RADAR (Radio Detection & Ranging) Short notes | Electromagnetics - Electronics and Communication Engineering (ECE) PDF Download

 Page 1


RAD AR (Radio Detection and Ranging) Notes
Introduction
RAD AR (Radio Detection and Ranging) is a system that uses r adio waves to de-
tect and locate objects, measure their distance, speed, and other char acteristics.
It is widely used in navigation, weather monitoring, military applications, and
autonomous systems.
K ey Concepts
• RAD AR Principle : Tr ansmits electromagnetic pulses, receives reflected echoes,
and analyzes them to determine target properties.
• Components : Tr ansmitter , antenna, receiver , and signal processor .
• Applications : Air tr affic control, weather forecasting, defense systems, and
automotive r adar .
Basic Oper ation
• Tr ansmission : A high-frequency r adio signal (pulse or continuous wave)
is emitted via an an tenna.
• Reflection : The signal reflects off a target and returns as an echo.
• Reception : The receiver detects the echo, and the signal processor analyzes
it for distance, s peed, and direction.
• Range Measurement : Distance to the target is calculated usin g the time-
of-flight:
R =
ct
2
wherec = 3×10
8
m/s is the speed of light, andt is the round-trip time.
Radar Equation
The received powerP
r
is given b y the r adar equation:
P
r
=
P
t
G
t
G
r
?
2
s
(4p)
3
R
4
where:
• P
t
: Tr ansmitted power (W).
• G
t
,G
r
: Tr ansmitter and receiver antenna gains.
• ? : W avelength (m).
• s : Radar cross-section of the target (m
2
).
• R : Range to the target (m).
1
Page 2


RAD AR (Radio Detection and Ranging) Notes
Introduction
RAD AR (Radio Detection and Ranging) is a system that uses r adio waves to de-
tect and locate objects, measure their distance, speed, and other char acteristics.
It is widely used in navigation, weather monitoring, military applications, and
autonomous systems.
K ey Concepts
• RAD AR Principle : Tr ansmits electromagnetic pulses, receives reflected echoes,
and analyzes them to determine target properties.
• Components : Tr ansmitter , antenna, receiver , and signal processor .
• Applications : Air tr affic control, weather forecasting, defense systems, and
automotive r adar .
Basic Oper ation
• Tr ansmission : A high-frequency r adio signal (pulse or continuous wave)
is emitted via an an tenna.
• Reflection : The signal reflects off a target and returns as an echo.
• Reception : The receiver detects the echo, and the signal processor analyzes
it for distance, s peed, and direction.
• Range Measurement : Distance to the target is calculated usin g the time-
of-flight:
R =
ct
2
wherec = 3×10
8
m/s is the speed of light, andt is the round-trip time.
Radar Equation
The received powerP
r
is given b y the r adar equation:
P
r
=
P
t
G
t
G
r
?
2
s
(4p)
3
R
4
where:
• P
t
: Tr ansmitted power (W).
• G
t
,G
r
: Tr ansmitter and receiver antenna gains.
• ? : W avelength (m).
• s : Radar cross-section of the target (m
2
).
• R : Range to the target (m).
1
Types of Radar
• Pulse Radar : Tr ansmits short pulses, measures time dela y of echoes. Used
in air tr affic c ontrol.
• Continuous W ave (CW) Radar : Tr ansmits continuous signals, often used
for speed measu rement (e.g., Doppler r adar).
• Doppler Ra dar : Measures target velocity using frequency shift:
f
d
=
2v
r
f
t
c
wheref
d
is the Doppler shift,v
r
is the r adial velocity , andf
t
is the tr ansmit-
ted frequency .
• S ynthetic Aperture Radar (S AR) : Uses motion of the r adar platform to
simulate a lar ge antenna, improving resolution.
K ey Par ameters
• Range Res olution : Ability to distinguish two closely spaced targets:
?R =
c
2B
whereB is the signal bandwidth.
• Angular Reso lution : Determined b y antenna beamwidth:
?˜
?
D
whereD is the antenna apertu re size.
• Maximum Ra nge : Limited b y signal power and receiver sensitivity:
R
max
=
(
P
t
G
t
G
r
?
2
s
(4p)
3
P
r, min
)
1/4
whereP
r, min
is the minimum detectable power .
Pr a ctical Consider ations
• Clutter : Unwanted echoes from non-target objects (e.g., terr ain, r ain), mit-
igated using s ignal processing.
• Noise : Thermal noise and interference reduce signal-to-noise r atio (SNR),
impacting detecti on.
• Propagation Effects : Atmospheric attenuation, multipath, and refr action
affect signal strength.
• Antenna Design : Directional antennas improve gain and resolution but
limit scann ing r ange.
• Signal Processing : T echniques lik e matched filtering and Doppler process-
ing enhance tar get detection.
2