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Bandpass Signaling Principles and Circuits Chap. 4
x 1 (t)
Baseband filter
h x (t)
x 2 (t)
Baseband filter
h y (t)
g 1 (t)
g 2 (t)
y 1 (t)
Baseband filter
h y (t)
y 2 (t)
Baseband filter
h x (t)
Figure P4–17
(a) Butterworth filter, second order:
H(f) =
1
1 + 32(jf>B) + (jf>B) 2
(b) Butterworth filter, fourth order:
H(f) =
1
[1 + 0.765(jf>B) + (jf>B) 2 ][1 + 1.848(jf>B) + (jf>B) 2 ]
Compare your results for the two filters.
4–20 Assume that the output-to-input characteristic of a bandpass amplifier is described by Eq. (4–42)
and that the linearity of the amplifier is being evaluated by using a two-tone test.
(a) Find the frequencies of the fifth-order intermodulation products that fall within the amplifier
bandpass.
(b) Evaluate the levels for the fifth-order intermodulation products in terms of A 1 , A 2 , and
the K’s.
4–21 An amplifier is tested for total harmonic distortion (THD) by using a single-tone test. The output
is observed on a spectrum analyzer. It is found that the peak values of the three measured harmonics
decrease according to an exponential recursion relation V n + 1 = V n e -n , where n = 1, 2, 3.
What is the THD?
★ 4–22 The nonlinear output–input characteristic of an amplifier is
v out (t) = 5v in (t) + 1.5v 2 in (t) + 1.5v 3 in (t)