ET 2530
Electronic Communications

Chapter 10 1. Explain what is meant by the term wireless.
It is used to describe telecommunication technologies that use radio waves to carry a signal. 2. What is a frequency shift key system? Describe two methods of generating FSK.
FSK is a form of FM in which the modulation wave shifts the output between two pre-determined frequencies. Methods of generation include a VCO and modifying the oscillating frequency of a tank circuit. 6. Explain a method used to generate BPSK using figure 10-5.
The +/- sin wct signals are input into 1 of 2 selectors. The binary data input is used to select the phase. 8. What is coherent carrier recovery?
A recovered carrier frequency is used as an input to a mixer to recover the data. 10. Provide a brief description of the QAM system. Explain why it is an efficient user of frequency spectrum.
Figure 10-14 and 10-15. The QAM system uses a four level baseband stream providing a 16 state QAM constellation in a limited bandwidth.

Chapter 11 3. Describe the sequence of events taking place when a telephone call is initiated through to its completion.
Subscriber lifts the handset, a switch is closed providing a a dc loop current between tip and ring. Telco senses the off hook condition and responds with a dial tone. Then the describer dials the desired number. 14. Why are telephones lines widely used for transmission of digital data? Explain the problems involved with their use.
Modems enable the transmission of digital data over analog phone lines. Phone lines are widely available. 32. Describe the concepts of frequency reuse and cell splitting.
Dual band indicates that a phone can operate in two different frequency bands.