ECE 488: RF Circuits and SystemsSpring 2009HOMEWORK 4: Mixer Frequencies, Class-C Amplifiers, and AC-DC SuppliesReference: Lectures 7-10; Chapters 4–8 , 11Due: February 18Problem 1:Do Problem 1 ofHagen’sChapter 6.Specify the upper and lower frequency limits.[10 points]Problem 2:Do Problem 1 ofHagen’sChapter10. Since answers are given, be especially careful toshow your work.[20 points]Problem 3:A 10 kW AM transmitter is operatingat a 20% modulation level.[18 points]a.What is the peak power being transmitted?b.What is the average power being transmitted?c.Ifan80% efficientClass-C finalamplifierisused with a class-B driver configured for full 100%modulation of the output, estimate the AC powerrequired to supply the system when operating atonly 20% modulation.You may assume the ACto DC converters are 100% efficient.Hints:SeeHagen’sProblem 1.b of Chapter 3,Hagen’ssectionon “High-Level Modulation” on pages 100–102 andFigure 11-5 on page 102.
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