400-PAGES-MB_LAST-TERM_240702_204510 PDF

SET A 1. x(n) * h(n) = [2, 3.5, -7, -5.25, 4.5]; and 11. What is meant by the term noise figure in 19. A diode noise generator is required to x(n) = [-Given that: x(n) * h(n) = 2, 3.5, a communications receiver? produce 20 µV of noise in a receiver with -...

SET A 1. x(n) * h(n) = [2, 3.5, -7, -5.25, 4.5]; and 11. What is meant by the term noise figure in 19. A diode noise generator is required to x(n) = [-Given that: x(n) * h(n) = 2, 3.5, a communications receiver? produce 20 µV of noise in a receiver with -7, -5.25, 4.5]; and x(n) = [-2, 0.5, 3]. a. The level of noise entering the an input impedance of 75 Ω, resistive, Determine: h(-n) receiver from the antenna and a noise power bandwidth of 200 a. [-1, -2, -1.5] b. The relative strength of a strength of kHz. What must the current through the b. [-1.5, -2, -1] a received signal 3 kHz removed from diode be? c. [-1, 2, -1.5] the carrier frequency a. 1.1 A d. [1.5, 2, -1] c. The level of noise generated in the b. 2.2 A 2. Given discrete values: x(n) = [2, 0.5, 3, front end and succeeding stages of a c. 3.3 A 1.5], h(n) = [-1, -2, 1.5]. Evaluate the receiver d. 4.4 A correlation of x(-n) and 2h(n). d. The ability of a receiver to reject 20. The resistor R1 and R2 are connected in a. [-3, -12, -8.5, 3, -6.5, 6] unwanted signals at frequencies series at 300 K and 400 K temperatures b. [-3, -12, 8.5, 3, -6.5, 6] close to the desired one respectively. If R1 is 200Ω and R2 is c. [-4, 9, -2, -13.5, 3, 4.5] 12. One of the following types of noise 300Ω, find the power produced at the d. [-4, 9, -2, 13.5, 3, 4.5] becomes of grate importance at high load (RL = 500Ω) over a bandwidth of 3. Given the equation: x(n) = x(n + mM), frequencies. It is the ___. 100 kHz. it is best described as: a. Shot noise a. 0.25 fW a. Periodic analog signal b. Agitation noise b. 0.50 fW b. periodic analog system c. Flicker noise c. 0.75 fW c. periodic discrete signal d. Transit-time noise d. 1.0 fW d. periodic discrete system 13. The power density of “flicker” noise is? 21. Which of the following conveys the 4. A type of system where the output of a. The same at all frequencies information in an AM signal? the system is dependent of future b. Greater at high frequencies a. Carrier values of input. c. Greater at low frequencies b. Sidebands a. Causal d. The same as “white” noise c. Neither a nor b b. Non-causal 14. Atmospheric noise is a great problem at d. Both a and b c. Dynamic frequencies ___. 22. What is an application for vestigial d. Static a. Above 30 MHz sideband transmission? 5. Given the function: x(t) = te4tu(t). b. Below 30 MHz a. AM broadcast Evaluate the Fourier transform X(Ω). c. Above 30 kHz b. FDM 1 a. (𝑗𝛺+4)2 d. Below 30 kHz c. Telephony 1 15. What is the reliable measurement for d. TV broadcast b. comparing amplifier noise characteristic? 23. The first symbol in the designation of (𝑗𝛺−4)2 c. −1 a. Thermal agitation noise radio emission under the ITU rules (𝑗𝛺+4)2 b. Noise factor refers to? −1 d. c. Noise margin a. Bandwidth (𝑗𝛺−4)2 6. Find the inverse z-transform of the d. Signal-to-noise b. Nature of signal(s) modulating the following expression. Assume causal 16. A type of noise that shows up as a time main carrier signals. variation of the leading and trailing edges c. Type of information to be of binary signal. transmitted a. 𝛿 (n-7)+𝛿 (n-6)+u(n-5) a. Aliasing d. Type of modulation of the main b. u(n-7)+u(n-6)+𝛿 (n-5) b. Jitter carrier c. u(n-7)+𝛿 (n-6)+𝛿 (n-5) c. Pink noise 24. The output of a balanced modulator d. 𝛿 (n-7)+u(n-6)+u(n-5) d. Transmit time noise a. LSB and USB 7. Solve for the Fourier transform of the 17. Calculate the overall noise figure referred b. LSB given function: f(t) = e^(-2t) u(t-3) to the input for a mixer stage that has a c. USB a. e^(-2*(2+jw)) / (2+jw) noise figure 15 dB, and this is preceded d. Carrier b. e^(-2*(3+jw)) / (3+jw) by an amplifier that has a noise figure of 9 25. Which of the following is not a baseband c. e^(-3*(2+jw)) / (2+jw) dB and an available power gain of 20 dB. signal of modulation? d. e^(-3*(3+jw)) / (3+jw) a. 9.2 dB a. Audio signal 8. Find the convolution of f and g if f(t) = b. 10.2 dB b. Video signal tu(t) and g(t) = cos(t)u(t) c. 11.2 dB c. RF carrier a. t – sin(t) d. 12.2 dB d. Binary coded pulses b. t + sin(t) 18. A 3-stage amplifier system has stages 26. A single-tone amplitude modulated c. 1 + cos(t) with the following specifications: First wave has ___. d. 1 – cos(t) stage with power gain and noise ratio of a. 2 components 9. Which one is an anti-causal system? 10 and 2 respectively, 25 and 4 for the b. 3 components a. y(n) = 3x[n] + 2x[n+1] second stage, and 30 and 5 for the third c. 4 components b. y(n) = 3x[n] – 2x[n-1] stage. Find the overall noise temperature d. 2n + 1 components c. y(n) = 3x[n+1] + 2x[n-1] in K. 27. What is the modulation index of an FM d. y(n) = 3x[n+1]*2x[n+1] + x[n+2] a. 238 K signal if its modulating frequency is 10. A(n) ___ signal is a composite analog b. 283 K doubled? signal with an infinite bandwidth. c. 328 K a. No effect a. Digital d. 382 K b. Twice the original index b. Analog c. Four times the original index c. Either a or b d. One-half the original index d. Neither a or b 28. ___ is the circuit used to detect 37. An AM signal in which the carrier is 45. Determine he decoded voltage from the frequency modulated signal. modulated 70% contains 1500 W at the 12-to-8 bit compressed code: 10011000 a. Discriminator carrier frequency. Determine the power if the resolution is 0.5 V b. Modulator content of each of the sidebands when the a. 8.5 V c. Modem percent modulation drops to 50% b. 17 V d. Detector a. 150.60 W c. 12 V 29. Which major element will not be found b. 75.30 W d. 24 V in every superheterodyne receiver? c. 187.5 W 46. For 16-PSK and a transmission system a. RF amplifier d. 93.75 W with a 20 kHz bandwidth, determine the b. Mixer 38. If the modulation index if an AM wave is maximum bit rate. c. Local oscillator doubled, the antenna current is also a. 5 kbps d. IF amplifier doubled, the AM system being used is b. 20 kbps 30. The change of the modulated carrier a. H3E c. 80 kbps frequency from the original RF to the b. J3E d. 320 kbps IF of the superheterodyne receiver is c. C3F 47. The output of a µ-law companding known as d. A3E system is 34% of the maximum a. Frequency multiplication 39. An FM signal in which the carrier is possible. Calculate the input voltage as b. Frequency allocation modulated 100% contains 1500 W at the a percentage of the maximum input. c. Frequency substitution carrier frequency. Determine the power a. 1.1% d. Frequency translation transmitted when the percent modulation b. 2.2% 31. The function which tends to silence the drops to 50% c. 3.3% receiver in the absence of transmitted a. 1500 W d. 4.4% carrier b. 750 W 48. It is defined as the difference in decibels a. Squelch c. 1687.5 W between the minimum input level b. Muting d. 1125 W necessary to discern the signal and the c. AGC 40. Determine the percentage power saving input level that will overdrive the receiver d. AFC for an AM system at 95% modulation if the and produce distortion. 32. Most of the power in AM signal is in the carrier is reduced to 20% of its value and a. Dynamic range a. Carrier one of the sidebands is suppressed. b. Noise figure b. USB a. 50.67% c. Bandwidth efficiency c. LSB b. 60.67% d. Bandwidth improvement d. Modulating signal c. 70.67% 33. A receiver has two uncoupled tuned d. 80.67% 49. Which type of signal is used to produce circuits before the mixer, each with a Q 41. Adding one bit to the word length, is a predetermined alteration in the carrier of 75. The signal frequency is 107.5 equivalent to adding ___ dB to the for spread spectrum communication? MHz. The local oscillator uses low-side dynamic range of the digitizer. a. Quantizing noise injection. Calculate the image rejection a. 6 dB b. Random noise sequence ratio b. 1 dB c. Pseudo-random sequence a. 33.59 dB c. 4 dB d. Freqeuncy-compended sequences b. 30.52 dB d. 3 Db 50. If the frequency spectrum of signal has c. 29.33 dB 42. If a constellation diagram has 32 symbols a bandwidth of 500 Hz with the highest d. 11.84 dB and the symbol period is one symbol frequency at 600 Hz, what should be the 34. A second modulating tone having the every 8 seconds, what is the bit rate? sampling rate, according to the Nyquist same amplitude but a different a. 26 bps theorem? frequency is added to the first at the b. 4 bps a. 500 samples/s input to the modulator. The modulator c. 0.625 bps b. 600 samples/s index will be increased by a factor of d. 1.6 bps c. 1000 samples/s a. 1.732 43. A uniform quantizer, but slightly offset d. 1200 samples/s b. 1.414 voltage range in order to protect the 51. A block of addresses is granted to a c. 3 quantizer, uses 4 bits whose input range small organization. If one of the d. 2 ranges from 3V to +12V. How large us addresses is (205.16.37.19/26). How 35. What is the capture effect? each quantization step in four decimal many addresses are usable? a. All signals on a frequency are places? a. 26 demodulated by an FM receiver a. 0.5625 V b. 32 b. All signals on a frequency are b. 0.6000 V c. 62 demodulated by an AM receiver c. 0.7500 V d. 64 c. The loudest signal received is the d. 0.8000 V 52. A block of addresses is granted to a only demodulated signal 44. What is the coding efficiency of a linear small organization. If one of the d. The weakest signal received is the PCM system that uses a sign bit and with addresses is (205.16.37.19/23). How only demodulated signal a dynamic range of 69 dB? many addresses are usable? 36. The lower the receiver noise figure a. 92.51% a. 255.255.255.0 becomes the greater will be the b. 95.51% b. 255.255.254.0 receiver’s ___. c. 95.86% c. 255.255.253.0 a. Rejection of unwanted signals d. 99.66% d. 255.255.252.0 b. Selectivity c. Stability d. Sensitivity 53. How many bits are in a IPV6 address? 61. What does an SWR reading of less than 70. With a 50 Ω lossless transmission line a. 32 1.5:1 mean? terminated in a load impedance 100+j50 b. 64 a. An impedance match is too low Ω, determine the fraction of the average c. 128 b. A fairly good impedance match (GPT) incident power reflected by the load. d. 256 c. An impedance mismatch; something a. ½ 54. An unauthorized user is a network ___ may be wrong with the antenna? b. 1/3 issue. d. An antenna gain of 1.5 c. ¼ a. Security 62. Why is a loading coil often used with an d. 1/5 b. Reliability HF mobile vertical antenna? 71. One antenna which will respond c. Performance a. To tune out capacitive reactance simultaneously to vertically- and d. All of the above b. To lower the losses horizontally-polarized signals is the: 55. What is one advantage of using ASCII c. To lower the quality factor a. Helical-beam antenna rather than Baudot code? d. To improve reception b. Folded dipole antenna a. ASCII characters contain fewer 63. The characteristic impedance of a cable: c. Ground-plane antenna information bits a. Increases with length d. Quad antenna b. The larger character set allows b. Increases with frequency store-and-forward c. Increases with voltage 72. A parabolic antenna is very efficient c. It includes both upper and lower d. None of the above because: case text characters in the code 64. An example of an unbalanced line is: a. A horn-type radiator can be used to d. ASCII includes built-in error a. A coaxial cable trap the received energy correction b. 300-ohm twin lead TV cable b. All the received energy is focused to 56. ___ it is designed to be used in c. An open-wire cable a point where the pick-up antenna is wireless applications in which stations d. All of the above located must be able to share the medium 65. Where does almost all RF current flow in c. A dipole antenna can be used to without interception by an a conductor? pick up the received energy eavesdropper and without being a. In a magnetic field in the centre of the d. No impedance matching is required subject to jamming from a malicious conductor intruder b. In a magnetic field around the 73. Why would one need to know the a. Multiplexing conductor radiation resistance of an antenna? b. Spread spectrum c. In the centre of the conductor a. To measure the near-field radiation c. Modulation d. Along the surface of the conductor density from a transmitting antenna d. None of the above 66. What kind of impedance does a quarter b. To calculate the front-to-side of the 57. When a host on network A sends a wavelength transmission line present to antenna message to a host on network B, which the source when the line is open at the far c. To calculate the front-to-back ratio address does the router look at? end? of the antenna a. Logical a. A very high impedance d. To match impedances for maximum b. Physical b. A very low impedance power transfer c. Port c. The same as the characteristic 74. Antenna beamwidth is the angular d. None of the above impedance of the transmission line distance between 58. The ___ layer establishes, maintains, d. Along the surface of the conductor a. The 3 dB power point on the first and synchronizes the interactions 67. A positive voltage pulse sent down a minor lobe between communicating devices. transmission line terminated in a short- b. The points on the major lobe at the a. Session circuit half-power points b. Physical a. Would reflect as a positive pulse c. The maximum lobe spread points on c. Transport b. Would reflect as a negative pulse the major lobe d. Network c. Would reflect as a positive pulse d. The 6 dB power points on the major 59. The ___ layer ensures interoperability followed by a negative pulse lobe between communicating devise d. Would not reflect at all 75. If a parasitic element slightly shorter through transformation of data into a 68. Calculate the minimum length of a than a horizontal dipole antenna is mutually agreed upon format. conductor to be considered as a placed parallel to the dipole 0.1 a. Network transmission line. Assume an operating wavelength from it and at the same b. Presentation frequency of 120 MHz and the dielectric is height, what effect will this have on the c. Transport air. antenna’s radiation pattern? d. Data link a. 0.625 m a. A major lobe will develop in the 60. A ___ topology is a multipoint data b. 2.5 m horizontal plane, from the dipole communications circuit that makes it c. 0.25 m toward the parasitic element relatively simple to control data flow d. 1.25 m b. A major lobe will develop in the between and among the computers 69. A system with operating frequency of 800 horizontal plane, from the parasitic because the configuration allows all MHz uses a lossless transmission line element towards the dipole stations to receive every transmission with C = 0.75556 pF/m and L = 50 µH/m, c. A major lobe will develop in the over the network. determine the dielectric material used in vertical plane, away from the ground a. Star the transmission line d. The radiation pattern will not be b. Mesh a. Polyethylene affected c. Bus b. Teflon d. Ring c. PVC d. Mica 76. A horizontal dipole transmitting 84. How does intermodulation interference 91. What dominant mode for circular antenna, installed at an ideal height so between two repeater transmitters usually waveguides in TE mode: that the ends are pointing North/South, occur? 1. TE_10 radiates: a. When the signals are reflected out of 2. TE_11 a. Mostly to the East and West phase by aircraft passing overhead 3. TM_10 b. Mostly to the South and North b. When they are in close proximity and 4. TM_11 c. Mostly to the South the signals mix in one or both of their 92. Given a waveguide, WR187, with d. Equally in all directions final amplifiers outside dimensions of 2” by 1” and 77. A passive device that allows c. When the signals are reflected in thickness of 0.064”. The range of transmitters operating on two different phase by aircraft passing overhead frequencies if only TE30 is allowed is in frequencies to use the same antenna d. When they are in close proximity and the form of A GHz < f 0 a. [-3, 4.75, 5.5, 6.5, 3] b. 119.6 K b. 𝑥(𝑡) = 0; 𝑡 ≥ 0 b. [-3, 4.75, 5.5, -6.5, -3] c. 205.3 K c. 𝑥(𝑡) = 0; 𝑡 < 0 c. [2, 3.5, -7, 5.25, -4.5] d. 409.6 K d. 𝑥(𝑡) = 0; 𝑡 ≤ 0 d. [2, 3.5, -7, -5.25, 4.5] 11. Evaluate the z-transform of: 𝑥(𝑛) = 18. A type of system where the output y[n] 2. Which signal is considered to be 2𝑛 𝑢(𝑛) at every value of n depends on the input unstable based on DT system stability 1 a. 1+2𝑧 x[n] at the same value of n. boundary principle? 1 a. casual a. DC signal b. 1+2𝑧 −1 b. non-casual 1 b. Unit Step c. 1−2𝑧 c. dynamic c. Exponential 1 d. static d. Sinusoidal d. 1−2𝑧 −1 19. A type of system where the output of the 3. Evaluate the convolution of the given 12. A diode noise generator is required to system is independent of the future discrete values: x(n) = [-0.75, 0.5, 0.7], produce 20 uV of noise in a receiver with values of input. h(n) = [2, -0.4, 3] an input impedance of 75 Ω, resistive, and a. casual a. [-1.5, 1.3, -1.05, 1.22, 2.1] a noise power bandwidth of 100 kHz. b. non-casual b. [-1.5, 1.3, -1.05, -1.22, 2.1] What must the current through the diode c. dynamic c. [-2.25, 1.8, 0.4, 0.72, 1.4] be? d. static d. [-2.25, 1.8, 0.4, -0.72, 1.4] a. 1.2 A 20. Given the system equation: 𝑦(𝑛) = 4. Noise always affects the signal in a b. 2.2 A 𝑥(𝑛) ∙𝑐𝑜𝑠 𝑐𝑜𝑠 (𝑛) , It is best described communications system at the _____. c. 3,2 A as: a. transmitter d. 4.2 A a. linear 𝑛 b. channel 13. Given the equation: 𝑥(𝑛) = 𝑥( ), It is best b. non-linear 2 c. information source described as: c. unstable d. destination a. Down Sampling d. time-invariant 1 5. Given 𝑟𝑛 = 𝑁 ∑𝑁−1 𝑥=0 𝑥1 (𝑛)𝑥1 (𝑛 + 𝑗), b. Up Sampling 21. All are reasons for modulation, except: The equation best represents the: c. Down Scaling a. To make transmission of information a. Normalized convolution d. Up Scaling secure b. Normalized correlation 14. Given the equation: 𝑥(𝑡) = 𝑥(𝑡 + 𝑚𝑡), It is b. To make the signal undetectable c. autocorrelation best described as: c. To make the signal go further d. cross correlation a. periodic analog signal d. To make the antenna size practical 6. A piece of communication equipment b. periodic analog system 22. In Amplitude modulation, the information has two stages of amplification with c. periodic discrete signal is in the______? gains of 51 and 77 and two loss stages d. periodic discrete system a. Carrier with attenuation factors of 0.05 and 15. Given the signal graph, It is best b. Sidebands 0.085. the output voltage is 2.9 V. described as: c. Noise What is the input voltage? d. Both A and B a. 1.750 V 23. Under ITU Radio Emission Types, J3E b. 0.174 V is? c. 0.546 V a. Single Sideband Super Carrier d. 4.092 V b. Single Sideband Full Carrier 7. Given the function: 𝑥(𝑡) = 𝛿(𝑡), c. Single Sideband Suppressed Evaluate the 𝑋 (𝛺) Carrier a. 1 d. Single Sideband Superseded b. 0 Carrier c. jΩ 24. This stage in the Superheterodyne d. -jΩ receiver made it possible to recover the a. digital 8. Noise that is associated with crystal suppressed carrier. b. deterministic surface defects in semiconductor and a. IF Stage c. discrete also found in vacuum tubes. b. RF Amplifier d. aperiodic a. Pink noise c. Mixer 16. Given the discrete exponential signal d. Detector b. Black noise graph, Determine the value of “a” on the 25. Any frequency other than the selected c. Crystal noise equation 𝑥(𝑛) = 𝑎𝑛 d. White noise radio frequency that, if allowed to enter 9. It quantifies the degree of similarity a receiver will produce a cross-product between one set of data (or sequence) frequency that is equal to the and another. Intermediate Frequency a. correlation a. Radio Frequency a. a>1 b. convolution b. Intermediate Frequency b. a=1 c. FFT c. Image Frequency c. a