How to generate ramp and square modulation waveform using PCI 5412?

[billfu]

I am doing a project using Arb waveform generator PCI 5412. The goal of my project is to generate a ramp up, a square,and ramp down modulation signal using this card. Attached is the output signal format.

      The carrier frequency shall be adjustable from 150kHz to 600kHz.

The period of the modulation, t_cycle, shall be adjustable from 50ms to 1000ms.

The ramp up and ramp down periods of the modulation, t_ramp, shall be selectable between 0.2ms, 0.5ms, and 1.0ms.

      The on period of the modulation, t_on, shall be adjustable from 10 to 100% of t_cycle

Is it possible to do that using PCI 5412? Could you please tell me how to do it?

Thanks a lot!

Bill Fu

[Evan R]

Hi Bill, What type of modulation do you need to perform? National Instruments has a modulation toolkit which would help you to create arbitrarily modulated signals. If you have this toolkit, I can point you to some examples which would help you to write the program in LabVIEW. Are you using LabVIEW? If so, which version. If not, what application development environment are you using? Best Regards, Evan R. Applications Engineer National Instruments http://www.ni.com/support

[billfu]

Dear Evan R.

The software I used is Labview 7.1. The modulation format is AM as shown in the attached Doc file.

I don't have Modulation Toolkit. Does it mean that I cannot generate a AM signal with this modulation toolkit?

Thanks a lot!

Bill Fu

[NeilF]

You can do what you want with just LabVIEW 7.1 and NI-FGEN.  You first need to create a waveform that represents your ramp up, high DC value, ramp down and low DC value.  This takes care of your requirements for duty cycle, rise time and fall time.

Then you take the resultant waveform that you have created and multiply it by a sine wave of the specified carrier frequency.  You can create the sine wave with a LV VI like Sine Waveform.vi from the Waveform >> Analog Waveform >> Waveform Generation Palette.  There are several VIs in LabVIEW that will create a sine wave for you.  Just search in the LabVIEW palette (using the text search capability) until you find the sine wave VI that suits your needs.

You'll want your sine wave to have the same number of points as your message signal (modulation waveform).  The 5412 requires waveforms to be multiples of 4 samples.

Then you download the waveform and generate it continuously.  You can take an existing FGEN example for generating a single waveform and just substitute your data for the data that the example uses.

Neil F.

Principal Engineer

Modular Instruments R&D

National Instruments

[Rainer Krafft]

dear Neil,

I just looked into your reply.

The first part of your answer is of interest to me as I tried recently to generate a very simple ramp in LabView. How exactly would I do that?

Rainer