1-1. Define electronic communications.
1-3. Define decibel.
1-5. What is the difference between a positive and a negative decibel?
1-7. What are the three primary components of an electronic communications system?
1-9. What arc the two basic types of electronic communications systems?
1-11. What are the three properties of a sine wave that can be varied? Name the types of modulation
that result from each.
1-13. Describe the terms frequency up-conversion and frequency down-conversion.
1-15. Briefly describe the ITU's frequency band designations.
1-17. Define information capacity.
1-19. Define electrical noise.
1-21. What is meant by the terms external noise and internal noise?
1-23. What is meant by the term man-made noise? Give several examples.
1-25. Define thermal noise and describe its relationship to temperature and bandwidth.
1-27. List and describe the two most significant forms of correlated noise.
1-29. Describe the term interference and list several sources.
1-31. Define noise factor and noire figure and describe their significance.
PROBLEM SOLVING
1-1. Convert the following absolute power ratios to dB:
a. 5 0. 15 c. 25 d. 125 e. 2000 f. 10,000 g. 100.000
1-3. Convert the following decibel values to absolute ratios:
a. 26 dB 0. 2 dB. c. 43 dB d. 56 dB
1-5. Convert the following powers to dBm:
a. 0.001 µW b. 1 pW, 2 X 10-15 W C. I.4 X 10-16 W
1.7. Given a three-stage system comprised of two amplifiers and one filter with an input of P in= 0.01 mW
and absolute power gains of Ap1= 200, A p2 = 0.1. and Ap3= 1000. Determine:
a. The input power in dBm
b. Output power (Pout) in watts and dBm
c. The dB gain of each of the three stages
d. The overall gain in dB
1-9. Determine the combined power when a signal with a power level of 10 dBm is combined with a
second signal with a power level of 8 dBm.
1-11. Determine the wavelengths for the following frequencies:
a. 50 MHz b. 400 MHz c. 4 GHz d. 100 GHz
1-13. What is the effect on the information capacity of a communications channel if the bandwidth, is
halved? Doubled?
1-15. Convert the following temperatures to Kelvin: a. 17°C b. 27°C c. —17°C d. —50°C
1-17. Determine the bandwidth necessary to produce 8 x 10 7 watts of thermal power at a temperature
of 17°C.
1-19. For a nonlinear amplifier with sine wave input frequencies of 3 kHz and 5 kHz, determine first
three harmonics present in the output for each input frequency and the cross-product frequencies
produced for values of m and n of I and 2.
1-21. Determine the voltage ratios in dB for the following input and output voltages (assume equal input
and output resistance values):
a. Vin= 0.001 V, Vout = 0.01 V b. Vin = 0.1 V, Vout = 2 V c. Vin = 0.5 V, Vout = 0.25 V d. Vin = I V, Vout = 4 V
1-23. Determine the overall noise factor and noise figure for three cascaded amplifiers with the
following parameters:
A1= 3 dB
A2 13 dB
A3 = 10 dB
NF10 = 10 dB
NF2 = 6 dB
NF3 = 10 dB
1-25. For an amplifier operating at a temperature of 27°C with a bandwidth of 20 kHz, determine
a. The total noise power in watts and dBm.
b. The rms noise voltage (Vn) for a 50- internal resistance and a 50-load resistor.
1-27. Determine the noise figure for an equivalent noise temperature of 1000 K (use 290 K for the
reference temperature).
1-29. Determine the noise figure for an amplifier with an input signal-to-noise ratio of 100 and an output
signal-to-noise ratio of 50.
1-31. Calculate the input signal-to-noise ratio for an amplifier with an output signal-to-noise ratio of 16
dB and a noise figure of 5.4 dB.
1-33. Determine the thermal noise voltages for components operating at the following temperatures,
bandwidths, and equivalent resistances:
a. T = —50°C, B = 50 kHz, and R =50
b. T= 100°C, B = 10 kHz. and R = 100
c. T = 50°C, B = 500 kHz, and R = 72
