diff --git a/Chapter1.tex b/Chapter1.tex index eb2b620..ad4cb88 100644 --- a/Chapter1.tex +++ b/Chapter1.tex @@ -669,9 +669,6 @@ \chapter{Solutions for Chapter 1} \[\frac{R}{hypotenuse} = \frac{R}{\sqrt{R^2 + (-j/\omega C)^2}} = \frac{R}{\sqrt{R^2 + \frac{1}{\omega^2 C^2}}}\] Thus, $V_\text{out} = V_\text{in} * \frac{R}{\sqrt{R^2 + \frac{1}{\omega^2 C^2}}}$ \ex{1.33} -\begin{enumerate} - \item find the frequency - For the lowpass filter, $V_\text{out}$ and $V_\text{in}$ have the following relationship. \[V_\text{out} = V_\text{in} * \frac{1}{\sqrt{1+\omega ^2 R^2 C^2}}\] Given $V_\text{out} = \frac{1}{2} V_\text{in}$, @@ -684,19 +681,46 @@ \chapter{Solutions for Chapter 1} Since $f = \frac{\omega}{2\pi}$, \[f = \frac{\sqrt{3}}{2\pi RC}\] - \item find the phase shift - From previous calculation, we have $C = \frac{\sqrt{3}}{RC}$ From the phasor diagram for lowpass filter at $3dB$ point, we know that \[\aleph = \arctan(\frac{\frac{-j}{\omega C}}{R}) =\arctan(-\frac{1}{\sqrt{3}}) = -30^\circ\] Thus, the phase shift is \[\phi = -90^\circ - (-30^\circ) = -60^\circ\] -\end{enumerate} - - -\todoex{1.34} - -\todoex{1.35} +\ex{1.34} +% \begin{plot}{fig:1.17.2}{Phasor diagram for highpass filter at $3dB$ point.} +% % node[left] {$Z$}(-1,1); +% \draw (-1,0) -- (4,0); +% \draw (0,1) -- (0,-4); +% \draw[->] (0,0) -- (2,0) node[right] {$R$}; +% \draw[->] (2,0) -- (2,-2) node[left] {$\frac{-j}{\omega C}$}; +% \draw[->] (0,0) -- (2,-2) node[left] {$R\sqrt{2}$}; +% \end{plot} + From the phasor diagram, we can see that + \[\frac{V_\text{out}}{V_\text{in}} = \frac{C}{hypotenuse}= \frac{C}{\sqrt{R^2 + C^2}}\] + pluging in $ C = \frac{-j}{\omega C}$ + \[\frac{V_\text{out}}{V_\text{in}} = \frac{\frac{-j}{\omega C}}{\sqrt{R^2 + \frac{1}{\omega^2 C^2}}} = \frac{-j}{\omega C} * \frac{\omega C}{\sqrt{R^2 \omega^2 C^2+1}} + = \frac{-j}{\sqrt{R^2 \omega^2 C^2+1}}\] + +\ex{1.35} + Resistor, inductor, and capacitor in series forms a voltage devider, so + \[\frac{V_\text{out}}{V_\text{in}} = \frac{Z_\text{LC}}{R + Z_\text{LC}}\] + Since the inductor and capacitor are in series and $\omega_0 = \frac{1}{\sqrt{LC}}$, which was derived from $f_0 = \frac{1}{2\pi \sqrt{LC}}$. + We can write $Z_\text{LC}$ as following, + \[Z_\text{LC} = Z_\text{L} + Z_\text{C} = j\omega L + \frac{-j}{\omega C} = j(\omega L - \frac{1}{\omega C}) + = jL(\frac{\omega^2 - \omega_0^2}{\omega})\] + We can describe the response in the following conditions: + \begin{enumerate} + \item + When $f=f_0$, $\omega = \omega_0$ and $Z_\text{LC} = 0$. Thus, $\frac{V_\text{out}}{V_\text{in}} = 0$. + \item + When $f Z_\text{L}$, which makes the circuit more capcitive. + Thus, the circuit has a similar response as capacitors. + %TODO: add plot + \item + When $f>f_0$, $\omega > \omega_0$ and $Z_\text{L} > Z_\text{C}$, which means the inductor has more impact on the general response of the whole circuit. + Thus, the circuit responses more like inductors. + \end{enumerate} + Thus, we see the response plot captured in the previous figure ($Figure 1.109$) \todoex{1.36} diff --git a/main.pdf b/main.pdf index edf83d3..65d38de 100644 Binary files a/main.pdf and b/main.pdf differ