Tutorial 4
EKT 313
EKT313 Electronic Communication Systems
PPKKP
TUTORIAL 4
Radio transmitters
1. Discuss the four basic requirements of a transmitter.
2. What circuits are typically part of every radio transmitter?
3. What is the name given to the bias for a class C amplifier produced by an input RC
network?
4. Name the capacitor and the process used for fine-tuning in an emitter follower
crystal oscillator.
5. Why are crystal oscillators used instead of LC oscillators to set a transmitter frequency?
6. How is the output frequency of a frequency of a PLL synthesizer changed?
7. What is the purpose of the loop filter in a PLL?
8. What are parasitic and how are they eliminated in a power amplifier?
9. Compare the differences between class D and Class E amplifier.
10. Explain how a feed forward power amplifier reduces distortion.
11. How is impedance matching handled in a broadband linear RF amplifier?
12. An antenna will be connected to class C amplifier that has a supply voltage of 36
V and a collector current of 2.5 A. Calculate the RF output power if the efficiency of the
amplifier is 80% and find the turns ratio of the transformer to match 6 Ω amplifier
impedance with the 72 Ω antenna load.
13. An FM transmitter has an 8.6 MHz crystal carrier oscillator and frequency multipliers of
2,3 and 4. What is the output frequency?
14. A PLL frequency synthesizer has an ouput frequency of 162.7 MHz. The reference is a 1
MHz crstal oscillator followed by a divider of 10. What is the main frequency divider
ratio?
15. Using the principles of PLL frequency synthesizers, create a synthesizer that will
generate all the AM radio broadcast frequencies from 1MHz to 10 MHz in 100 KHz
increments. This unit will be used as the carrier source in an AM broadcast transmitter.
.
16. Design an LCC T network that will match 5Ω internal resistance to a 52 Ω load at 54
MHz. Assume Q of 12.
Sahadah ahmad
Page 1
Tutorial 4
EKT313 Electronic Communication Systems
PPKKP
Communication Receivers
1. Define the terms sensitivity, selectivity and image frequency.
2. With the aid of the block diagram of a simple receiver, explain the basic superheterodyne
principle.
3. What are the advantages that the superheterodyne receiver has over the TRF receiver? Are there
any disadvantage?
4. With the aid of circuit diagram , explain the operation of practical diode detector circuit,
indicating what changes have been made from the basic circuit. How is AGC obtained from this
detector.
5. What is the difference between forward AGC and reverse AGC?
6. Name the three main sources of selectivity for receivers implemented with ICs.
7. Design a receiver with no separate IF filter and using only single detector. Besides that
propose a low cost filter at the mixer output for selectivity in your design.
Sahadah ahmad
Page 2