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TLT-6306: RF Eguipment for Wireless Networks Exam 30.01.2012
Compiler: Jarno Niemelä Answer to all guestions!

Calculators are allowed in this exam. Total maximum points: 30 (+ exercise bonus)

I: Explain shortly:

a) Receiver sensitivity (2 p) b) Space diversity (2 P) c) Phase noise (2p)

Explain the non-idealities (the phenomena) caused by typical analogue receiver front end
components.

Using the values given in Figure 1, caleulate the signal-to-noise ratio (SNR) at the receiver
output (S2), when it is measured that the SNR at the LNA input (S1) is 13 dB. (6P)

SI Cable s2

I

Fina = 2 dB, Frx= 5 dB
Gina = 15 dB,
Cable loss between LNA and RX unit: 1 dB
Figure 1

 

 

 

 

 

a) What additional RF-eguipment you need and how to make the connections in Figure 2?
Space diversity reception is implemented and only two feeders can be used. Antenna 2 is the
diversity antenna. (3P)

=

RX/TX uplink
BS a

= 3] — fd! 0 doimiink
senast
a Feeder 2

DIV RX

ANT

 

 

 

 

Figure 2
0
How does the tapper differ from splitter? Consider a 2-way tapper. What is the power ratio in
decibel scale between the output port 42 and the input port, if the power ratio between output
port 41 and the input port is set to -7 dB. (3P)

On a Rayleigh fading channel, the received average signal energy is measured to be 17 dB
above the noise level. Assume additive white Gaussian noise. The receiver in use is assumed
to work satisfactory if the SNR is larger than 6 dB. How many branches are reguired for a
diversity system exploiting selection combining to obtain a time availability of 99.54?