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1、eee334_2021_examEEE334 1 TURN OVERData Provided: None The University of SheffieldDEPARTMENT OF ELECTRONIC AND ELECTRICAL ENGINEERINGSpring Semester 2004-2005 (2 hours)Antennas, Radar and Navigation 3 Answer THREE questions. No marks will be awarded for solutions to a fourth question.Solutions will b
2、e considered in the order that they are presented in the answer book. Trialanswers will be ignored if they are clearly crossed out. The numbers given after eachsection of a question indicate the relative weighting of that section. 1. a. In the context of antenna design define the terms: gain, direct
3、ivity, efficiency andeffective area.(4) b. A 10GHz satellite comms link consists of a 3.0m diameter dish transmit antennawith an aperture efficiency of 0.7, and a receive dish antenna of 1.4m diameterwith an aperture efficiency of 0.55. If the distance between the link is 35787kmand the the transmit
4、 power is 100W, calculate the magnitude of the receivedpower.(8) c. An electrically large aperture antenna has 3dB far-field principal planebeamwidths of y x and respectively. Derive an approximate expression for thegain of the antenna, stating any assumptions you make(6) d. Estimate the gain of an
5、antenna with azimuth and elevation 3dB beamwidths of 3degrees(2)2. a. With the aid of simple sketches, explain how the radiation pattern of an array canbe expressed in terms of the element pattern and an array factor(4) b. Derive an expression for the normalised array factor of a simple 2-element ar
6、raywith element spacing d and uniform, equal phase excitationPlot the array factor for an element spacing of /2.(12) c. List the some of the advantages of a two-dimensional electronically scannedphased-array antenna compared to mechanically scanned reflector antenna(4)3. a. Derive the radar range eq
7、uation.(6) b. A radar system operating at 9.4GHz uses a common transmit/receive antennawith an effective aperture size of 3.4m (horizontal) by 0.75m (vertical) and a firstsidelobe level of 20dB relative to the main beam. Calculate the approximate azimuth and elevation beamwidth and estimate the ante
8、nna gain. (5)c. If the transmit power is 12kW, the noise level is 130dBW and the total lossesare 4dB, calculate the maximum range at which an aircraft with an RCS of 1m2could be detected with a SNR of 13dB. (5)d. Calculate the RCS of a target that would produce a similar output level at halfthis ran
9、ge if detected by the antennas first sidelobe. (4)CONTINUED EEE334 24. a. Explain the terms: spot jamming, sweep jamming and barrage jamming.What are the three standard jamming tactics used in EW? (3) b. A 10GHz radar with a boresight gain of 40dB and a peak transmit power of100kW is used to track a
10、 target with an RCS of 1m2. The radar antenna alsoreceives a jamming signal in a sidelobe which has a gain of 10dB. The jammeroperates at a distance of 100km from the radar and has an antenna gain of 30dBand a transmit power level of 1kW. Calculate the burnthrough range.(7) c. With the aid of a bloc
11、k diagram, describe the basic operation of a continuouswave Doppler radar system. (4)In Figure 1, A denotes a moving police car with an onboard CW Doppler radaroperating at 10GHz. The radar detects returns from each of the targets B to Fsimultaneously and without obstruction. Sketch a graph of the f
12、requencyspectrum of the radar receive signal indicating the features that correspond toeach of the targets B to F. Assume that the magnitude of the received signalsfrom each target is identical. The speed of each target is given in the table belowand the direction of travel is indicated by the arrows in Figure 1.Object DescriptionA Police car with 10GHz radar travelling at 80km/HB Car travelling at 130km/HC Car travelling at 60km/HD Car travelling at 100km/HE Car travelling at 100km/HF Stationary road sign(6) AT / GGCEEE334 3 END OF PAPER