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    By: Sam ShearmanAs a part of collections:"SubVI Specifications for "Communication Systems Projects with LabVIEW"", "Communication Systems Projects with LabVIEW"

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bpm_ProductModulator.vi

Module by: Ed Doering

Summary: Build a LabVIEW subVI to modulate a baseband signal by a sinusoidal carrier wave.

Note: Your browser may not currently support MathML. See our browser support page for additional details. You can always view the correct math in the PDF version.

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: bpm_ProductModulator.vi

  • Description: Modulate a baseband signal by a sinusoidal carrier wave that has unit energy as measured over a single bit interval.
  • Category: Bandpass modulation ("bpm" prefix)

Inputs (Controls)

  1. waveform in -- waveform
  2. Tb, bit interval [s] -- DBL
  3. fc, carrier frequency [Hz] -- DBL
  4. fs, sampling frequency [Hz] -- DBL

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

Outputs (Indicators)

  1. waveform out -- waveform
  2. carrier -- waveform

Required Behavior

  • waveform out is the product of waveform in and the sinusoidal carrier signal A c cos⁡(2π f c t) A c cos⁡(2π f c t) MathType@MTEF@5@5@+=feaagaart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYb1uaebbnrfifHhDYfgasaacH8srps0lbbf9q8WrFfeuY=Hhbbf9v8qqaqFr0xc9pk0xbba9q8WqFfea0=yr0RYxir=Jbba9q8aq0=yq=He9q8qqQ8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGbbWaaSbaaSqaaiaadogaaeqaaOGaci4yaiaac+gacaGGZbGaaiikaiaaikdacqaHapaCcaWGMbWaaSbaaSqaaiaadogaaeqaaOGaamiDaiaacMcaaaa@40D1@ , where A c A c MathType@MTEF@5@5@+=feaagaart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYb1uaebbnrfifHhDYfgasaacH8srps0lbbf9q8WrFfeuY=Hhbbf9v8qqaqFr0xc9pk0xbba9q8WqFfea0=yr0RYxir=Jbba9q8aq0=yq=He9q8qqQ8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGbbWaaSbaaSqaaiaadogaaeqaaaaa@3720@ is the carrier amplitude and f c f c MathType@MTEF@5@5@+=feaagaart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYb1uaebbnrfifHhDYfgasaacH8srps0lbbf9q8WrFfeuY=Hhbbf9v8qqaqFr0xc9pk0xbba9q8WqFfea0=yr0RYxir=Jbba9q8aq0=yq=He9q8qqQ8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGMbWaaSbaaSqaaiaadogaaeqaaaaa@3745@ is the carrier frequency in Hz.
  • The carrier sinusoid amplitude must be A c = 2 T b A c = 2 T b MathType@MTEF@5@5@+=feaagaart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYb1uaebbnrfifHhDYfgasaacH8srps0lbbf9q8WrFfeuY=Hhbbf9v8qqaqFr0xc9pk0xbba9q8WqFfea0=yr0RYxir=Jbba9q8aq0=yq=He9q8qqQ8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGbbWaaSbaaSqaaiaadogaaeqaaOGaeyypa0ZaaOaaaeaadaWcaaqaaiaaikdaaeaacaWGubWaaSbaaSqaaiaadkgaaeqaaaaaaeqaaaaa@3AF8@ in order to achieve the "unit energy per bit interval" criterion. The Figure 1 screencast video explains the origin of this equation.
  • carrier is the output of the sinusoidal oscillator used to modulate the inbound signal.
Figure 1: [video] Explanation of the "unit energy per bit" amplitude equation
Figure 1 (subVI_bpm_ProductModulator-theory.htm)

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 bpm_ProductModulator.vi
Figure 2 (subVI_bpm_ProductModulator-vi.htm)

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