7 t324 Flashcards on T324, created by george162store on 04/10/2015.
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Created by badgermd163
over 8 years ago
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Copied by badgermd163
over 8 years ago
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Copied by george162store
over 8 years ago
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A radio wave has a period of 250 µs.
Calculate the frequency in MHz.
Express your answer to one significant figures.
Frequency = MHz
Calculate the wavelength of a radio wave of frequency 875 MHz
assuming that its speed is
3 × 108 m/s.
Express your answer in millimetres to two significant figures.
Wavelength = mm
An antenna receives 0.6 µW of power at a distance of
10 km from a transmitter.
Assuming isotropic conditions and an inverse square power law, calculate
the received power at the antenna if it is moved to 2.5 km from
the transmitter.
Express your answer in µW to one significant figure.
Power = µW
Calculate the power loss (in dB) through a material of thickness 50 mm
and attenuation coefficient of 50 dB/m.
Express your answer to one significant figure.
Power loss = dB
An electronic system comprises three different sections with gains of:
10 dB,
-14 dB and -15 dB.
Calculate the overall gain in dB.
Overall gain = dB
An antenna receives 10 µW of power at a distance of
1 km from a transmitter.
Assuming 1/d^4
relationship, calculate
the power received if the distance is increased to 9 km.
Express your answer in µW to two significant figures.
Power received = µW
It is proposed to use a half-wavelength dipole of physical size 9 m to
produce a short wave radio.
Calculate the corresponding frequency of the radio station in MHz. Take the speed
of light to be 3 × 10^8 m/s.
Express your answer to two significant figures.
Frequency = MHz
Calculate the number of bits that can be represented by each symbol for a modulation system with
32 symbols.
Number of bits =
In a version of MSK one symbol uses a segment of a 5.622 MHz sinusoid, the
other symbol using a segment of a 5.635 MHz sinusoid.
Calculate the signalling rate of the signal in kbaud.
Signalling rate = kbaud
The spectral efficiency for a bandwidth of 65 kHz is 19 bit/s/Hz.
Calculate the data rate in Mbit/s.
Express your answer to two significant figures.
Data rate = Mbit/s
Calculate the width of a continuous frequency band containing 250 µW
of power if the power density is 0.65 mW/MHz.
Express your answer to two significant figures.
Bandwidth = MHz
Calculate the noise power in a signal of power of 0.56 mW
if the signal-to-noise ratio is 6.
Express your answer in µW to two significant figures.
Noise power = µW
The theoretical maximum data rate for a bandwidth of 6.0 MHz is 23.4 Mbit/s.
Calculate the approximate value of the signal-to-noise ratio.
Signal-to-noise ratio =
In an OFDM system, the data rate per subcarrier is 100 bit/s.
If the data is evenly distributed across all of 182 subcarriers,
calculate the approximate, overall data rate in Mbit/s to three significant figures.
Overall data rate = Mbit/s
Calculate the total time (in ns) it takes for a signal to be transmitted over this
link and be reflected back to the source, assuming no time delay at reflection.
Assume the speed of propagation is
3 × 10^8 m/s.
Express your answer to three significant figures.
Total time = ns
Perform a bit by bit XOR operation on the following two binary numbers:
10101010101100010011
XOR =
In a WEP encryption system it takes 9 hours for an initialisation vector
value to be repeated.
If the initialisation vector is 22 bits long and is incremented by 1 for
each frame transmitted by an access point, calculate the operating data rate in
Mbit/s assuming the frames are, on average, 2000 bytes long.
Express your answer to three significant figures.
Data rate = Mbit/s
A wireless sensor device employs a battery of lifetime 27 days when used over a
distance of 6 m.
Assuming the transmitter power is proportional to 1/d^3,
estimate how long the battery will last if the distance of operation is reduced
to 2.5 m and the same power is received.
Give your answer to the nearest day.
Battery life = days
A 0.7 GHz bandwidth is centred on a frequency of 7 GHz
Is this situation considered to be ultra wideband?
Tick the box if the situation is considered to be ultra wideband. Leave it blank if it is not.
Ultra wideband?
A battery can supply a current of 75 µA for 150 days.
Calculate its capacity in mAh.
Battery capacity = mAh
One source estimated the population of a country in 2007 to be 10.5 million people
of which appromimately 3.1 million possessed mobile telephones.
Calculate the percentage of the total poplulation in 2007 that possessed mobile phones.
Express your answer to three significant figures.
Percentage = %
In one part of a country the number of people using mobile telephones increased from
250000 to 325000, in one year.
Calculate the percentage increase in the number of people using mobile phones.
Express your answer to two significant figures.
Percentage increase = %
At one time is was estimated that out of a population of 16400000 in a country
only about 100000 were users of the internet.
Calculate the number of internet users per 100 persons in the population.
Express your answer to two significant figures.
Internet users/100 persons =
A country is said to have approximately one landline for every 26 people. If this country has a total of 217400 landlines, calculate the population of the country.
Express your answer to two significant figures.
Population =
