DACS App Note

Pulse Stream Object Description (#6)

A Pulse Stream Object is added to the sound model for each simultaneous threat source audio stream to be played in the headset. Interface parameters include the following:

Pulse Type

The pulse type is a 1 byte integer value which defines the pulse stream frequency modulation type:

  • 1: steady
  • 2: sine
  • 3: triangle
  • 4: sawtooth
  • 5: square
  • 6 - 8: steady
  • 9: external
  • 10 - 100: steady
  • 101: dwell1
  • 102 - 150: dwell2 - dwell50
  • 151: random dwell1
  • 152 - 198 random dwell48
  • 199: random dwell
  • 200: stagger1
  • 201: stagger1
  • 202 - 208: stagger2 - stagger8
  • 209 - 219: stagger8
  • 220 - 255: steady

Steady refers to a steady pulse train with no frequency modulation; requires PRI, Pulse Width values.

Sine refers to a steady pulse train with sinusoidal frequency modulation; requires Base PRI value, Pulse Width, Modulation Frequency, and Modulation Depth.

Triangle, Sawtooth, Square refers to a steady pulse train with the indicated frequency modulation; requires PRI, Pulse Width, Modulation Frequency, and Modulation Depth.

External refers to a steady pulse train with a frequency modulation input from another signal object in the sound model (a connection for the signal is located in the Pulse Stream Object); requires Base PRI value, Pulse Width.

Dwell1 thru Dwell50 refers to a step and dwell frequency modulation with the number of steps equal to 1 plus the number indicated (e.g. dwell3 has 4 total steps); PRI values for each step are determined by the modulation depth and the number of steps with values increasing as time passes; requires Base PRI, Pulse Width, Modulation Depth, and Dwell Time.

Random Dwell1 thru Random Dwell48 also refers to a step and dwell frequency modulation with the number of steps equal to 1 plus the number indicated (e.g. dwell3 has 4 total steps); PRI values for each step are determined randomly within the envelope defined by the modulation depth; requires PRI, Pulse Width, Modulation Depth, and Dwell Time.

Random Dwell provides a truly random step and dwell sequence; requires Base PRI value, Pulse Width, Modulation Depth, and Dwell Time.

Stagger1 thru Stagger8 refers to a stagger frequency modulation with the number of stagger frequencies equal to the number indicated (e.g. stagger3 has 3 stagger PRIs); PRI values for each stagger frequency are determined by the value supplied; requires Base PRI value (effectively stagger1 PRI), additional stagger PRI values as required, and Pulse Width.

Pulse Width
Defines the pulse width in microseconds (smallest pulse width resolution is determined by the iteration rate of the DSP)

Main PRI
Defines the PRI of the pulse stream in microseconds. For frequency modulation with multiple PRIs such as stagger modulation, this defines the first PRI of the sequence.

Stagger PRI2 - PRI6
Defines the second through sixth PRI values for a stagger modulated pulse stream in microseconds.

PRI Modulation Signal
A connection point is available for using an external signal to frequency modulate the pulse stream. An external signal can be a recorded sequence or some other signal generated from within the sound model.

PRI Modulation Frequency
Defines the modulation frequency of the pulse stream in Hertz.

PRI Modulation Depth
Defines the modulation depth of the pulse stream frequency modulation based on the PRI value. Input values are from 0.0 - 1.0 with 0.0 meaning no modulation and 1.0 meaning full modulation. Example: The PRI is set to 800Hz. The Pulse Type is 2 (sinusoid frequency modulation). A PRI modulation depth value of 0.1 will cause the Pulse Stream to modulate between a PRI value of 720 and 880. A value of 1.0 would cause modulation between 1600 and 0. Use this field to define the upper and lower limits of the frequency modulation.

Dwell Time
Defines the duration of the dwell period in seconds for step and dwell modulation.

Gain Modulation Signal
A connection point is available for using an external signal to amplitude modulate the pulse stream. An external signal can be a recorded sequence or some other signal generated from within the sound model.

Gain
A connection point is available for gain control of the pulse stream audio. This is a useful connection point for the RWR volume control, signal strength, or amplitude modulation via the host computer.

General Notes

The Pulse Stream Object can also be connected to a radio transmitter within the model and then received by a simulated RWR receiver. In this way ranging effects, background noise, signal strength can all be modeled easily.

Please note that the interface and functionality of this object are continually being updated. If you have a need for additional features for your specific simulation application please contact ASTi.