Hi,

I am trying to generate an FM signal using the Agilent E8257C Signal Generator.

Can you please tell me how FM_Dev is incorporated into the FM Signal equation. According to my textbook, if the model for the FM signal is:

x(t) = cos (2 pi f t + 2 pi Delta_f y(t))

where y(t) is a modulating information tone which has normalized amplitude (i.e. maximum amplitude = 1). I define Delta_f as the frequency deviation.

I realize that when I set FM_Dev = 25 KHz (5 KHz increment) on the scope I get the output signal (measured on Spectrum Analyzer), as setting the Delta_f = 0.2 for an FM signal with the center frequency f = 100 MHz and y(t) is of frequency 20 KHz.

Can you please tell me what the relation between FM_Dev and Delta_f is?

Thanks,

Sushil

I am trying to generate an FM signal using the Agilent E8257C Signal Generator.

Can you please tell me how FM_Dev is incorporated into the FM Signal equation. According to my textbook, if the model for the FM signal is:

x(t) = cos (2 pi f t + 2 pi Delta_f y(t))

where y(t) is a modulating information tone which has normalized amplitude (i.e. maximum amplitude = 1). I define Delta_f as the frequency deviation.

I realize that when I set FM_Dev = 25 KHz (5 KHz increment) on the scope I get the output signal (measured on Spectrum Analyzer), as setting the Delta_f = 0.2 for an FM signal with the center frequency f = 100 MHz and y(t) is of frequency 20 KHz.

Can you please tell me what the relation between FM_Dev and Delta_f is?

Thanks,

Sushil

When you set FM_Dev to 25 kHz you get +/-25 kHz deviation; i.e. it deviates each side of center frequency by 25 kHz. The magnitude of the modulating frequency sets or determines the deviation about center frequency. Even though the input to the E8257C is set as 1V for full calibration, the gain is varied inside the source modulation circuits to increase or decrease deviation. The modulation signal (20 kHz) is the rate of FM or the rate at which the carrier (100 MHz) is deviated +/-25 kHz.

Regards -