1
GATE ECE 2003
+2
-0.6
A DSB-SC signal is to be generated with a carrier frequency fc = 1MHz using a nonlinear device with the input-output characteristic $$v_0=a_0v_i\;+\;a_1v_i^3$$.where a0 and a1 are constants. The output of the nonlinear device can be filtered by an appropriate band-pass filter. Let $$v_0=A_c'\;\cos\left(2{\mathrm{πf}}_\mathrm c'\mathrm t\right)\;+\;m\left(t\right)$$ where m(t) is the message signal. Then the value of $$f_c'$$ (in MHz) is
A
1.0
B
0.333
C
0.5
D
3.0
2
GATE ECE 2003
+2
-0.6
Let $$m\left(t\right)\;=\cos\left[\left(4\mathrm\pi\times10^3\right)t\right]$$ be the message signal and $$c\left(t\right)\;=5\cos\left[2\mathrm\pi\times10^6t\right]$$ be the carrier.

c(t) and m(t) are used to generate an AM signal. The modulation index of the generated AM signal is 0.5. Then the quantity $$\frac{Total\;sideband\;power}{Carrier\;power}$$ is

A
1/2
B
1/4
C
1/3
D
1/8
3
GATE ECE 2003
+2
-0.6
Let $$m\left(t\right)\;=\cos\left[\left(4\mathrm\pi\times10^3\right)t\right]$$ be the message signal and $$c\left(t\right)\;=5\cos\left[2\mathrm\pi\times10^6t\right]$$ be the carrier.

c(t) and m(t) are used to generate an FM signal. If the peak frequency deviation of the generated FM signal is three times the transmission bandwidth of the AM singal, then the coefficient of the term $$\cos\left[2\mathrm\pi\left(1008\times10^3\right)t\right]$$ in the FM signal (in terms of the Bessel coefficients) is

A
$$5\;J_4\left(3\right)$$
B
$$\left(5/2\right)\;J_8\left(3\right)$$
C
$$\left(5/2\right)\;J_8\left(4\right)$$
D
$$5\;J_4\left(6\right)$$
4
GATE ECE 2000
+2
-0.6
In an FM system, a carrier of 100 MHz is modulated by a sinusoidal signal of 5 KHz. The bandwidth by Carson’s approximation is 1 MHz. If y(t) = (modulated waveform)3, then by using Carson’s approximation, the bandwidth of y(t) around 300 MHz and the and the spacing of spectral components are, respectively.
A
3 MHz, 5 KHz
B
1 MHz, 15 KHz
C
3 MHz, 15 KHz
D
1 MHz, 5 KHz
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