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Microwave and RF Design: Transmission Lines Volume 2

Michael Steer

Chapter 3

Planar Transmission Lines - all with Video Answers

Educators


Chapter Questions

00:43

Problem 1

At low frequencies a microstrip line has a capacitance of $1 \mathrm{nF} / \mathrm{m}$ and when the dielectric is replaced by air its capacitance is $0.5 \mathrm{nF} / \mathrm{m}$. What is the phase velocity of signals on the line with the dielectric substrate in place? Consider that the relative magnetic permeability is $1 .$

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- -
Numerade Educator
00:43

Problem 2

A non-magnetic microstrip line has a capacitance of $100 \mathrm{pF} / \mathrm{m}$ and when the dielectric is replaced by air it has a capacitance of $25 \mathrm{pF} / \mathrm{m}$ What is the phase velocity of signals on the line with the dielectric?

- -
- -
Numerade Educator
03:06

Problem 3

At low frequencies a non-magnetic microstrip transmission line has a capacitance of $10 \mathrm{nF} / \mathrm{m}$ and when the dielectric is replaced by air it has a capacitance of $2.55 \mathrm{nF} / \mathrm{m}$. What is the effective permittivity of the microstrip line of signals on the line with the dielectric substrate in place?

Prachita Kush
Prachita Kush
Numerade Educator
01:01

Problem 4

A microstrip line on $250 \mu \mathrm{m}$ thick GaAs has a minimum and maximum strip widths of $50 \mu \mathrm{m}$ and $250 \mu \mathrm{m}$ respectively. What is the range of characteristic impedances that can be used in design?

Narayan Hari
Narayan Hari
Numerade Educator
01:42

Problem 5

A microstrip line with a substrate having a relative permittivity of 10 has an effective permittivity of 8 . What is the wavelength of a $10 \mathrm{GHz}$ signal propagating on the microstrip?

Khoobchandra Agrawal
Khoobchandra Agrawal
Numerade Educator
02:45

Problem 6

A microstrip line has a width of $500 \mu \mathrm{m}$ and a substrate that is $635 \mu \mathrm{m}$ thick with a relative permittivity of $20 .$ What is the effective permittivity of the line?

Suhas Katkar
Suhas Katkar
Numerade Educator
05:07

Problem 7

The strip of a microstrip has a width of $250 \mu \mathrm{m}$ and is fabricated on a lossless substrate that is $500 \mu \mathrm{m}$ thick and has a relative permittivity of 2.3. [Parallels Example 3.2]
(a) What is the effective relative permittivity of the line?
(b) What is the characteristic impedance of the line?
(c) What is the propagation constant at $3 \mathrm{GHz}$ ignoring any losses?
(d) If the strip has a resistance of $0.5 \Omega / \mathrm{cm}$ and the ground plane resistance can be ignored, what is the attenuation constant of the line at $3 \mathrm{GHz} ?$

Khoobchandra Agrawal
Khoobchandra Agrawal
Numerade Educator
01:16

Problem 8

A microstrip line on a $250 \mu \mathrm{m}$ -thick silicon substrate has a width of $200 \mu \mathrm{m}$. Use Table 3 -3.
(a) What is line's effective permittivity.
(b) What is its characteristic impedance?

Chai Santi
Chai Santi
Numerade Educator
01:01

Problem 9

A $600 \mu$ m-wide microstrip line on a $500 \mu \mathrm{m}$ thick alumina substrate. Use Table $3-3$.
(a) What is line's effective permittivity.
(b) What is its characteristic impedance?

Narayan Hari
Narayan Hari
Numerade Educator
01:01

Problem 10

A microstrip line on a $1 \mathrm{~mm}$ -thick FR4 substrate has a width of $0.497 \mathrm{~mm}$. Use Table 3 -3.
(a) What is line's effective permittivity.
(b) What is its characteristic impedance?

Narayan Hari
Narayan Hari
Numerade Educator
02:44

Problem 11

Consider a microstrip line on a substrate with a relative permittivity of 12 and thickness of $1 \mathrm{~mm}$
(a) What is the minimum effective permittivity of the microstrip line if there is no limit on the minimum or maximum width of the strip?
(b) What is the maximum effective permittivity of the microstrip line if there is no limit on the minimum or maximum width of the strip?

Aja S
Aja S
Numerade Educator
00:58

Problem 12

A microstrip line has a width of $1 \mathrm{~mm}$ and a substrate that is $1 \mathrm{~mm}$ thick with a relative permittivity of $20 .$ What is the geometric filling factor of the line?

Manish Kumar ( Iit K )
Manish Kumar ( Iit K )
Numerade Educator
02:46

Problem 13

The substrate of a microstrip line has a relative permittivity of 16 but the calculated effective permittivity is 12 . What is the filling factor?

Khoobchandra Agrawal
Khoobchandra Agrawal
Numerade Educator
04:16

Problem 14

A microstrip line has a strip width of $250 \mu \mathrm{m}$ and a substrate with a relative permittivity of 10 and a thickness of $125 \mu \mathrm{m}$. What is the filling factor?

Andrew Eddins
Andrew Eddins
Emory University
06:46

Problem 15

A microstrip line has a strip width of $250 \mu \mathrm{m}$ and a substrate with a relative permittivity of 4 and thickness of $250 \mu \mathrm{m}$. Determine the filling factor and thus the effective relative permittivity of the line?

Andrew Eddins
Andrew Eddins
Emory University
02:49

Problem 16

A microstrip line has a strip with a width of $100 \mu \mathrm{m}$ and the substrate which is $250 \mu \mathrm{m}$ thick and a relative permittivity of 8 .
(a) What is the filling factor, $q$, of the line?
(b) What is the line's effective relative permittivity?
(c) What is the characteristic impedance of the line?

Zulfiqar Ali
Zulfiqar Ali
Numerade Educator
02:16

Problem 17

An inhomogeneous transmission line is fabricated using a medium with a relative permittivity of 10 and has an effective permittivity of 7 . What is the fill factor $q$ ?

Narayan Hari
Narayan Hari
Numerade Educator
02:43

Problem 18

A microstrip technology uses a substrate with a relative permittivity of 10 and thickness of $400 \mu \mathrm{m}$. The minimum strip width is $20 \mu \mathrm{m}$. What is the highest characteristic impedance that can be achieved?

Sheh Lit Chang
Sheh Lit Chang
University of Washington
01:57

Problem 19

A microstrip transmission line has a characteristic impedance of $75 \Omega,$ a strip resistance of $5 \Omega / \mathrm{m},$ and a ground plane resistance of $5 \Omega / \mathrm{m}$ The dielectric of the line is lossless.
(a) What is the total resistance of the line in $\Omega / \mathrm{m} ?$
(b) What is the attenuation constant in $\mathrm{Np} / \mathrm{m}$ ?
(c) What is the attenuation constant in $\mathrm{dB} / \mathrm{cm} ?$

Surendra Kumar
Surendra Kumar
Numerade Educator
01:01

Problem 20

A microstrip line has a characteristic impedance of $50 \Omega,$ a strip resistance of $10 \Omega / \mathrm{m},$ and a ground plane resistance of $3 \Omega / \mathrm{m}$
(a) What is the total resistance of the line in $\Omega / \mathrm{m} ?$
(b) What is the attenuation constant in $\mathrm{Np} / \mathrm{m}$ ?
(c) What is the attenuation constant in $\mathrm{dB} / \mathrm{cm} ?$

Narayan Hari
Narayan Hari
Numerade Educator
05:33

Problem 21

A microstrip line has $10 \mu \mathrm{m}$ -thick gold metallization for both the strip and ground plane. The strip has a width of $125 \mu \mathrm{m}$ and the substrate is $125 \mu \mathrm{m}$ thick.
(a) What is the low frequency resistance (in $\Omega / \mathrm{m})$ of the strip?
(b) What is the low frequency resistance of the ground plane?
(c) What is the total low frequency resistance of the microstrip line?

Nathan Nowack
Nathan Nowack
Numerade Educator
01:27

Problem 22

A $50 \Omega$ microstrip line has $10 \mu \mathrm{m}$ -thick gold metallization for both the strip and ground plane. The strip has a width of $250 \mu \mathrm{m}$ and the lossless substrate is $250 \mu \mathrm{m}$ thick.
(a) What is the low frequency resistance (in $\Omega / \mathrm{m}$ ) of the strip?
(b) What is the low frequency resistance of the ground plane?
(c) What is the total low frequency resistance of the microstrip line?
(c) What is the attenuation in $\mathrm{dB} / \mathrm{m}$ of the line at low frequencies?

Akshaya Rs
Akshaya Rs
Numerade Educator
03:06

Problem 23

A $50 \Omega$ microstrip line with a lossless substrate has a $0.5 \mathrm{~mm}$ -wide strip with a sheet resistance of $1.5 \mathrm{~m} \Omega$ and the ground plane resistance can be ignored. What is the attenuation constant at
$1 \mathrm{GHz}$ ? [Parallels Example 3.3]

Prachita Kush
Prachita Kush
Numerade Educator
03:06

Problem 24

A microstrip line operating at $10 \mathrm{GHz}$ has a substrate with a relative permittivity of 10 and a loss tangent of $0.005 .$ It has a characteristic impedance of $50 \Omega$ and an effective permittivity of 7
(a) What is the conductance of the line in $\mathrm{S} / \mathrm{m}$ ?
(b) What is the attenuation constant in $\mathrm{Np} / \mathrm{m}$ ?
(c) What is the attenuation constant in $\mathrm{dB} / \mathrm{cm} ?$

Prachita Kush
Prachita Kush
Numerade Educator
01:51

Problem 25

A microstrip line has the per unit length parameters $L=2 \mathrm{nH} / \mathrm{m}$ and $C=1 \mathrm{pF} / \mathrm{m},$ also at $10 \mathrm{GHz}$ the substrate has a conductance $G$ of $0.001 \mathrm{~S} / \mathrm{m}$. The substrate loss is solely due to dielectric relaxation loss and there is no substrate conductive loss. The resistances of the ground and strip are zero.
(a) What is $G$ at $1 \mathrm{GHz}$ ?
(b) What is the magnitude of the characteristic impedance at $1 \mathrm{GHz}$ ?
(c) What is the dielectric attenuation constant of the line at $1 \mathrm{GHz}$ in $\mathrm{dB} / \mathrm{m}$ ?

Surendra Kumar
Surendra Kumar
Numerade Educator
09:02

Problem 26

A microstrip line has the per unit length parameters $L=1 \mathrm{nH} / \mathrm{m}$ and $C=1 \mathrm{pF} / \mathrm{m},$ also at $1 \mathrm{GHz}$ the substrate has a conductance $G$ of $0.001 \mathrm{~S} / \mathrm{m}$. The substrate loss is solely due to dielectric relaxation loss and there is no substrate conductive loss. The resistance of the strip is $0.5 \Omega / \mathrm{m}$ and the resistance of the ground plane is $0.1 \Omega / \mathrm{m}$
(a) What is the per unit length resistance of the microstrip line at $1 \mathrm{GHz}$ ?
(b) What is the magnitude of the characteristic impedance at $1 \mathrm{GHz}$ ?
(c) What is the conductive attenuation constant in $\mathrm{Np} / \mathrm{m} ?$
(d) What is the dielectric attenuation constant of the line at $1 \mathrm{GHz}$ in $\mathrm{dB} / \mathrm{m}$ ?

Ameer Said
Ameer Said
Numerade Educator
11:55

Problem 27

A microstrip line operating at $2 \mathrm{GHz}$ has perfect metallization for both the strip and ground plane. The strip has a width of $250 \mu \mathrm{m}$ and the substrate is $250 \mu \mathrm{m}$ thick with a relative permittivity of 10 and a loss tangent of 0.001 .
(a) What is the filling factor, $q,$ of the line?
(b) What is the line's effective relative permittivity?
(c) What is the line's attenuation in $\mathrm{Np} / \mathrm{m} ?$
(d) What is the line's attenuation in $\mathrm{dB} / \mathrm{m}$ ?

Yaqub Khan
Yaqub Khan
Numerade Educator
11:55

Problem 28

A $50 \Omega$ microstrip line operating at $1 \mathrm{GHz}$ has perfect metallization for both the strip and ground plane. The substrate has a relative permittivity of 10 and a loss tangent of 0.001 . Without the dielectric the line has a capacitance of $100 \mathrm{pF} / \mathrm{m}$
(a) What is the line conductance in $\mathrm{S} / \mathrm{m}$ ?
(b) What is the line's attenuation in $\mathrm{Np} / \mathrm{m}$ ?
(c) What is the line's attenuation in $\mathrm{dB} / \mathrm{m} ?$

Yaqub Khan
Yaqub Khan
Numerade Educator
01:01

Problem 29

Design a microstrip line having a $50 \Omega$ characteristic impedance. The substrate has a permittivity of 2.3 and is $250 \mu \mathrm{m}$ thick. The operating frequency is $18 \mathrm{GHz}$. You need to determine the width of the microstrip line.

Narayan Hari
Narayan Hari
Numerade Educator
03:46

Problem 30

A load has an impedance $Z=75+\jmath 15 \Omega$.
(a) What is the load reflection coefficient, $\Gamma_{L}$, with reference impedance of $75 \Omega ?$
(b) Design an open-circuited stub at the load that will make the impedance of the load plus the stub, call this $Z_{1}$, be purely real. Choose a stub characteristic impedance of $75 \Omega$. At this stage do an electrical design only. (This requires complete electrical information such as the electrical length of the stub.)
(c) Following on from
(b), now design a quarter-wave transformer between the source and the stub that will present $50 \Omega$ at the input. (The design must include the characteristic impedance of the transmission line and its electrical length. Thus the structure is a $\lambda / 4$ transformer, a stub, and the load.)
(d) Now convert the electrical specifications of the design into a physical design at $1 \mathrm{GHz}$ using microstrip technology with substrate thickness $h=0.5 \mathrm{~mm}$ and relative permittivity $\varepsilon_{r}=10$. You must design the widths and lengths of the stub and the quarterwave transformer.

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
01:01

Problem 31

Design a microstrip line to have a characteristic impedance of $65 \Omega$ at $5 \mathrm{GHz}$. The substrate is $635 \mu \mathrm{m}$ thick with a relative permittivity of 9.8 Ignore the thickness of the strip. [Parallels Example 3.5$]$
(a) What is the width of the line?
(b) What is the effective permittivity of the line?

Narayan Hari
Narayan Hari
Numerade Educator
06:20

Problem 32

Design a microstrip shorted stub at $10 \mathrm{GHz}$ with the following characteristics:
- Characteristic impedance of $60 \Omega$.
- A substrate with a relative permittivity of 9.6 and thickness of $500 \mu \mathrm{m}$.
- Input impedance of $\jmath 60 \Omega$.
(a) What is the width of the microstrip line?
(b) What is the length of the line in centimeters?
(c) What is the effective permittivity of the line?
(d) If the line is one-quarter wavelength longer than that calculated in (b), what will the input reactance be?
(e) Regardless of your calculations above, what is the input admittance of a one-quarter wavelength long shorted stub?

Khoobchandra Agrawal
Khoobchandra Agrawal
Numerade Educator
01:01

Problem 33

Design a microstrip line to have a characteristic impedance of $20 \Omega$. The microstrip is to be constructed on a substrate that is $1 \mathrm{~mm}$ thick with a relative permittivity of 12. [Parallels Example 3.5]
(a) What is the width of the line? Ignore the thickness of the strip and frequencydependent effects.
(b) What is the effective permittivity of the line?

Narayan Hari
Narayan Hari
Numerade Educator
14:29

Problem 34

A load has an impedance $Z=75+\jmath 15 \Omega$.
(a) What is the load reflection coefficient, $\Gamma_{L}$, if the system reference impedance is $75 \Omega ?$
(b) Design a shorted stub at the load that will make the impedance of the load plus the stub, call this $Z_{1}$, be purely real; that is, the reflection coefficient of the effective load, $\Gamma_{1}$ has zero phase. Choose a stub characteristic impedance of $75 \Omega$. At this stage do an electrical design only. ( This require complete electrical information, e.g. the electrical length of the stub.)
(c) Following on from
(b), now design a quarter-wave transformer between the source and the stub that will present $50 \Omega$ at the input. (The design must include the characteristic impedance of the transmission line and its electrical length. Thus the structure is a $\lambda / 4$ transformer, a stub, and the load.)
(d) Now convert the electrical design into a physical design at $1 \mathrm{GHz}$ using microstrip technology with substrate thickness $h=$ $0.5 \mathrm{~mm}$ and relative permittivity $\varepsilon_{r}=10$ You must design the widths and lengths of the stub and the quarter-wave transformer.

Sheh Lit Chang
Sheh Lit Chang
University of Washington
03:04

Problem 35

The strip of a symmetrical stripline has a width of $1 \mathrm{~mm}$ and the ground planes of the stripline are separated by $2 \mathrm{~mm}$. The dielectric has a relative permittivity of 4.2 . The strip has negligible thickness.
(a) What is the effective permittivity of the stripline?
(b) What is the characteristic impedance of the stripline at $1 \mathrm{GHz}$ ?

Sarah Mccrumb
Sarah Mccrumb
Numerade Educator
05:47

Problem 36

The strip of a symmetrical stripline has a width of $500 \mu \mathrm{m}$ and the ground planes of the stripline are separated by $1 \mathrm{~mm}$. The dielectric has a relative permittivity of 10 . The strip has a thickness of $0.1 \mathrm{~mm}$
(a) What is the effective permittivity of the stripline?
(b) What is the characteristic impedance of the stripline?
(c) What is the total fringing capacitance in $\mathrm{pF} / \mathrm{m} ?$

Vishal Gupta
Vishal Gupta
Numerade Educator
07:22

Problem 37

The strip of a symmetrical stripline has a width of $200 \mu \mathrm{m}$ and the ground planes of the stripline are separated by $1 \mathrm{~mm}$. The dielectric has a relative permittivity of 4 . The strip has a thickness of $0.1 \mathrm{~mm}$.
(a) What is the effective permittivity of the stripline?
(b) What is the characteristic impedance of the stripline?
(c) What is the total fringing capacitance in $\mathrm{pF} / \mathrm{m} ?$

Sunita  Kumari
Sunita Kumari
Numerade Educator
02:55

Problem 38

The strip of a symmetrical stripline has a width of $50 \mu \mathrm{m}$ and the ground planes of the stripline are separated by $300 \mu \mathrm{m}$. The dielectrichas a relative permittivity of 10 . The strip has a thickness of $10 \mu \mathrm{m}$. What is the characteristic impedance of the stripline?

Ameer Said
Ameer Said
Numerade Educator
05:47

Problem 39

The strip of a symmetrical stripline has a width of $0.25 \mathrm{~mm}$ and the ground planes of the stripline are separated by $1 \mathrm{~mm}$. The dielectric has a relative permittivity of $80 .$ What is the effective width of the strip?

Vishal Gupta
Vishal Gupta
Numerade Educator
05:20

Problem 40

The strip of a symmetrical stripline has a width of $100 \mu \mathrm{m}$ and is embedded in a lossless medium that is $400 \mu \mathrm{m}$ thick and has a relative permittivity of $13,$ thus the separation, $h,$ from the strip to each of the ground planes is $200 \mu \mathrm{m}$.
(a) Draw the effective waveguide model of a stripline with magnetic walls and an effective strip width, $w_{\text {eff }}$
(b) What is the effective relative permittivity of the stripline waveguide model?
(c) What is $w_{\text {eff }}$ ?

Vishal Gupta
Vishal Gupta
Numerade Educator
04:24

Problem 41

A symmetrical stripline has a thin strip with a width of $200 \mu \mathrm{m}$, is embedded in a dielectric of relative permittivity 12 , and is between ground planes separated by $500 \mu \mathrm{m}$. What is $Z_{0}$ of the line? [Parallels Example 3.6]

Donya Dobbin
Donya Dobbin
Numerade Educator
02:34

Problem 42

At $1 \mathrm{GHz}$ a $60 \Omega$ stripline has the per unit parameters $R=2 \Omega / \mathrm{m}$ and $G=1 \mathrm{mS} / \mathrm{m} .$ What is the attenuation of the line in $\mathrm{dB} / \mathrm{m}$ ?

Amit Srivastava
Amit Srivastava
Numerade Educator
10:00

Problem 43

$\begin{array}{llll}\text { A } & 50 & \Omega & \text { symmetrical stripline has a } & 0.5 & \mathrm{~mm}-\end{array}$
wide strip and the ground planes are separated by $1.2 \mathrm{~mm}$. The strip has a sheet resistance of $1.5 \mathrm{~m} \Omega$ and each ground plane has a sheet resistance of $1 \mathrm{~m} \Omega$. (Ignore high frequency effects on resistance.) The substrate has a loss tangent of 0.005 and a relative permittivity of 6 . [Parallels Example 3.7]
(a) What is the line's effective permittivity?
(b) What is its characteristic impedance?
(c) What is the attenuation constant of the line in $\mathrm{dB} / \mathrm{m}$ at $2 \mathrm{GHz}$ ?

Donald Albin
Donald Albin
Numerade Educator
02:45

Problem 44

The strip of a CPW line has a width $w=400 \mu \mathrm{m}$ and separations from the in-plane grounds of $s=250 \mu \mathrm{m} .$ The substrate is $h=1000 \mu \mathrm{m}$
thick and the thickness of the metal is $t=5 \mu \mathrm{m}$. What is the effective permittivity and characteristic impedance of the CPW line.

Suhas Katkar
Suhas Katkar
Numerade Educator
04:16

Problem 45

A CPW line with a $250 \mu \mathrm{m}$ thick GaAs substrate, has a width of $125 \mu \mathrm{m}$ and thickness of $3 \mu \mathrm{m},$ and a gap of $125 \mu \mathrm{m}$ between the strip and ground planes. [Parallels Example 3.8]
(a) What is the line's effective permittivity?
(b) is the $Z_{0}$ of the line?

Andrew Eddins
Andrew Eddins
Emory University