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regen_ExtractPreamble.vi

Module by: Ed Doering. E-mail the authorEdited By: Sam Shearman, Erik Luther, Brett Hern

Summary: Build a LabVIEW subVI to detect and extract the preamble from a baseband signal.

Table 1
LabVIEWtop.png This module refers to LabVIEW, a software development environment that features a graphical programming language. Please see the LabVIEW QuickStart Guide module for tutorials and documentation that will help you:
• Apply LabVIEW to Audio Signal Processing
• Get started with LabVIEW
• Obtain a fully-functional evaluation edition of LabVIEW

Note:

Visit LabVIEW Setup to learn how to adjust your own LabVIEW environment to match the settings used by the LabVIEW screencast video(s) in this module. Click the "Fullscreen" button at the lower right corner of the video player if the video does not fit properly within your browser window.

LabVIEW SubVI: regen_ExtractPreamble.vi

  • Description: Detect and extract the preamble from a baseband signal. A preset number of alternating 1s and 0s (also designated as marks and spaces) typically starts the preamble to "wake up" the receiver's carrier sync and bit sync subsystems. This subVI assumes the received signal is quiet (nominally zero) prior to the preamble.
  • Category: Bitstream regeneration ("regen" prefix)

Inputs (Controls)

  1. signal in -- waveform
  2. Tb [s] -- DBL
  3. bit intervals to skip (4) -- I32
  4. bit intervals to keep (32) -- I32
  5. threshold (0.1) -- DBL

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

Outputs (Indicators)

  1. preamble out -- waveform
  2. preamble detected? -- Boolean

Required Behavior

  • signal in is scanned from the beginning to detect when the signal amplitude exceeds threshold. If the input signal never exceeds the threshold, preamble out returns an empty waveform and preamble detected? returns F.
  • Once a valid threshold crossing is detected, preamble out extracts a portion of signal in of duration bit intervals to keep times the bit interval Tb; the extracted signal begins at the location of the first threshold crossing plus bit intervals to skip times the bit interval. The Boolean indicator preamble detected? is set to T.

LabVIEW Coding Tips

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

Refer to the Figure 1 screencast video for LabVIEW coding tips and techniques specific to this subVI.

Figure 1: [video] LabVIEW coding tips and techniques for regen_ExtractPreamble.vi
Figure 1 (subVI_regen_ExtractPreamble-vi.htm)

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Definition of a lens

Lenses

A lens is a custom view of the content in the repository. You can think of it as a fancy kind of list that will let you see content through the eyes of organizations and people you trust.

What is in a lens?

Lens makers point to materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

Who can create a lens?

Any individual member, a community, or a respected organization.

What are tags? tag icon

Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.

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My Favorites (?)

'My Favorites' is a special kind of lens which you can use to bookmark modules and collections. 'My Favorites' can only be seen by you, and collections saved in 'My Favorites' can remember the last module you were on. You need an account to use 'My Favorites'.

| A lens I own (?)

Definition of a lens

Lenses

A lens is a custom view of the content in the repository. You can think of it as a fancy kind of list that will let you see content through the eyes of organizations and people you trust.

What is in a lens?

Lens makers point to materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

Who can create a lens?

Any individual member, a community, or a respected organization.

What are tags? tag icon

Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.

| External bookmarks