A Unique Approach to Frequency-Modulated Continuous-Wave ...glcharvat.com/website...

A Unique Approach to Frequency-Modulated

Continuous-Wave Radar Design

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EM GroupEM Group

5/6/08



Electromagnetics Research Group

G.L. Charvat, L.C. Kempel, Michigan State University

AMTA 2004



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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



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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.



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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



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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



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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



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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



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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



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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


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


Am

pli

tud

e (

V*1

0,0

00

)

Series1


from the system

Range to Target

0

50

100

150

200

250

300

350

400

450

500

0 20 40 60 80 100 120


Am

pli

tud

e (

V*1

0,0

00

)

Series1


from the system



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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)



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5/6/08

Synthetic Aperture Radar

• SAR experimental

setup

20 dBsm

Target

30 dBsm

Target



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5/6/08


• 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



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EM GroupEM Group

5/6/08


• 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



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EM GroupEM Group

5/6/08


• 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



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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

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