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CONFIDENTIAL

s{ F4{.HJT]NTVERSITI TUN TIUSSEIN OI\N MALAYSIA

FINAL EXAMINATIONSEMESTER NSESSION 20r0t20rrCOURSECOURSE CODEPROGRAMMEEXAMINATIONDATEDIIRATIONINSTRUCTION

COMMLINICATION ENGINEERINGBEE 3123 /BEX3I403BEEAPRIL IMAY2OII2 HOURS 30 MINUTESANSWERFOUR (4) QUESTTONS ONLY

THIS PAPER CONSISTS OF FOT]RTEEN (I4) PAGESCONF'IDENTIAL

7/28/2019 Final BEE 3123 S2 10-11

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Q1

BEE3l23 / BEX314,03

(a) List TWO general elements between a transmitter and a receiver. Then,explain the meaning for ONE of the elements. (4 marks)A Short Wave (SW) radio broadcast and a television broadcast can transmitsignals for one complete cycle at 0.104 p and 17.543 ns respectively. Whichofthe two applications has the longest wavelength? Justiff your answer.

(6 marks)

(c) A four stage system comprising of two loss stages and two gain stages whichis ananged altemately as in Figure Ql(c). The first and third stage haveattenuation factor of 0.075 and 0.3 respectively. The second and final stagehave gain of40 dB and 14 dB respectively. Given that the input voltage to thefrst stage is 40 rzV.(i) Determine the final output voltage, Vo,,1 of the system.(ii) Determine the output power, P6 in dBm if a l0 lf,) load resistor is

cormected to the final stage.(iii) If Stage 3 is a voltage divider networh design the network so that thefinal output voltage is increased to I V. Given thar, one of the resistorvalues is fixed to 2.2 lf). (15 marks)

(b)

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BEE3l23 / BEx3l,l03

Q2 (a) Signals can be classified into five main calegories and the requirementsneeded to represent a signal in terms of Fourier Series are called Dirichlet'sconditions. Based on that term, a Trigonometry Fourier Series expression for asignal firnction is given below.

@f/ r \ /, \. .l/1r)=to+)ll-| .1"'osnrt *l -- lslmnnt IfrL\n'+l) \n'+l/ .J(i) State ONE ofthe signals glassi6cati.ns.(ii) Explain TWO of the Dirichlet's conditions.(ii1) Generalized the above expression in tenns of Exponential Fourier

Series up to 3' harmonics. (10 marks)(b) Given a non-periodic sipaU(t) in Figure Q2@).

(1) Fhd the/(t)'s piece-wise function.(ii) Determine the Fourier Transform for/(t).(iii) Distinguish whetier the signal has either power or energy content.(iv) Justiff your answer in Q2OXiii). (15 marks)

7/28/2019 Final BEE 3123 S2 10-11

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Q3

BEE3t23 / BEX31403

(a) An amplifier is an important circuit in a receiver. For a 12 dB gain amplifier atroom temperatw, it is observed that the equivalent temperature is 522K whenit is injected with 9zW input power and 50pW noise power. The amplifier isfound to have an amount ofadditional noise.(i) Describe the importance ofequivalent temperature in a receiver.(ii) Detennine the noise power contributed by the amplifier in dB,z.

(c)

(12 marks)

Noise is a general form of impairment that is divided into two categories.Thermal noise however, is an example of Intemal Noise where both noisepower and noise voltage can be predicted using a simple noise generatorequivalent circuit.(D Identiff the TWO types of noise.(ii) Relate the significance between white noise and thermal noise. Useappropriate equations to support your answer. (5 marks)Given two resistor values of 3.3if,) and 6810, to be used in ttre noise generalorcircuit at temperature of 27oC, over a 500 tFIz bandwidth.

(i) Develop a load resistive network so that the noise voltage drop at theoutput is measued to be 2.55 pV-" for the worst case condition.(iD From your synthesis in Q3(cXi), criticize on the main element thatinfluences low therrnal noise voltage. (8 marks)

o)

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BEE3l23 / BEX3l,103

Q4 (a) (i) Base on your understanding, explain in brief about Image Frequency.(ii) TherL use any related figure to show the relative frequency spectrumfor the radio frequency (RI), interrnediaG frequency (IF), localoscillator (LO) and image frequencies for a super-heterodyne teceiverusing high-side injection. (4 marks)

O) A 500 ftHz canier signal with peak amplitude of 32V is mixed in an amplitudemodulation double sideband full carrier (AM-DSBFC) Modulator with a 12ftH2 singls tone whose amplitude is sufficient to produce a l4-Vp change inthe amplitude of the envelope. Assume that the load resistance is 72Q,determine the following:(i) upper and lower sideband frequency,(i1) modulationcoeflicient,(iii) maximum and minimurn amplitudes of the envelope,(19 modulated carrier power,(v) upper, lower sideband powers and total sideband power,(vi) total transmitted power and(vii) draw the output AM signal and its power spctrum. (13 marks)

(c) (D Construct the equation for amplitude modulation signal by rcfgrrin* toTable Q4(c). Assume that the load resistance R;: 50O.(ii) Predist what happen to the sideband power and carrier power if themodulation index. m becomes an ideal modulation. (8 marks)

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BEE3l23 / BEX31403

Q5 (a) (i) fgfins ths 6saning of Direct Phase Modulation @M).(iii) Visualize how the PM wavefomr can be generated from carrier andmodulating signal. (a ma*s)(b) A modulating signal, ,/.() = 2cos(20004r) is pumped into a frequencymodulation (FM) modulator with a peak frequency deviatioq Lf =l.sktlz.Given that the amplitude ofa carrier signal, V" = lOV and its frequency,f,:500 &Hz. Determine,

(i) modulation index of the FM modulator,(ii) number of sets of sigrificant side frequencies, and(iii) theiramplitudes.(iv) Draw the frequency spectrum showing their relative amplitudes.(v) Compare the values of actual minimum bandwidth from the BesselFunction Table and the approximate minimum bandwidth usingCarson's Rule. Justifo vour answer (15 marks)

(c) A commercial HOTFM radio station transmits 90.10 MtIz FM signal throughthe free space to your radio.

O Desip an FM Demodulator which has the simplest and easiest conceptso that the FM signal can be recovered clearly.(ii) Then" explain the operation of your FM Demodulator as in Qs(c)(i)using your own words. (6 marks)

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BEE3l23 / BEX31403

a6 (a) Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK) and PhaseShift Keying (PSK) are the three basic digital modulation techniques.(D If the given binary input is 10100, draw the digital modulation output

waveform of ASK and FSK technique.(ii) Then, explain briefly the operation of the simplest digital modulationtechnique among those three techniques. (a marks)(b) An information signal to be transmitted digitally with a period of 83.33ps. Ithas been determined that the wave will be adequately pass if the bandwidthincludes the fifttr harmonics. After that the signal has to be converted to an 8-bit PCM signal for hansmission over a digital telephone system. Calculate,

(i) the signal frequency,(ii) the fourth harmonic,(iil) the minimum sampling rate,(iv) the bit rate, and(v) the bandwidth when a sirx/x pulse shape is used. (10 marks)(c) Compute the ASCII code for each character of LOG and followed by an eightbits for error detection per character. The eight bit is chosen so that the

number of ones in the total 8 bits is odd number. (3 marks)

(d) A sinusoidal wavefonrl x(t)=V.sn(2ttft) with a dynamic range of 14 Voois quantized using 3-bits scheme.(i) How many quantization levels?(iD What is bit pattern corresponding to each quantization levels andvoltage level correspond to each bit pattem?(iiD Suggest one method so that we can minimize the quantization error if

the value of quantization error is high. (g marks)

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BEE3 t23 / BEX3l,t03FINAL EXAMINATION

SEMESTEFJSESSION : SEM tr,20101201I PROGRAMME :BEECOURSENAME : COMMLINICATION COURSE CODE :BEE3I23 /ENGINEERING BEX314O3

trIGURE Ol(c)

(sec)X'IGI]RE 02(b)

ABLE O4(cCanier sisnal Carrier power, P" = I W Carrier frequency,f" = 500 kHzUpper sideband usb power, P*u : 0.04 W usb frequency,/*5 : 501 kHzLower sideband lsb power, P66 = 0.04 W lsb freqnency,l st: 449 kllz

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BEE3l23 / 8EX31403FINAL EXAMINATION

SEMESTER/SESSION : SEM IL 20l0l20ll PROGRAMME :BEECOURSENAME : COMMLJNICATION COURSE CODE :BEE3I23 |ENGINEERING BEX3I4O3

TABLE I : TNGONOMATRY PROPERTIESTrigonometry Identity Trigonometry Integral

sliA _ ssE;A* jsinA f snna'"t dt=0;f co"na4t dt -o"oo+|("tn +"-'n);"i"A=+(r/ -r-'^)

( snnan cosra..t dt =0cos2A+sin2A=l;cos'A - sint A - cos2A f snnco,tsnm@.t dt -0,(m*n)2cosAsinA=sin2A ( cosna^t cosma."t dt -0,(m* n)"or',4 = 111 + co s2A\ ; sn')l = ! (1 - cosi.A) f s 'nt;at:!:f "o! nr,tat=Lcos(l + B) = coslcosf + sinAsinB f co, ot at -lsnot ,f sinat dt = -lcos atsin(l t B) = sinlcosB + coslsinB It*, ot at =\cosot+lsinat

Ir;o,a.ig= i(co(l- B)-cos(/+ B)) It"a* a, = \sinat -lcosatI.o*.og = i(cos(l- a)+cos(l +B)) f^ .e^at --tt-f, !,*' .r"a,

,io,l"ora = |(sin(,4 - B) + sin(l + B))

7/28/2019 Final BEE 3123 S2 10-11

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BEE3l23 / BEX3l,103FINAL EXAMINATION

SEMESTER/SESSION : SEM II,201012011 PROGRAMME :BEECOURSENAME : COMMUNICATION COURSE CODE :BEE3I23 /ENGINEERING BEX3I4O3

TABLE 2: Values of cosine, sine and exponential functionsfor integral multiples of n.

Function Valuecosznn Isin2ntt 0cosfl7, (-1)',srnwf 0

nrtcos-2 [{-t)'''Io n=eve424,6,8"-)n=odd. nrtsln -2

[*,l(-r) '[0

n = odd(1,59,13".)n = eyen. 3nt

2( ,-tl-(-1)'It0 n = odd(3,7,11".)n = eVen

e! i2nr Iexinrr (-D"

. ntf

e'[ {-r)'''I "-lu(-1)'

n = evenn=odd

10

7/28/2019 Final BEE 3123 S2 10-11

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BEE3l23 / BEX31403FINAL EXAMINATION

SEMESTER/SESSION : SEM II,20101201I PROCRAMME :BEECOURSENAME : COMMUNICATION COURSE CODE :BEE3I23 /ENGINEERING BEX3I4O3

TABLE 3: Fourier Transform PairTimedoman,f(t) Frequency domai4 F(ar)t(/) I

1 2z'd(a)u(t) 16@)+J-la)u(t + r)- u(t - r) .slnatal'l 7sgl(/) 2jat

e-'u(t) Id+ ja)e'u(-t) Id- Ja)t'e-'u(t) n!(a+ jat)'"'-d|lle " 2a---;------;d- +o-

et'J 2n6(a-a")sino.t ix[d@t+a,\-6(o-o.\]c.os,,.t zl\fut+ot"\+5(r-r.)l

e-'sina"t u(t) aro(a + iatf +aje-'cosa"t u(t\ a+ ja(a + iotl +al

l1

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BEE3l23 / BEx3l,[03FINAL EXAMINATION

SEMESTER"/SESSION : SEM II, 201012011 PROCRAMME : BEECO|jRSE NAME : COMMLJNICATION COURSE CODE :BEE3|23 |ENGINEERING BEX3I4O3

TABLE 4: Properties of Fourier TransformProperty Time domain,f(t) Frequency domain, F ((D)Linearity arf,(t)+ arfr(t) qFr(a)+arFr(at)Scaling f(at) *"telvla

Time Shift "f(t-a) e-r* F(a)Frequency Shift e-j'" f(t\ F(a - at"\Modulation cos(aror) /(t) )lr

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BEE3l23 / BEX3I/m3FINAL EXAMINATION

SEMESTER/SESSIONCOURSENAME : sEM II,201012011:COMMTJNICATIONENGINEERINGPROGRAMMECOURSE CODE : BEE: BEE3I23 IBEX31403

TABLE 5: Bessel Function

rCt'F -e

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BEE3I23 lBEX3l403X'INAL EXAMINATION

SEMESTER./SESSION : SEM IL 20101201I PROGRAMME : BEECOURSENAME : COMMUNICATION COURSE CODE :BEE3I23 |ENGINEERING BEX3I4O3

TABLE 6: ASCII Table

Constant:Speed oflight, c = 3.01 x 108 rnlsBoltzrnann constanl /r: l.38xl0-B J/K

Absolute ternperature , T = l/'C or 290K

Bits 0 I 0 1 0 I 0.l

6l 0 0 I I 0 0 11 2 3 4 7l 0 0 0 0 1 10 0 0 0 NUL DLE SP 0 @ P p1 0 0 o soH DCr I I A o a q0 1 0 0 STX DC2 2 B R b ft 1 0 0 ETX DC3 # ? c s s0 0 ,| 0 EOT DC4 $ 4 u T d1 0 1 0 ENO NAK % F E U o u0 1 1 0 ACK SYN & 6 F f1 1 I 0 BEL ETB 7 w s0 0 0 1 BS CAN ( I H X h XI 0 0 1 HT EM l 9 i0 1 0 t LF SUB J z t zI I 0 1 w ES + K t k {0 I I FF FS II ,| CR GS M I m )0 I 1 1 so RS N n1 1 1 1 SI US ? o DEL