Robust low frequency spread-spectrum navigation system

US 20080088507Al
(12) Patent Application Publication (10) Pub. No.: US 2008/0088507 A1
(19) United States
Smith et al. (43) Pub. Date: Apr. 17, 2008
(54) ROBUST LOW-FREQUENCY
SPREAD-SPECTRUM NAVIGATION SYSTEM
Publication Classi?cation
(51) Int. Cl.
G01S 1/08 (2006.01)
(76) Inventors: Stephen F. Smith, Loudon, TN Gols 3/02 (2006-01)
(US); James A. Moore, Powell, (52) US. Cl. ...................................... .. 342/386; 342/464
TN (Us) (57) ABSTRACT
Methods and apparatus are described for a navigation sys
Correspondence Address: - - - - -
tem. A process mcludes prov1d1ng a plurality of transmltters
JOHN BRUCKNER PC distributed throughout a desired coverage area; locking the
R0‘ BOX 490 plurality of transmitters to a common timing reference;
FLAGSTAFF’ AZ 86002-0490 transmitting a signal from each of the plurality of transmit
ters. An apparatus includes a plurality of transmitters dis
(21) Appl NO . 11/583 374 tributed throughout a desired coverage area; Wherein each of
' " ’ the plurality of transmitters comprises a packet generator;
and Wherein the plurality of transmitters are locked to a
(22) Filed: Oct. 17, 2006 common timing reference.
801 PN CODE PULSE
GENERATOR J SHAPING 805 806
80/3 5|N / / 807
802 PACKET 804 /
GENERATOR 803 N00 J DAG _' LPF
* A?“PN CODE f PULSE X
801/ GENERATOR j SHAPING /

Patent Application Publication Apr. 17, 2008 Sheet 1 0f 18
SEARCH
SEARCH
SYSTEM
6)CONT
FIG. I
SYSTEM CONTROLLER
SENSOR TELEMETRY
GPS/INS/RF INTEGRATION
POWER MANAGEMENT
202 THEATER (TPS) RE ‘
LOCATING RECEIVER
203 MIL-SPEC ADAPTIVE ‘ V
GPS RECEIVER OPERATOR INTERFACE
QOS MONITORING
LOW-POWER |N5 PRECISION TIMEBASE
/ (INERTIAL SENSOR A V '
204 + SENSOR ARRAY) 2%
FIG. 2
GOOD GPS
FIX REGION
303
FALSE
GPS FIX
302
FIG. 3
US 2008/0088507 A1
MICROCANTILEVER
SENSOR ARRAY
(OPTIONAL)
205
OPERATOR
INTERFACE

Patent Application Publication Apr. 17, 2008 Sheet 2 0f 18 US 2008/0088507 A1
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CONTROLLER AND
MASTER OSCILLATOR
99% POWER BW A,
LORAN-C
@9603 602
TPS "A" TPS "c" TPS "D"
80 R41 9'0 100 11'0 120' kHz
FIG. 6A
99.9% POWER BW
"3.3 MHz"
TPS SIGNAL
FIG. 6B
3.25 MHZ 3.314'5 MHZ 3.38 MHz
H 99.9% POWER BW
' "2.45 GHz"
TPS
2409951 1' 2450: MHZ ' 2475‘951
FIG. 6C

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(10-100kW)
0 tew tsw I
. CORRELATOR OUTPUTS vs DELAY
>FIG. 16
m 1601

MAIN (GW) 1603
’ CORRELATOR
v /
CANCEL PROCESSING OUT
LOGIC
M
SECONDARY
CORRELATOR
/
1602

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ALL INPUTS
READY?
I201 SELECT ALGORITHM 3D vs 2D
T
1202 COORDINATE
CONVERSION LLHZECEF
T
I 2C3 CALCULATE
STRAIGHT-LINE DISTANCE
T
1204 CONVERT TO
GREAT-CIRCLE OISTANCE
T
MULTIPLY BY ASFs (PROPAGATION
1205 / CORRECTION OVER GROUND)
POSITIONING
1206 / ALGORITHM (N-R/KF)
COOROINATE
1207 / CONVERSION ECEF2LLH
T
DISPLAY USER POSITION
FIG. 12
1208/

ALL INPUTS
READY?
1301 INITIAL ESTIMATE
v
UPDATE
ATE = T5-T5
ax1ay1az1
H = n 0 a
V
1303 +_ T -1 T +
APLS—(H H )HASp
V
1304 —> -* ->xSTEPSIzE
PI+1 PI‘LAPLSI
A?LSi
< ERROR THRESHOLD OR
NLTER > NLTER
THRESHOLD
ErA LSi OUTPUT
< ERROR THRESHOLD ERROR FLAG
1306
OUTPUT USER POSITION
FIG. I3

ALL INPUTS
READY?
1401 INITIAL ESTIMATE
II=
UPDATE
1402 Ag?: g5-gb‘i
H25 OR H35
V
KF=PHT(HPHT+R)1
1403 P=P-KFXHXP
P:(P+PT)/2
‘I
1404 —: —> —>
PiT1i+KFX A PLSi
< ERROR THRESHOLD OR
NLTER > NLTER
THRESHOLD
OUTPUT
ERROR FLAGMfg] < ERROR THRESHOLD
OUTPUT USER POSITION
FIG. 14

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1801“? TPs SIGNALS IN
1802 TPS IvIuLTICRANNEL
RECEIVER FRONT-END
12-24 CHANNEL/
1803 CHIP DEIvIODuLATOR
(CO-STATS PLL) E'TGREQLGTH
PHASE NOISE LEvELsCHIPS LOOP
II FEEDBACK STATISTICS f1810
1804 CODE CORRELATORS B|ASES
(3/5/7 - STEP DLL) /1811
1 809
"DATA BITS CORRELATION
PEAK SHAPE
1805/ DATA DECODERs CORRELATION
AMPLITUDE
‘ V v V
1806/ PRT DATA STATUS SIGNAL QUALITY ASSESSMENT 1808
12-24/ 12-24/
V ‘V ‘
1807/ PSEUDORANGE/TIME/QUALITY DATA VALIDATION
0-24,,
1812/ vALID FIX DATA OuT AND
STATUS INFORMATION
V
TO TRINAv PROCESSING
FIG. 18

1901POWER-UP
I902 INITITIALIZE TRINAV UNIT
1903 INITITIALIZE GPS, TPS, INS MODULES
km904
I905 ACQUIRE GPS, TPS, INS FIXES
REPEAT
CYCLE
1916
ERROR! SET
STATUS DATA
1912
OUTPUT LAST GOOD FIX, TIME,
1914 _/ STATUS MESSAGES TO USER
INTERFACE (DISPLAY)
I
STORE ALL DATA FOR PROCESSING
1915 / UPDATES TPS AND INS RECALIBRATION
I
FIG. 19

Patent Application Publication
2001 POWER-ON
TRINAV
START
2002
2003
OBTAIN INITIAL NORTH VIA MAGNETIC
COMPASS LOCAL GRAVITY VERTICAL
VIA EOUATE OR INCLINOMETER
2004NMZ_>NT’?
V
2005 OBTAIN TPS FIX (2-0 OR 3-0)
I
2006 INPUT TPS TX COORDINATES
2007
ROTATE TPS ORTHOGONAL ANTENNA
ASSEMBLY VIA MECHANICAL OR ELECTRONIC
MEANS TO FIND DIRECTIONAL-PATTERN
NULLS; IE, ORIENTATIONS TO TPS TXs
I
2008 ESTABLISH TRUE NORTH
FROM TPS TX VECTORS
I
2009/
COMPARE WITH MAGNETIC NORTH
STORE DECLINATION CORRECTION
I
2010 /
OUTPUT NORTH AND VERTICAL
REFERENCES TO TRINAV INS SUBSYSTEM
I_—____
FIG. 20
2100
TX1;————
Apr. 17, 2008 Sheet 16 0f 18
REPEAT
CYCLE
[2011
US 2008/0088507 A1
FIG. 2] TX2
ON
————————————————— -— OFF
ON
——————— —- OFF
ON
— ———— ——— OFF

FIG. 24A FIG. 24B
ON
FIG. 25

US 2008/0088507 A1
ROBUST LOW-FREQUENCY
SPREAD-SPECTRUM NAVIGATION SYSTEM
STATEMENT AS TO RIGHTS TO INVENTIONS
MADE UNDER FEDERALLY-SUPPORTED
RESEARCH OR DEVELOPMENT
[0001] This invention Was made With United States Gov
ernment support under prime contract No. DE-AC05
00OR22725 to UT-Battelle, L.L.C. awarded by the Depart
ment of Energy. The Government has certain rights in this
invention.
BACKGROUND INFORMATION
[0002] 1. Field of the Invention
[0003] Embodiments of the invention relate generally to
the ?eld of communication systems. More particularly, an
embodiment of the invention relates to navigation systems,
and methods of performing navigation.
[0004] 2. Discussion of the Related Art
[0005] Prior art navigation systems, such as the Global
Positioning System (GPS), are knoWn to those skilled in the
art. For instance, a conventional global positioning system
consists of more than tWo doZen GPS satellites broadcasting
precise timing signals by radio to GPS receivers, alloWing
them to accurately determine their location (longitude, lati
tude, and altitude) anyWhere on Earth.
[0006] A problem With this technology has been the lack
ofreliability in thick foliage, rough terrain, and urban areas.
Therefore, What is required is a solution that provides
navigation systems able to reliably function under such
conditions.
[0007] Another problem With this technology has been the
long time required to obtain a neW ?x, as Well as suscepti
bility to multipath elfects, jamming, or spoo?ng signals.
Therefore, What is also required is a solution that provides
a quicker and more robust ?x, able to detect multipath,
jamming or spoo?ng induced errors.
[0008] One unsatisfactory approach, in an attempt to solve
the above-discussed problems involves the use of narroW
correlator spacing to reduce noise and multipath effects.
HoWever, a disadvantage of this approach is that it does not
substantially improve time-to-?rst-?x, nor does it improve
reliability in areas Where GPS signals cannot penetrate.
[0009] Heretofore, the requirements of reliable signals in
dif?cult terrain, quick time-to-?rst-?x, and robustness ofthe
?x referred to above have not been fully met. What is needed
is a solution that simultaneously solves this all of these
problems.
SUMMARY OF THE INVENTION
[0010] There is a need for the folloWing embodiments of
the invention. Of course, the invention is not limited to these
embodiments.
[0011] According to an embodiment of the invention, a
process comprises: providing a plurality of transmitters
distributed throughout a desired coverage area; locking the
plurality of transmitters to a common timing reference;
transmitting a signal from each of the plurality of transmit
ters. According to another embodiment of the invention, a
machine comprises: a plurality of transmitters distributed
throughout a desired coverage area; Wherein each of the
plurality of transmitters comprises a packet generator; and
Wherein the plurality oftransmitters are locked to a common
Apr. 17, 2008
timing reference. According to another embodiment of the
invention, a process comprises: providing Global Position
ing System ?x having a plurality of tracking parameters;
providing a Theater Positioning System ?x; monitoring the
plurality of tracking parameters for predetermined condi
tions; and, When the predetermined conditions are met,
sending a notifying signal and sWitching to the Theater
Positioning System ?x as a primary ?x. According to
another embodiment of the invention, a machine comprises:
a system controller; a Global Positioning System receiver
coupled to the system controller; a radio frequency locating
receiver coupled to the system controller; and an operator
interface coupled to the system controller.
[0012] These, and other, embodiments of the invention
Will be better appreciated and understood When considered
in conjunction With the folloWing description and the
accompanying draWings. It should be understood, hoWever,
that the folloWing description, While indicating various
embodiments ofthe invention and numerous speci?c details
thereof, is given by Way of illustration and not of limitation.
Many substitutions, modi?cations, additions and/or rear
rangements may be made Within the scope of an embodi
ment of the invention Without departing from the spirit
thereof, and embodiments of the invention include all such
substitutions, modi?cations, additions and/or rearrange
ments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The drawings accompanying and forming part of
this speci?cation are included to depict certain embodiments
ofthe invention. A clearer conception of embodiments ofthe
invention, and of the components combinable With, and
operation of systems provided With, embodiments of the
invention, Will become more readily apparent by referring to
the exemplary, and therefore nonlimiting, embodiments
illustrated in the draWings, Wherein identical reference
numerals (ifthey occur in more than one vieW) designate the
same elements. Embodiments ofthe invention may be better
understood by reference to one or more ofthese draWings in
combination With the description presented herein. It should
be noted that the features illustrated in the draWings are not
necessarily draWn to scale.
[0014] FIG. 1 shoWs a functional overvieW of one embodi
ment of the invention.
[0015] FIG. 2 shoWs one embodiment of the apparatus of
the invention.
[0016] FIG. 3 shoWs the resistance to spoo?ng signals of
the invention.
[0017] FIG. 4 shoWs a precision timing apparatus used by
the invention.
[0018] FIG. 5 shoWs one arrangement of a precision
timing apparatus of the invention.
[0019] FIG. 6A shoWs one possible frequency allocation
used by one embodiment of the invention.
[0020] FIG. 6B shoWs one possible frequency allocation
used by another embodiment of the invention.
[0021] FIG. 6C shoWs one possible frequency allocation
used by another embodiment of the invention.
[0022] FIG. 6D shoWs one basic con?guration of an
indoor line-of-sight TPS scheme used by the invention.
[0023] FIG. 7 shoWs one basic con?guration of a TPS
scheme used by the invention.
[0024] FIG. 8 shoWs the block diagram of a transmitting
system used by the invention.

Robust low frequency spread-spectrum navigation system

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