27 real Signals & Systems questions from the Electrical Core bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.
1. What is LTI system?
Junior
A.system obeying superposition whose response to a shifted input is the same output shifted, fully described by its impulse response
B.a band-limited signal can be reconstructed exactly when sampled at a rate greater than twice its highest frequency component
C.total energy of a signal computed in the time domain equals the energy computed from the squared magnitude of its Fourier transform
D.integral of the product of input and the time-reversed, shifted impulse response giving LTI output; becomes multiplication in the frequency domain
2. Which term means: "system obeying superposition whose response to a shifted input is the same output shifted, fully described by its impulse response"?
A.Causality — a band-limited signal can be reconstructed exactly when sampled at a rate greater than twice its highest frequency component
B.Causality — folding of frequency components above half the sampling rate into lower frequencies, prevented by a low-pass filter placed ahead of the sampler
C.Causality — every bounded input produces a bounded output, which is equivalent to an absolutely integrable (or summable) impulse response
D.Causality — output at any instant depends only on present and past inputs, requiring the impulse response to be zero for negative time
A.Nyquist sampling theorem — total energy of a signal computed in the time domain equals the energy computed from the squared magnitude of its Fourier transform
B.Nyquist sampling theorem — integral of the product of input and the time-reversed, shifted impulse response giving LTI output; becomes multiplication in the frequency domain
C.Nyquist sampling theorem — every bounded input produces a bounded output, which is equivalent to an absolutely integrable (or summable) impulse response
D.Nyquist sampling theorem — a band-limited signal can be reconstructed exactly when sampled at a rate greater than twice its highest frequency component
11. Which term means: "folding of frequency components above half the sampling rate into lower frequencies, prevented by a low-pass filter placed ahead of the sampler"?
A.Aliasing — set of s or z values for which the transform sum converges; a causal stable system's region includes the jω axis or unit circle
B.Aliasing — every bounded input produces a bounded output, which is equivalent to an absolutely integrable (or summable) impulse response
C.Aliasing — a band-limited signal can be reconstructed exactly when sampled at a rate greater than twice its highest frequency component
D.Aliasing — folding of frequency components above half the sampling rate into lower frequencies, prevented by a low-pass filter placed ahead of the sampler
14. Which term means: "integral of the product of input and the time-reversed, shifted impulse response giving LTI output; becomes multiplication in the frequency domain"?
A.Convolution — integral of the product of input and the time-reversed, shifted impulse response giving LTI output; becomes multiplication in the frequency domain
B.Convolution — set of s or z values for which the transform sum converges; a causal stable system's region includes the jω axis or unit circle
C.Convolution — output at any instant depends only on present and past inputs, requiring the impulse response to be zero for negative time
D.Convolution — total energy of a signal computed in the time domain equals the energy computed from the squared magnitude of its Fourier transform
17. Which term means: "set of s or z values for which the transform sum converges; a causal stable system's region includes the jω axis or unit circle"?
A.Region of convergence — about 9% overshoot next to a discontinuity in a Fourier series partial sum that does not shrink as more terms are added
B.Region of convergence — system obeying superposition whose response to a shifted input is the same output shifted, fully described by its impulse response
C.Region of convergence — set of s or z values for which the transform sum converges; a causal stable system's region includes the jω axis or unit circle
D.Region of convergence — folding of frequency components above half the sampling rate into lower frequencies, prevented by a low-pass filter placed ahead of the sampler
A.BIBO stability — folding of frequency components above half the sampling rate into lower frequencies, prevented by a low-pass filter placed ahead of the sampler
B.BIBO stability — total energy of a signal computed in the time domain equals the energy computed from the squared magnitude of its Fourier transform
C.BIBO stability — about 9% overshoot next to a discontinuity in a Fourier series partial sum that does not shrink as more terms are added
D.BIBO stability — every bounded input produces a bounded output, which is equivalent to an absolutely integrable (or summable) impulse response
23. Which term means: "total energy of a signal computed in the time domain equals the energy computed from the squared magnitude of its Fourier transform"?
A.Parseval's theorem — integral of the product of input and the time-reversed, shifted impulse response giving LTI output; becomes multiplication in the frequency domain
B.Parseval's theorem — total energy of a signal computed in the time domain equals the energy computed from the squared magnitude of its Fourier transform
C.Parseval's theorem — a band-limited signal can be reconstructed exactly when sampled at a rate greater than twice its highest frequency component
D.Parseval's theorem — about 9% overshoot next to a discontinuity in a Fourier series partial sum that does not shrink as more terms are added
A.Gibbs phenomenon — every bounded input produces a bounded output, which is equivalent to an absolutely integrable (or summable) impulse response
B.Gibbs phenomenon — output at any instant depends only on present and past inputs, requiring the impulse response to be zero for negative time
C.Gibbs phenomenon — total energy of a signal computed in the time domain equals the energy computed from the squared magnitude of its Fourier transform
D.Gibbs phenomenon — about 9% overshoot next to a discontinuity in a Fourier series partial sum that does not shrink as more terms are added
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