1
GATE ECE 2016 Set 1
+1
-0.3
A continuous -time function $$x\left( t \right)$$ is periodic with period $$T$$. The function is sampled uniformly with a sampling period $${T_s}$$. In which one of the following cases is the sampled signal periodic?
A
$$T\,\, = \,\,\sqrt 2 \,\,{T_s}$$
B
$$T\,\, = \,\,1.2T$$
C
Always
D
Never
2
GATE ECE 2015 Set 2
+1
-0.3
The signal $$\cos \left( {10\pi t + {\pi \over 4}} \right)$$ is ideally sampled at a sampling frequency of 15 Hz. The sampled signal is passed through a filter with impulse response $$\,\left( {{{\sin \left( {\pi t} \right)} \over {\pi t}}} \right)\,\cos \left( {40\pi t - {\pi \over 2}} \right).$$ The filter output is
A
$${{15} \over 2}\cos \left( {40\pi t - {\pi \over 4}} \right)$$
B
$${{15} \over 2}\left( {{{\sin \left( {\pi t} \right)} \over {\pi t}}} \right)\cos \left( {10\pi t + {\pi \over 4}} \right)$$
C
$${{15} \over 2}\cos \left( {10\pi t - {\pi \over 4}} \right)$$
D
$${{15} \over 2}\left( {{{\sin \left( {\pi t} \right)} \over {\pi t}}} \right)\cos \left( {40\pi t - {\pi \over 2}} \right)$$
3
GATE ECE 2014 Set 3
Numerical
+1
-0
A modulated signal is $$y\left( t \right)\, = \,\,\,\,\,\,\,\,\,m\left( t \right)\,\cos \left( {40000\pi t} \right),$$ where the baseband signal $$m\left( t \right)\,$$ has frequency components less than 5 kHz only. The minimum required rate (in kHz) at which $$y\,\,\left( t \right)$$ should be sampled to recover $$m\,\,\left( t \right)$$ is ________.
4
GATE ECE 2014 Set 3
+1
-0.3
Let $$\,x\,\,\left( t \right)\,\,\, = \,\,\,\cos \,\,\,\left( {10\pi t} \right)\,\, + \,\,\cos \,\,\left( {30\pi t} \right)$$ be sampled at $$20\,\,\,Hz$$ and reconstructed using an ideal low-pass filter with cut-off frequency of $$20\,\,\,Hz$$. The frequency/frequencies present in the reconstructed signal is/are.
A
5 Hz and 15 Hz only
B
10 Hz and 15 Hz only
C
5 Hz, 10 Hz and 15 Hz only
D
5 Hz only
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