sinusoidal steady-state analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · complete...
TRANSCRIPT
![Page 1: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/1.jpg)
Sinusoidal Steady-state Analysis
Complex number reviews
Phasors and ordinary differential equations
Complete response and sinusoidal steady-state response
Concepts of impedance and admittance
Sinusoidal steady-state analysis of simple circuits
Resonance circuit
Power in sinusoidal steady –state
Impedance and frequency normalization
![Page 2: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/2.jpg)
Complex number reviews
1, −=+= jjyxz
yzxz == )Im()Re(
| |j
z z eθ=
Complex number
In polar form
2 2 1/ 2 1| | ( ) tan
yz x y
xθ −= + =
| |z z θ= ∠or | | cos | | sinx z y zθ θ= =
The complex number can be of voltage, current, power, impedance etc..in any circuit with sinusoid excitation.
z
Magnitude
Phase or angle
Operations: Add, subtract, multiply, divide, power, root, conjugate
![Page 3: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/3.jpg)
Phasors and ordinary differential equationsA sinusoid of angular frequency is in the formω
)cos( φω +tAm
Theorem
The algebraic sum of sinusoids of the same frequency and of their derivatives is also a sinusoid of the same frequency
Example 1
( ) 2cos(2 60) 4sin 2 2sin 2
2cos 2 cos 60 2sin 2 sin 60 4sin 2 4cos 2
cos 2 3 sin 2 4sin 2 4cos 2
5cos 2 (4 3)sin 2 7.6cos(2 48.8)
df t t t t
dt
t t t t
t t t t
t t t
= + − +
= − − +
= − − +
= − + = +
![Page 4: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/4.jpg)
Phasors and ordinary differential equations
jmA A e
φ@
)3/602cos(2110)( ππ += ttv
phasor form
Example 2
/ 3110 2
jA e
π=(120 )
( ) Re(110 2 )j t
v t eπ=
phasor
( )Re( ) Re( )
Re( cos( ) sin( ))
cos( ) ( )
j t j tm m
m m
m
A e A e
A t jA t
A t x t
ω ω φ
ω φ ω φ
ω φ
+=
= + + +
= + =
![Page 5: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/5.jpg)
Phasors and ordinary differential equations
Ordinary linear differential equation with sinusoid excitation
1
0 1 1.. cos( )........(1)
n n
n mn n
d x d xa a a x A t
dt dtω φ
−
−+ + + = +
Lemma: Re[.. ] is additive and homogenous
)](Re[)](Re[)]()(Re[ 2121 tztztztz +=+
1 1 2 2 1 1 2 2Re[ ( ) ( )] Re[ ( )] Re[ ( )]z t z t z t z tα α α α+ = +
Re( ) Re Re( )j t j t j td d
Ae Ae j Aedt dt
ω ω ωω = =
![Page 6: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/6.jpg)
Phasors and ordinary differential equations
Application of the phasor to differential equation
,j j
m mA A e X X eφ ψ
@ @Let
substitute ( ) Re( )j t
x t Xeω= in (1) yields
0 Re( ) .. Re( ) Re( )
nj t j t j t
nn
dXe Xe Ae
dt
ω ω ωα α+ + =
0Re( ) .. Re( ) Re( )
nj t j t j t
nn
dXe Xe Ae
dt
ω ω ωα α+ + =
0Re( ( ) ) .. Re( ) Re( )n j t j t j t
nj Xe Xe Aeω ω ωα ω α+ + =
![Page 7: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/7.jpg)
Phasors and ordinary differential equations
10 1 1Re [ ( ) ( ) .. ( ) ] Re( )
n n j t j tn nj j j Xe Ae
ω ωα ω α ω α ω α−−+ + + + =
12
10 1 1
10 1 1
2 2 3 22 1 3
[ ( ) ( ) .. ( ) ]
[ ( ) ( ) .. ( ) ]
[( .. ) ( ..) ]
n nn n
n nn n
mm
n n n n
j j j X A
AX
j j j
AX
α ω α ω α ω α
α ω α ω α ω α
α α ω α ω α ω
−−
−−
− − −
+ + + + =
=+ + + +
=− + + + − +
even powerodd power
31 1 3
22
..tan
..
n n
n n
α ω α ωψ φ
α α ω− − −
−
− += −
− +
![Page 8: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/8.jpg)
Phasors and ordinary differential equations
)cos(||)Re()( φωω +== tEEetetj
s
Example 3
From the circuit in fig1 let the input be a sinusoidal voltage source and the output is the voltage across the capacitor.
( ) | | cos( )se t E tω φ= + ( ) | | cos( )c cv t V tω ψ= +
( )se t( )cV t
Fig1
![Page 9: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/9.jpg)
Phasors and ordinary differential equations
)()()()( tetvtRitidt
dL sc =++
2
2
( ) ( )( ) ( )c c
c s
d v t dv tLC RC v t e t
dtdt+ + =
)cos(||)Re()( ψωω +== tVeVtv ctj
cc
KVL
2[ )( ) ( ) 1] (2)cLC j RC j V Eω ω+ + =
Particular solution
![Page 10: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/10.jpg)
Phasors and ordinary differential equations
2
2 2 2 1/ 2
1
2
1
| || |
[(1 ) ( ) ]
tan1
c
c
EV
LC j RC
EV
LC RC
RC
LC
ω ω
ω ωω
ψ φω
−
=− +
=− +
= −−
![Page 11: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/11.jpg)
Complete response and sinusoidal steady-state
responseComplete reponse
)()()( tytyty ph +=
)(ty p = sinusoid of the same input frequency (forced component)
( )hy t =solution of homogeneous equation (natural component)
1
( ) i
ns t
h i
i
y t k e
=
=∑ (for distinct frequencies)
![Page 12: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/12.jpg)
Complete response and sinusoidal steady-state
responseExample 4
)(2cos)( tuttes =For the circuit of fig 1, the sinusoid input is appliedto the circuit at time . Determine the complete response of theCapacitor voltage. C=1Farad, L=1/2 Henry, R=3/2 ohms.
0=t
1)0(,2)0( 0 === cL vIi
2
2
( ) ( )1 3( ) cos 2 ( )
2 2
c cc
d v t dv tv t t u t
dtdt+ + =
From example 3
Initial conditions
2)0()0(
,1)0( ===−−
−
C
i
dt
dvv Lc
c
![Page 13: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/13.jpg)
Complete response and sinusoidal steady-state
responseCharacteristic equation
2,1,01232
21 −−==++ sss
tth ekektv
221)(
−− +=2
( ) Re( ) | | cos(2 )j t
pv t Ve V t ψ= = +
2( ) Re( ) cos 2
j tse t Ee t= =
From (2) 2 312 2[ ( ) ( ) 1]j j V Eω ω+ + =
108.4
2 312 2
10.316
1 31
jEV e
jjω ω−= = =
− +− +
o
Natural component
Forced component
![Page 14: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/14.jpg)
Complete response and sinusoidal steady-state
responseThe complete solution is
21 2
( ) ( ) ( )
0.316cos(2 108.4 )
c h p
t t
v t v t v t
k e k e t− −
= +
= + + − o
1 2
1 2
(0) 1 0.316cos( 108.4 )
1.1
cv k k
k k
= = + + −
+ =
o
1 2
1 2
(0) 2 2 0.316 2sin( 108.4 )
2 1.4
c
dv k k
dt
k k
= = − − − × −
+ = −
o
6.31 =k 2 2.5k = −
![Page 15: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/15.jpg)
Complete response and sinusoidal steady-state
response
2( ) 3.6 2.5 0.316cos(2 108.4 )
t tcv t e e t
− −= − + − o
The complete solution is
![Page 16: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/16.jpg)
Complete response and sinusoidal steady-state
responseSinusoidal steady-state response
)(ty
In a linear time invariant circuit driven by a sinusoid source, the response
Is of the form
1 21 2( ) .. cos( )ns ts t s t
n my t k e k e k e A tω ψ= + + + + +
Irrespective of initial conditions ,if the natural frequencies lie inthe left-half complex plane, the natural components converge
to zero as and the response becomes close to a sinusoid. The sinusoid steady state response can be calculated
by the phasor method.
∞→t
![Page 17: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/17.jpg)
Complete response and sinusoidal steady-state
response
40
220
4220
22)( ωωω ++=+ sss
1 2 0 3 4 0,s s j s s jω ω= = = = −
0 0
1 2 3 4( ) ( ) ( )j t j t
hy t k k t e k k t eω ω−= + + +
Example 5
Let the characteristic polynomial of a differential a differential equationBe of the form
The characteristic roots are
and the solution is of the form
1 0 1 2 0 2( ) cos( ) cos( )hy t k t k t tω φ ω φ= + + +In term of cosine
The solution becomes unstable as ∞→t
![Page 18: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/18.jpg)
Complete response and sinusoidal steady-state
response
0 01 2 0( ) cos( )
j t j thy t k e k e K t
ω ω ω φ−= + = +
∞→t0ωω =
220s ω+
1 0 2 0,s j s jω ω= = −
( ) ( ) ( )h py t y t y t= +
Example 6
Let the characteristic polynomial of a differential a differential equationBe of the form
The characteristic roots are
and the solution is of the form
( ) cos( )py t B tω ψ= +and
The solution is oscillatory at different frequencies. If the output isunstable as ( ) cos( )y t At tω θ= +
![Page 19: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/19.jpg)
Complete response and sinusoidal steady-state
responseSuperposition in the steady state
If a linear time-invariant circuit is driven by two or more sinusoidalsources the output response is the sum of the output from each source.
Example 7
The circuit of fig1 is applied with two sinusoidal voltage sources and the output is the voltage across the capacitor.
1 1 1cos( )mA tω φ+( )cV t
2 2 2cos( )mA tω φ+
![Page 20: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/20.jpg)
Phasors and ordinary differential equations
1 2( ) ( ) ( ) ( ) ( )c s s
dL i t Ri t v t e t e t
dt+ + = +
2
1 1 1 2 2 22
( ) ( )( ) cos( ) cos( )c c
c m m
d v t dv tLC RC v t A t A t
dtdtω φ ω φ+ + = + + +
21 1
1 1 1 12
( ) ( )( ) cos( )
p p
p m
d v t dv tLC RC v t A t
dtdtω φ+ + = +
KVL
Differential equation for each source
22 2
2 2 2 22
( ) ( )( ) cos( )
p p
p m
d v t dv tLC RC v t A t
dtdtω φ+ + = +
![Page 21: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/21.jpg)
Phasors and ordinary differential equations
)cos()cos(
)()()(
22221111
21
θφωθφω +++++=
+=
tVtV
tvtvtv
mm
ppp
The particular solution is
1
1 1
2
2 2
( ) 11 2
1 1
( ) 22 2
2 2
1
1
jj m
m
jj m
m
A eV e
LC j RC
A eV e
LC j RC
φφ θ
φφ θ
ω ω
ω ω
+
+
=− +
=− +
where
![Page 22: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/22.jpg)
Complete response and sinusoidal steady-state
response
Summary
A linear time-invariant circuit whose natural frequencies are all withinthe open left-half of the complex frequency plane has a sinusoid steady state response when driven by a sinusoid input. If the circuit has Imaginary natural frequencies that are simple and if these are differentfrom the angular frequency of the input sinusoid, the steady-stateresponse also exists.
The sinusoidal steady state response has the same frequencyas the input and can be obtained most efficiently by the phasor method
![Page 23: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/23.jpg)
Concepts of impedance and admittance
Properties of impedances and admittances play important roles in
circuit analyses with sinusoid excitation.
Linear time-invariant
circuit in sinusoid
steady stateElement
( ) Re( )j t
i t Ieω=
( ) Re( )j t
v t Veω=
+
-
Phasor relation for circuit elements
( ) Re( ) | | cos( )j t
v t Ve V t Vω ω= = + R
( ) Re( ) | | cos( )j t
i t Ie I t Iω ω= = + R
Fig 2
![Page 24: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/24.jpg)
Concepts of impedance and admittance
( ) ( ), ( ) ( )
,
v t Ri t i t Gv t
V RI I GV
I V
= =
= =
=R R
Resistor
The voltage and current phasors are in phase.
Capacitor
1,
90 , 90 ,
dvi C
dt
I j CV V Ij C
V I I V
ωω
=
= =
∠ = ∠ − ∠ = ∠ +o o
The current phasor leads the voltage phasor by 90 degrees.
![Page 25: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/25.jpg)
Concepts of impedance and admittance
Inductor
1,
90 , 90 ,
div L
dt
V j L I I Vj L
V I I V
ωω
=
= =
= + = −o oR R R R
The current phasor lags the voltage phasor by 90 degrees.
![Page 26: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/26.jpg)
Concepts of impedance and admittance
Definition of impedance and admittance
ℜThe driving point impedance of the one port at the angular frequency is the ratio of the output voltage phasor V to the input current phasor Iω
| || ( ) | , ( )
| |
VZ j Z j V I
Iω ω= = −R R R
( ) | ( ) || | cos( )s sv t Z j I t Z Iω ω= + +R Ror
ℜThe driving point admittance of the one port at the angular frequency is the ratio of the output current phasor I to the input voltage phasor Vω
| || ( ) | , ( )
| |
IY j Y j I V
Vω ω= = −S R R
( ) | ( ) || | cos( )si t Y j V t Y Vω ω= + +R Ror
![Page 27: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/27.jpg)
Concepts of impedance and admittance1
| ( ) | , ( ) ( )| ( |
Z j Z j Y jY j
ω ω ωω
= = −R R
Inductor
Capacitor
Resistor
YZAngular frequency ω
RG
1=
1
j Cωj Cω
j Lω1
j Lω
R
![Page 28: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/28.jpg)
Sinusoidal steady-state analysis of simple circuits
0)()()( 321 =++ tvtvtv
ω
0)cos()cos()cos( 332211 =+++++ φωφωφω tVtVtV mmm
In the sinusoid steady state Kirchhoff’s equations can be written directlyin terms o voltage phasors and current phasors. For example:
If each voltage is sinusoid of the same frequency
1 2 3
1 2 3
1 2 3
1 2 3
Re( ) Re( ) Re( ) 0
Re( ) 0
Re[( ) ] 0
0
j t j t j t
j t j t j t
j t
V e V e V e
V e V e V e
V V V e
V V V
ω ω ω
ω ω ω
ω
+ + =
+ + =
+ + =
+ + =
![Page 29: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/29.jpg)
Sinusoidal steady-state analysis of simple circuits
n
n
VVVV
IIII
....
....
21
21
++=
====
Series parallel connections
In a series sinusoid circuit
I1I 2I nI
1V 2V nV
V
1
( ) ( )
n
i
i
Z j Z jω ω=
=∑
Fig 3
![Page 30: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/30.jpg)
Sinusoidal steady-state analysis of simple circuits
1 2
1 2
....
....
n
n
V V V v
I I I I
= = = =
= + +
In a parallel sinusoid circuit
Y1 YnY2
I
1I 2I nI
1V
+
-
2V
-
++
nV
-
+
-
V
1
( ) ( )
n
i
i
Y j Y jω ω=
=∑
Fig 4
![Page 31: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/31.jpg)
Sinusoidal steady-state analysis of simple circuits
Node and mesh analyses
)302cos(10)(ο+= ttis
Node and mesh analysis can be used in a linear time-invariant circuit to
determine the sinusoid steady state response. KCL, KVL and the concepts
of impedance and admittance are also important for the analyses.
Example 8
Fig 5
In figure 5 the input is a current source
Determine the sinusoid steady-state voltage at node 3
1 32
2FCi
-
+++
--1v 2v 3v1
1 1
2H
Lisi
![Page 32: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/32.jpg)
Node and mesh analyses2 30
( ) 10cos(2 30 ) Re( ) 10j t j
s s si t t I e or I e= + = =o
o
)Re()(),Re()(),Re()(2
332
222
11tjtjtj eVtveVtveVtv ===
1 1 3 1 24( ) ( ) sV j V V V V I+ − + − =
1 3 1 3 2 1 3( ) ( ) 4( )C CI Y V V j C V V V j V Vω= − = − = −
2224
11V
jV
LjVYI LL ===
ω
KCL at node 1
KCL at node 2 22 1 2 3( ) ( ) 0
4
VV V V V
jω+ − + − =
KCL at node 33
3 1 3 24( ) ( ) 02
Vj V V V V+ − + − =
![Page 33: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/33.jpg)
Node and mesh analysesRearrange the equations
1 2 3(2 4) 4 sj V V j V I+ − − =
1 2 3
1(2 ) 0
4V V V
j− + + − =
1 2 3
34 ( 4) 0
2j V V j V− − + + =
By Crammer’s Rule
3
32
2 4 1
11 2 0
4
4 1 0 2 8
6 11.252 4 1 4
11 2 1
4
4 1 4
s
s
j I
j
j jV I
jj j
j
j j
+ −
− +
− − += =
++ − −
− + −
− − +
![Page 34: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/34.jpg)
Node and mesh analyses
3010
jsI e=
o44
3 6.45j
V e=o
3 ( ) 6.45cos(2 44 )v t t= + o
Since
and the sinusoid steady-state voltage at node 3 is
Then
Example 9
Solve example 8 using mesh analysis
2i
Lv3v
sv 1i 3i
Fig 6
![Page 35: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/35.jpg)
Node and mesh analyses2 30
( ) 10cos(2 30 ) Re( ) 10j t j
s s sv t t V e or V e= + = =o
o
2 2 21 1 2 2 3 3( ) Re( ), ( ) Re( ), ( ) Re( )
j t j t j ti t I e i t I e i t I e= = =
1 1 2 1 3( ) 4( ) sI I I j I I V+ − + − =
3 3
1C CV Z I I
j Cω= =
1 24( )L L L LV Z i j LI j I Iω= = = −
KVL at mesh 1
KVL at mesh 2
3 3 2 3 12 ( ) 4( ) 0I I I j I I+ − + − =KVL at mesh 3
2 2 3 3 1
1( ) 4( ) 0
4I I I j I I
j+ − + − =
![Page 36: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/36.jpg)
Node and mesh analyses
1 2 3(2 4) 4 sj I I j I V+ − − =
1 2 3
1(2 ) 0
4I I I
j− + + − =
1 2 34 (3 4) 0j I I j I− − + + =
By Crammer’s Rule
3
2 4 1
11 2 0
4
4 1 0 2 8
12 22.52 4 1 4
11 2 1
4
4 1 3 4
s
s
j V
j
j jI V
jj j
j
j j
+ −
− +
− − += =
++ − −
− + −
− − +
Rearrange the equations
![Page 37: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/37.jpg)
Node and mesh analyses
303 310 2
jsV e and V I= =
o
443 6.45
jV e=
o
3 ( ) 6.45cos(2 44 )v t t= + o
Since
and the sinusoid steady-state voltage at node 3 is
Then
The solution is exactly the same as from the node analysis
![Page 38: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/38.jpg)
Resonance circuit
Resonance circuits form the basics in electronics and communications. It is
useful for sinusoidal steady-state analysis in complex circuits.
( ) Re( )j t
s si t I eω= C L
G=1/R
+
-
V
Y
CI LI RI
Impedance, Admittance, Phasors
Fig 7
Figure 7 show a simple parallel resonant circuit driven by a sinusoid source.
( ) Re( ) | | cos( )j t
s s s si t I e I t Iω ω= = + R
![Page 39: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/39.jpg)
Resonance circuit
1( )
1( )
Y j G j Cj L
G j CL
ω ωω
ωω
= + +
= + −
ω
( )Y jω
The input admittance at the angular frequency is
The real part of is constant but the imaginary part varies with frequency
1( )B j C
Lω ω
ω= −
At the frequency 0 00
1
2 2 2f
LC
ω ωπ π π
= = =
the susceptance is zero. The frequency is called the resonant frequency.0f
![Page 40: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/40.jpg)
Resonance circuit
LCjY
GjY
ωωω
ω1
)](Im[
)](Re[
−=
=
2 2
2 2
Re[ ( )]( )
( )Im[ ( )]
( )
GZ j
G B
BZ j
G B
ωω
ωω
ω
=+
−=
+
2 2 2 2
1 1( )
( ) ( )
( )
( ) ( )
Z jY j G jB
G Bj
G B G B
ωω ω
ω
ω ω
= =+
−= +
+ +
The admittance of the parallel circuit in Fig 7 is frequency dependant
ω
B
Cω
1
Lω
0ω
Susceptance plot
Fig 8
![Page 41: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/41.jpg)
Resonance circuit
0ω =
GRe( )Y
Im ( )Y
ω = ∞
| |Y
Y0ω ω=
Admittance Plane
1( ) ( )Y j G j C
Lω ω
ω= + −
1( )
1( )
Z j
G j CL
ωω
ω
=+ −
Locus of Y
Re( )Z
ω
0ω ω=
Im( )Z
1
2G
1
G
0ω =ω = ∞
Locus of Z
Fig 9
![Page 42: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/42.jpg)
Resonance circuit
CVjIVLj
IGVI CLR ωω
=== ,1
,
SCLR IIII =++
)Re(cos)(jt
ss eItti ==
The currents in each element are
and
If for example1
1 , , 14
R L H C F= Ω = =
0, 1 /
jsI e rad sω =
The admittance of the circuit is
71.6( 1) 1 (1 4) 1 3 10
jY j j j e
−= + − = − =o
The impedance of the circuit is71.61 1
( 1)( 1) 10
jZ j eY j
= =o
![Page 43: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/43.jpg)
Resonance circuit
71.61( 1)
10
jsV Z j I e= =
o
71.6 18.4 161.61 1 1, ,
10 10 10
j j jR L CI e I e I e
−= = =o o o
The voltage phasor is
Thus
Re
ImV
LI
CIRI
SI
Fig 10
![Page 44: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/44.jpg)
Resonance circuit
sradLC
/21
0 ==ω2
( ) cos 2 Re( )j t
s si t t I e= =
0, 2 /
jsI e rad sω =
Similarly if and
( 2) 1, ( 2) 1, 1Y j Z j V= = =90 90
1, 2 , 2j j
R L CI I e I e−= = =
o o
The voltage and current phasors are
LI
CI
R sI I=
SI
Note that it is a resonance and
,L s C sI I I I> >
Fig 11
![Page 45: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/45.jpg)
Resonance circuit
| || |
| | | |
pCLp
s s
RIIQ
I I Lω= = @
1>>Q
)1
()(C
LjRjZω
ωω −+=
The ratio of the current in the inductor or capacitor to the input current is the quality factor or Q-factor of the resonance circuit.
Generally and the voltages or currents in a resonance circuit is very large!
Analysis for a series R-L-C resonance is the very similar
( )( )
ss
VI j
Z jω
ω=
S R L CV V V V= + + | || |
| | | |
CLs
s s s
VV LQ
V V R
ω= = @
![Page 46: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/46.jpg)
Power in sinusoidal steady-state
)()()( titvtp −ℜ
ℜ
The instantaneous power enter a one port circuit is
The energy delivered to the in the interval is
∫=t
t
o
o
dttpttW ')'(),(
),( tto
ℜ
( )i t
( )v t
Fig 12
![Page 47: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/47.jpg)
Power in sinusoidal steady-state
Instantaneous, Average and Complex power
ℜIn sinusoidal steady-state the power at the port is
( ) cos( ) Re( )j t
mv t V t V Veωω= + =R
, | |j V
m mV V e V V=R@
where
If the port current is
( ) cos( ) Re( )j t
mi t I t I Ie ωω= + =R
, | |j I
m mI I e I I=R@
where
![Page 48: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/48.jpg)
Power in sinusoidal steady-state
m
1 1m m2 2
( ) ( ) ( )
cos( )cos( )
cos( ) cos(2 )
m
m m
p t v t i t
V I t V t I
V I V I V I t V I
ω ω
ω
=
= + +
= − + + +
R R
R R R R
1m2
0
1( ') ' cos( )
T
av mP p t dt V I V It
= −∫@ R R
)(tp
Then
avP)(tv
)(ti
Fig 13
![Page 49: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/49.jpg)
Power in sinusoidal steady-state Remarks
The phase difference in power equation is the impedance
angle
Pav is the average power over one period and is non negative. But p(t) may be negative at some t
The complex power in a two-port circuit is 1
2 rms rmsP V I V I=@( )1
2
1 1
2 2
| || |
| || | cos( ) | || | sin( )
j V IP V I e
V I V I j V I V I
−=
= − + −
R R
R R R R
1
2Re( ) Re( ) Re( )av rms rmsP P V I V I= = =
2
2 21 12 2
2
| | Re[ ( )] | | Re[ ( )]
Re[ ( )] Re[ ( )]rms rms
avP I Z j V Y j
I Z j V Y j
ω ω
ω ω
= =
= = Average power is additive
![Page 50: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/50.jpg)
Power in sinusoidal steady-state
Maximum power transfer
SL ZZ =
The condition for maximum transfer for sinusoid steady-state is thatThe load impedance must be conjugately matched to the source imedance
s
sav
R
VP
8
||2
max=
2| |
4
ss
s
VP
R=
Q of a resonance circuit
0
0
212
0 212
| |
| |
RQ CR
L
C V
G V
ωω
ω
=
=
@
For a parallel resonance circuit
0
energy storedQ
average power dissipated in the resistorω=
(Valid for both series and parallel resonance circuits)
![Page 51: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/51.jpg)
Impedance and frequency normalization
In designing a resonance circuit to meet some specification component
values are usually express in normalized form.
L
R
Qbandwidthdb
LCRZ ==∆−== 0
00 3,1
,ω
ωωFrom
200
1,
RL C and
QR
ω ωω ωω
∆ ∆= = =∆
Let the normalized component values are
0 0 0
11, ,R L Q C
Q= = =
Then
0 00 2
0 0 0 0 0
1, ,
QZ ZR Z L C
Q Z Z
ωω ω ω ω
∆= = = = =
∆
![Page 52: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/52.jpg)
Impedance and frequency normalization
Popularity of normalized design: The circuit design can be made at any impedance level and
center frequency
Well-known solutions exist
n
desired impedance levelr
impedance level of normalized design=
Let
n
desired typical frequency
typical frequency of normalized designΩ =
Then
nnn
nn
r
CCL
rLRrR
Ω=
Ω== 0
00 ,,
![Page 53: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/53.jpg)
Impedance and frequency normalization
Example
6
2
1
2
1
1
ω+=
I
E
Fig. 14 shows a low pass filter whose transfer impedance
1I1.5F 0.5F
1.333H
1
+
-
E2
ω
2
1
E
I
1
2
10Rad/s
1
The gain of the filter is 1 at 0ω = And at 1ω =
Design the circuit to have an impedance of 600 ohms at 0ω =and equal to 1/ 2 at 3.5 kHz then
600nr = 3 42 3.5 10 2.199 10n πΩ = × ⋅ = ×and
2/1
![Page 54: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/54.jpg)
Impedance and frequency normalization
0
0 4
011 4
022 4
600
6001.333 36.37
2.199 10
1.50.1137
600 2.199 10
0.50.0379
600 2.199 10
n
n
n
n n
n n
R r R
rL L mH
C FC F
r
C FC F
r
µ
µ
= =
= = =Ω ×
= = =Ω ⋅ ×
= = =Ω ⋅ ×
![Page 55: Sinusoidal Steady-state Analysiseestaff.kku.ac.th/~jamebond/182304/chapter2.pdf · Complete response and sinusoidal steady-state response Superposition in the steady state If a linear](https://reader035.vdocuments.us/reader035/viewer/2022062317/5e7da66e17386f5ee21fa45b/html5/thumbnails/55.jpg)
Impedance and frequency normalization
1I6 00
+
-
E2
ω
2
1
E
I
600
2
2 x35000Rad/s
600
0.11378 F0.0379 F
36.37mH
Designed circuit