).

To summarize the design process, the frequency of our calculations was set to 110 Hz. The capacitor values were then set to a common value such that the resistor values (which were tied directly to these values) would be reasonable given the resistors we currently had. This was accomplished with capacitors of 47nF each, making the largest resistor ~600k ohms. The final designed circuit is below.

Screenshot 2017-04-10 at 8.10.13 PM




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