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alc95
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Homework Statement
The analog signal x(t) = cos(2pi f t) is sampled at a rate of 1 kHz, using ideal
impulse sampling, to obtain the sampled signal x^(s)(t). The sampled signal is then sent through an ideal
lowpass filter with transfer function H(2pi f ) = 0.001 rect (0.001 f ).
(a) If f =1.01kHz, what is the output frequency from the filter? Is there aliasing or not?
(b) If f = 0.99kHz, what is the output frequency from the filter? Is there aliasing or not?
(c) If f = 0.49kHz, what is the output frequency from the filter? Is there aliasing or not?
Homework Equations
To perfectly reconstruct a signal, we need: sampling rate > 2*signal frequency
The Attempt at a Solution
I think these are correct, not 100% sure though:
(a)
aliasing occurs, as 1.00 kHz !> 2 × 1.01 kHz
fout = 1.01 kHz – n × 1.00 kHz = 1.01 kHz – 1 × 1.00 kHz = 0.01 kHz
(b)
aliasing occurs, as 1.00 kHz !> 2 × 0.99 kHz
fout = 0.99 kHz – n × 1.00 kHz = 0.99 kHz – 1.00 kHz = - 0.01 kHz
(c)
aliasing does not occur, as 1.00 kHz > 2 × 0.49 kHz
fout = 0.49 kHz