Lecture-3 Microwave Engineering Instructor: Athar Hanif.

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Lecture-3 Microwave Engineering Instructor: Athar Hanif

Transcript of Lecture-3 Microwave Engineering Instructor: Athar Hanif.

Lecture-3

Microwave Engineering

Instructor: Athar Hanif

Quiz-1 Time Allowed: 30 minutes Total Marks: 20

Q.1:A plane wave traveling in z- direction in a dielectric medium with єr =2.55 has an electric field given by Ey = E0 cos(ωt-βz). The frequency is 2.4 GHz, and E0 = 30 V/m.

a) Find the amplitude and direction of the magnetic field. (2 Marks)

b) Find the phase velocity and wavelength. (3 Marks)

a) Find the phase shift between the positions Z1 = 0.5 m and Z2 = 1.7 m. (5 Marks)

Quiz-1 Time Allowed: 30 minutes Total Marks: 20

Q.2: A RFC is constructed by winding four turns of AWG 38 copper wire(σcu =64.516х106S/m) on a 2 mm ceramic core diameter(μr = 1) of 0.1 mm length. Estimate

a) The inductance (3 Marks)b) Stray capacitance (2 Marks)c) Resistance (2 Marks)d) Resonance frequency (3 Marks)

Microstrip Transmission Line

Most popular type of planer transmission line

Geometry of microstrip line

Microstrip Transmission Line

Dielectric were not present(єr =1) Simple TEM waves

Dielectric were present(єr ≠1) Does not support TEM waves

Microstrip Transmission Line

In practical application, h<<λ Fields are quasi-TEM

Єe is the effective dielectric constant

1< єe< єr

p

e

cv

0 ek

Microstrip Design

Step-1: find W/h ratio

єr and Z0 = known Step-2: For W/h ≤ 2

Microstrip Design

For W/h ≥ 2

Step-3: Effective dielectric constant

Microstrip Design

Step-4: Find Z0

For W/h ≤ 1

For W/h ≥ 1

Microstrip Design

Step-5: (1) Attenuation due to dielectric loss

Where tanδ is the loss tangent of the dielectric

0 1 tan/

2 1r e

d

e r

Np m

Microstrip Design

Attenuation due to conductor loss

Rs is the surface resistivity of the conductor

0

0

/

2

sc

s

RNp m

Z W

R

Microstrip Design

Microstrip Design

Design Problems

Problem-1: calculate the width and the length of a microstrip line for a 50Ω characteristic impedance and a 900 phase shift at 2.5 GHz. The substrate thickness is h = 0.127cm, with єr = 2.20

Problem-2: Design a microstrip transmission line for a 100Ω characteristic impedance. The substrate thickness is 0.158cm, with єr = 2.20. What is the guide wavelength on this transmission line if the frequency is 4.0 GHz.

Assignment

Problem: A 100Ω microstrip line is printed on a substrate of thickness 0.0762 cm, with a dielectric constant of 2.2. Ignoring losses and fringing fields, find the shortest length of this line that appears at its input as a capacitor of 2.5 pF at 2.5 GHz. Repeat for an inductance of 5 nH.

Stripline

Most popular type of planer transmission line

Geometry of microstrip line

Stripline

Phase velocity and the propagation constant of the stripline is given by

p

r

cv

Stripline

0 rk

Stripline Design

Step-1: Find√ єr Z0

Step-2: Find the strip width

0

0

0

; 120

0.85 0.6 ; 120

300.441

r

r

r

x for ZW

b x for Z

where

xZ

Stripline Design

• Step-3: Dielectric attenuation

tan

2

2

d

r

k

where

fk

c

Stripline Design

Attenuation due to conductor loss3

00

00

2.7 10120

30 ( )/

0.16120

2 1 21 ln( )

0.414 1 41 (0.5 ln(0.5 0.7 ) 2

s rr

c

sr

R Zfor Z

b tNp m

RBfor Z

Z b

with

W b t b tA

b t b t t

b t WB

W t W t

Stripline Design

Where ‘t’ is the thickness of the strip

Rs is the surface resistivity of the conductor and given by

02sR

Stripline Design

Step-4: Total attenuation constant is given by

Step-5: The wavelength on the stripline is

Attenuation in term of wavelength

( / )

20log ( / )

d c Np m

dB e dB m

r

c

f

Design Problems

Problem-1: Find the width for a 50Ω copper stripline conductor, with b = 0.32cm and єr = 2.20. If the dielectric loss tangent is 0.001 and the operating frequency is 10 GHz, calculate the attenuation in dB/λ. Assume a conductor thickness of t = 0.01mm.

Problem-2: Design a stripline transmission line for a 70Ω characteristic impedance. The ground plane separation is 0.316 cm, and the dielectric constant of the filling material is 2.20. What is the guide wavelength on this transmission line if the frequency is 3.0 GHz.

Assignment (due on 22-06-2009)

Problem: A microwave antenna feed network operating at 5 GHz a 50 Ω printed transmission line that is 16λ long. Possible choices are (1) copper microstrip, with d = 0.16 cm, єr = 2.20, and tanδ = 0.001, or (2) copper stripline, with b = 0.32 cm, єr = 2.20, and tanδ = 0.001. Which line should be used, if attenuation is to be minimized?

Project-1(due on 06-07-2009)

Design a microstrip line (characteristic impedance = 50 Ω, phase shift = 900,substrate FR-4 thickness = 31mil, 61mil, dielectric constant = 4.47, and tangent loss = 0.019) Hand calculations Verify your design using SERENADE HARDWARE implementation Results (hardware )

Instructions

Each group has two students. Do your own work. Write project report. No late submission.

Instructions

The format for design report should be as follows 1. Title page (including your name, the course number

and the date) Your signature after the statement I certify that this design is the result of my own efforts. (Signature) Date: 2. Design objectives and specifications 3. Design steps (including all, mentioned in problem

statement) 4. Design modifications, if any 5. Computer design verifications 6. Results (hardware) 7. Conclusions