QUESTION: A communications engineer at IBM Zuerich Research Laboratory who developed an encoding technique called Trellis Code Modulation (TCM), which combines encoding and modulation to reduce the probability of error. ANSWER: Dr. Gottfried Ungerboeck

Reference: Electronics Communications Systems Wayne Tomasi, p. 391 QUESTION: Is a registered trademark of Varian Associates which is a hybrid combination of klystron driver and travelling wave tube output section in tandem in the same envelope. ANSWER: Twystron

Reference: Electronic Communication System by Kenedy page 411 QUESTION: Cavity magnetron, like the klystron, causes electrons to bunch. This is an important effect known as ___________. ANSWER: Phase-focussing effect

Reference: Electronic Communication System by Kenedy page 395 QUESTION: The WARC was a technical conference of the International Telecommunications Union (ITU) which provides satellite frequency assignments. WARC stands for ____________. ANSWER: World Administrative Radio Conference

Reference: Electronics Communications Systems Wayne Tomasi, p. 1054

QUESTION: XMODEM is the first file transfer protocol designed to facilitate transferring data between two personal computers (PCs) over the public switched telephone network. It was developed in 1979 by a man named _________________. ANSWER: Ward Christiansen

Reference: Electronics Communications Systems Wayne Tomasi, p. 943 QUESTION: ___________ is a wireless networking scheme that competes with both 802.11 and bluethooth schemes. It uses frequency hopping and spread spectrum communication at 2.4GHz and is intended for small home networks. ANSWER: HomeRF

Reference: Electronics Communications Systems Roy Blake, p. 870

QUESTION: Determine the fade margin for the following conditions: Distance between sites, D=50km; Frequency, f=1.8GHz; very dry mountainous terrain and a reliability of 99.9999% ANSWER: 36.25db SOLUTION: Fm = 30logD + 10log(6ABf) 10log9=(1-R) 70

where: D - distance in kilometre A - roughness factor 0.25 for mountainous terrain B factor to convert a worst-month probability to an annual probability 0.125 for very dry mountainous terrain R reliability expressed in decimal F frequency in Gigahertz

Fm = 30log(50) + 10log(6x0.25x0.125x1.8) 10log9=(1-.999999) 70 Fm = 36.25dB

Reference: Electronics Communications Systems Wayne Tomasi, p. 628-629

QUESTION: A fiber is rated as having a bandwidth-distance product of 500kHz-km. Find the rise time of a pulse in a 5km length of this cable. ANSWER: 5000ns SOLUTION: D = 500/Bl Where D pulse spreading constant in ns/km Bl Bandwidth-distance product in Mhz-km D = 500/(0.500Mhz) D = 1000ns/Km TRT = D x l Where I = length of the cable TRT = 1000ns/km x 5km TRT = 5000ns

Reference: Electronics Communications Systems Roy Blake, p. 924 QUESTION: For a 2m diameter parabolic reflector with 10W of power radiated by the feed mechanism operating at 6GHz with a transmit antenna efficiency of 55% and an aperture efficiency of 45%, determing the receive power gain. ANSWER: 39.4dB SOLUTION: = c / f where c speed of light (m/s) f frequency of operation (Hz) = 3x108m/s / 6x109 Hz = 0.05meters

AP = 10 log ( 5.4 (D/)2 )

Where D Dish diameter in meters wavelength in meters per cycle AP = 10 log ( 5.4 (2/0.05)

2 ) Ap = 39.4 dB

Reference: Electronics Communications Systems Wayne Tomasi, p. 670 QUESTION: Calculate the minimum receivable signal in a radar receiver which has an IF bandwidth of 1.5MHz and a 9-dB noise figure. ANSWER: 4.17x10-14 W SOLUTION: NF = antilog (9/10) NF = 7.943 PMIN = KTOBW (NF 1) Where K Boltzmanns Constant TO Ambient Temperature BW Bandwidth NF Noise Figure in decimal PMIN = 1.38x10

23 x 290 x 1.5x106 (7.493 1) PMIN = 4.17x10

-14 W

Reference: Electronics Communications Systems George Kennedy, p. 610