Microwaves and Radar 10EC54 MICROWAVES AND RADAR

197 Pages·2016·8.22 MB·English

Microwaves and Radar
10EC54

MICROWAVES AND RADAR

SYLLABUS

Subject Code
: 10EC54
IA Marks : 25

No. of Lecture Hrs/Week : 04
Exam Hours: 03

Total no. of Lecture Hrs
: 52
Exam Marks: 100

PART - A

UNIT - 1

MICROWAVE TRANSMISSION LINES: Introduction, transmission lines equations and
solutions, reflection and transmission coefficients, standing waves and SWR, line
impedance and line admittance. Smith chart, impedance matching using single stubs,
Microwave coaxial connectors.

7 Hours

UNIT - 2

MICROWAVE
WAVEGUIDES
AND
COMPONENTS:
Introduction,
rectangular

waveguides, circular waveguides, microwave cavities, microwave hybrid circuits,
directional couplers, circulators and isolators.

7 Hours

UNIT - 3

MICROWAVE DIODES,

Transfer electron devices: Introduction, GUNN effect diodes – GaAs diode, RWH theory,
Modes of operation, Avalanche transit time devices: READ diode, IMPATT diode,
BARITT diode, Parametric amplifiers Other diodes: PIN diodes, Schottky barrier diodes.

7 Hours

UNIT - 4

Microwave network theory and passive devices. Symmetrical Z and Y parameters, for

reciprocal Networks, S matrix representation of multi port networks.

6 Hours

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PART - B

UNIT - 5

Microwave passive devices, Coaxial connectors and adapters, Phase

shifters, Attenuators, Waveguide Tees, Magic tees.

4 Hours

UNIT - 6

STRIP LINES: Introduction, Microstrip lines, Parallel strip lines, Coplanar strip lines,

Shielded strip Lines.

6 Hours

UNIT - 7

AN INTRODUCTION TO RADAR: Basic Radar, The simple form of the Radar equation,

Radar block diagram, Radar frequencies, application of Radar, the origins of Radar.

8 Hours

UNIT - 8

MTI AND PULSE DOPPLER RADAR: Introduction to Doppler and MTI Radar, delay line

Cancellers, digital MTI processing, Moving target detector, pulse Doppler Radar.

7 Hours

TEXT BOOKS:

1. Microwave Devices and circuits- Liao / Pearson Education.
2. Introduction to Radar systems-Merrill I Skolnik, 3rd Ed, TMH, 2001.
3. Microwave Engineering – Annapurna Das, Sisir K Das TMH Publication,

2001.

REFERENCE BOOK:

1.
Microwave Engineering – David M Pozar, John Wiley, 2e, 2004

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10EC54

INDEX SHEET

SL.NO
TOPIC
PAGE NO.

UNIT – 1 MICROWAVE TRANSMISSION LINES
5 to 22

1
Introduction to transmission lines equations and solutions
6 to 10

2
Reflection and transmission coefficients
10 to 15

3
standing waves and SWR
15 to 17

4
line impedance and line admittance
17 to 19

5
Smith chart, impedance matching using single stubs
19 to 22

Recommended questions
23

UNIT - 2: MICROWAVE WAVEGUIDES AND COMPONENTS
24 to 58

1
Introduction rectangular waveguides
25 to 31

2
circular waveguides
32 to 41

3
microwave cavities, microwave hybrid circuits
42 to 50

4
directional couplers,
50 to 52

5
circulators and isolators
52 to 57

Recommended questions
58

UNIT – 3 MICROWAVE DIODES
58 to 90

1
Introduction, GUNN effect diodes – GaAs diode
59 to 63

2
RWH theory, Modes of operation
63 to 70

3
Avalanche transit time devices: READ diode
70 to 72

4
IMPATT diode, BARITT diode
72 to 78

5
Parametric amplifiers
78 to 83

6
Other diodes: PIN diodes, Schottky barrier diodes
83 to 89

Recommended questions
90

UNIT – 4 Microwave network theory and passive devices
91 to 104

1
Symmetrical Z and Y parameters for reciprocal Networks
92 to 94

2
S matrix representation of multi port networks
94 to 97

3
Properties of S-parameter
98 to 103

Recommended questions
104

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SL.NO
TOPIC
PAGE NO.

UNIT – 5 Microwave passive devices
105 to 129

1
Coaxial connectors and adapters,
106 to108

2
Attenuators
108 to 111

3
Phase shifters
111 to 114

4
Waveguide Tees, Magic tees.
118 to 121

5
Directional coupler
122 to 127

Recommended questions
128

UNIT – 6 STRIP LINES
129 to 142

1
Microstrip lines
130 to 131

2
Parallel strip lines
132 to 135

3
Coplanar strip lines
135 to 136

4
Shielded strip Lines
137 to 139

5
Losses
139 to141

Recommended questions
142

UNIT- UNIT -7
AN INTRODUCTION TO RADAR
143 to 158

1
The simple form of the Radar equation
146 to 149

2
Radar block diagram
149 to 151

3
Radar frequencies
151 to 153

4
Origins of Radar
154 to 55

5
Application of Radar
155 to 157

Recommended questions
158

UNIT – 8 MTI AND PULSE DOPPLER RADAR

159 to 190

1
Introduction to Doppler and MTI Radar
160 to 175

2
Delay line Cancellers
175 to 181

3
digital MTI processing
182 to 183

4
Moving target detector,
183 to 188

5
Pulse Doppler Radar
189

Recommended questions
190

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UNIT – 1

MICROWAVE TRANSMISSION LINES: Introduction, transmission lines equations and
solutions, reflection and transmission coefficients, standing waves and SWR, line
impedance and line admittance. Smith chart, impedance matching using single stubs,
Microwave coaxial connectors.

7 Hours

TEXT BOOKS:

1.Microwave Devices and circuits- Liao / Pearson Education.
2.Microwave Engineering – Annapurna Das, Sisir K Das TMH Publication, 2001.

REFERENCE BOOK:

1.
Microwave Engineering – David M Pozar, John Wiley, 2e, 2004

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UNIT- 1

MICROWAVE TRANSMISION LINES

INTRODUCTION:

Any pair of wires and conductors carrying currents in opposite

directions form transmission lines. Transmission lines are essential

components in any electrical/communication system. They include coaxial

cables, two-wire lines, microstrip lines on printed-circuit-boards (PCB).

The characteristics of transmission lines can be studied by the electric

and magnetic fields propagating along the line. But in most practical

applications, it is easier to study the voltages and currents in the line instead.

Different types of transmission lines

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A typical engineering problem involves the transmission of a signal from a

generator to a load. A transmission line is the part of the circuit that

provides the direct link between generator and load.

Transmission lines can be realized in a number of ways. Common

examples are the parallel-wire line and the coaxial cable. For simplicity, we

use in most diagrams the parallel-wire line to represent circuit connections,

but the theory applies to all types of transmission lines.

If you are only familiar with low frequency circuits, you are used to treat all

lines connecting the various circuit elements as perfect wires, with no voltage

drop and no impedance associated to them (lumped impedance circuits). This is

a reasonable procedure as long as the length of the wires is much smaller than

the wavelength of the signal. At any given time, the measured voltage and

current are the same for each location on the same wire.

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For sufficiently high frequencies the wavelength is comparable with the length of

conductors in a transmission line. The signal propagates as a wave of voltage

and current along the line, because it cannot change instantaneously at all

locations. Therefore, we cannot neglect the impedance properties of the wires.

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TRANSMISSION LINE EQUATIONS AND SOLUTIONS:

A transmission line can be analyzed

equations or by distributed circuit

theory in addition to the time variable.

wither by solution of Maxwells field

which involves only one space variable

Voltage and Current Waves in general transmission lines

Equivalent circuit of an element section (length z) of the transmission line:

L, R are the distributed inductance and resistance (per unit length) of the

conductor; C,G are the distributed capacitance and conductance (per unit

length) of the dielectric between the conductors.

Relation between instantaneous voltage v and current i at any point along the line:

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For periodic signals, Fourier analysis can be applied and it is more

convenient to use phasors of voltage V and current I.

Decoupling the above equations, we get

where γ is called the propagation constant, and is in general complex.

α is the attenuation constant, β is the phase constant

The general solutions of the second-order, linear differential equation for V, I are :

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V+, V-, I+, I- are constants (complex phasors). The terms containing e-γz represent

waves traveling in +z direction; terms containing e+γz represent waves traveling in

–z direction.

It can be shown that the ratio of voltage to current is given by:

where Zo is the characteristic impedance of the line, given by

The current I can now be written as:

Lossless transmission lines:

In lossless transmission lines, the distributed conductor resistance R and

dielectric conductance G are both zero. In this case the characteristic

impedance is real and is equal to:

The propagation constant γ is also imaginary with:

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Expressing the waves in time-domain

The velocity with which a front of constant phase travels is called the
phase velocity up.

In any transmission line

In lossless transmission line

Therefore

In a coaxial cable,

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εo – permittivity of vacuum
εr – relative permittivity (dielectric constant) of
dielectric μo – permeability of vacuum

Example: Calculate the characteristic resistance Ro of a RG-58U coaxial

cable which has a inner conductor of radius a=0.406 mm and a braided outer

conductor with radius b=1.553 mm. Assume the dielectric is polyethylene with

dielectric constant of 2.26.

Solution: The distributed capacitance and inductance of the cable can be

calculated to be:

L = 0.268 μH/m

C = 93.73 pF/m

Ro = L / C = 53.47Ω

Reflection and Transmission:

Reflection co-efficient is defined as the ratio of amplitudes of reflected

voltage wave to the incident voltage wave at the receiving end.

E

r 0
2 1

E

2

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i 0
1

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Transmission co-efficient is defined as the ratio of transmitted voltage or

current to the incident voltage or current .

E

t 0
2 2

E

2
i 0
1

A transmission line terminated in its characteristic impedance is called a

properly terminated line. According to the principle of conservation of

energy, the incident power minus the reflected power must be equal to the

power transmitted to the load.

v(z 0) vi (z 0) vr (z 0)

i(z 0) ii (z 0) ir (z 0)

1 [vi ( z
0) vr ( z
0)]

Z o

v(z 0)Z vi (z 0) vr (z 0)Z
i(z 0)

o vi (z 0) vr (z 0)

L

Standing wave ratio:

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GCEM
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In a lossless line, the amplitude of the forward (or backward) voltage
remains constant as the wave propagates along z, only with a shift in the
phase angle. The superimposition of the forward wave and backward wave
results in a standing wave pattern.

1 z
S
E
max
1

1 z
1
E
min

• In a standing wave, there are positions at the line where the amplitude of

the resultant voltage has maximum and minimum.

The voltage standing wave ratio (VSWR) is the ratio of the maximum and

minimum voltage magnitudes. The distance between two successive

maximums is equal to λ/2.

VSWR is useful to find the maximum voltage magnitude on the line due to

reflection from the load. If Vinc is the incident voltage on the load,

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