Upload
camron-heath
View
231
Download
1
Embed Size (px)
Citation preview
ElectroScience Lab
ULTRA WIDE BAND SPREAD SPECTRUM RADAR
Jodhpur Feb. 28-29, 2008
Bangalore Mar. 3-4, 2008
Eric K. WaltonThe Ohio State University, ElectroScience Lab.
Columbus, OH
2
ElectroScience Lab
BASIC CONCEPT
BASIC NOISE RADAR CONCEPT
NOISE RADAR
X
L.P.F.
SLOW A/D
NOISE GEN.
delay time
UWB antennas
3
ElectroScience Lab
DIGITAL NOISE RADAR
pseudo- noise #1
lowpassfilter
output
antennas
pseudo-noise #2
clock
delay
4
ElectroScience Lab
PREVIOUS STUDIES(dual FIFO system)
Teoman Ustun MS Thesis, Design and development of stepped frequency Continuous wave and fifo noise radar sensors For tracking moving ground vehicles OSU EE Dept, 2001.
5
ElectroScience Lab
DIFFERENT TYPES OF RADAR WAVEFORMS
6
ElectroScience Lab
SUPPRESSION OF INTERFERENCE/JAMMING
7
ElectroScience Lab
BUILDING PENETRATION UWB NOISE RADAR
8
ElectroScience Lab
TRANSMIT
RECEIVE
SIDE VIEW
TRANSMIT
RECEIVE
RECEIVE
RANGEBINS
DUALBISTATICRANGE
BINS
TOP VIEW
Conceptual Scenario for Dual Bistatic Building Penetration Radar
BUILDING PENETRATION UWB NOISE RADAR
9
ElectroScience Lab
Walton - Wall Penetration Example
• SEQUENCE OF IMAGES SHOWING THE TRACKING OF A HUMAN AS HE WALKS FROM UPPER RIGHT TO LOWER LEFT. • THE HUMAN IS INSIDE A CONCRETE BLOCK BUILDING.• THE RADAR WAS APPROXIMATELY 50 FEET AWAY ON THE OUTSIDE.
10
ElectroScience Lab
Walton - Wall Penetration Example
NOISERADAR
11
ElectroScience Lab
TARGET SPECIFIC DIGITAL NOISE RADAR
Computer& digital I/O
64K x 9 FIFOCypress
CY7C4282(100 MHz)
100 MHzD/A
100 MHzD/A
3.4 GHzLO
DATA LOAD (TX & RX)
TX
RX
100 MHz TRANSMIT
WAVEFORM
100 MHZRECEIVE
WAVEFORM
MODULATED RF
RECEIVED RF
LOWPASS
FILTERAUDIO BAND
ANALOG DATATO COMPUTER
Burr BrownDAC900
ANTENNAS3.4 GHz +/- 50 MHz
CLOCK100 MHZ
BPFilt.
BPFilt.
64K x 9 FIFOCypress
CY7C4282(100 MHz)
Target Specific Noise RadarTarget Specific Noise Radar
RIGHT
LEFTSW
12
ElectroScience Lab
UWB Noise Radar Example
Human Walking Toward the Radar Carrying C-Reflector
3.4 GHz
13
ElectroScience Lab
PATENT
14
ElectroScience Lab
RECENT STUDIES
15
ElectroScience Lab
DOPPLER FROM NOISE
16
ElectroScience Lab
SIGNAL TO NOISE CALCULATIONS
Here is the model:Let us assume RCS of object: -40 DBSM (1 sq. cm.)Power transmitted: 0.25 wattCenter Frequency: 10 GHzAntenna Power Gain: 5 wrt isotropic: (~7 dBi) Radar Range Equation :
34
22
)4(
LR
GPP t
r
Where Pr is the received reflected power and L is a set of loss factors lumped together (we use 0.5 here).
Eq. 1
17
ElectroScience Lab
SIGNAL TO NOISE CALCULATIONS
Next, we have signal power received due to thermal noise power at the receiver.
Eq. 2where:k is Boltsman’s constant 1.38*10^-23,T= ambient temperature in deg. Kelvin (taken as 290 deg.)B = bandwidth in Hertz. (We use 300 MHz as the front end frequency bandwidth).This allows us to compute the pre-processing S/N ratio as Pr/Pn.
Eq. 3.
kTBPn
n
rprocpre P
P
N
S
18
ElectroScience Lab
SIGNAL TO NOISE CALCULATIONS
Then the signal processing power gain is based on the final audio filter BW.
So:
Eq. 4bandwidth) (audio
bandwidth) (RF// . procprefinal NSNS
19
ElectroScience Lab
SIGNAL TO NOISE CALCULATIONS
We wrote a MATLAB program to evaluate this equation. An example result is shown below for a specific set of conditions:>> nradarG (dB) = 6.9897 Ant. GainPt = 0.25 Power trans.R (m) = 30 Range in metersRCS - DBSM = -40 Target RCS (DBSM)Pr = 6.999e-016 Pow. Rec. (watts)Pno = 1.2006e-012 Noise Pow. Rec. (watts)SoNraw = 0.00058296 S/N power ratio - rawGsp = 60000 Signal processing gainSoNfin = 34.9777 Final signal to noise power ratioPrdbm = -121.5496 Rec. Power (dBm)Pnodbm = -89.206 Rec. N. Power (dBm)SoNfindb = 15.4379 S/N – post processing - dBIf we model it so that we get the post-processing S/N as a function of range, we get figure 1.
20
ElectroScience Lab
SIGNAL TO NOISE CALCULATIONS
Post processing S/N for -40 DBSM object(based on parameters from previous slide)
Note that at +8 dB S/N, we can see this very small target out to 50 meters.
21
ElectroScience Lab
CONCLUSIONS
Note that this is not the best that can be done:
The raw data can be further processed using FFT processing.
The final bandwidth then is the incremental bandwidth of the FFT. (sometimes called the bin bandwidth)
In other words we get the signal processing gain of the FFT where a signal can be extracted from the noise. There are examples in some of my data where the signal can not be seen in the raw data but can be seen in the spectral (Doppler) plots. If we process 128 point FFT, for example, we get another factor of 128 signal processing gain.
22
ElectroScience Lab
NOISE RADAR -BACKGROUND
Publications:“Ultrawide-Band Noise Radar in the VHF/UHF Band,” (co-authors, I.P. Theron, S. Gunawan and L. Cai), IEEE Transactions Antennas Propagation, Volume 47 Number 6, pp. 1080-1084, Jun. 1999.
“Compact Range Radar Cross Section Measurements Using a Noise Radar,” (co-authors, I.P. Theron and S. Gunawan), IEEE Trans. Antennas Propagation, Vol. 46, No. 9, pp. 1285-1288, Sep. 1998.
23
ElectroScience Lab
NOISE RADAR BACKGROUND
Papers:“Development and Applications of a 16 Channel UHF/L-Band Noise Radar,” (co-author, S. Gunawan), Twentieth Annual Meeting and Symposium of the Antenna Measurement Techniques Association, pp. 210-213, Montreal, Canada, Oct. 26-30, 1998.“Signatures of Surrogate Mines using Noise Radar,” (co-author, L. Cai), AeroSense PIERS Meeting, Orlando, Florida, Apr. 13-17, 1998.“Future concepts for Ground Penetrating Noise Radar,” (invited paper) PIERS Workshop on Advances in Radar Methods, Joint Research Centre of the European Commission (Space Applications Institute), Baveno, Italy, Jul. 20-22, 1998.“Noise Radar A-P Mine Detection and Identification,” Demining MURI review, Night Vision Laboratory, Delphi, Maryland, Aug. 10-13, 1998.“Comparative Analysis of UWB Underground Data Collected Using Step-Frequency, Short pulses and Noise,” (co-author, S. Gunawan), Ultra-Wideband, Short Pulse Electromagnets 3, Proceedings of the Third International Conference on Ultra-Wideband, Short Pulse Electromagnetics, May 27-31, 1996, Albuquerque, New Mexico. (refereed; digest released as book for, Jan. 1997) “Moving Vehicle Range Profiles Measured Using a Noise Radar, “ (co-authors, I.P. Theron, S. Gunawan and L. Cai), 1997 IEEE AP-S Symposium and URSI Meeting, Montreal, Canada, Jul. 13-18, 1997.“Use of Fixed Range Noise Radar for Moving Vehicle Identification,” ARL 1997 Sensors and Electron Devices Symposium, College Park, MD, Jan. 14-15, 1997.“UWB Noise Radar Using a Variable Delay Line,” (co-authors, I. Theron and S. Gunawan), Nineteenth Annual Meeting and Symposium of the Antenna Measurement Techniques Association, Boston, Massachusetts, Nov. 17-21, 1997.“Comparative Analysis of UWB Underground Data Collected using Step-Frequency, Short Pulse and Noise Waveforms,” (co-author, S. Gunawan), AMEREM ‘96 International Conference on “The World of Electromagnetics” Albuquerque, New Mexico, May 27-31, 1996.“ISAR Imaging Using UWB Noise Radar,” (co-authors, V. Fillimon and S. Gunawan), Antenna Measurement Techniques Association Symposium, Seattle, Washington, Sep. 30-Oct. 3, 1996.“Comparison of Impulse and Noise-Based UWB Ground Penetrating Radars,” (co-author, F. Paynter), URSI Radio Science Meeting (Joint with AP-S), Seattle, WA, Jun. 19-24, 1994. “High Resolution Imaging of Radar Targets using Narrow Band Data,” (co-author, A. Moghaddar), Joint URSI Meeting and International IEEE/AP-S Symposium, London, Ontario, Jul. 1991.“Use of Stepped Delay Line Noise Radar for ISAR Imaging in the OSU Compact RCS Measurement Range,” (co-authors S. Gunawan), Joint Tech. Report 732168-2 and 727723-12, The Ohio State University ElectroScience Laboratory, Sep. 1997.
24
ElectroScience Lab
AVAILABLE AS AN OSU REPORT:
“Signal to Noise Ratio Calculations and Measurements for the OSU Noise Radar”
I. P. Theron, E. K. Walton, S. Gunawan and L. Cai
Technical Report 732168-1, The Ohio State Univ. ElectroScience Laboratory, Nov. 1996
25
ElectroScience Lab
NOTE THAT THE SPECTRAL DISPERSION OF THE SPHERE MAKES THE ABSOLUTE VALUE OF THE PEAK LOWER EVEN WHILE THE TOTAL ENERGY REMAINS HIGH.
TIME DOMAIN SIGNATURES
26
ElectroScience Lab
TIME DOMAIN SIGNATURES
27
ElectroScience Lab
Mathematical Description of the Noise Radar
)2 to0( phase random is
:where
]cos[
n
nn
nn Ah A noise signal can be written as (finite freq. band).
The delayed signal is:
function transfer linedelay )()(~where
])(cos[
dnjd
nnd
n
dnncn
dn
d
eTT
tATh
28
ElectroScience Lab
The received signal consists of environmental noise
and reflections from both the target of interest and clutter for an overall “target” transfer function of
Next there is the propagation factor (delay and attenuation)
enje
nne eAS )(
~
tnjt
nnt eTT )(
~
in vacuumlight of speed c
targetodistanct t
where
/1 and /2
where2
p
r
rTcr
eT
p
jt np
29
ElectroScience Lab
The received signal is:
snjs
nns
enn
n
en
n
tn
snnpn
tn
sn
pr
eTT
tA
tTTATth
)(~
system ing transmitt theof influence theincludeswhich
]cos[
])(cos[)(
The output of the mixer (mixing the received signal and the delayed transmitted signal) and remembering that the low pass filter will retain only the difference frequencies, we have
n l
dll
endln
tl
en
n l
dl
tn
snlndlpn
dl
tn
sn
pm
ttTAA
ttTTTTAth
])(cos[2
1
])()(cos[
2
1)(
2
This is the signal part of the S/N value.
Mathematical Description of the Noise Radar
30
ElectroScience Lab
So what is the “noise” part of the “signal – to - noise ratio”?
1. Output of low pass filter (without external noise)2. External wide band noise sources
1. Lightning2. Man-made unintentional signals3. Jammers
3. External narrow band signal sources1. Radio transmitters2. Computer equipment
31
ElectroScience Lab
Noise from Low Pass Filter internal processes
Even in the absence of external noise, the LPF will contain DC and some low freq. noise as:
])(cos[
])(cos[)(
)0(0
0
knn
nknn
s
tk
tkAkH
ANH
Leaving out a number of steps, we eventually show that the output signal to noise ratio in the absence of environmental noise is:
bandwidth system theis and
frequency cutoff LPF theis :where
220
s
f
f
s
f
s
no
s
B
B
B
B
N
N
P
P
This is the best that we can hope for.
Mathematical Description of the Noise Radar
32
ElectroScience Lab
EXTERNAL SOURCE OF WIDE BAND NOISE:
•Assume an external signal with a flat spectrum but that is incoherent with the transmitted radar signal•Power computed as before ( ) •For large BW(noise) the total noise power is thus:
•So the final S/N in this case is:
2AN s2
0 ANNP fsn
f
s
f
s
no
s
B
B
N
N
P
P0
33
ElectroScience Lab
External source of narrow band signal:
Using similar logic, we can show that the average power at each frequency due to a narrow band source is based on the average power over the BW of the radar (IE: NsA2 ).
Thus we obtain the same total noise power as for the wide band external noise signal with a flat spectrum.
(We simply must compute the total external signal power in the BW of the radar.)
34
ElectroScience Lab
The signal power must be averaged in the t-domain and the noise power must be computed relative to the signal peak (IE: Lets assume a threshold target detection algorithm).
If we plan on using a threshold level to determine the detection of a target, then we must consider the peak signal response to the peak noise response. (not the average noise power).
We can thus compute the peak response of a random noise with a known power based on a useful number of statistical (sigma) widths.
We usually find that the result yields a requirement of a factor of as much as 10 in the ratio of signal to noise to reliably “detect” a target.
Of course, this depends on the desired ratio of false alarms to missed detections. (As does nearly all radar target detection processes.)
35
ElectroScience Lab
QUESTIONS? / DISCUSSION?