tut3_problems_07_02_09

tut3_problems_07_02_09 - demodulated using the available...

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Department of Electrical Engineering EE 308: Communication Systems (Spring 2009) Course Instructor: Prof. Abhay Karandikar Problem Set 3 1. Let x c ( t ) = A c cos [2 πf c t + θ ( t )] and x i ( t ) = A i cos [2 πf c t + θ i ( t )] be any two bandpass signals with ρ = A i A c . (a) Derive expressions for the amplitude and phase of r ( t ) = x c ( t ) + x i ( t ). (b) What is the output when r ( t ) is applied to an ideal i) amplitude ii) phase and iii) frequency demodulator? (c) Repeat the above for ρ << 1 , θ ( t ) = 0. (d) Comment on your results when θ i ( t ) = 2 πf i t + φ ( t ), where φ ( t ) is the message component of a PM or FM signal. 2. An AM signal having a bandwidth W = 5 kHz is transmitted over a carrier with frequency f c = 1 MHz. The demodulator at the receiver can operate only in the range of f IF = 450 - 500 kHz. (a) Design an appropriate receiver so that the received AM signal may be successfully
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Unformatted text preview: demodulated using the available equipment. (b) The frequency and bandwidth values in this problem are close to the ones used in commercial AM. What is the problem with designing an AM demodulator matched to f c = 1 MHz? 3. A signal with bandwidth W = 4 kHz, is transmitted using indirect FM with f c = 1 MHz and Δ f = 12 kHz. If the initial frequency deviation &lt; 100 Hz and the (initial carrier frequency) f c 1 = 10 kHz, how many doublers will be needed to achieve the desired output parameters? Draw the block diagram of the sytem indicating the value and location of the local oscillator such that no frequency exceeds 10 MHz. 1...
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