midterm Spring 2023 with Answers
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Feb 20, 2024
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AAE 590 Modern Avionics
Midterm
Spring, 2023
Name:_________________
Multiple Choices (100 points, 4 points each)
1.
Which of the following is NOT a parameter of sinusoidal function? ( D )
A. amplitude
B. frequency
C. phase
D. wavenumber
2.
When cos50
t is mixed with cos70
t, which of the following frequency will be
generated? ( D )
A. 120Hz
B. 3500Hz
C. 20Hz
D. 60Hz
3.
Which of the following frequency band is NOT used in avionics? ( D )
A.
S band of satellite communications
B.
L band of satellite communications.
C.
HF band
D.
LF band
4.
Which of the following is the spatial counterpart of frequency? ( A )
A. wavenumber
B. wavelength
C. period
D. amplitude
5.
What is the Doppler shift when the moving speed is 3m/s while the carrier
frequency is 1Ghz? ( B )
A. 1Hz
B. 10Hz C. 100Hz
D. 1000Hz
6.
What is the major reason for fading in communications? ( C )
A. Diffraction
B. Refraction
C. Interference
D.
Doppler shift
7.
If 6 bits are used for the quantization, how many levels of quantization should
there be? ( C )
A. 512
B. 256
C. 64
D. 32
8.
What is the purpose of modulation? ( A )
A.
Up-convert the baseband signal to higher frequency band
B.
Down-convert the high frequency signal to base band
C.
Detecting the signal envelop D.
Convert the signal to the intermediate frequency
9.
What is the geometric intuition of demodulation in digital communications? ( D )
A.
Evaluating the signal amplitude
B.
Putting the coordinates to the corresponding basis signals
C.
Calculating the phase
D.
Projection to the basis functions
10. Suppose that the signal bandwidth is 200kHz. The carrier frequency is 850kHz. A
local oscillation of 395kHz is used for down-converting the signal to the
intermediate frequency 455kHz. Then, which of the following interference will
interfere the signal? ( B )
A.
An interference at 455kHz
B.
An interference at 105kHz
C.
An interference at 1780kHz
D.
An interference at 10Hz
11. What is the advantage of DPSK? ( B )
A.
Has better performance than PSK in all aspects
B.
Pilot (reference) signals are not needed for eliminating the phase uncertainty
C.
Can eliminate the necessity of matched filter
D.
Can eliminate the necessity of local oscillator at the receiver
12. Which of the following is random access? ( C )
A. TDMA
B. CDMA
C. CSMA
D. FDMA
13. Who is the inventor of CDMA? ( A )
A.
C. B.
D.
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14. Which of the following aircraft communication signal covers the largest distance?
( B )
A. VHF
B. HF
C. VDL
D. ADS-B
15. Which of the following communication signals is the most sensitive to the sun
activity? ( B )
A.
VHF communications
B.
HF communications
C.
WiFi communications
D.
Cellular (say 5G) communications
16. Which of the following modulation schemes is NOT used in aircraft
communications? ( D )
A. DSB
B. SSB
C. DPSK
D. FSK
17. Which of the following is not a function of radar? ( D )
A. Detection
B. Tracking
C. Ranging
D. Demodulation
18. To achieve a range resolution of 0.5 meter, what is the minimum needed
bandwidth? ( B )
A. 30MHz
B. 300MHz
C. 3GHz
D. 30GHz
19. Which of the following is used for measuring the direction of the target? ( C )
A.
Round trip time
B.
Doppler shift
C.
Antenna array
D.
Chirp pulse
20. Pulse compression is used to ( )
A.
To increase the total bandwidth
B.
To suppress clutters
C.
To reduce noise
D.
To improve the signal energy
21. Which of the following is NOT used in FMCW radar receiver? ( D )
A. Mixing
B.
Low pass filter
C. FFT
D. Correlation
22. Which of the following is NOT significantly related to the performance of
Doppler shift and velocity estimation? ( )
A.
Time duration
B. Bandwidth
C.
Pulse energy
D.
Noise power spectral density
23. Which of the following is correct for transponders? ( C )
A.
It reflects the incoming signal back to the radar transmitter.
B.
It does not need a local oscillator
C.
The incoming and outgoing signals are in different frequency bands
D.
It uses SSB modulation
24. TCAS is used to ( A )
A.
Prevent mid-air collisions
B.
Broadcast GNSS position information
C.
Measure the aircraft altitude
D.
Reflect the secondary surveillance radar signal back to the ground station
25. In pulsed radar, the maximum unambiguous range is inversely proportional to
(C )
A. Power
B. Bandwidth
C.
Pulse repetition frequency
D.
Noise power
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