GENERATE Version 1.0
 1996 G.V.Associates Inc.

If you continue to use this program please send a license fee of (US)$15.00 to:

G.V.Associates Inc.
2440 Hamline Ave.
St. Paul, MN.  55113
U.S.A.

Thank you for your support of further development.

The program is designed to provide great flexability in the generation of audio frequency signals using the output of your Sound Card.  The minimum computer is a 486/66 with a sound card supporting a sample rate of 44100 samples per second.

The Control Panel for the program contains three identical panels which define the waveform characteristics for three generator sequences. Within each of the panels is a control that allows you to select the duration of each sequence.  If "Continuous" is selected, the program will not move on beyond the selected sequence.  The other choices specify the Time in milliseconds or the number of Modulation Cycles that the program will remain in this sequence before moving to the next sequece.

Two "Slider Controls" are present which control the level of noise added to the signal and the overall output level from the sound card.  The program reads the volume level at the start of the program and resets that volume when you leave the program. Since the sound card is used with other programs, this prevents any changes you make from altering the preferred settings in the sound card mixer.  The Output level control sets the peak to peak total output from the program. This includes both the audio signal and any noise that is added.  Therefore, as noise is injected, the signal level is reduced to keep the total peak to peak output level nearly constant.  The Noise control sets the percent noise in the composite output. If the noise is set to 50%, the signal to noise ratio will be 1. When the noise is set to 100% the signal will become zero.  Because the program is about 2 seconds ahead of the sound card's output, changing the noise setting will not alter the actual output until 2 seconds has elapsed.

Near the bottom right of the Control Panel you will find the "Loop" controls.  If "No Loop" is selected, the output will stop after the third sequence.  Alternatives are provided which cause the program to continuously loop back to sequence 1, thereby continuously repeating the whole process.  Another alternative causes the program to loop back to repeat only sequence 2 and 3.  Of course, if any of the sequences is has "Continuous" duration selected, the looping process will never occur.

PRIMARY FREQUENCY SELECTION:
Within each sequence panel is a primary frequency setting which can be between 0 and 15000 Hz. The zero number is a very special case which will be discussed later.  In general you will want this frequency to be within the pass band of the sound card.  The sound card's low frequency response must be considered. If the modulation is not enabled, the resulting output from this sequence will be a sine wave at the frequency selected.

MODULATION SELECTION:
When modulation is enabled the output waveforms can become quite complex. Normally the modulation frequency will be set to much less than the primary (carrier) frequency.  The waveform of the modulation can be either sine, triangle, sweep, or square wave. If "Invert" is not selected, the sine wave, triangle, and square wave will start by going positive.  The sweep will start with a positive slope from a "most negative" value.	If "Invert" is selected, the starting polarities are reversed. A 50% plus selection for the square wave results in equal positive and negative durations. A 10 percent setting will result in the modulation starting with positive value for 10 percent of the cycle followed by a negative value for the remaining 90 percent of the cycle.  "Invert" would cause this example to start as 10% negative followed by 90% positive.

	FM Modulation:
	If this mode is selected, the modulation waveform (above) will cause the primary frequency to change by the amount set by the "Deviation" setting. Note that this is the peak deviation so the actual frequency will vary by this amount above and below the primary frequency.

	DSB Modulation:
	This mode (Double Side Band) actually takes the mathematical product of the modulation and the primary frequency contents to determine the output.  If the "Carrier" is set to 100 percent, the result will be a 100 percent modulation AM signal. The setting for the percent carrier is defined here as the ratio of the carrier amplitude to the peak amplitude of the modulation content. Therefore, if a 300 percent carrier is selected, the carrier will be equal to 75% of the signal amplitude while the modulation will swing between 50% and 100% ( plus and minus 1/3 of the carrier).

SPECIAL CONDITIONS (IT'S JUST MATH)
The only restrictions on the fidelity of the output waveform is the frequency limitations of the sound card.  At the low end, the amplitude will fall off and major shifts in phase will occur.  Sound card filtering and the limitations of the 44100 Hz sample frequency will influence the fidelity of rapidly rising waveforms.

With this in mind, it is possible to select zero for the primary frequency and have the output waveform be determined totally by the DSB modulation .  This will allow you to generate a triangular waveform.  Frequency limitations make the generation of square waves or sweep waveforms rather impractical. 

Again, using the DSB selection, the modulation frequency need not be less than the primary frequency.  If both are sine waves, and the carrier is set to zero, the modulation and primary frequencies are interchangeable. By selecting a triangle modulation waveform, and exchanging the modulation and primary frequencies, you can generate a triangle waveform modulated by a sine wave.

   


 