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In .26, we considered one procedure for bandpass sampling and reconstruction. Another

Chapter 7, Problem 7.27

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QUESTION:

In Problem 7.26, we considered one procedure for bandpass sampling and reconstruction. Another procedure, used when (\(x)t\) is real, consists of multiplying (\(x)t\) by a complex-exponential and then sampling the product. The sampling system is shown in Figure P7.27(a). With (\(x)t\) real and with \(X(j \omega)\) nonzero only for \(\omega_{1}<|\omega|<\omega_{2},\) the frequency is chosen to be\(\omega_{0}=(1 / 2)\left(\omega_{1}+\omega_{2}\right)\), and the lowpass filter \(H_{1}(j \omega)\) has cutoff frequency \((1 / 2)\left(\omega_{2}-\omega_{1}\right)\).

(a) For \(X(j \omega)\) as shown in Figure P7.27(b), sketch \(X_{p}(j \omega)\).

(b) Determine the maximum sampling period \(T\) such that \(x(t)\) is recoverable from \(x_{p}(t)\).

(c) Determine a system to recover \(x(t)\) from \(x_{p}(t)\).

Figure P7.27

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QUESTION:

In Problem 7.26, we considered one procedure for bandpass sampling and reconstruction. Another procedure, used when (\(x)t\) is real, consists of multiplying (\(x)t\) by a complex-exponential and then sampling the product. The sampling system is shown in Figure P7.27(a). With (\(x)t\) real and with \(X(j \omega)\) nonzero only for \(\omega_{1}<|\omega|<\omega_{2},\) the frequency is chosen to be\(\omega_{0}=(1 / 2)\left(\omega_{1}+\omega_{2}\right)\), and the lowpass filter \(H_{1}(j \omega)\) has cutoff frequency \((1 / 2)\left(\omega_{2}-\omega_{1}\right)\).

(a) For \(X(j \omega)\) as shown in Figure P7.27(b), sketch \(X_{p}(j \omega)\).

(b) Determine the maximum sampling period \(T\) such that \(x(t)\) is recoverable from \(x_{p}(t)\).

(c) Determine a system to recover \(x(t)\) from \(x_{p}(t)\).

Figure P7.27

ANSWER:

Step 1 of 9

(a) Redraw the sample system with signal \(X_{1}(j \omega)\) and \(X_{2}(j \omega)\) indication.

Let \(X_{1}(j \omega)\) be the Fourier transform of the signal \(x_{1}(t)\) obtained by multiplying \(x(t) with \(e^{-j \omega_{0} t}\).

Let \(X_{2}(j \omega)\) be the Fourier transform of the signal \(x_{2}(t)\) obtained at the output of the low pass filter \(H(j \omega)\).

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