Question

Question 1

The noise floor, also known as additive white Gaussian noise (AWGN), is a continuous noise level that appears over a wide spectrum when viewed in the frequency domain.

True

False

10 points

Question 2

When considering the impact of impulse noise, we find that it is more devastating to a digital communications link, than an analog one. Therefore, error control methods should be used on all digital links.

True

False

10 points

Question 3

When two transmitters operate on the same frequency in close proximity to each other, cochannel interference can occur.

True

False

10 points

Question 4

A receive system temperature is found to be 290 Kelvin over a frequency bandwidth of 4000 Hz. Determine the thermal noise in decibels.

		a. -137.96 dBW
		b. 167.96 dBW
		c. -167.96 dBW
		d. 137.96 dBW Question 5 Determine the thermal noise power density [No] in decibels, given the following information: T=295oK, signal bandwidth of 4kHz. a. -167.88 dB b. +203.9 dB c. -203.9 dB d. -137.88 dB 10 points Question 6 Select the correct statement(s) regarding signal-to-noise ratio (SNR) calculations. a. When determining the non-decibel value of S/N, mixing units (i.e., mW and W) between S and N is permissible   (e.g., S(mW)/N(W)) b. SNR can only be given in decibel form because it represents a ratio of powers c. The decibel value of SNR is given by: [SNR]=[S]-[N], where "[ ]" indicates decibel values d. The decibel value of SNR is given by: [SNR]=[S]/[N], where "[ ]" indicates decibel values 10 points Question 7 Low SNR is preferred in a communications link, since it means that the noise will also be low. True False 10 points Question 8 Determine the SNR in decibels given a receive signal of 10E-6 watts, and [N]=-128 dBW. a. 128dB b. 48.41 dB c. 78 dB d. -98.41dB 10 points Question 9 For guided mediums, insertion loss is dependent upon which of the following? a. number of connectors and splices b. wire diameter c. signal frequency d. all of the above 10 points Question 10 Delay distortion occurs when the frequency components of a transmitted signal arrives out-of-phase from one another. While this is a problem for digital communication systems, it is simply an annoyance for analog systems. True False

Answer 1

1)The noise floor, also known as additive white Gaussian noise (AWGN), is a continuous noise level that appears over a wide spectrum when viewed in the frequency domain

True

As they have uniform power over all frequency.

2)When considering the impact of impulse noise, we find that it is more devastating to a digital communications link, than an analog one. Therefore, error control methods should be used on all digital links

True

As it helps to counter data loss

3)When two transmitters operate on the same frequency in close proximity to each other, cochannel interference can occur.

True

4)A receive system temperature is found to be 290 Kelvin over a frequency bandwidth of 4000 Hz. Determine the thermal noise in decibels.

P_n = kTB

B is bandwidth = 400Hz

T is temperature = 290K

M is Boltzmann constant = 1.38 x 10^-23 Joules/K

P_in = 1.38 x 10^-23 x 290 x 4000

=1.6008 x 10^-17 W

P_dB = 10 log(P_in)

= 10 log(1.6008 x 10^-17)

=-167.9566

C) -167.96 dBW

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