Chapter Questions
Explain what is meant by a baseband transmission.
no number 2
Provide some possible reasons why an analog signal is digitized when an analog output is desired.
How are analog signals converted to digital?
List two advantages of pulse modulation and explain their significance.
With a sketch similar to Figure 7-1, explain the basics of pulse-amplitude modulation (PAM), pulse-width modulation (PWM), and pulse-position modulation (PPM).
Describe a means of generating and detecting PWM.
Describe a means of generating and detecting PPM.
Draw a diagram showing demodulation of a PWM signal.
Define acquisition time for a sample-and-hold $(\mathrm{S} / \mathrm{H})$ circuit.
Define aperture time for a $\mathrm{S} / \mathrm{H}$ circuit.
What is the typical capacitance value for a $\mathrm{S} / \mathrm{H}$ circuit?
Draw the PAM signal for a sinusoid using(a) Natural sampling.(b) Flat-top sampling.
An audio signal is band-limited to $15 \mathrm{kHz}$. What is the minimum sample frequency if this signal is to be digitized?
A sample circuit behaves like what other circuit used in radio-frequency communications?
What is the dynamic range (in $\mathrm{dB}$ ) for a 12-bit pulse-code modulation (PCM) system?
Define the resolution of a PCM system. Provide two ways that resolution can be improved.
Calculate the number of bits required to satisfy a dynamic range of $48 \mathrm{~dB}$.
What is meant by quantization?
Explain the differences between linear PCM and nonlinear PCM.
Explain the process of companding and the benefit it provides.
A $\mu$-law companding system with $\mu=100$ is used to compand a 0 - to $10-\mathrm{V}$ signal. Calculate the system output for inputs of $0,0.1,1,2.5,5,7.5$, and $10 \mathrm{~V} .(0,1.5,5.2,7.06,8.52,9.38,10)$
What is $D_{\min }$ ?
How can the minimum distance between two data values be increased?
Determine the number of errors that can be detected and corrected for data values with a Hamming distance of(a) 2 .(b) 5 .
Determine the distance between the following two digital values:$$\begin{aligned}& 110001010 \\& 010000010\end{aligned}$$
What is the minimum distance between data words if(a) Five errors are to be detected?(b) Eight errors are to be detected?
Cyclic redundancy check (CRC) codes are commonly used in what computer networking protocol?
Provide a definition of systematic codes.
With regard to $(n, k)$ cyclic codes, define $n$ and $k$.
What is a block check code?
How are the feedback paths determined in a CRC code-generating circuit?
Draw the CRC generating circuit if $G(x)=x^4+x^2+x+1$.
Given that the message value is 101001 and $G(x)=1101$, perform modulo-2 division to determine the block check code (BCC). (111)
What is a syndrome?
What does it mean if the syndrome value is(a) All zeros?(b) Not equal to zero?
What does it mean for a code to be forward error-correcting?
What popular commercial application uses Reed-Solomon (RS) coding and why?
What is the type of difference equation that makes use of past output values?
What is the type of difference equation that makes use of only the present and past input values?
What is the order of a difference equation that requires four past input and output values?
What is the order of the following difference equation? Is this a recursive or a nonrecursive algorithm?$$y_0=x_0-x_{(1)}$$
Given the following difference equations, state the order of the filter and identify the values of the coefficients.(a) $y=0.9408 x_0-0.5827 x_1+0.9408 x_2+0.5827 y_1-0.8817 y_2$(b) $y_0=0.02008 x_0-0.04016 x_2+0.02008 x_4+2.5495 y_1-3.2021 y_2+2.0359 y_3-0.64137 y_4$
Explain why a technique such as CRC coding is used. Can you achieve the same results using parity checking?
A PCM system requires $72 \mathrm{~dB}$ of dynamic range. The input frequency is $10 \mathrm{kHz}$. Determine the number of sample bits required to meet the dynamic range requirement and specify the minimum sample frequency to satisfy the Nyquist sampling frequency. ( 12 bits, $20 \mathrm{kHz}$ )
The voltage range being input to a PCM system is 0 to 1 V. A 3-bit analog-to-digital (ADC) converter is used to convert the analog signal to digital values. How many quantization levels are provided? What is the resolution of each level? What is the value of the quantization error for this system? $(8,0.125,0.0625)$