Reference no: EM132456157
ELEC 331 Digital and Analog Communications
M1A1 Assignment: Signals and Amplitude Modulation
Question 1. Draw a block diagram showing the key elements of a communication system. Describe the function(s) of each of the elements of this block diagram.
Question 2. (a) What is meant by decibel (dB) in the context of signal transmission?
(b) A signal is measured at two different points in a transmission medium. The power is P1 micro watts at the first point and P2 micro watts at the second point. The dB value for the ratio of P1 to P2 is zero. What can be concluded regarding the values of P1 and P2?
(c) A transistor amplifier has a measured Signal-to-Noise (S/N) ratio of 25/8. What is its noise figure in dB?
Question 3. (a) Convert 300W to dBW
(b) A laser diode outputs +8 dBm. Convert this value to watts.
Question 4. (a) What is meant by bandwidth in the context of signal transmission? What is channel bandwidth and how is it related to the information capacity of a channel?
Question (b) What is meant by the term baseband signal? Explain the process of modulation and demodulation for the baseband signal.
Question 5. (a) What is meant by analog modulation? Name its different types.
(b) Define the term modulation index for amplitude modulation.
(c) If the % modulation of an AM transmitter is 60% and the unmodulated antenna current is 10 amperes, calculate the modulated current. Also if in this case, the carrier transmits 12 kW, what is the modulated power? (Note that we are not asking the transmitted current and power respectively, but the current and power of the intelligence signal).
Question 6. (a) A 300-watt carrier signal is to be modulated at an 85% modulation level. Calculate the total transmitted power.
(b) A 4.5 MHz carrier is modulated by a sound signal that has frequency components ranging from 100 Hz to 5 kHz. What is the range of frequencies generated for the upper sideband?
Question 7. (a) Draw a block diagram showing the key elements of an AM (Amplitude Modulated) transmitter. Describe the function(s) of each of the elements.
(b) If the total power transmitted by an AM transmitter is 100 W at a percent modulation of 60%, calculate the value of upper sideband power.