A Unique Approach to Frequency-Modulated
Continuous-Wave Radar Design
1
EM GroupEM Group
5/6/08
A Unique Approach to Frequency-Modulated
Continuous-Wave Radar Design
Electromagnetics Research Group
G.L. Charvat, L.C. Kempel, Michigan State University
AMTA 2004
A Unique Approach to Frequency-Modulated
Continuous-Wave Radar Design
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EM GroupEM Group
5/6/08
Overview of Presentation
• Principles of Frequency-Modulated Continuous-Wave
(FMCW) Radar
• The unique approach to FMCW Radar
• Range Profile Data
• Synthetic Aperture Radar (SAR) Imagery
• Conclusions and future work
A Unique Approach to Frequency-Modulated
Continuous-Wave Radar Design
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EM GroupEM Group
5/6/08
Motivation
• Requirement: Low cost, short range, low power radar solutionfor use in high volume applications
o Example: Vehicle radar sensors, such as a backup aid or sideobject detection
• Problem: Conventional radar becomes more complex as thedesired detection range is decreased
o Resulting in use of a wider bandwidth shorter pulse which requireexpensive digitizers to acquire the range to target information
• Solution: FMCW radar uses a simple FM modulatedtransmitter, causing the resulting range to target informationto be in the form of low frequency (near audio) beats. Thelower the beat the shorter the range to target.
A Unique Approach to Frequency-Modulated
Continuous-Wave Radar Design
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EM GroupEM Group
5/6/08
Principles of FMCW Radar
• FMCW radar is different because it provides range to target
information in the form of low frequency (near audio) beats.
o This is done by frequency modulating a transmit oscillator, and
comparing the current transmitted carrier to the carrier which is
reflected from the target
o The closer a target, the lower the beat frequency
o The further a target, the higher the beat frequency
A Unique Approach to Frequency-Modulated
Continuous-Wave Radar Design
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EM GroupEM Group
5/6/08
Principles of FMCW Radar
• Practical FMCW design considerations
o Transmit to receive antenna coupling
• Limits sensitivity and dynamic range
• Causes a false target beat
• May require delay lines in the system
o Producing a linear FM chirp
• Poor chirp linearity causes degradation in rangeresolution and maximum unambiguous range
• Overall decrease in range accuracy
A Unique Approach to Frequency-Modulated
Continuous-Wave Radar Design
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5/6/08
The MA87127-1 ‘Gunnplexer’
• This transceiver module is basedaround a voltage controlled GunnDiode oscillator, a single Schottkydiode mixer, and a fixed ferromagneticcirculator
• This component has many interestingproblems…
o Tuning linearity
o Tuning instability due to temperatureand VSWR reflections
o Noise figure of 10 dB, or worse
o Poor mixer response near DC
A Unique Approach to Frequency-Modulated
Continuous-Wave Radar Design
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EM GroupEM Group
5/6/08
A Unique Approach to FMCW
Radar Design
• Taking into account the FMCW radar design considerations, andthe drawbacks to using ‘Gunnplexer’ type transceiver modules, aunique approach to FMCW radar design was created.
• Design approach based on 2 transceiver modules, coupling powerfrom one to the other for use as an LO reference
A Unique Approach to Frequency-Modulated
Continuous-Wave Radar Design
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5/6/08
System Implementation
• The system is broken downinto three major subsystemso The Front End Assembly
o The IF Chassis
o Data Acquisition
A Unique Approach to Frequency-Modulated
Continuous-Wave Radar Design
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EM GroupEM Group
5/6/08
Range Profile Data
Range to Target
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120
Beat Freqeuncy (Hz/20)
Am
pli
tud
e (
V*1
0,0
00
)
Series1
30 dBsm target located 20 ft
from the system
Range to Target
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120
Beat Frequency (Hz/20)
Am
pli
tud
e (
V*1
0,0
00
)
Series1
30 dBsm target located at 25
ft from the system
Range to Target
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120
Beat Frequency (Hz/20)
Am
pli
tud
e (
V*1
0,0
00
)
Series1
30 dBsm target located at 30 ft
from the system
Range to Target
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120
Beat Frequency (Hz/20)
Am
pli
tud
e (
V*1
0,0
00
)
Series1
30 dBsm target located at 35 ft
from the system
Range to Target
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120
Beat Frequency (Hz/20)
Am
pli
tud
e (
V*1
0,0
00
)
Series1
30 dBsm target located at 40 ft
from the system
A Unique Approach to Frequency-Modulated
Continuous-Wave Radar Design
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EM GroupEM Group
5/6/08
Range Profile Data
• The results indicate a small range offset within the
system of approximately 13.98 ft on average.
15.96255.69240
15.33750.33735
14.98244.18230
13.19938.19925
10.7230.70220
Range Difference (ft)Measured Distance (ft)Actual Distance (ft)
A Unique Approach to Frequency-Modulated
Continuous-Wave Radar Design
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5/6/08
Synthetic Aperture Radar
• SAR experimental
setup
20 dBsm
Target
30 dBsm
Target
A Unique Approach to Frequency-Modulated
Continuous-Wave Radar Design
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EM GroupEM Group
5/6/08
Synthetic Aperture Radar
• 30 dBsm target located at 25 ft from the system
17
13
19
25
31
37
43
49
55
61
67
73
79
85
91
97
103
109
115
121
S1
S7
S13
S19
S25
S31
S37
S43
S49
S55
S61
S67
S73
S79
S85
S91
S97
S103
01000
2000
3000
4000
5000
6000
7000
8000
9000
8000-9000
7000-8000
6000-7000
5000-6000
4000-5000
3000-4000
2000-3000
1000-2000
0-1000
A Unique Approach to Frequency-Modulated
Continuous-Wave Radar Design
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EM GroupEM Group
5/6/08
Synthetic Aperture Radar
• 20 dBsm target located at 25 ft from the system
18
15
22
29
36
43
50
57
64
71
78
85
92
99
106
113
120
S1
S7
S13
S19
S25
S31
S37
S43
S49
S55
S61
S67
S73
S79
S85
S91
S97
S103
0500
1000
1500
2000
2500
3000
2500-3000
2000-2500
1500-2000
1000-1500
500-1000
0-500
A Unique Approach to Frequency-Modulated
Continuous-Wave Radar Design
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EM GroupEM Group
5/6/08
Synthetic Aperture Radar
• 20 dBsm target located at 25 ft from the system, and the 30 dBsm target located at 40 ftfrom the system
17
13
19
25
31
37
43
49
55
61
67
73
79
85
91
97
103
109
115
121
S1
S7
S13
S19
S25
S31
S37
S43
S49
S55
S61
S67
S73
S79
S85
S91
S97
S103
0500
1000
1500
2000
2500
3000
3500
4000
3500-4000
3000-3500
2500-3000
2000-2500
1500-2000
1000-1500
500-1000
0-500
A Unique Approach to Frequency-Modulated
Continuous-Wave Radar Design
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EM GroupEM Group
5/6/08
Conclusions and Future Work
• A unique low-cost FMCW radar system that uses commonly
available parts
• Good Synthetic Aperture Radar performance using the unique
FMCW radar solution
• This research has shown that the unique solution to FMCW
radar works, and proven capable for use in more advanced
applications such as Synthetic Aperture Radar
• Future outlook:
o Increasing chirp bandwidth
o Greater transmit power
o A better solution to the range linearity problem