A superhet is receiving a signal from an AM modulator where the carrier signal h

Question

A superhet is receiving a signal from an AM modulator where the carrier

signal has an amplitude Ec and carrier frequency fc. The frequency of the information signal is fi

.

The modulator has following parameters.

*output -load- resistance - RT,

* modulation index - m,

* total amplification through the modulator stages - G_T

During the propagation through the air signal power is attenuated by a factor C (C < 1).

a. Calculate the input power received at the receiver.

This should probably be power available to the reciever? Where using modern electronic communications as the subjust textbook (this question is not out of the book though). I have been playing with a standard DSB-FC signal and chcanging that to power and then muliplying by the attenuation. not sure if thats the right approach though.

b. If the intermediate frequency of the receiver is f_IF, what is the maximum RF bandwidth

the device can have if the receiver is not to suffer from image frequency problem.

c. If the RF bandwidth from part b is used and noise density (noise power per Hz) is

N0, calculate the SNR at the input of the receiver.

d. If the total power amplification through the receiver stages is G_R find the output power

of the receiver.

e. If the noise power at the output is identical to the noise power at the input of the

receiver, find the NF for the receiver.

Please try to explain the answers -

Thanks

Explanation / Answer

This is the ratio of the signal power to1 milliwatt. If the input power is 0ne microwatt, that is 1/1000 of 1mW. The log of 1/1000 is -3. The ratio in dBm is 10 times that, so -30dBm.

dBm = 10 x log(ratio with 1mW) where log is base 10 logarithm..

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