ASU IFT 372 Fall 2023 Helm Weeks 1-7 Quizzes + Midterm Multisource with complete solution

ASU IFT 372 Fall 2023 Helm Weeks 1-7 Quizzes + Midterm Multisource with complete solution What is a logarithm? Correct answer: A logarithm is an exponent based mathematical representation of a numerical value. What logarithmic base is used in digital communications? Correct answer: Two How do you find a log2 value on a calculator that only has log10 functionality? (Hint: what is the formula?) Correct answer: log2(a) = [log10(a) / log10(2)] What is the definition of a decibel? Correct answer: a = 10lob(b), where a is the decibel value and b is the decimal value Correct answer: A decibel is a mathematical representation of a power level on a logarithmic scale. You cannot mix decimal and decibel values in an equation (i.e., you either have to work with decimal values or decibel values) Correct answer: True There can be more than one power value in a decibel (dB) equation. Correct answer: False When you add two decibel values, you are multiplying those values in decimal (I.e. 3 dB + 6 dB = 9 dB which is equivalent to 2 * 4 = 8 in decimal) Correct answer: True is a decibel value referenced to watts and is a decibel value referenced to milliwatts. Correct answer: dBW & dBm How do you convert dBW to dBm? Correct answer: Add 30 dB to dBW to obtain dBm value The net gain or (loss) of a transmission system is a radio between the and where the is the numerator and the is the denominator. Correct answer: Output power & Input power What parameter of the intelligent signal causes or determines the instantaneous rate of carrier frequency? Correct answer: Amplitude of the modulating signal What parameter of the intelligent signal causes frequency deviation of the carrier? Correct answer: Amplitude of the modulating signal Determine the noise power (in dBm) at 27° C in a 500 kHz bandwidth. Correct answer: PN = 10 log (1.38*10^-23*(27+273)*500kHz) = -146.8 dBw = -116.8 dBm Determine the noise power (in dBm) at 27° C in a 20 MHz bandwidth system. Correct answer: Pn=kTB; k=1.38*(10^-23)W°K-Hz; T(°K)=27°C+273=300°K; B=20*10^6Hz =10log(1.38*(10^-23)*300*20*10^6) =10log(8.28*(10^-14)) =-130.82 dBW =-130.82 dBW +30 dB =-100.8 dBm