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WLS 610 Cellular and PCS1
Assignment # 2
Transmitters/Receivers/Antennas/AMPS
Section A: Transmitters and Receivers
1. State the functions of the following cell site components. Also draw a diagram
showing their respective locations within a cell site. Where applicable also sketch
their frequency responses
(a)
An Isolator
(b)
Hybrid combiners
(c)
Duplexers
(d)
Multicouplers
(e)
Cavities
(f)
Filters.
2. An Isolator is connected between the __________ and the ________
3. An Isolator ____________energy in one direction and _______in another
direction.
4. An Isolator typically provides a separation of ___________dB
5. An Isolator is used in a ___________ to provide separation between the ________
and the _________
6. Explain the function of a hybrid combiner:
____________________________________________________________
7. Explain the function of cavities in a Communication system.
8. Hybrid combiners typically have ________dB insertion loss .
9. A duplexer must provide a minimum of ________dB isolation between the
____________and the Receiver.
10. For maximum transfer of Power between the Transmitter and the Antenna, the
SWR should be = _____________.
11. If Vmax on mismatched transmission line is 12 V rms and the Vmin = 8 V rms,
the SWR will be. ____________.
12. An SWR of 1.5 means? ___________________________________________.
13. Calculate the SWR for transmission line characteristic Impedence of 48 ohms and
load impedence of 75 ohms: ______________
14. Explain the purpose of combining and with the help of sketches, describe at least
2 methods of combining.
15. Fig below shows the partial diagram of a communication site. Calculate the
Effective Radiated Power (ERP) of this site
Antenna
+10dB
-1.5dB
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42.75 dBm
-0.25dB
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-1.0dB
16. A Transmitter sends 50mw down a 50-ohm line. The Transmitter is matched to
the line but the load is not. If the =0.5, how much power is reflected and how
much is dissipated in the load.
17. A transmitter supplies 50W to a load through a line with an SWR of 2. Calculate
the power absorbed by the load
18. Draw the block diagram of a transmitter and describe the function of each block
19. Draw the block diagram of a Receiver and describe the function of each block
20. Define diversity and describe 3 basic diversity techniques employed in
communication systems.
21. Define and explain following performance criteria for a Radio Receiver.
(a)
(b)
(c)
(d)
(e)
(f)
(g)
Sensitivity
Selectivity
Noise
Distortion
SINAD
Dynamic range
1-dB compression
22. Noise power is given by the equation PN =kTB, where k= Boltzmann’s constant
=1.3810 –23 J/K, T= Temperature in Kelvins =T in centigrade +273, B= BW in
Hz. The Noise power in dB is given by 10log(PN). Calculate the Noise power in
dB/Hz generated by a receiver at the following carrier frequencies at 30 degree C:
824 MHz, 849MHz, 869MHz, and 894MHz.
23. Sensitivity is given by the following equation:
Sensitivity= 10Log (PN) +10log BW +Noise Figure (NF)
Calculate the Receiver’s Sensitivity for an AMP, GSM and CDMA voice channel.
The BW of an AMP channel=30 KHz, GSM=200KHz, CDMA=1.23 MHz for a
Noise Figure (NF) of 5dB and at a temperature of 30 C.
24. Signal to Noise ratio is defined as Signal Voltage/Noise voltage=S/N. In dB S/N
Ratio is = 10log (S/N), Noise Figure (NF) =10log{(Si/Ni) /(So/No)}, where i=input
and o=output. The pure ratio with in the parenthesis is called Noise factor. When
there are several stages of amplification in a receiver, the total NFT is given by the
equation.
NFT = NF1+ (NF2 –1/ G1) +(NF3 –1/G1G2 ) +……. Where G1, G2, G3 are the
gains of amplifiers. Notice that gains here are pure gains, not in dB.
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For the system shown, calculate the overall Noise Figure
G1=10
NF1= 2
G2 =25
G3 =30
NF2=4
NF3=5
Section B : Antennas
25. Name the Antenna most commonly used for a Mobile. _____________
26. List the Antennas most commonly used at the BS
___________ _____________ _____________ __________________
27. Two Antennas have gains of 5.3dBi and 4.5 dBd, respectively. Which has greater
gain.
28. For the Antenna pattern sketched in the fig enclosed, find
(a)
The Antenna gain in dBi and dBd
(b)
The front –to-back ratio in dB
(c)
The Beam Width (BW) for the major Lobe
(d)
The Beam Width and the gain for the most important minor Lobe
29. The ERP of a Transmitter is 17W in a given direction. Express this as an EIRP in
dBm.
30. Calculate the length of a half wave dipole at 500MHz.
31. Sketch the radiation pattern of 120 degree and 60 degree sectorized LPDA and
YAGI Antennas
32. List 4 Major types of Antennas
33. Sketch the physical structure and the current and voltage radiation patterns of a
half wave length dipole
34. Sketch the physical structure of a LPDA and YAGI Antennas.
35. List and define 5 major performance criteria for Antennas.
36. Where would you use a Patch Antenna
Section C: AMPS AND NA –TDMA
37. AMPS uses _____________multiple Access for channel access
38. Sketch a diagram to show the essential components of an AMP System
39. The communication link between the BS and the MTSO could be (list at least 3
types of links): ____________ _____________ ___________
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40. How does a Mobile find out whether it is connected to its Home Network or
another Network: _________________________
41. What 2 pieces of Information the MTSO uses to validate and authorize a call.
_____________________
_____________________________
42. AMPS system allows how many channels/operator? ____________. How many
are voice? ___________ and how many are Control? ______________
43. List 4 functions performed by the Control channels
44. The paging signals are transmitted by the _______ on __________Channel
45. As long as the Mobile is On, it keeps ___________ for ___________Calls
46. Calculate the number of available traffic channels/sector in a 120 degree
sectorized, 7 cell reuse system.
47. AMP channel BW is : ______
48. The maximum mobile transmit power is: __________. The maximum BS transmit
power is : ___________49. The data transmission rate for control channel is : __________.
50. The purpose of the SAT is to identify the __________ assigned to the call.
51. During a call, the _________ and the ________inject the ______same SAT .
52. The NA-TDMA provides ___________times as much capacity as compared to
AMPS
53. The NA-TDMA is based on ____________multiple access..
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