stepped-frequency nonlinear radar simulation -...
TRANSCRIPT
THE CITADEL, THE MILITARY COLLEGE OF SOUTH CAROLINA
171 Moultrie Street, Charleston, SC 29409
Stepped-Frequency Nonlinear Radar
Simulation
Anthony F. Martone
U.S. Army Research Laboratory
Adelphi, MD, 20783
Kyle A. Gallagher, Ram M. Narayanan
Pennsylvania State University
University Park, PA, 16802
Gregory J. Mazzaro
The Citadel, The Military College of South Carolina
Charleston, SC, 29409
2
Presentation Overview
• Nonlinear Radar
• Concept, Motivations
• Nonlinearity, Sources, Harmonics
• Harmonic Radar Measurements
• Nonlinear Stepped-Frequency Radar
• Stepped-Frequency
+ Harmonic Radar Concept
• Nonlinear SFR Measurements
• Summary & Future Work
U.S. Army Research Laboratory
Synchronous Impulse
Reconstruction (SIRE) Radar
3
Nonlinear Radar Concept
Applications:
Advantages:
• It is easier to separate targets from clutter because most clutter is linear.
Disadvantages:
• Targets require high incident power to drive them into non-linear behavior.
• Received responses are usually very weak compared to the transmitted “probe” signals.
Target presence/location
is indicated by receiving
frequencies that were
not transmitted.
Tx
Rx
• locate personal electronics during emergencies
• detect electronically-triggered devices
electronic
target
4
Linearity vs. Nonlinearity
For a linear system,
For a non-linear system,
1 1 2 2 1 1 2 2a x a x a y a y
1 1
2 2
x y
x y
?
input output
0 0 0 0 0 0cos cosA t A H t
0 0 0 0 0 0 0 0 0cos , cos , ,A t A H A A t A
1 1 2 2 1 1 2 2a x a x a y a y
transfer function depends on amplitude, and
output frequency does not necessarily equal input frequency
5
Sources of Nonlinearity
+
_ +
_
Active elements & components – by design; above system noise floor
Passive elements & components – unintended; below system noise floor
diodes transistors amplifiers mixers
f1
f2
f1 + f2
contacts [1,2]
metal 1
metal 2
oxide
metal
temperature
-dependent [5] connectors [3]
V R
ferro-electrics [4]
6
Temperature-Dependent Resistance
Vin R
Iout
voltage applied,
current flows
resistor
heats up
resistance
increases current
decreases
resistor cools
down resistance
decreases
current
increases
input: constant
output: sinusoidal
nonlinear system
Vin
time
Iout R
time time
0 01R T R T T
7
Nonlinear Radar Research
Tx
Rx
The target is viewed
as a collection of
nonlinearities. Ein
Erefl... LNA
BPF
one possible
signal path:
8
Harmonic Radar Theory
2 3
out 1 in 2 in 3 in ...E a E a E a E Let the nonlinearity
be approximated by
a power series [6]
Let the input waveform be a sinusoid: in 0 0cosE E t
Then the device response (output) is
2 3
out 1 0 0 2 0 0 3 0 0cos cos cos ...E a E t a E t a E t
2 3
2 0 3 0out 1 0 0 0 0 0cos 1 cos 2 3cos cos 3 ...
2 4
a E a EE a E t t t t
harmonics
input
output
from [7]
9
Recent 1-Tone Experiment
1-dB step
attenuator
Ptrans
targ
et
antenna
1.1
m
5 m
GTEM cell
Prec
Tektronix AWG7052
arbitrary waveform generator Amplifier Research
50-W 1-GHz RF amplifier
Rohde & Schwarz FSP
40-GHz spectrum analyzer GTEM = Gigahertz Transverse Electromagnetic
10
Transmitted Frequency (MHz)
Pow
er R
ecei
ved
at
2n
d H
arm
on
ic (d
Bm
)
10-12 W
10-15 W
PD = 16 mW/cm2
GTEM cell
Recent 1-Tone Measurements
Nonlinear (harmonic) device response is
experimentally verified,
but ranging/imaging is not possible when
receiving a single continuous frequency.
11
Stepped-Frequency Radar
A1
f1
A2
f2
A3
f3
A4
f4
A5
f5
f0 f0 + Df f0 + 2Df f0 + 3Df f0 + 4Df
amplitude
phase
frequency
…
…
…
…
Tra
nsm
itte
d
Rec
eived
P
roce
ssed
IDFT
2
cR t
12
Nonlinear Stepped-Frequency Radar
A1
f1
A2
f2
A3
f3
A4
f4
A5
f5
2f0 2f0 + 2Df 2f0 + 4Df 2f0 + 6Df 2f0 + 8Df
amplitude
phase
frequency
…
…
…
…
Tra
nsm
itte
d
Rec
eived
P
roce
ssed
IDFT
2
cR t
13
Transmitter
Receiver
Vrec
Tektronix
AWG7052
Simulated Radar
Environment
MiniCircuits
NLP-1000+
MiniCircuits
NLP-1000+
Amplifier Research
AR4W1000
Lecroy 8300A
channel 2
Lecroy 8300A
channel 3
HP 778D
MiniCircuits
VHF-1320+
MiniCircuits
VHF-1320+MiniCircuits
VHF-1320+
MiniCircuits
VHF-1320+
MiniCircuits
PSA-5453+
MiniCircuits
PSA-5453+
MiniCircuits
PSA-545+
MiniCircuits
CBL-25FT x4
target
Vtrans
Tx coupled
Rx coupled
in out
Hardware Simulation Experiment
d = 100 ft
14
Hardware Simulation Measurements
blue = transmitted to target,
880 MHz to 920 MHz ,
Tenv = 1 ms , N = 40
red = received from target,
1760 to 1840 MHz
15
Hardware Simulation Results
d = 102 ft
1 ft0.34
2 nsr
cd t t
tgt
tgt
NL
2 21
0
sin 2
2
j f tM
M
B th t
t
E E e
As long as (a) the phase response of
the target is linear and (b) the amplitude
response is nearly flat over the band of
interest…
Range-to-target is found from
an inverse DFT of the nonlinear
SFR response, as with linear SFR.
nonlinear impulse response,
constructed from an IDFT
of the data in red
16
Transmitter
Receiver
Vrec
Tektronix
AWG7052
Simulated Radar
Environment
MiniCircuits
NLP-1000+
MiniCircuits
NLP-1000+
Amplifier Research
AR4W1000
Lecroy 8300A
channel 2
Lecroy 8300A
channel 3
HP 778D
MiniCircuits
VHF-1320+
MiniCircuits
VHF-1320+MiniCircuits
VHF-1320+
MiniCircuits
VHF-1320+
MiniCircuits
PSA-5453+
MiniCircuits
PSA-5453+
MiniCircuits
PSA-545+
MiniCircuits
CBL-25FT x4
target
Vtrans
Tx coupled
Rx coupled
in out
Nonlinear stepped-frequency radar was
demonstrated by hardware simulation of a
nonlinear target in a linear radar environment.
Summary & Near-Term Future
17
Summary & Near-Term Future
Nonlinear stepped-frequency radar was
demonstrated by hardware simulation of a
nonlinear target in a linear radar environment.
step
atten
uator
targ
et
3 m
Prec
Ptrans
Wireless experiments &
verification of the NL SFR concept
with multiple electronic targets.
Next step(s):
18
References
[1] C. Vicente and H. L. Hartnagel, “Passive-intermodulation analysis between rough rectangular waveguide flanges,”
IEEE Transactions on Microwave Theory and Techniques, Vol. 53, No. 8, Aug. 2005, pp. 2515–2525.
[2] H. Huan and F. Wen-Bin, “On passive intermodulation at microwave frequencies,” in Proceedings of the Asia-Pacific
Electromagnetic Conference, Nov. 2003, pp. 422–425.
[3] J. Henrie, A. Christianson, and W. J. Chappell, “Prediction of passive intermodulation from coaxial connectors in
microwave networks,” IEEE Transactions on Microwave Theory and Techniques, Vol. 56, No. 1, Jan. 2008.
[4] G. C. Bailey and A. C. Ehrlich, “A study of RF nonlinearities in nickel,” Journal of Applied Physics, Vol. 50, No. 1,
Jan. 1979, pp. 453-461.
[5] J. R. Wilkerson, K. G. Gard, A. G. Schuchinsky, and M. B. Steer, “Electro-thermal theory of intermodulation distortion
in lossy microwave components,” IEEE Transactions on Microwave Theory and Techniques, Vol. 56, No. 12, Dec.
2008.
[6] J. C. Pedro and N. B. Carvalho, Intermodulation Distortion in Microwave and Wireless Circuits. Boston, MA: Artech
House, 2003.
[7] G. J. Mazzaro and A. F. Martone, “Harmonic and multitone radar: Theory and experimental apparatus,”
U.S. Army Research Laboratory Technical Report, No. 6235, Oct. 2012.