Agilent Technologies E1441A user service Frequency Modulation FM, Amplitude Modulating Source

Amplitude Modulating Source

Modulation depth: 0% to 120%. The default is 100%.

Use the following command to set the modulation depth:

AM:DEPTh <depth in percent>MINimumMAXimum

The function generator will accept an internal modulating signal, an external modulating signal, or both.

Modulating source: Internal-External (both) or External only. The default is Both (internal-external).

The External modulating source is always enabled.

When both sources are enabled (internal-external), the function generator adds the internal and external modulating signals (the carrier waveform is actually modulated with two waveforms).

When the internal source is disabled (external only), the carrier waveform is expecting a modulating signal on the AM Modulation terminal.

You apply the external modulating waveform to the AM Modulation terminal. The modulation depth is controlled by the signal level present (5 volts peak corresponds to 100% modulation).

Frequency Modulation (FM)

Figure 2-2. AM Modulation Input Signal

Use the following command to set the modulating source:

AM:SOURce BOTHEXTernal

A modulated waveform consists of a carrier waveform and a modulating waveform. In FM, the frequency of the carrier is varied by the amplitude of the modulating waveform. The function generator will accept only an internal FM modulating signal (no external source is available). Topics covered on frequency modulation are:

•FM Carrier Waveform Shape

30 Agilent E1441A Application Information Chapter 2