pam_RaisedCosinePulse.vi

LabVIEW SubVI: pam_RaisedCosinePulse.vi

• Description: Create a raised cosine pulse shape suitable for a pulse amplitude modulation (PAM) transmitter.
• Category: Pulse amplitude modulation (PAM) ("pam" prefix)

Inputs (Controls)

1. Tb, bit interval (0.01) [s] -- DBL
2. alpha, excess bandwidth factor (0.5) -- DBL
3. N, bit intervals for support (4) -- DBL
4. fs, sampling frequency (1000) [Hz] -- DBL

Parentheses ( ) indicate default value; square brackets [ ] designate units.

Outputs (Indicators)

1. pulse shape -- 1-D DBL array

Required Behavior

• "pulse shape" is an array containing the raised cosine pulse shape defined by the equation p(t)=sinc(2B₀t)(

  cos(2παB0t)

  1−16(αB0t)2

   )
• B₀ = Nyquist bandwidth, the minimum possible transmit bandwidth achieved by a sinc pulse
• B₀=

  1

  2Tb

   , where Tb is the bit interval
• α = roll-off factor (also called excess bandwidth factor), 0≤α≤1 (alpha = 0 creates an unmodified sinc pulse, and alpha = 1 creates a fully damped sinc pulse with twice the Nyquist bandwidth).
• The "alpha" control value must be limited to the range 0 to 1 and be incrementable by steps of 0.1.

The raised cosine pulse shape is fundamental to digital communication systems. Its name derives from its frequency-domain shape. Refer to the Figure 1 screencast video to learn more about the raised cosine pulse.

Figure 1: [video] Explanation of raised cosine pulse

LabVIEW Coding Tips

View the screencast video in Create a SubVI in LabVIEW to learn the mechanics of subVIs.

Refer to the Figure 2 screencast video for LabVIEW coding tips and techniques specific to this subVI.

Figure 2: [video] LabVIEW coding tips and techniques for pam_RaisedCosinePulse.vi

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