low cost radar; eric walton 2012 cerf project eric walton, electroscience laboratory, ece dept., the...
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1.504 -3.8491
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2.998 -9.748
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3.808 -14.7667
FREQ
LOW COST RADAR; ERIC WALTON 2012 CERF PROJECTEric Walton, ElectroScience Laboratory, ECE Dept., The Ohio State University
Email: [email protected];
Frequency Synthesizer• Windfreak SynthNV module • based on the Analog Devices ADF-4350• 400 TO 4,400 MHz• USB controlled and powered
$574
MEASUREMENT COMPUTING USB-7202
• ONE A/D PER CHANNEL
• UP TO 8 SIMULTANEOUS
• INDEPENDENT RANGE SETTINGS
• 16-BITS
• USB POWERED
• 100 KS/S CUMULATIVE RATE
• (IE; 50 KS/S EACH CHAN. FOR TWO ETC.)
• SIMULTANEOUS SAMPLING
• DOUBLE SPEED IN BURST MODE (32 K INTERNAL FIFO)
$399
PRELIMINARY TESTING
SYN3 DB
SPLITTER
I/Q
MIXA/D
COMPUTER
USB
USB
I
Q
0.5-4.4 GHz
3.25 AND 5.88 INCH
DIAMETER SPHERES
1-12 GHz ridge-waveguide
UWB horns
1000 1500 2000 2500 3000 3500-70
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0
10
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FREQ
SIG
NA
L (D
B)
STABILITY TEST
EMPTYEMPTY2SUBTRACT
IT IS CRITICAL THAT THE RADAR SYSTEM BE STABILE AND REPEATABLE FROM SCAN TO SCAN SO THAT SCANS CAN BE DIRECTLY COMPARED AND SO THAT THE BACKGROUND CAN BE SUBTRACTED FROM THE DATA OF INTEREST AS WELL AS SO THAT THE “THRU” DATA CAN BE USED FOR NORMALIZATION.
As a stability test, the empty target support at the beginning of the series can be compared to the one at the end; (time elapsed = 20 minutes) Note the difference is less than -25 dB.
0 20 40 60 80 100-100
-90
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TIME (ns)
SIG
NA
L (D
B)
EMPTYEMPTY2SUBTRACT
• IF WE LOOK AT THE EMPTY VS. EMPTY DATA IN THE TIME DOMAIN, WE NOTE THAT THE MOST STABILE REGION IS NEAR THE ANTENNA COUPLING REGION. (difference less than -35 dB)
• IT IS LESS STABILE AT TIMES GREATER THAN 20 ns. This may be simply due to people moving around near the measurement system.
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0
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4sphere5p88.txt
FREQ (GHZ)
RA
W I/Q
da
ta
IN PHASEQUADRATURE
-4 -2 0 2 4-4
-2
0
2
4sphere5p88.txt
REAL)
IMA
GIN
AR
Y
EXAMPLE RAW DATA
EXAMPLE STABILITY TEST
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10
20divided/normalized sphere5p88.txt
sphere5p88.txtsphere5p88.txt normalizedempty
FREQUENCY (MHZ)
Green = no-target data
Blue = raw sphere data
Red = sphere data divided by thru data
DB
EXAMPLE RESULTS FOR 5.88” DIA. SPHERE
0 50 100 150 200-120
-100
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sphere5p88.txt
sphere5p88.txtsphere5p88.txt normalizedemptysphere5p88.txt - backgroundsphere5p88.txt - BKG - NORMALIZED
TIME DOMAIN (ns)
DB
FULL TIME SCALE
Coupling in pow. Divider
(thus negative time)
TIME (ns)
DB
NOTE;
1. background subtraction suppresses the room clutter (background) by more than 30 dB.
2. Normalization to the “thru” connection removes the effects of system and cables. (IE: moves the response from 11.2 ns to 4.2 ns. antennas and propagation distance remain)
0 2 4 6 8 10 12 14 16 18-50
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sphere5p88.txt
sphere5p88.txtsphere5p88.txt normalizedemptysphere5p88.txt - backgroundsphere5p88.txt - BKG - NORMALIZED
0 2 4 6 8 10 12 14 16 18-70
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-10sphere3p25.txt
sphere3p25.txtsphere3p25.txt normalizedemptysphere3p25.txt - backgroundsphere3p25.txt - BKG - NORMALIZED
We can also do this
for the 3.25” diam sphere
BLOW UP
CONCLUSIONS;• WE HAVE BUILT A VERY USEFUL RADAR FOR LESS THAN $2,000.
• 400 TO 4,400 MHz; SYNTHESIZED
• OUTPUT POWER (-30 TO 0 DBm) (COMPUTER CONTROLLED)
• EXCELLENT SENSITIVITY AND REPEATABILITY
• PORTABLE (LAPTOP CONTROLLED)
• RUNNING TOTALLY IN MATLAB
• CAN OPERATE IN STEP FREQUENCY MODE
• CAN OPERATE IN SINGLE FREQUENCY(WITH DOPPLER) MODE.
6. Acknowledgements
The authors wish to thank The Ohio State University ElectroScience Laboratory Consortium on Electromagnetics and Radio Frequencies (ESL-CERF) (sponsors of this project) as well as Polyphase Corporation for their assistance.
$918 (Univ. Disc.)
1.5 GHZ
In the future;
One of our goals is to extract I/Q Doppler waveform signatures from the human heartbeat.
On the left is an I/Q Doppler measurement done with an ESL network analyzer on a volunteer.
Note the repeating I/Q pattern synchronized with the heartbeat. We hope to collect more of this type of data using our new portable radar and to compare the I/Q signature with MRI or EKG data.
• Polyphase Microwave • I/Q demodulator • 0.5 to 4.0 GHz• built in LO amplifier • Built in I/Q low pass filters. • Characteristics;
• LO/RF freq. 500-4,000 MHz• I/Q bandwidth DC-275 MHz • 50 Ω• Input IP3 +30 dBm
Spectrumanalyzer
1.5 GHZ
3.0 GHZ
3.8 GHZ
FROM SPECTRUM ANALYZER TESTING; NOTE THE SIDELOBE STRUCTURE
I/Q PATTERN
10 HEARTBEATS
I
Q