User`s manual

Using Phase Modulation

Phase modulation allows you to change the output deviation or phase of a

sinusoid wave while it is output. This only works in the sinusoid function.

The PHS_MOD program shows how change the deviation from 0

° to 180°.

The commands are:

1. Reset the AFG

*RST

This command aborts any waveform output and selects the 42.9 MHz

reference oscillator source, DDS sample source (that is, trigger start

source), sinusoid function, arm start immediate, 0 V offset, and a 50 Ω

output impedance and output load.

2. Set the Waveform Frequency

[SOURce:]FREQuency[1][:FIXed] <frequency>

This command specifies the waveform frequency. You must use the

direct synthesis frequency generator for the sinusoid function. Refer to

Table B-3 in Appendix B for the frequency limits.

3. Select the Phase Modulation Source

[SOURce:]PM:SOURce <source>

This command sets the phase modulation source. The command

determines which source to use for a phase change. The available

sources are:

INTernal – [SOURce:]PM:DEViation sets the deviation angle

(power-on value)

DPORt – The front panel “Dig Port” connector

LBUS – The VXI Local Bus

VXI – The VXI Backplane

4. Enable Phase Modulation

[SOURce:]PM:STATe <mode>

This command turns phase modulation on or off. A "1" (one) or

"ON" turns it on, and a "0" (zero) or "OFF" turns it off.

Chapter 2 Generating Standard Waveforms 75