Dr. Driessen testing the prototype PCB
Dr. Driessen testing the prototype PCB

Over the past 7 months, our group has been designing, implementing and testing a multiple input AM modulator. This project was commissioned by Dr. Peter Driessen as part of a computer music research project.

The project was an exercise in both circuit design and communication theory. Careful planning and calculation were required in designing second-order Butterworth filters for inputs, several low-pass filters in each channel to decrease the signal to noise ratio, amplifiers, carrier frequency generators and AM modulation circuitry.

The 8-channeled circuit board was designed by our group using Protel 99SE and was manufactured locally in Victoria. Components were purchased from various local and US suppliers. All subsequent manufacturing and testing were carried out by the group.

The 'Radio Drum' was used as the input device, supplying eight analog DC signals. The eight analog DC inputs are modulated by independent carrier channels. The modulated signals were combined through a summing circuit. Un-modulated forms of the carriers were also summed for output. The two signals are then sent, through the left and right channels of a standard 3.5mm audio jack, to an audio input jack of a computer's soundcard.

©2003 JOBE