Communication Principle (Please Help to answer)

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Communication Principle (Please Help to answer)

Postby lawrence kee » Mon Jan 18, 2010 6:49 am

QUESTION 1

A mixer of an AM radio receiver converts the carrier frequency fc to a fixed
intermediate frequency (IF) of 455 kHz by using a local oscillator of frequency fLO. The broadcast band frequencies range from 540 kHz to 1600 kHz.

a) Determine the range of tuning that must be provided in the local oscillator and the respective image frequencies when high-side injection is used.
b) What is the range of tuning in the local oscillator if low-side injection is used?
c) Which of these injection (high or low) methods would be highly recommended for designing this AM radio receiver? Explain why.


QUESTION 2

a) Calculate the bandwidth of a frequency modulation (FM) signal (using the Bessel function table in Figure 6.4 of the module) when the maximum deviation (δ) is 30 kHz and the maximum modulating frequency fm = 3 kHz. Repeat for fm = 5kHz.

b) An FM transmitter puts out 2 kW of power. When mf = 1, calculate the
distribution of power in the carrier and all significant sidebands. Can you verify that the sum of these powers is 2 kW?


QUESTION 3
A slope detector has a filter with straight-line roll-off slopes in its amplitude (dB) characteristics - “dB versus frequency”. The output of the filter at these slopes ranges from 0 dB at the nominal center frequency to –20 dB at 5000 Hz above or below the center frequency. If the zero dB signal is 1 V, what is the slope detector output in volts at 2500 Hz off the center frequency? What will the detector output at 5000 Hz off the center frequency?
lawrence kee
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Re: Communication Principle (Please Help to answer)

Postby Jerry » Fri Nov 25, 2011 5:23 am

WHY?

Is this a test?

What is the reward?
Jerry
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Callsign: AB3NK


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