john-proposal

LOGO
John W. Franklin
1
"Bistatic radars have fascinated surveillance and tracking researcher for
decades. Despite evolution from the early Chain Home radars in Britain to
today's coherent multimode monostatic radars, there remains a rich research in
bistatic and multistatic applications. The promise of quite receivers, aspect
angle diversity, and improved target tracking accuracy are what fuel this
interest.“
Mark E. Davis
Defense Advanced Projects Research Agency (DARPA)
(2007)
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Presentation Flowchart
Bistatic
Radar
Passive
Bistatic Radar
Objective:
Explore the use of ATSC
(HDTV) as a Passive
Illuminator via
Simulation
ATSC (HDTV)
Signals
Practical
Passive Radar
Systems
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Outline
 Overview

 Properties of Bistatic Radar
 Geometry
 Range Equation
 Doppler
 Cross Section
 Properties of Passive Bistatic Radar
 The Concept and How it Works
 Why Passive Radar?
 Applications
 Performance Evaluation
 Signal Processing
 Practical System Examples
 FM
 Digital Video Broadcast
 High Definition Television Signals
 ATSC Terrestrial Transmission Standard
 Research Objective
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Overview-Bistatic Radar Concepts
 Bistatic radar may be defined as a radar in which the transmitter and
receiver are at separate locations as opposed to conventional
monostatic radar where they are collocated.
 The very first radars were bistatic, until pulsed waveforms and T/R
switches were developed
 Bistatic radars can operate with their own dedicated transmitters or
with transmitters of opportunity
 Radars that use more than one transmitter or receiver or both are
referred to as multistatic
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LOGO

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Geometry
 Geometry of a Bistatic Radar is Important - it determines
many of the operating characteristics
 Radar Range Equation
 Doppler Velocity Equation
 Radar Cross Section
 Coverage area
 Bistatic Angle: Angle between the illumination path and
echo path
 Bistatic Angle vs. Radar Mode
 β<20 degrees – (Monostatic)
 20<β<145 degrees – (Bistatic)
 145<β<180 degrees – (Forward/Fence)
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Monostatic and Bistatic Geometry
Monostatic Radar Geometry Bistatic Radar Geometry
β<20 degrees
20<β<145 degrees
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Forward/Fence Geometry
Forward/Fence Radar Geometry (limiting case)
145<β<180 degrees
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Bistatic Radar Range Equation
2
2
2
1
44 r

A
G
r
PP
e
t
B
tr



[
[
Fraction of transmitted power
that is reflected to receiver
Fraction of reflected power that is
intercepted by receiving antenna
2
2
2
1
3
2
)4( rr
GGP
P
Brtt
r




(Bistatic Radar Equation)
where
P
r
is the received signal power
P
t
is the transmit power
G
t
is the transmit antenna gain
r
1
is the transmitter-to-target range

b
is the target bistatic RCS
r
2
is the target-to-receiver range
G
r
is the receive antenna gain

is the radar wavelength


4
2

r
e
G
A 
Using: then:
Transmitted Power
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Bistatic Doppler
Given the target velocity V and the transmitter and
receiver velocities being stationary (V
R
= V
T
= 0), the
doppler frequency shift is:
The change in the received frequency relative
to the transmitted frequency is called the
Doppler frequency, denoted by fD
Doppler shift is
proportional to the
target velocity
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Doppler lets you separate things that are moving from things that aren’t
Bistatic Radar Cross Section
 Function of target size, shape, material, angle and carrier frequency
 Usually, a bistatic RCS is lower than the monostatic RCS
 At some target angles a high bistatic RCS is achieved (forward scatter)
 Bistatic measurements are essential to understanding the stealth characteristics of vehicles
 Almost no data has appeared in the open literature, open research topic
-Low frequencies are more favorable for the

exploitation of forward scatter
-Target detection may be achieved over an
adequately wide angular range
The angular width of the scattered signal
horizontal or vertical plane:
Target cross-sectional area A gives a radar
cross-section of:
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LOGO
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Concepts
 A Subtype of Bistatic Radar (all bistatic/multistatic analysis apply)
Geometry, Doppler, RCS
 A Passive Bistatic Radar is a Bistatic Radar that does not emit any Radio
Frequency (RF) of its own to detect targets
 It utilizes the already existing RF energy in the atmosphere
 Examples of such sources of RF energy are Broadcast FM stations, Global
Positioning Satellites, Cellular Telephones, and Commercial Television.
 When the transmitter of opportunity is another radar transmission, the
term such as: hitchhiker, or parasitic radar are often used
 When the transmitter of opportunity is from a non-radar transmission,
such as broadcast communications, terms such as: passive radar, passive
coherent location, or passive bistatic radar are used
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How does it Work?
 By exploiting common RF energy such as Commercial FM Broadcasts,
as an “Illuminators of Opportunity”, scattered by a target
 The scattered RF energy is received by one antenna and this signal is
then compared to a reference signal from second antenna.
 By using Digital Signal Processing (DSP) techniques, target

parameters such as range, range-rate, and angle of arrival may be
determined
 We are extracting typical radar information from a communication
signal
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Idea of a Passive Bistatic/Multistatic Radar
Bistatic
Multistatic
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Why Passive Radar?
Advantages
 Lower cost, no dedicated transmitter
 No need for frequency allocations
 Covert (receiver), Difficulty of Jamming
 Virtually immune to Anti-Radiation Missiles
 Fast updates
 Potential ability to detect stealth targets
Disadvantages
 More Complicated Geometry
 No direct control of transmitting signal
 Technology is immature
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Applications
Detection of Low Probability of Intercept (LPI)
Radar signals
Detection of Stealth Targets
Low Cost Air Traffic Control (ATC) Systems
Law Enforcement (Traffic Monitoring)
Border Crossing/Intrusion Detection
Local Metrological Monitoring

Planetary Mapping
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Performance Evaluation
 What Type of Waveforms should we use in a PBR System
 Modulation Type (Analog/Digital) of the exploited signal
 Analyze using the Ambiguity Function
 We Need to Know
 What Type of Power do we need
 Signal Power Density of the exploited signal at Target
 Analyze using the Bistatic Range Equation
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Ambiguity Function
 What is it used for?
 As a means of studying different waveforms
 To determine the range and Doppler resolutions for a specific transmission
waveform
The radar ambiguity function for a signal is defined as the modulus squared of its
2-D correlation function:
The 3-D plot of the ambiguity function versus frequency and time delay is called the radar
ambiguity diagram
Where:
- is the complex envelope of the transmitted signal
- is the time delay
- is the Doppler frequency shift
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Radar Ambiguity Diagram
The thumbtack ambiguity function is common to noiselike or pseudonoise
waveforms. By increasing the bandwidth or pulse duration the width of
the spike narrow along the time or the frequency axis, respectively.
This shows that as we increase the bandwidth B, we have better range

resolution. Conversely if we increase the pulse width T, we increase the
doppler resolution.
Where:
B - bandwidth
T - pulse width
f
d
- doppler delay
t
d
- time delay
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Doppler
Delay
Radar Ambiguity Diagram
The first null occurs at
The main peak of the ambiguity function corresponds to the resolution of the system in
terms of range and Doppler.
The additional peaks correspond to potential ambiguities, resulting in confusion at
choosing the correct range of the target and its velocity
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Analog FM Waveforms
 FM analysis has been performed extensively in the U.S. and in Europe
(England/Germany)
 FM radio transmissions 88–108 MHz VHF band
 The modulation bandwidth typically 50 kHz
 Highest power transmitters are 250 kW EIRP
 Range resolution c/2B = 3000 m (monostatic)
 Power density = –57 dBW/m
2

(target range @ 100 km)
 Existing commercial FM transmitters provide low-to-medium altitude
coverage
 The ambiguity performance of FM transmissions will depend on the
instantaneous modulation
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FM Range Resolution Variance
 Variance is due to instantaneous modulation
Four types of VHF FM radio modulation over a two-second interval
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Analog FM Ambiguity Diagram
Analog FM – Speech Ambiguity Plot
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