T/F RAT REVIEW Flashcards
True/False? The system below illustrates a parallel connection of two LTI systems with system
functions H(s) and G(s
False (Feedback)
True/False? In the system in the figure above, H(s) is the system function for the feedforward
path
True
True/False? Negative feedback can be used to make an unstable system stable by moving a
pole from the right half-plane to the left half-plane.
True
Which example listed below is NOT an application of feedback discussed in the reading and
videos:
* Stabilization of Unstable Systems
* Compensation for Nonideal Elements
* Creating Inverse Systems
* Transmuting Lead into Gold
Transmuting Lead into Gold
True/False? If an LTI system is causal and stable, all of the poles of H(s)
are in the right half plane, i.e., all of the poles have Re{s}>0.
False
True/False? If an LTI system is stable, then the ROC for H(s) includes the
real axis in the s-plane, i.e., s=σ
False (Imaginary jw)
True/False? If two LTI systems are connected in series, the overall
transfer function is the sum of their individual transfer functions
Htotal (s) = H1(s) + H2(s)
False (Parallel)
Which of the following connection of systems is shown in the figure?
* Parallel
* Inverse
* Feedback
* Series
Parallel
True/False? The frequency response magnitude |H(jω)| increases for
the region of the imaginary axis near a pole.
FALSE
True/False? Moving a pole closer to the imaginary axis makes the
corresponding peak in |H(jω)| broader and less sharp.
False (sharp)
True/False? Taking the integral of a signal in time corresponds to
multiplying the Laplace transform by (1/s), i.e., (1/s)X(s)
True
True/False? Shifting a signal in time by t 0 corresponds to a Laplace
transform of X(s/t 0).
False (use the table bozo)
True/False? The region of convergence (ROC) for a Laplace transform
must contain all of the poles of X(s).
False
True/False? The ROC for a Laplace transform X(s) must always be a
circle or disk shaped region in the complex plane.
False
True/False? For a rational Laplace transform X(s) = N(s)/D(s), the roots
of D(s) are called the poles of the transform
True
True/False? Evaluating the Laplace transform on the unit circle s =
ejω gives the Fourier Transform (assuming the signal x(t) had a Fourier
Transform)
False
True/False? A spectrogram plots the magnitude of the time dependent
Fourier transform obtained by breaking a time signal into shorter
blocks.
TRUE
True/False? The default window for Matlab’s spectrogram command is
the Hamming window.
TRUE
True/False? The FFT size used by spectrogram should be greater than
or equal to the block size specified by the window length.
TRUE
True/False? By default, Matlab only plots the spectrogram for positive
frequencies since we know the magnitude of the Fourier transform is
even symmetric for real signals.
TRUE
True/False? An FM transmitter can always operate at peak power
because the carrier envelope is constant.
True
True/False? Wideband FM signals generally require more bandwidth
than AM signals to transmit the same information.
True
True/False? The instantaneous frequency of the signal x(t) = A cos(θ(t))
is defined as
False (dtheta(t)/dt)
True/False? For sinusoidal FM transmittingthe quantity (Δω/ωm ) is the modulation index
True
True/False? Embedding an information bearing
signal on a carrier by multiplication is called
interpolation.
FALSE
True/False? Amplitude Modulation systems assume
that the modulating signal has finite bandwidth.
TRUE
True/False? Frequency Division Multiplexing is a technique for simultaneously transmitting several
information bearing signals by assigning each signal a
unique carrier frequency.
TRUE
True/False? Single-sideband Amplitude Modulation
increases the bandwidth required to transmit a signal
by a factor of ten if you want to avoid losing
information.
FALSE
True/False? An automobile suspension system can
be modeled as an example of a second-order system
TRUE
True/False? For the frequency response
𝐻𝐻(𝑗𝑗𝜔𝜔) = 𝜔𝜔𝑖𝑖
2
(𝑗𝑗𝜔𝜔)2+2𝜁𝜁𝜔𝜔𝑖𝑖(𝑗𝑗𝜔𝜔) + 𝜔𝜔𝑖𝑖
2
The resonance frequency of this system is approximately 2𝜁𝜁𝜔𝜔𝑖𝑖
TRUE
True/False? For the frequency response
𝐻𝐻(𝑗𝑗𝜔𝜔) = 𝜔𝜔𝑖𝑖
2
(𝑗𝑗𝜔𝜔)2+2𝜁𝜁𝜔𝜔𝑖𝑖(𝑗𝑗𝜔𝜔) + 𝜔𝜔𝑖𝑖
2
If 𝜁𝜁 > 1, the system is overdamped
TRUE
True/False? For the frequency response
𝐻𝐻(𝑗𝑗𝜔𝜔) = 𝜔𝜔𝑖𝑖
2
(𝑗𝑗𝜔𝜔)2+2𝜁𝜁𝜔𝜔𝑖𝑖(𝑗𝑗𝜔𝜔) + 𝜔𝜔𝑖𝑖
2
The height of the peak of |𝐻𝐻 𝑗𝑗𝜔𝜔 | at resonance is inversely proportional to 𝜁
TRUE
True/False? To find the log magnitude response 20 log |H(jω)| for a
cascade of systems, we can add the log magnitudes of the individual
systems.
TRUE
True/False? Bode plots approximate the frequency response
magnitude in dB using parabolas and exponentials.
FALSE
True/False? The high frequency region of a Bode plot of a first-order
lowpass filter has a slope of +60 dB/decade.
FALSE
True/False? The figure below shows
the Bode plot approximation for log
|H(jω)| for a first-order lowpass
filter.
(flat, then slope of -20db)
TRUE
True/False? The magnitude of the frequency response |H(jω)| is also commonly
called the gain of the system.
TRUE
True/False? The magnitude of the output Fourier transform is the sum of the
magnitude of the input Fourier transform and the magnitude of the system’s
frequency response, i.e., 𝑌𝑌 𝑗𝑗𝜔𝜔 = 𝑋𝑋 𝑗𝑗𝜔𝜔 + 𝑋𝑋 𝑗𝑗𝜔𝜔
FALSE MULTIPLY
True/False? In the filter specification shown below, δ2 is the passband ripple.
False (stopband)
True/False? In the filter specification below, the region ω>ωs is the passband for
the filter.
False (stopband)
