E9B Free-space antenna patterns: E and
H plane patterns (ie, azimuth
and
elevation in free-space); gain as a function of pattern; antenna
design (computer modeling of antennas)
E9B01
(C)
What
determines the free-space polarization of an antenna?
A. The orientation of its magnetic field (H
Field)
B. The orientation of its free-space
characteristic impedance
C. The orientation of its
electric field (E Field)
D. Its elevation pattern
E9B02
(D)
Which
of the following statements is true about the radiation pattern shown in Figure
A9-1?
A. The
pattern shows the beamwidth of the antenna
B. The
pattern shows the azimuth or directional pattern of the antenna
C. The
pattern shows the front to back pattern of the antenna
D. All of these choices are correct
E9B03
(B)
In the
free-space H-Field radiation pattern shown in Figure A9-1, what is the 3-dB
beamwidth?
A. 75 degrees
B. 50 degrees
C. 25 degrees
D. 30 degrees
E9B04
(B)
In the
free-space H-Field pattern shown in Figure A9-1, what is the front-to-back
ratio?
A. 36 dB
B. 18 dB
C. 24 dB
D. 14 dB
E9B05
(D)
What
information is needed to accurately evaluate the gain of an antenna?
A. Radiation resistance
B. E-Field and H-Field patterns
C. Loss resistance
D. All of these choices
E9B06
(D)
Which
is NOT an important reason to evaluate a gain antenna across the whole
frequency band for which it was designed?
A. The gain may fall off rapidly over the whole
frequency band
B. The feedpoint impedance may change radically
with frequency
C. The rearward pattern lobes may vary
excessively with frequency
D. The dielectric constant
may vary significantly
E9B07
(B)
What
usually occurs if a Yagi antenna is designed solely for maximum forward gain?
A. The front-to-back ratio increases
B. The feedpoint impedance
becomes very low
C. The frequency response is widened over the
whole frequency band
D. The SWR is reduced
E9B08
(A)
If the
boom of a Yagi antenna is lengthened and the elements are properly retuned,
what usually occurs?
A. The gain increases
B. The SWR decreases
C. The front-to-back ratio increases
D. The gain bandwidth decreases rapidly
E9B09
(B)
What
type of computer program is commonly used for modeling antennas?
A. Graphical analysis
B. Method of Moments
C. Mutual impedance analysis
D. Calculus differentiation with respect to
physical properties
E9B10
(A)
What is
the principle of a "Method of Moments" analysis?
A. A wire is modeled as a
series of segments, each having a distinct value of current
B. A wire is modeled as a single sine-wave
current generator
C. A wire is modeled as a series of points,
each having a distinct location in space
D. A wire is modeled as a series of segments,
each having a distinct value of voltage across it
E9B11
(B)
In the
free-space H-field pattern shown in Figure A9-1, what is the front-to-side
ratio?
A. 12 dB
B. 14 dB
C. 18 dB
D. 24 dB