Fourier Circuit Analysis

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Questions

Question 1

What is the relationship between the period T of a periodic function's fundamental frequency and its radian frequency ω0?

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Question 2

What does the Fourier series coefficient a0 represent?

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Question 3

For the half-sinusoidal waveform shown in Figure 18.2, which has a period of 0.4 seconds, what is the value of the dc component a0 in terms of the peak voltage Vm?

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Question 4

If a periodic function f(t) possesses even symmetry, where f(t) = f(-t), which coefficients in its trigonometric Fourier series are guaranteed to be zero?

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Question 5

If a periodic function f(t) possesses odd symmetry, where f(t) = -f(-t), which coefficients in its trigonometric Fourier series are guaranteed to be zero?

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Question 6

A periodic function f(t) has half-wave symmetry if it satisfies the condition f(t) = -f(t - T/2). What is the primary characteristic of the Fourier series for such a function?

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Question 7

In the circuit of Figure 18.8a, a periodic voltage source with a dc component of 5 V is applied to a series RL circuit with R=4 ohms and L=2 H. What is the dc component of the forced current response?

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Question 8

How is the complex Fourier coefficient cn related to the trigonometric Fourier coefficients an and bn for n = 1, 2, 3, ...?

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Question 9

How is the amplitude of the nth sinusoidal component of a Fourier series related to the magnitude of the complex coefficients |cn|?

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Question 10

For the square wave in Figure 18.10 with T=2 and V=1, the complex coefficient is given by cn = (1/nπ) * [2sin(nπ/2) - sin(nπ)]. What is the value of c1?

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Question 11

The sampling function is defined as Sa(x) = sin(x)/x. What is its value at x = 0?

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Question 12

What is the Fourier transform of a unit impulse function located at t = t0?

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Question 13

What is the Fourier transform of a constant function of time, f(t) = K?

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Question 14

According to Parseval's theorem, the total 1-ohm energy delivered by a signal f(t) is found by integrating the squared magnitude of its Fourier transform, |F(jω)|^2, over all radian frequency ω. What is the correct scaling factor for this integral?

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Question 15

In the frequency domain, how is the Fourier transform of the output of a linear system, F0(jω), related to the Fourier transform of the input, Fi(jω), and the system function, H(jω)?

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Question 16

What is the relationship between a linear system's impulse response h(t) and its system function H(jω)?

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Question 17

What is the relationship between the system function H(jω) derived from Fourier transform analysis and the sinusoidal steady-state transfer function G(ω)?

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Question 18

A circuit has a system function H(jω) = j2ω / (4 + j2ω). An input voltage vi(t) = 5e^(-3t)u(t) is applied. What is the Fourier transform of this input voltage?

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Question 19

A voltage pulse is given by v(t) = 4e^(-3t)u(t) volts. What is the total 1-ohm energy in this signal?

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Question 20

What is the frequency of the first harmonic of a sinusoid also known as?

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Question 21

The Fourier theorem states that a periodic function f(t) can be represented by an infinite series. Which of the following is the trigonometric form of the Fourier series?

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Question 22

What is the integral expression used to calculate the cosine coefficient 'an' for the trigonometric Fourier series of a function f(t) with period T?

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Question 23

In a line spectrum for a Fourier series, if a harmonic component has both a sine term (coefficient bn) and a cosine term (coefficient an), what represents the total amplitude of that component?

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Question 24

For a function with both half-wave and even symmetry, how can the coefficient 'an' for odd harmonics be calculated more efficiently?

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Question 25

For a function with both half-wave and odd symmetry, which set of coefficients is guaranteed to be zero for all n?

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Question 26

The exponential Fourier series represents a periodic function f(t) as a sum of complex exponentials. What is the integral used to calculate the coefficient cn?

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Question 27

For a periodic function f(t) that has even symmetry, how does the calculation of its complex Fourier coefficient cn simplify?

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Question 28

For a periodic function f(t) that has odd symmetry, how does the calculation of its complex Fourier coefficient cn simplify?

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Question 29

What is a sufficient condition for the Fourier transform F(jω) of a function f(t) to exist?

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Question 30

If f(t) is an even function of time, what are the characteristics of its Fourier transform F(jω)?

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Question 31

If f(t) is an odd function of time, what are the characteristics of its Fourier transform F(jω)?

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Question 32

For a voltage v(t) with Fourier transform Fv(jω), what physical quantity does |Fv(jω)|^2 represent?

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Question 33

What is the Fourier transform of cos(ω0t)?

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Question 34

What is the Fourier transform of the signum function, sgn(t)?

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Question 35

What is the Fourier transform of the unit-step function, u(t)?

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Question 36

The Fourier transform of a periodic function f(t) with complex Fourier coefficients cn and fundamental radian frequency ω0 is a series of impulses. What is the correct expression for this transform?

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Question 37

What is the Fourier transform of the convolution of two time functions, f(t) * g(t)?

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Question 38

In the analysis of the half-wave rectified sinusoid in Example 18.1, with peak voltage Vm, what is the value of the coefficient a1?

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Question 39

For the half-wave rectified sinusoid in Example 18.1, the coefficient an for n > 1 is given by an = (2Vm/π) * cos(nπ/2) / (1 - n^2). What is the value of a2?

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Question 40

For the square wave in Fig. 18.10, the complex Fourier coefficient for n odd is cn = (2/nπ) * sin(nπ/2). What is the value of c3?

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Question 41

For a periodic train of rectangular pulses of duration τ and period T, the 'width' of the envelope of its discrete spectrum is primarily determined by which parameter?

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Question 42

The frequency-shift theorem for Laplace transforms states that replacing 's' with '(s+a)' in the frequency domain corresponds to what operation in the time domain?

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Question 43

Differentiating a Laplace transform F(s) with respect to s corresponds to what operation in the time domain?

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Question 44

Integrating a Laplace transform F(s) from s to infinity corresponds to what operation in the time domain?

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Question 45

The time-scaling theorem for Laplace transforms relates the transform of f(at) to the transform of f(t), which is F(s). What is the correct relationship?

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Question 46

In Example 18.2, a periodic signal is applied to a series RL circuit with R=4 ohms and L=2 H. The fundamental radian frequency is 2 rad/s. What is the impedance Zn of the circuit at the nth harmonic frequency?

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Question 47

Examine the square wave in Figure 18.4b. What type of symmetry does this waveform possess?

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Question 48

What type of symmetry does the triangular waveform shown in Figure 18.4c possess?

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Question 49

A fundamental voltage is v1(t) = 2 cos(ω0t). A third-harmonic voltage v3a(t) = cos(3ω0t) is added to it. What is the period of the resultant waveform v(t) = v1(t) + v3a(t)?

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Question 50

Using the summary of Fourier Transform pairs in Table 18.2, what is the Fourier transform of e^(-αt)u(t)?

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