Frequency Modulation (FM) Flashcards
What is the definition of frequency modulation ?
The frequency of the carrier is changed in sympathy with the amplitude of the modulating wave.
If the modulating wave increases in amplitude what will be the result ?
The frequency of the carrier wave will increase and versa
Name the 3 waves in FM?
Modulating wave
Carrier wave
Resultant modulated carrier
What is centre (carrier) frequency?
The frequency occupied by the carrier when in an unmodulated state.
What is frequency deviation ? (fd)
The amount of change in frequency from the centre frequency in the modulated wave that occurs with the maximum modulating wave amplitude
What is frequency swing?
The difference from the lowest deviation of amplitude from the centre wave to the highest deviation.
What is the deviation ratio?
Deviation ratio is the maximum frequency deviation and the highest permissible modulating frequency.
What is the modulation index ?
The decimal representing the ratio of frequency deviation and the highest frequency of the modulating wave.
How do we work out modulation index ?
fm = modulation index
Test example:
Modulation index = 2
Name the graph we use to show modulation index results on ?
Bessels function curve.
The frequency spacing of the side frequencies is equal to what frequency ?
The frequency of the modulating wave (fm)
With regards to side order frequency amplitude what can we get rid of and under what value ?
Side order frequencies under 10%.
Name the rule that is put in place to calculate the transmission bandwidth ?
Carsons rule
