Topic 7 Flashcards
Math and circuits
What is modulation?
The process of transmitting information by changing a characteristic of a sine wave known as the carrier.
What is Amplitude Modulation?
Modulation where information is impressed on the amplitude of the carrier.
What is Frequency Modulation?
Modulation where information is impressed on the frequency of the carrier.
What is Phase Modulation?
Modulation where information is impressed on the phase of the carrier.
What is the modulation index?
The ratio of the modulating signal voltage to the carrier signal voltage.
What is the carrier frequency in the practice example?
630 kHz.
What is the signal frequency in the practice example?
1 kHz.
What is the carrier amplitude in the practice example?
3.5 Vp.
What is the signal amplitude in the practice example?
2.1 Vp.
What is the modulation index in the practice example?
60%.
What radio station would be playing the 1kHz test tone?
630 CHED.
What happens with too much modulation?
Results in ‘splatter’ and generates significant interference.
What are the three frequencies expected in the frequency domain?
- 2 kHz
- 1.75 kHz
- 2.25 kHz
What does E_c represent?
The peak carrier amplitude.
What does E_m represent?
The peak signal amplitude.
What does E_max represent?
The max peak-to-peak carrier+signal amplitude.
What does E_min represent?
The min peak-to-peak carrier+signal amplitude.
What is DSB-FC?
Double Side Band Full Carrier, the form of AM most familiar in AM radio.
Fill in the blank: Information is transmitted or conveyed by ______.
[changing] the expected signal.
What is one application of Amplitude Modulation?
AM Radio.
What is another application of Amplitude Modulation?
NTSC (National Television Systems Committee) Analog Video.
What is frequency translation?
Moving a band of frequencies up or down in frequency.
What is the peak-to-peak amplitude of the carrier plus signal when 100% modulated?
E_max.
How do the amplitudes of the sidebands compare to the carrier amplitude when fully modulated?
They equal the carrier amplitude.
True or False: The modulation index should always be less than or equal to 100%.
True.
What is the maximum modulation index for Amplitude Modulation?
100%.
What is the expected amplitude change in a modulated signal?
The amplitude gets larger.
What is the expected frequency change in a modulated signal?
The frequency gets faster.
What is the expected phase change in a modulated signal?
The phase changes.
