1
GATE ECE 2006
MCQ (Single Correct Answer)
+2
-0.6
A signal m(t) with bandwidth 500 Hz is first multiplied by a signal g(t) where $$g(t)\, = \,\,\sum\limits_{k = - \infty }^\infty {{{( - 10)}^k}\,\delta (t - 0.5x{{10}^{ - 4}}k)} $$
The resulting signal is then passed through an ideal low pass filter with bandwidth 1 kHz. The output of the low pass filter would be
A
$${\delta (t)}$$
B
m(t)
C
0
D
m(t) $${\delta (t)}$$
2
GATE ECE 2006
MCQ (Single Correct Answer)
+1
-0.3
A solution for the differential equation $$\mathop x\limits^. $$(t) + 2 x (t) = $$\delta (t)$$ with intial condition $$x({0^ - }) = 0$$ is
A
$${e^{ - 2t}}\,u(t)$$
B
$${e^{2t}}\,u(t)$$
C
$${e^{ - t}}\,u(t)$$
D
$${e^t}\,u(t)$$
3
GATE ECE 2006
MCQ (Single Correct Answer)
+1
-0.3
The Dirac delta function $$\delta (t)$$ is defined as
A
$$\delta (t) = \left\{ {\matrix{ {1,} & {t = 0} \cr {0,} & {otherwise} \cr } } \right.$$
B
$$\delta (t) = \left\{ {\matrix{ {\infty ,} & {t = 0} \cr {0,} & {otherwise} \cr } } \right.$$
C
$$\delta (t) = \left\{ {\matrix{ {1,} & {t = 0} \cr {0,} & {otherwise\,\,\,and\,\,\int\limits_{ - \infty }^\infty {\delta (t)\,dt = 1} } \cr } } \right.\,\,$$
D
$$\delta (t) = \left\{ {\matrix{ {\infty ,} & {t = 0} \cr {0,} & {otherwise\,\,\,and\,\,\int\limits_{ - \infty }^\infty {\delta (t)\,dt = 1} } \cr } } \right.\,\,$$
4
GATE ECE 2006
MCQ (Single Correct Answer)
+2
-0.6
As x is increased from $$ - \infty \,\,to\,\infty $$, the function $$f(x) = {{{e^x}} \over {1 + {e^x}}}$$
A
monotonically increases
B
monotonically decreases
C
increases to a maximum value and then decreases
D
decreases to a minimum value and then increases
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