bananasiong
New Member
Hi,
I'm doing simulation on frequency modulation. The modulating signal is 5 kHz, 500 mV and the carrier is around 30 MHz, 2 V.
As shown in the schematic, the blue waveform is the modulating signal. The red waveforms are the carrier signal and the modulated signal. With the switch opened, there is only carrier signal at the output, which is around 30 MHz. When the switch is closed, I can see the modulated waveform. I found that when the amplitude of the modulating signal is peak, the frequency of the modulated is higher than the carrier frequency. When the amplitude of the modulating signal is low, the frequency of the modulated signal is lower than the carrier frequency. These are expected except the amplitude of the modulated signal keeps changing but is not as the same as the carrier signal.
I'm not sure whether the schematic is correct or not because I took the modulation part of a FM transmitter and modified it, just want to see the modulated waveform as compared to the reference book.
EDIT: The bottom waveforms are the carrier signal, I zoom in and display on the right hand side.
Thanks
I'm doing simulation on frequency modulation. The modulating signal is 5 kHz, 500 mV and the carrier is around 30 MHz, 2 V.
As shown in the schematic, the blue waveform is the modulating signal. The red waveforms are the carrier signal and the modulated signal. With the switch opened, there is only carrier signal at the output, which is around 30 MHz. When the switch is closed, I can see the modulated waveform. I found that when the amplitude of the modulating signal is peak, the frequency of the modulated is higher than the carrier frequency. When the amplitude of the modulating signal is low, the frequency of the modulated signal is lower than the carrier frequency. These are expected except the amplitude of the modulated signal keeps changing but is not as the same as the carrier signal.
I'm not sure whether the schematic is correct or not because I took the modulation part of a FM transmitter and modified it, just want to see the modulated waveform as compared to the reference book.
EDIT: The bottom waveforms are the carrier signal, I zoom in and display on the right hand side.
Thanks