# Digital Modulation

## Digital Modulation

﻿ECE 123 – Chapter 9 Tomasi
1 Questions
1. Explain digital transmission and digital radio.
Digital transmission is the transmission of digital data, using either an analog or digital signal, in which the digital data are recovered and repeated at intermediate points to reduce the effects of noise.
Digital radio is radio that uses digital technology to transmit and/or receive across the radio spectrum
2. Define information capacity.
The maximum data rate that can be attained over a given channel.
3. What are the three most predominant modulation schemes used in digital radio systems?
a. FSK, PSK, QAM
4. Explain the relationship between bits per second and baud for an FSK system.
The relationship between bits per second or bps and the baud rate for an FSK is system is equal, this is because the rate of change of information in the input of the FSK system is the same as the rate of change of information in the output of the FSK system.
5. Define the following terms for FSK modulation:

a. Frequency deviation - is the swing or change of the carrier frequency with respect to an input signal.
b. Modulation index - Modulation index and deviation ratio of an FSK modulation system is just the ratio of how the frequency of the modulated signal varies with respect to its unmodulated level.
c. Deviation ratio - Deviation Ratio: Deviation ratio (DR) is the worst-case modulation index and is equal to the maximum peak frequency deviation divided by the maximum modulating-signal frequency. The worst-case modulation index produces the widest output frequency spectrum.
6. Explain the relationship between:
a. The minimum bandwidth required for an FSK system and bit rate
b. The mark and space frequencies.
7. What is the difference between standard FSK and MSK? What is the advantage of MSK?
The difference between them is that MSK unlike FSK is a particular form of Continuous-Phase FSK where the frequency of the carrier signal is changed by the input data exactly...