A1 EST Problems 1 Masterfile 2013

7/27/2019 A1 EST Problems 1 Masterfile 2013

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EST Coaching Notes 1

1. In fiber optics, one of the factors affecting loss in connectors and splices is optical gaploss that causes what is known as Fresnel loss in going from core (N 1) to air (N g) and

then back to core (N 1). If N1 = 1.1 and N 2 = 1.2, what is the Fresnel loss in dB?

2. The velocity of electromagnetic in a transmission line depends on the dielectric constantof the insulator separating the two conductors. What is the velocity of propagation in atransmission line using a Polyethelyne (PE) insulator?

3. A balanced two wire transmission line with unequal diameter has a spacing of 5cm fromcenter to center. What is its impedance if the bigger diameter is 1.5cm and smallerdiameter is 0.5cm.

4. What is the cutoff wavelength of a circular waveguide whose internal radius is 10cmoperated in TE 10 mode.

5. In fiber optics, what is the number of modes if an unclad fiber has a refractive index of 1.3? The diameter is λ.

6. The European TDM uses an added channel frame for frame synchronization. If thenumber of bits per frame is 256 and the number of bits per code is 8. What is theaverage number of synchronization bits?

7. The North American TDM uses an added digit for synchronizing. What is the averagetime for synchronization for DS-1 T1?

8. The broadside dimension of a rectangular waveguide is 0.8 in and is fed from a coaxialcable by a 12 GHz frequency. What is the cut off wavelength for the dominant mode?

9. What is the Doppler frequency difference if it has a relative velocity of 2.8x10 8 m/s anda transmit frequency of 10GHz?

10. Given a crosstalk coupling loss of 60dB. What is the crosstalk coupling?

11. Given an open circuit longitudinal balance voltage of 12V and a metallic voltage of 5V,what is the longitudinal balance?

12. Given a 120 Voice band channel and a 3.1 kHz voice bandwidth in an FM FDM, what isthe bandwidth ratio?

13. Given the scatter angular components of 0.2r & 0.3r, find the angular distance betweenthe antennas.



30. For an SSB, 200 peak to peak volt source with a 100 ohm antenna, what is the peakeffective power?

31. What is the average voltage of an SSB with 15 V voltage and 12 A current?

32. In radio wave propagation, the actual velocity of propagation is 250 x 106. What is the

velocity factor of the dielectric material used in the transmission?

33. A double tuned IF amplifier with an optimized coupling has a critical coupling of 0.02and a resonant frequency of 5MHz. Find the overall bandwidth.

34. Find the frequency deviation constant of a clap oscillator with an unmodulatedfrequency of 50MHz, biased voltage of 15V and n=0.1.

35. See solution…

36. Find attenuation factor (AF) given cascaded gain of the amplifier 50000, output voltageof 50mV and input voltage of 15µv.

37. Calculate the shape factor.

38. Calculate n

39. Find the 10 th octave… given 1 Hz as the first frequency, ratio of 2:1.

40. What is the open circuit voltage of λ/2 dipole if a 25W at 170MHz is radiated by anotherλ/2 dipole 100 km distant? Assume that the effective length is λ/π.

41. A single mode step index fiber of 25km length is utilized by a light source of 1.5 m. Thespectral bandwidth is 5nm. What is the total wave guide dispersion?

42. What is the equivalent noise temperature of an antenna with spectrum density of available noise signal received of 20 aW/Hz?

43. A transmission line consisting a single wire line near the ground has a radius of 10mm.what is the characteristic impedance of the said line if it is 1m above the earth ground?

Single wire line near ground d h.

44. The total distance between two points on earth is 20 mile. What is the earth’s curvaturewhen the surface refractivity is 250.

45. Microwave radio communication , a reliability of 99.9 % will translate to outage time peryear for how many hour or minutes or second?



EST Coaching Notes 1 Solutions

1.

Fresnel…

Fresnel = = = 27.23 dB

2. The velocity ….

For PE material: k = = 2.27

VP = cVF =

√ =

√ = √

= 199.12 x 10 6

3. A balanced …

√

N = 65

Zo = 292 ohms

4. What is the cutoff …

For TE10;;kr = 3.83



5. In fiber optics…

6. In European …

7. The North American …

For DS-1: N= 193 bits per frame; T: Frame period (1/8000bps)

8. The broadside dimension …

For the Dominant mode , TE 10 :

⁄

9. What is the Doppler …

10. Given a crosstalk …



ln* + 17. Stripline…

ln

18. Given 500 W …

19. In a microwave radio system…

Solution:U = (1-R) x 100%

U = (1 - x 100 = 99.9999%

*31536000 -> seconds in a year

20. In a microwave radio system, what is...

Solution:Multipath Effect = 30 log 30 (Km) = 44.31 dB

21. In a CDMA…

Solution:Pt(dBm) = -76dB –Pr(dBm)

Pt(dBm) = -76dB - 10log = -1dBm = 794.33uW



31. What is the average…

Vavg = to

PEP = (15)(12) = 180 W

Vavg = 180/4 to 180/3Vavg = 45 W to 60 W

32. In a radio wave propagation…

Vp

= c Vf

Vf = Vp / cVf = 250 x 10 6 / 300 x 10 6 = 0.8333

33. A double tuned…

BW = kopt x fokopt = 1.5kc

34. Find the frequency deviation…

k = fo/(2(1+n)(1+2Vo))

35. No question was given (Gr.11)

Solution:

36. Find the attenuation…

Solution:



AF = 0.066666

37. Calculate the shape factor…

Shape factor =

= = 4

38. Calculate n…

Note: f1 = the first frequency in Hzf2 = frequency of the whole spectrum = Hz

solution: n = 3.32

= 3.32 = 73.04

39. Find the 10 th octave…

Formula: let n = the number of octavesa = the first frequency given; 1 Hzr = common ratio

= 1024 Hz

40. What is the open circuit…



[ ]

Note:Gt for λ/2 dipole is 1.64

41. A single step …

Note:Dw = Dispersion Coefficient = 6.6 ps/ns-km (peak value for single mode step index fiber)

42. What is the equivalent …

Note:k = Boltzmann constant

43. A transmission line…

√

√

44. The total distance…

assume d1 = d2 ;



= 54.16 mi

( )

= 1.23

45. Microwave radio communication…

Outage hour = 8.76 hours

A1 EST Problems 1 Masterfile 2013

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