Physics 426 Homework 4: Amplitude Modulation and Demodulation - Prof. N. Duller, Assignments of Physics

Download Physics 426 Homework 4: Amplitude Modulation and Demodulation - Prof. N. Duller and more Assignments Physics in PDF only on Docsity! HW #4 Due Thursday, March 2 Physics 426 C:\TEACHING\PHYS426\SPRING00\HW4.DOC 1 1. Show that K m t t K t Km t tm c c c m c m1 1 2 + = + + + −cos cos cos cos cosω ω ω ω ω ω ωb g b g b g , as is claimed on page 2 of the handout, Concepts of Amplitude Modulation of a Carrier Frequency and “AM Demodulation”. 2. A very bright but misguided student is asked to build a circuit to demodulate a 1-MHz carrier which has been amplitude modulated sinusoidally at a rate of 1 kHz. To accomplish her task, she builds the following: (a.) Explain why this student’s choice of values for R1 and C1 is a bad idea. What values of R1 and C1 might she use to fix the problem? (b.) Explain why the choice of 20 k for R2 and 5 pF for C2 is bad. (c.) What undesireable effect will the above choice of R2 and C2 have on the demodulator’s output signal? 3. Show that the time-varying voltage v t A t B t( ) cos sin= +ω ω can be written as v t D t( ) cos= −ω φb g for some D and φ . IN OUT C1 R1 R2 C2 C3 R3 5 pF 1 k 5 pF 2.2 uF 20 k