Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02576754 2007-02-02
METHOD AND APPARATUS FOR DETECTING
AND INDICATING BATTLEFIELD THREATS
Field of the Invention
This invention is related to methods of detecting and direction finding radio
signals
and small arms fire. It is also related to providing type, range, and bearing
information of the detected threats.
Description of Related Art
Radio direction finding equipment is commercially available and has been in
use
for decades. Such equipment is capable of giving a bearing to the transmitter
dependant upon the type of modulation and frequency used. By having two or
more radio direction finders operating, or by moving one radio direction
finder, it is
possible to generate multiple bearings which "triangulate" or give an
approximate
location of the transmitter. Military forces routinely use this method of
locating
transmitters in an effort to determine the general location and movement
patterns
of opposing forces. This method of radio direction finding is not currently
used,
however, to detect threats to individual soldiers or vehicles. Radio direction
finders are also not currently used to detect transmissions consistent with
attempts to initiate radio-controlled improvised explosive devices (IED).
Acoustic direction finding equipment has also been in use for decades, and
very
effective systems for determining the location of small arms fire have
recently
been produced. These systems seek to give an accurate bearing to the source of
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small arms fire, which can be very difficult to determine, especially in urban
areas.
Laser range finders use a laser to determine the exact distance, or range, to
a
specific point. They are in common use with military forces as determining
accurate range is a vital factor in bringing effective fire (direct or
indirect) onto a
target.
Laser designators/pointers have a variety of military uses, most applicably as
a
weapons sight where a red dot is used to indicate where the bullet will
strike.
Laser designators or pointers are not currently used as a method of visually
indicating threats.
Summary of the Invention
A method for detecting threats to security forces is provided, using a
combination
of acoustic and radio direction finders, spectrum analysis to locate a threat
and a
laser pointer, audio warning, on-screen display, and a laser range finder to
visually mark the location of the threat, both on-screen, and at the actual
site of
the threat.
The apparatus comprises a mast, which houses the antenna, sensors and laser
indicators, and the main system, which houses the bulk of the electronics and
the
audio and video outputs.
In a broad aspect, the present invention relates to a device for locating the
source
of an electromagnetic radiation (emr) transmission including: a direction
finding
antenna for detecting said emr transmission and establishing, as an output
signal,
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the direction in at least the horizontal x=y, plane, from which said
transmission
emanates; a radio signal receiver for receiving said emr transmissions and
establishing, as an output signal, the nature of said transmission; a
controller for
receiving the output signals from said direction finding antenna and radio
signal
receiver , establishing the threat level of said emr transmission, and
outputting a
signal to a user discernable output device, to indicate the nature and threat
level
of the emr transmission; and a signal to a 360 positionable laser pointer to
provide a visible line pointing in the direction of the emr transmission.
In drawings that illustrate the present invention by way of example:
Figure 1 is a perspective/schematic of the multi-threat indication system
(MTIS) of the present invention.
Figure 2 is a photograph showing the system of the present invention
identifying and pointing to a threat source.
Figure 3 is a diagram showing the arrangement and function of a Doppler
shift direction finding antenna.
Figure 4 is a block diagram showing the major components of the MTIS
system of the present invention.
Figure 5 is a block diagram of the main board of the MTIS of the present
invention.
Figure 6 is a block diagram of input devices_ and input interface for the
MTIS of the present invention.
Figure 7 comprises block and display diagrams for the output interface and
output devices of the MTIS of the present invention.
Figure 8 is a block diagram of the Mast assembly of the MTIS of the
present invention.
Figure 9 is a perspective/schematic of the horizontal and vertical polarized
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Doppler antenna arrays of the MTIS of the present invention.
Figure 10 is a block diagram and perspective of the laser sub-assembly of
the MTIS of the present invention.
Figure 11 is a diagram showing location of stepper motor assembly in the
mast assembly of the MTIS of the present invention.
Figure 12 is a schematic of the horizontal stepper motor assembly and
function.
Figure 13 is a schematic of the vertical stepper motor assembly and
function.
Figure 14 is a pair of block diagrams for the horizontal and vertical mast
sub-system electronics modules of the MTIS of the present invention.
Figure 15 is a block diagram of the mast power module.
Figure 16 is a diagram of a moving vehicle or more than one vehicle
employing the MTIS of the present invention to locate and identify a threat.
Figure 17 is a front view of a MTIS LCD display layout.
Figure 18 is a front view of an LED directional and bearing display.
Detailed Description of the Invention
The invention as illustrated in Figure 1 consists of a suite of sensors built
into a
mast, and a series of output devices designed to show the type and.location of
the
threat.
The mast is mounted externally on a vehicle, at a facility such as a forward
operating base, or carried on the back of a soldier in a pack device. The
mast's
primary purpose is to house and protect the sensor suite and laser pointer.'
The
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sensor suite consists of a laser range finder, an acoustic direction finder
such as
that described in US Patent No. 6178141, and a radio direction finder antenna
array. The inputs from these sensors are fed into a computer housed inside the
vehicle, base location, or soldiers pack, where software is used to determine
if a
threat exists and, if so, the bearing and distance to that threat.
The threats detectable by the sensor suite are: small arms fire, active
hostile
communications devices indicating possible ambush or other activity, and
attempts to initiate improvised explosive devices using radio devices such as
cell
phones, walkie-talkies, garage door openers, etc.
Once a threat has been identified, the invention uses a stabilised high-power
laser
pointer to indicate the direction of the threat, the laser range finder to
determine
range to the threat, and may provide a unique audio warning to identify the
type of
threat detected. It also displays all known information about the threat on a
screen. An example of a visual threat identification is shown in Figure 2,
wherein
the laser pointers on adjacent vehicles in a convoy have each located an IED
threat source (a garage door opener signal source in an inappropriate
location)
Each vehicle mounted system will independently point to the threat, and the
point
of intersection of the laser be the source of the threat.
Doppler Shift Direction Finding - Background
The direction finding (DF) capability of the MTIS is derived from the use of
Doppler
shift, however Time Difference of Arrival (TDOA) systems are applicable also.
The Doppler system is capable of detecting Frequency Modulated (FM), Amplitude
Modulated (AM), Carrier Wave (CW) and Single Side Band (SSB) signals. Four
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vertical antennas are arranged at known points around the perimeter of a
circle
and the receiver is sequentially switched to each antenna in turn. The result
is a
single virtual antenna that revolves in a circle. The resulting Doppler shift
causes
the received signal to be Doppler modulated with a sine wave, whose frequency
is
equal to the rotation frequency of the virtual antenna.
The shift to the different antennas is performed by fast switching diodes
located at
the base of the antenna.
Audio filtering is required to remove any voice modulation and construct a
Doppler
sine wave. The Doppler sine wave has two zero-crossing points which occur
when the virtual antenna is closest to the signal source and farthest from the
signal source. The closest signal source zero crossing always occurs at the
end
of the positive half cycle or falling edge zero crossing point, as shown in
Figure 3.
Doppler modulation is a form of frequency modulation (FM) caused by relative
motion between the transmitter and the receiver. Because it is a form of
frequency modulation, an FM receiver is required to detect it.
The system of the present invention can be fitted with two Doppler antenna
arrays
to detect direction and elevation of the incoming signal. To achieve this, one
array
is horizontally polarized and the other vertically polarized, as shown in
Figure 1,
and schematically in Figure 4.
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Logic and Processing System
Referring now to Figure 5, the logic and processing system processes the
receiver
output audio and sends the directional information to the output interface
using an
Agrello Direction Finding format. This system includes the antenna control
that
performs the electrical switching operation for the antennas and combines the
resulting signals into a single signal to be connected to the radio receiver's
antenna input. The processing unit will also translate DF messages into the
military (Mils) bearing units of 0-6400 if that is required. (The output
devices will
typically perform their own unit transformations.)
The Logic and Processing System includes a microprocessor and memory
component that analyzes the incoming signal to determine the type of threat
against an internal database. The software, firmware and database are able to
be
changed through the Input Interface to allow the unit to be updated regularly
as
new threat information becomes available and software changes are made.
Agrello Format Messages - Background
The received bearings are translated to Agrello format messages by the
Logic and Processing Board. This format is %xxx/n <cr>. The following
table summarizes the format.
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Symbol Meaning
/o Separator between
essa es.
xx 3earing in degrees.
)-359.
n rhe "n" is the
elative strength of
he signal from 1-7.
cr> arria e Return
Input Interface
The input interface has three main functions. These are:
1. Interface to the Doppler Antenna
2. Interface to the radio receiver antenna and audio connectors; and
3. Interface to another computer or memory device for software/firmware
and database updates.
Output Interface
The output interface (see Figure 7) physically connects the logic and
processing
system to the various output devices that are able to be used with the MTIS
unit.
The basic equipment includes the Audio Warning device and the LED Directional
Display. Additional equipment can also be added for Graphical User Interfaces
and other indicators.
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Antenna Array
The antenna array module (see Figure 9), that is part of the mast assembly
(schematic of Figure 8) contains two antenna systems, each containing a
minimum of four antenna elements. One antenna is horizontally polarized, the
other vertically. The ground plane of the antenna array contains diodes that
allow
each antenna element to be switched on and off. These diodes are controlled by
the antenna control electronics contained on the Logic and Processing System.
Each antenna element is a'/4 wave whip antenna. They are typically mounted
between .22 and .25 wavelength apart in a square pattern, on a ground plane.
Laser Range Finder
The laser range finder part of the laser sub-assembly (see Figure 10) is a
device which
uses a laser beam in order to determine the distance to a reflective object.
It measures
the distance to an object by measuring the time it takes for the laser pulse
to be returned
to the laser range finding equipment. The laser range finder in the MTIS mast
is activated
once a signal is detected. The MTIS stepper motor assembly will rotate the
laser range
finder to the correct bearing and the secondary motor in the laser assembly
will raise or
lower the lasers if the horizontally polarized antenna array is able to
determine the relative
elevation of the target. If the circumstances permit, a distance to the target
will be
determined and the information processed to the output devices attached to the
MTIS
mast. If an elevation cannot be determined, the laser will remain horizontal.
Laser Designator
The laser designator is a device which uses a laser beam in order to give a
visual
indication of the threat direction. The MTIS stepper motor assembly (see
Figure 11) will
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rotate the laser to the correct bearing and the secondary motor in the laser
assembly will
raise or lower the laser if the horizontally polarized antenna array is able
to determine the
relative elevation of the target. The target area will then be indicated by
the visual laser
end point for engagement. If an elevation cannot be determined, the laser will
remain
horizontal.
Stepper Motor Assembly
There are two parts to the Stepper Motor Assembly. The first is a stepper
motor shown in
Figure 12, that rotates the laser sub-assembly 360 degrees on the horizontal
plane to the
bearing detected by the (Vertical) Doppler antenna array and associated
electronics. The
second part shown in Figure 13 is a stepper motor that raises or lowers the
laser sub-
assembly on the vertical access to indicate relative elevation of the target.
A
microcontroller is used to translate the Agrello format bearing messages to
the correct
motor step to point to the lasers to the appropriate bearing. The Vertical
Stepper Motor
driver will receive Agrello format messages, however they are limited to 0-180
degrees
(vertical).
Mast Sub-system Electronics Module
This module (Figure 14) contains the Stepper motor microcontrollers, and
delivers the
required power to the mast systems, including the Stepper Motor Assembly and
Laser
Sub-assembly.
This module contains the batteries required to drive the Stepper Motors,
Lasers and the
Mast Sub-system Electronics Modules.
CA 02576754 2007-02-02
Input Devices
Radio Receivers
The FM radio receivers are used to determine the operating frequency for the
direction
finding unit. They are connected to the Antenna Arrays for horizontal and
vertical
polarization. The receiver speaker output is connected to the main board audio
input.
The Doppler modulation results in an audio tone that is detected and. fed to
the speaker of
the MTIS display unit.
The radio receivers are typically set to scan the appropriate frequency
spectrum and
pause on that frequency if a signal is intercepted. Resumption of the scan can
be manual
or automatic.
GPS
The GPS input is optional, however the GPS data can be combined with the DF
Agrello
format messages for plotting onto a map display. For example:
If the user of the MTIS is moving, the GPS and Doppler data can be combined to
give a
more accurate fix on the transmitted signal with one MTIS. As lines of
intersection are
made, the most likely position will be processed in real-time and the stepper
motor will
adjust the laser sub-assembly to the new coordinate.
As shown in Figure 16, combining GPS with moving map display and bearing
information
will allow accurate position information to be calculated. The vehicle moves
from point 1
to point 5 and as it moves, the bearing to the transmitter will change. The
previous known
position will be stored in the MTIS and the line of intersection to the next
bearing
calculation will indicate the approximate position of the target.
Additionally, if the five
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points in Figure 16 represented separate vehicles in a convoy, the target
location will be
determined as each MTIS comes to bear on the transmitter. The intersection of
the five
lasers will indicate the vicinity of the target. Accordingly, it will be
understood that use of
the MTIS of the present invention for locating an immediate threat does not
depend on
communication from vehicle to vehicle.
Output Devices
Liquid Crystal Display (LCD)
A Liquid Crystal Display (LCD) is provided, and illustrated in exemplary form
only in
Figure 17, to interpret the direction and strength data received in Agrello DF
format and
translates this data into textual messages for display. The display will
typically show
bearing, signal strength, type of signal, frequency, elevation and the range
to the signal or
target. If a GPS is used, the geographic coordinates will also be shown. If
desired, the
display may also be transmitted to a driver or gunner as a visor borne heads
up desplay.
Light Emitting Diode (LED) Directional and Bearing Display
The LED directional and bearing display (see Figure 18) device gives a visual
indication of
the direction a signal is coming from. It used 36 LEDs positioned in a
circular fashion for
a 10 degree resolution. Different colour LEDs are installed for the cardinal
points for
orientation purposes. A three digit numeric display consisting of three, seven
segment
LED modules is positioned within the LED circle to provide bearing information
in the form
of numbers from 0 - 359 degrees.
Audio Warning
The audio warning will give an indication as to the type of signal being
received by the
MTIS unit. The warning tone is pre-programmed depending upon the type of
threat
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encountered. The threats are determined by frequency, content and duration of
signal.
For example a frequency is intercepted at 450 Mhz and consists of DTMF tones.
The
corresponding threat is possibly a wireless teiephone triggering device. A
distinctive
audio warning for an IED threat is heard on the speaker. A toggle switch can
be
employed to switch from Audio Warning to Receive mode whereby the original
broadcast
signal is heard such as voice, or data.
Personal Digital Assistant (PDA)
A PDA can be connected to the main board to provide a graphical user interface
and
storage to display bearing, elevation, threat indication, GPS position data
and other data
available from the Doppler Main Board. An infra-red or other wireless
interface can be
employed to use the PDA remotely from the MTIS terminal, or as a secondary
display
system for additional operators.
Computer
A computer can be connected to the MTIS terminal to provide a more
sophisticated user
interface, provide software updates to the on-board processors and for record
and
playback. The software updates can be firmware updates as well as threat
profile
updates.
Examples
Three examples of how the system works are listed below:
a. Attempt to initiate an improvised explosive device (IED) - as a friendly
convoy is
moving, its MTIS system detects that someone is transmitting dual-tone multi-
frequency
signals from a nearby Motorola-type radio (DTMF signals are produced by
pressing on
the number keys). As this is a known method for initiating an IED, the system
lets out an
audio warning and uses its radio direction finding equipment to establish the
x-, y-, and z-
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axes to the Motorola radio. Using that information, the system points a high-
power
stabilised laser pointer at the source of the transmission, and uses the laser
range finder
to determine the exact range. It also displays information on the type of
transmission
detected and the range on a screen. The forces using the MTIS system can now
see the
exact location and range to the person attempting to target them with an IED,
and can
take appropriate defensive measures.
b. Locating small arms fire - a friendly vehicle patrol comes under small arms
fire in
an urban setting in which there are many multiple-story buildings. They are
able to
determine the approximate direction from which the fire is coming, but cannot
pick out
exactly which apartments contain the gunmen. Returning fire under these
conditions
threatens to cause civilian casualties. Using the MTIS system's acoustic
direction finder
and laser pointers, however, friendly forces will rapidly be able to determine
the exact
point from which the fire is coming, allowing for much safer reaction.
c. Locating hostile forces - a group of hostile forces are preparing to attack
a remote
forward operating base (FOB) at night. They are communicating using hand-held
radios.
The FOB has an MTIS system which detects these transmissions, gives warning
that
radios are active in the area, and indicates where they are by using the laser
pointer.
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