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TLT-6306: RF Eguipment for Wireless Networks Exam 15.12.2011
Compiler: Jarno Niemelä Answer to all guestions!
Calculators are allowed in this exam. Total maximum points: 30 (+ exercise bonus)
J Explain shortly:
4 a) Noise figure , b) Grating lobes 49 Circular polarization
p 2 p) (2)
2. a)

4 Show by calculation (provide also the explanation) what is the power ratio in decibel scale
between the first output port and the input port in:

2-way splitter, 3-way splitter, 4-way splitter.
Assume that the splitters are ideal (e.g. no internal losses). (2 p)

b) 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 1 and the input port is set to -5 dB. (3 p)

= c) Draw/sketch an example of a radio system where you could use these kind of components.

(1p)

EN Two collinear, z-directed, and short dipoles are placed at a distance of half wavelength as
depicted in Figure 1. The amplitude gain of each element is 1 (i.e., 0 dB) and the feeding
phase difference between each element is 0". Formulate the normalized radiation pattern as a

function of elevation angle 0 produced by such antenna array. w-

M2 A
«<>
Sat 1. a
Figure 1

(6 p)

4. 4 a)
Describe and explain three different ways to produce antenna diversity. (3 P)

1)

Consider a mobile receiver (operating bandwidth 200 kHz). Calculate, how strong should be

4 (he input signal level to the receiver if the signal-to-noise reguirement at the output is 9 dB?
The receiver noise figure is 7 dB. Assume that the input signal does not experience attenuation
when inside the receiver structure. GP)

Sä Explain, how the following parameters affect the radiation properties of linear antenna array

a) Number of array elements (with fixed inter-element spacing) (2P)
b) Element spacing (2p)
c) Phase difference between the feeding current of different elements (2P)