Q1 The incident electric field strength at an antenna aperture is 10mV/m. Given that the received signal power is 1 picoWatt the antenna effective aperture is:
a 10-7 m2
b 3.8 m2
c 0.01 m2
d 107 m2
e 1 m2
Q2 A 10GHz antenna has a physical aperture of 1 metre x 10cm. The antenna gain will be approximately:
a 31.4 dBd
b 42
c 31.4 dBi
d 62.8 dB
e 30 dBd
Q3 An antenna has a horizontal beamwidth of 10o and a vertical beamwidth of 20o , the antenna directivity is approximately:
a 206
b 0.06
c 0dB
d 46dB
e 16.7
Q4 A certain monopole antenna provides a system gain of 3 dB in service and is 90% efficient. What is its directivity?
a 2
b 5.1 dB
c 3.5 dB
d 3 dBd
e 3.2
Q5 An antenna radiates 100 watts and has a directivity of 10dB. The power received at a range of 1km in free space is 1 milliwatt. The antenna used to receive the signal has an effective aperture of:
a 12.6 m2
b 5 m2
c 126 m2
d 1.26 m2
e 10 m2
Q6 Each element in a linear array of two isotropic antennas is fed with the same signal, given that the element spacing is l, the resulting radiation pattern will:
a be a broadside pattern
b be an endfire pattern
c contain a radiation null along the axis of the array
d contain a main lobe in both endfire and broadside directions
e contain a main lobe at 45o to broadside
Q7 The element spacing in an array is
a determined solely on the grounds of element size
b required to be less than l/2 if the beam is to be steered
c limited to l if the beam is to be steered
d determined by the necessary input impedance
e is determined by the required beam steering angle
Q8 A 25 watt 900MHz basestation transmitter uses a half wave dipole antenna.
a the antenna feed current will be 0.59 A
b the transmitter output voltage will be approximately 1.8 kV
c the safe radius from the antenna will be 10m
d the antenna gain will be 5.1 dB
e the transmitter output voltage will be approximately 30 V
Q9 A helical antenna:
a provides a radiation pattern similar to a l/4 monopole
b will operate in the normal mode if its circumference is more than l
c will operate in the axial mode if its circumference is less than l
d will produce an endfire pattern when the circumference is more than l
e will always give more gain than a l/4 monopole
Q10 A parabolic dish antenna with diameter 1.5m operates at 30GHz, the distance to the far field is approximately:
a 450m
b 225m
c 1mm
d 10mm
e 0.1mm
Q11 An antenna with maximum dimension 2cm operates at 150MHz. The distance to the far field is approximately:
a 0.4mm
b 0.2mm
c 20cm
d 1m
e 10m
Q12 An antenna with gain 10 dB at 900 MHz delivers 1mW to a matched load from an off air signal. The power density at the antenna aperture is:
a 100mW/m2
b 8.8mW/m2
c 44.9mW/m2
d 6mW/m2
e 11.3mW/m2
Q13 A system transmits a 1 microwatt signal using an antenna with gain 10dB, the free space loss to the receiver is 100dB and the receiver antenna provides no additional gain. The signal to noise ratio at the output of the receiver low noise amplifier is 0dB and the system is thermal noise limited. Given that the noise figure for the low noise amplifier is negligible and its gain is 20dB, the receiver bandwidth is:
a 250 kHz
b 500 Hz
c 25 MHz
d 2.5 MHz
e 25 kHz
Q14 A 5 element linear array antenna has an element spacing of l/4 along the axis of the array. If all the elements are fed in phase,
a The radiation pattern would be end-fire.
b The radiation pattern would contain nulls in the end-fire direction
c The radiation pattern would contain grating lobes
d The radiation pattern would be broadside
e The antenna input impedance would be reactive
Q15 A 5 element linear array antenna has an element spacing of l/4 along the axis of the array. If the progressive phase shift across the array is 90o, the beam will be steered to:
a endfire
b 45o
c broadside
d -45o
e 90o
Q16 A vertical slot will give:
a horizontal polarisation
b vertical polarisation
c a radiation pattern similar to a horizontal dipole
d a radiation pattern similar to a vertical loop
e a low input impedance
Q17 A short horizontal loop will give a radiation pattern:
a like a short horizontal dipole
b like a short horizontal slot
c like a short horizontal slot but with opposite polarisation
d exactly like a short vertical dipole
e exactly like a short vertical slot
Q18 A linear array is constructed with the maximum possible spacing between elements which can be used with beam steering. The phase shift required between each element to steer the beam through 20o is:
a 0.53 radians
b 0.53 degrees
c 15 degrees
d 1.07 radians
e 30 degrees
Q19 A microstrip rectangular patch antenna is constructed using a substrate with er = 4. The length of the patch for operation at 3.4 GHz is approximately:
a 22 mm
b 44 mm
c 11 mm
d 88 mm
e 100 mm
Q20 The directivity of an antenna
a is not the same on transmit and receive
b is a measure of its in service gain
c is given by gain multiplied by efficiency
d is purely a measure of the focussing in the radiation pattern
e is lower on transmit than receive.
发表于 2005-3-13 22:44:00
