Chapter Questions
Define continuous-wave transmission. In what ways is this name appropriate?
Explain the automatic gain control (AGC) difficulties encountered in the reception of continuous wave $(\mathrm{CW})$. What is two-tone modulation, and how does it remedy the receiver AGCC problem of $\mathrm{CW}$ ?
Calculate all possible transmitted frequencies for a two-tone modulation system using a $21-\mathrm{MHz}$ carrier with $300-$ and $700-\mathrm{Hz}$ modulating signals to represent mark and space. Calculate the channel bandwidth required.
What is a frequency-shift-keying (FSK) system? Describe two methods of generating FSK.
Explain how the FSK signal is detected.
Describe the phase-shift keying (PSK) process.
What do the $M$ and $n$ represent in Table 8-1?
Explain a method used to generate binary phase-shift keying (BPSK) using Figure 8-7 as a basis.
Describe a method of detecting the binary output for a BPSK signal using Figure 8-10 as a basis.
What is coherent carrier recovery?
Describe the recovery of quadrature phase-shifting keying (QPSK) using Figure 8-19 as a basis.
Provide a brief description of the quadrature amplitude modulation (QAM) system. Explain why it is an efficient user of frequency spectrum.
Describe how to generate a constellation.
What is the purpose of any eye pattern?
The input data to a differential phase-shift keying (DPSK) transmitter is 1101 . Determine the DPSK digital data stream and the DPSK radio-frequency (RF) output.
What is a pseudonoise (PN) code and why is it noiselike?
What does it mean to spread the RF signal?
What is the PN sequence length of a PN sequence generator with each of the following?(a) four shift registers(b) nine shift registers(c) twenty-three shift registers
What does it mean for a PN sequence to be of maximal length?
Draw the circuit for a $\mathrm{PN}$ sequence generator with $n=5$.
Explain the concept of frequency hopping spread spectrum.
Define dwell time.
Generate the shift-register contents for a PN sequence generator with $n=3$ and a seed value of 101 .
Define code division multiple access.
Define the term hit relative to spread spectrum.
What is a signature sequence?
Draw the block diagram of a direct-sequence spread spectrum (DSSS) transmit-receive system.
Determine the spreading of a DSSS signal if the chip rate is $1 \mathrm{Mbps}$ and the modulation rate is $56 \mathrm{kbps}$.
Draw the block diagram of an orthogonal frequency-division multiplexing (OFDM) transmission.
How does flash OFDM differ from OFDM?
Determine the received OFDM signal for the traces shown in Figure 8-49.
What is a hybrid amplitude modulation (AM) or frequency modulation (FM) signal?
What is the digital data rate for AM digital and what is its comparable quality?
What is the digital data rate for FM digital and what is its comparable quality?
Draw a picture of the RF spectrum for (a) hybrid AM and (b) hybrid FM.
What technology does HD radio use to transport the digital signal?
Why is OFDM not considered a true spread-spectrum system?
Determine the 7-bit code generated for the PN generator shown in Figure 8-31 if a seed value of 111 is used. What happens if a seed value of 000 is used?
Explain how it is possible for multiple code-division multiple access (CDMA) communications devices to share the same RF spectrum.