Electrical engineering MCQ Quiz Hub

Microwave Engineering MCQs Set-8

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1. Low is the G/T ratio of an antenna, higher is its efficiency.




2. The noise temperature of an antenna is given by the expression:




3. _________ has a constant power spectral density.




4. A __________ is a device that converts a guided electromagnetic wave on a transmission line into a plane wave propagating in free space.




5. Antennas are bidirectional devices.




6. Dipole antennas are an example for:




7. _________ antennas consist of a regular arrangement of antenna elements with a feed network




8. A parabolic reflector used for reception with the direct broadcast system is 18 inches in diameter and operates at 12.4 GHz. The far-field distance for this antenna is:




9. ________ of an antenna is a plot of the magnitude of the far field strength versus position around the antenna.




10. Antennas having a constant pattern in the azimuthal plane are called _____________




11. Beamwidth and directivity are both measures of the focusing ability of an antenna.




12. If the beam width of an antenna in two orthogonal planes are 300 and 600. Then the directivity of the antenna is:




13. If the power input to an antenna is 100 mW and if the radiated power is measured to be 90 mW, then the efficiency of the antenna is:




14. Most of the wireless systems today operate at a frequency of about:




15. Point to point communication systems use low gain antennas for communication.




16. In this method of wireless communication, communication happens only in one direction:




17. If the distance between a transmitting station and receiving station is 1 Km and if the antennas are operating at a wavelength of 5 cm, then the path loss is:




18. The amount of power by which the received power must be greater than the threshold level required to maintain a minimum quality of service is called _______




19. Link margin that is used to account for fading effects is called fade margin.




20. One of the most important requirements of a radio receiver is high gain.




21. A radio receiver operating at microwave frequencies must have very high selectivity.




22. All modern wireless communication systems rely on digital modulation methods due to:




23. The probability of error depends on the ratio of bit energy to noise power density.




24. Probability of bit error is greater for ASK as compared to FSK.




25. Probability of bit error rate is greater for QPSK as compared to FSK.




26. Global positioning system uses _____ satellites in medium earth orbits to provide accurate position information.




27. GPS operates at a single frequency band.




28. WLAN is used for providing connection between a host computer and satellite for communication.




29. There is no standard to be formed by commercial WLAN products.




30. Bluetooth devices operate at a frequency of :




31. The modulation technique in which both amplitude and phase of the carrier are varied simultaneously is:




32. The noise power will determine the maximum detectable signal level for a receiver.




33. In a receiver, if the noise figure of the mixer stage in the receiver is 7 dB, then the equivalent noise temperature is given that the receiver is operating at 290 K:




34. Given that the antenna efficiency is 0.9, equivalent brightness temperature is 200 K; physical temperature is 300 K, noise temperature of an antenna is:




35. If a receiver is operating at a bandwidth of 1 MHz and has antenna noise temperature of 210 K, then the input noise power is:




36. Antenna noise temperature of a system is 210 K, noise temperature of transmission line is 123 K, loss of a transmission line connecting the antenna to receiver is 1.41 and noise temperature of the receiver cascade is 304 K. then the total system noise temperature is:




37. If the received power at antenna terminals is -80dBm, and if the input noise power is -115 dBm, then the input SNR is:




38. A receiver system is operating at a bandwidth of 1 MHz and has a total system noise temperature of 762 K. then the output noise power is:




39. If the received power at the antenna terminals is Si=-80 dBm and the output noise power is -110 dBm then the output signal to noise ratio is given by:




40. In a RADAR system the transmitter of the radar is more sensitive than the receiver.




41. For radar system, antennas with a large beam width are preferred over narrow beam antennas.




42. The radar in which both transmission and reception is done using the same antenna are called:




43. For applications like missile fire control, bistatic radars are used.




44. The term radar cross section defines the:




45. A ________ determines the target range by measuring the round trip time of a pulsed microwave signal.




46. Construction of pulse radar is much simpler than a Doppler radar.




47. In military applications the radar cross sections of vehicles is minimized.




48. Pulse radar operating at 10GHz frequency has an antenna with a gain of 28 dB and a transmitted power of 2kW. If it is desired to detect a target of cross section 12m2, and the minimum detectable signal is -90 dBm, the maximum range of the radar is:




49. __________ system obtains information about a target by transmitting a signal and receiving the echo from the target.




50. Radiometry is a technique or the principle on which radar works.




51. According to Planck’s radiation law, a body can radiate energy to the medium surrounding it under all conditions invariably.




52. A major challenge in designing a radiometer is:




53. The receiver model of a total power radiometer is based on the:




54. The system bandwidth of a total power radiometer is determined by the:




55. The integrator circuit after the detector in the receiver circuit is used to smooth out the short term variations in the signal power.




56. The dominant factor affecting the accuracy of the total power radiometer is the variation of ___________




57. A Dicke radiometer is identical to the total power radiometer in all aspects except that they have different receiving antenna.




58. A typical radiometer would measure the brightness temperature over the range of about:




59. The basic requirements of transmitting antennas are:




60. _________ is a device that converts electrons to photons or vice-versa.




61. The basic equation of radiation that is applied to any antenna irrespective of the type of the antenna is:




62. When the separation between two lines that carry the TEM wave approaches λ the wave tends to be radiated.




63. The number of patterns radiation pattern required to specify the characteristic are :




64. The beam width of the antenna pattern measured at half power points is called:




65. The solid area through which all the power radiated by the antenna is:




66. Power radiated from an antenna per unit solid angle is called radiation intensity.




67. As the beam area of an antenna decreases, the directivity of the antenna:




68. If an antenna radiates over half a sphere, directivity of the antenna is:




69. The half power beam width of an antenna in both θ and φ are 400 each. Then the gain of the antenna is:




70. The number N of radio transmitters or point sources of radiation distributed uniformly over the sky which an antenna can resolve is given by:




71. Ideally, the number of point sources an antenna can resolve is numerically equal to:




72. Effective aperture is a parameter of the antenna that gives the physical aperture of the antenna.




73. _______ of an antenna is defined as the ratio of the induced voltage to the incident electric field.




74. The members of the antenna family which are made of wires of certain value in terms of operating wavelength are called:




75. The antenna in which location of the feed determines the direction of the lobe are:




76. Based on the size of the loops, loop antennas are classified as small and large loops. This is the only classification of loop antenna.




77. Antenna that does not belong to the horn antenna family among the following are:




78. Patch antennas are the antennas of small size and are made of:




79. Reflector antennas are widely used to modify radiation patterns of radiating elements.




80. The pattern of the reflector in a reflector antenna is called:




81. ______ antennas have gain less than reflector antennas but have more lenient tolerance on surfaces.




82. Lens antennas are classified into two types. One being fast antenna, the other one is:




83. The antennas which offer high operational bandwidth and the antenna parameters are maintained over a wide range of antennas are called:




84. High directivity required in RADAR communication is satisfied using this type of antennas:




85. The terminal impedance of a dipole antenna is 710 Ω. The terminal impedance of the slot antenna given the intrinsic impedance of air is 377 Ω is:




86. An antenna source that radiates energy uniformly in all the directions is called:




87. Antennas that radiate energy only in a specified are called anisotropic antennas.




88. A source has a cosine power pattern that is bidirectional. Given that the directivity of a unidirectional source with cosine power pattern has a directivity of 4, then the directivity of the unidirectional source is:




89. A source has a sine squared radiation intensity power pattern. The directivity of the given source is:




90. The hybrid-π model of a BJT is useful for analysis at all frequency ranges and variation of other transistor parameters.




91. The output collector to emitter current of a BJT amplifier is independent of the input base current of the amplifier.




92. The current gain of a BJT ________ with frequency.




93. If a transistor has a short circuit current gain of 25 and the capacitance measured in the hybrid-π model of the transistor was 60 pF. Then the threshold frequency of operation of the transistor is:




94. Hetero junction bipolar transistors have the same working principle and operation as that of a BJT.




95. Advantage of HJT over BJT is that it has:




96. _____ is a device that produces a phase shift of a required amount of the input wave.




97. Reciprocal phase shifters give different phase shift in different direction.




98. If a ferrite slab produces a phase shift of 0.836 rad/ cm, then the length of the slab required to produce a phase shift of 135⁰ is:




99. A gyrator can be made a passive device by certain design methods so that they do not affect the power levels of the circuit in which they are used.




100. Ferrite phase shifters have more advantages over FETs and diodes in using them in microwave integrated circuits.