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310
Bandpass Signaling Principles and Circuits Chap. 4
F(f)
R
C
Figure P4–34
★ 4–35 Assume that the phase noise characteristic of a PLL is being examined. The internal phase noise
of the VCO is modeled by the input u n (t), as shown in Fig. P4–35.
¨i(t)
K d
F 1 (f)
v 2 (t)
¨n(t)
¨0(t)
VCO
K v
F 2 (f)=–––– j2∏f
¨0(t)
Figure P4–35
(a) Find an expression for the closed-loop transfer function Θ 0 (f)Θ n (f), where u i (t) = 0.
(b) If F 1 (f) is the low-pass filter given in Fig. P4–34, sketch the Bode plot [|Θ 0 (f)Θ n (f)|] dB for
the phase noise transfer function.
4–36 The input to a PLL is v in (t) = A sin(v 0 t + u i ). The LPF has a transfer function F(s) = (s + a)s.
(a) What is the steady-state phase error?
(b) What is the maximum hold-in range for the noiseless case?
★ 4–37 (a) Refer to Fig. 4–25 for a PLL frequency synthesizer. Design a synthesizer that will cover a
range of 144 to 148 MHz in 5-kHz steps, starting at 144.000 MHz. Assume that the frequency
standard operates at 5 MHz, that the M divider is fixed at some value, and that the N divider is
programmable so that the synthesizer will cover the desired range. Sketch a diagram of your
design, indicating the frequencies present at various points of the diagram.
(b) Modify your design so that the output signal can be frequency modulated with an audiofrequency
input such that the peak deviation of the RF output is 5 kHz.
4–38 Assume that an SSB-AM transmitter is to be realized using the AM–PM generation technique, as
shown in Fig. 4–27.
(a) Sketch a block diagram for the baseband signal-processing circuit.
(b) Find expressions for R(t), u(t), and v(t) when the modulation is m(t) = A 1 cos v 1 t +
A 2 cos v 2 t.