

Homework 2  Electronic Communications
Problem 13.
Given a nonlinear amplifier with two input frequencies of 7kHz and 4kHz, determine (a) the
first three harmonics in the output for each of the two input frequencies, and (b) the
cross product frequencies produced in the output for values of m and n of 1 and 2.
{ Solution }
Problem 14.
Determine the percent second order, third order, and total harmonic distortion for
the output spectrum in Figure 1 below.
{ Solution }
Problem 15.
Calculate the bandwidth necessary to produce 8 X 10^{17} watts of thermal
noise power at a temperature of 17 degrees C.
{ Solution }
Problem 17.
Determine the second, fifth, and fifteenth harmonics for a repetitive wave with a
fundamental frequency of 2.5kHz.
{ Solution }
Problem 19.
For a nonlinear amplifier with sine wave input frequencies of 3kHz and 5kHz, calculate
the first three harmonics present in the output for each input frequency and the cross
product frequencies produced for values of m and n of 1 and 2.
{ Solution }
Problem 21.
Determine the signal to noise power ratios in decibels (dB) for the following input
and output voltages. Assume the resistance values on both the inputs and outputs are equal.
a) V_{in} = 0.001V, and V_{out} = 0.1V
b) V_{in} = 0.1V, and V_{out} = 2.0V
c) V_{in} = 0.5V, and V_{out} = 0.25V
d) V_{in} = 1.0V, and V_{out} = 4.0V
{ Solution }
Problem 23.
Determine the overall noise factor and noise figure for three cascaded amplifier stages with
the following specifications: Amp1 = 3dB, Amp2 = 13dB, Amp3 = 10dB, NF1 = 10dB, NF2 = 6dB, and NF3 = 10dB.
{ Solution }
Problem 25.
For an amplifier operating at a temperature of 27 degrees Celsius with a bandwidth
of 20kHz, find (a) the total noise power in watts and dBm, and (b) the RMS noise
voltage for a 50 ohm internal resistance and a 50 ohm load resistor.
{ Solution }
Problem 27.
Determine the noise figure for an equivalent noise temperature of 1000 Kelvin,
assuming 290K for the reference temperature.
{ Solution }
Problem 29.
Calculate the noise figure for an amplifier with an input signal to noise (S/N)
ratio of 100 and an output signal to noise ratio of 50.
{ Solution }
Problem 31.
Determine the input signal to noise ratio for an amplifier with an output signal
to noise ratio of 16dB and a noise figure of 5.4dB.
{ Solution }
Engineering key words: total harmonic distortion, frequency spectrum, THD, noise figure,
noise power, thermal noise, NF, temperature, amplifier characteristics, input voltage,
output voltage, dB, bandwidth, load, signal to noise ratio, S/N, internal noise.
