This is the Coaching materials in Microwave Communications Part 3 as one topic in ECE Board Exam taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies (EST), Communications Books, Journals and other Communications References. This particular Coaching Notes in Communications Engineering has random Questions and Answers in random topics. Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.
Microwave Communications Coaching Materials Part 3
141. A surface-search radar normally scans how many degrees of azimuth?
360 degrees
142. What limits the maximum range of a surface-search radar?
Radar Horizon
143. What is the shape of the beam of a surface-search radar?
Wide vertically, narrow horizontally
144. Why is the range capability of 3D radar usually less than the range of 2D radar?
Higher operating frequency
145. Fire-control tracking radar most often radiates what type of beam?
A narrow circular beam
146. Tracking radar searches a small volume of space during which phase of operation?
Acquisition
147. What width is the pulse radiated by fire-control tracking radar?
Very Narrow
148. Which beam of missile-guidance radar is very wide?
Capture Beam
149. What is the purpose of the synchronizer in a radar system?
Controls system operation and timing
150. What is the purpose of the majority of circuits in a radar system?
Timing and Control
151. A self-synchronized radar system obtains timing trigger pulses from what source?
Transmitter
152. What type of multivibrator can be used as a radar master oscillator?
Free-running
153. In an externally synchronized radar, what determines the prr of the transmitter?
The Master Oscillator
154. Which of the basic timing circuits produces sharp trigger pulses directly?
Blocking oscillators
155. What are the two basic types of transmitters?
Keyed oscillator and power-amplifier chain
156. What controls transmitter pulse width?
Modulator
157. In addition to a flat top, what characteristics must a modulator pulse have?
Steep leading and training edges
158. What type of modulator is most commonly used in modern radar systems?
Line-pulsed
159. What type of tube best meets the requirements of a modulator switching element?
Thyratron
160. What modulator element controls the rate at which the storage element charges?
Charging Impedance
161. What two forms of instability are common in magnetrons?
Mode Skipping and Mode Shifting
162. What is the effect on magnetron operation if the magnetic field strength is too high?
Magnetron will not oscillate
163. What is the typical frequency range about the center frequency of a tunable magnetron?
± 5 percent
164. What is the primary advantage of power-amplifier transmitters over keyed-oscillator transmitters?
Frequency Stability
165. What type of klystron is used as the final stage of a power-amplifier transmitter?
Multicavity Klystron
166. What transmitter component allows the radiation of a large number of discrete frequencies over a wide band?
Frequency Synthesizer
167. What is the greatest limiting factor in a receiver’s detectable range?
Noise
168. What type of receiver is most often used in radar system?
Superheterodyne
169. What IF frequencies are normally used in radar receivers?
30 or 60 MHz
170. Which component of the receiver produces the signal that is mixed with the received signal to produce the IF signal?
Local Oscillator
171. What receiver circuit actually produces the IF frequency?
Mixer
172. The IF amplifiers are connected in what amplifier configuration?
Cascade
173. Which receiver component converts the IF pulses to video pulses?
Detector
174. What type of target has a fixed phase relationship from one receiving period to the next?
Stationary
175. What signal is used to synchronize the coherent oscillator to a fixed phase relationship with the transmitted pulse?
Coho Lock Pulse
176. What is the phase relationship between the delayed and undelayed video?
Opposite
177. A monopulse receiver has how many separate channels?
Three
178. If a target is on the bearing axis of the radiated beam, what is the input to the bearing IF channel?
Zero
179. What characteristic of the bearing and elevation output signals determines the direction of antenna movement?
Phase
180. What are the three fundamental quantities involved in radar displays?
Range, Bearing, and Elevation
181. What coordinates are displayed on an rhi scope?
Range and Elevation
182. What coordinates are presented on a ppi scope?
Range and Bearing
183. What type of deflection is preferred for a crt electron beam?
Electromagnetic
184. Which of the two types of deflection coils (fixed or rotating) is used most often?
Fixed
185. What type of ranging circuit is most often used with a radar that requires extremely accurate range data?
Range gate or range step
186. The range sweep in a range-gate generator is started at the same time as what other pulse?
Transmitter
187. Range-marker generators produce pulses based on what radar constant?
The radar mile (12.36 microseconds)
188. What radar scope uses a range step for range measurement?
The A Scope
189. Which of the two general classes of antennas is most often used with radar?
Directional
190. The power gain of an antenna is directly related to what other antenna property?
Directivity
191. A parabolic reflector changes a spherical wavefront to what type of wavefront?
Plane
192. How many major lobes are produced by a paraboloid reflector?
One
193. What type of radiator normally drives a corner reflector?
Half-wave
194. The broadside array consists of a flat reflector and what other elements?
Two or more half-wave dipoles
195. Horn radiators serve what purpose other than being directional radiators?
Waveguide impedance matching devices
196. The spectrum of a radar transmitter describes what characteristic of the output pulse?
Frequency Distribution
197. Where should the transmitter spectrum be located with respect to the receiver response curve?
In the center
198. The ideal radar spectrum has what relationship to the carrier frequency?
Symmetrical above and below the carrier frequency
199. The display screen of a spectrum analyzer presents a graphic plot of what two signal characteristics?
Power and Frequency
200. The peak power of radar depends on the interrelationship of what other factors?
Average Power, Pulse Width, and prt
201. Transmitter power readings are most often referenced to what power level?
1 milliwatt
202. Receiver bandwidth is defined as those frequencies spread between what two points of the receiver response curve?
Half-power points
203. What type of cooling is used to control ambient room temperature?
Air conditioning
204. A typical liquid-cooling system is composed of what loops?
Primary and Secondary
205. A pulsed magnetron with an average power of 1.2 kW and a peak power of 18.5 kW. One pulse is generated every 10 ms. Find the duty cycle and the length of a pulse.
D = 6.5% ; T = 0.65 ms
206. A radar transmitter has a power of 10 kW and operates at a frequency of 9.5 GHz. Its signal reflects from a target 15 km away with a radar cross section of 10.2 square meters. The gain of the antenna is 20 dBi. Calculate the received signal power.
10.1 fW
207. Find the Doppler shift caused by a vehicle moving toward a radar at 60 mph, if the radar operates at 10 GHz.
1.778 kHz
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