and Compensation of Frequency Sweep Nonlinearity . in FMCW. *. . Ranging Systems. Committee. members. Applied. Physics. Prof. dr. A.P. Mosk. (COPS), . ir.. R. . Vinke. (Thales), prof. dr. W.L. Vos (COPS), . ID: 427184
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Effects, Estimation, and Compensation of Frequency Sweep Nonlinearity in FMCW* Ranging Systems
Committee membersApplied PhysicsProf. dr. A.P. Mosk (COPS), ir. R. Vinke (Thales), prof. dr. W.L. Vos (COPS), ir. H.T. Griffioen (Thales)Applied MathematicsDr. G. Meinsma (MSCT), prof. dr. A.A. Stoorvogel (MSCT), dr. A. Zagaris (AAMP)
*
Frequency-Modulated Continuous-Wave
Slide2Contents
Introduction
Digital chirp generation and its effect on the performance of a FMCW radar
Compensation of frequency sweep nonlinearity by digital post-processing
Applications of FMCW to optics
Conclusions
Slide3Radar
Radio Detection And Ranging“To see and not be seen”
RAF Chain Home radar site
German U-boat surrendering (depth charge in profile)
Heinkel
HE-111 bombers
Slide4Pulsed radar
Slide5Intercept receivers
JammingDirection finding (DF)Anti-radiation missiles (ARMs)
Prowler armed with HARM high-speed anti-radiation missiles
DRS ZA-4501 shipboard DF antenna array
Slide6LPI radar
pulse with high peak power
continuous wave with low peak power
time
power
Low probability of intercept
Thales Smart-L
power
megaWatt
Thales Scout Mk2
power
milliWatt
Slide7
FMCW radar
Frequency-modulated continuous-wave
time
time
frequency
amplitude
bandwidth
= 50 MHz
sweep period
= 500
µ
s
carrier frequency
= 10 GHz
Slide8
Principle of FMCW ranging
transmitted linear chirp
received
echoes
frequency difference
frequency
time
time
target
‘beat’
frequencies
Slide9FMCW transceiver
chirp generator
spectrum analyzer
time
coupler
mixer
transmit antenna
receive antenna
target
RF
LO
IF
frequency
power
frequency
Slide10Frequency sweep nonlinearity
transmitted non-linear chirp
received target echoes
beat frequency
frequency
time
time
Slide11“Ghost” targets
beat frequency
frequency
time
time
power
frequency
transmitted non-linear chirp
received target
echo
“ghost” targets
target
Slide12Analog chirp generation
YIG (Yttrium, Iron, and Garnet)-tuned oscillator
A.G. Stove,
Measurement of Spectra of Microwave FMCW Radars
, Thales Aerospace UK, working paper (2006).
Slide13Digital chirp generation
Direct digital synthesizer (DDS)
address generator
RAM or ROM
D/A converter
low-pass filter
clock
to transmitter
Clock speed 1 GSPS
Integrated 14-bit DAC
Output of a AD9910 sweeping from 180 MHz to 210 MHz
Source: J. Ledford, Master’s Thesis, University of Kansas (2008).
Slide14Quantization of phase
‘jump’ size
sine look-up table (ROM)
‘phase accumulator’
AD9910 synthesizer
AD9910 synthesizer
clock
Slide15Worst-case “ghost” target
‘Spurious-free dynamic range’
“Ghost” targets practically negligible
power
frequency
SFDR = 92 dB
Slide16Compensation of phase errors
Burgos-Garcia et al., Digital on-line compensation of errors induced by linear distortion in broadband FM radars, Electron. Lett. 39(1), 16 (2002).Meta et al., Range non-linearities correction in FMCW SAR, IEEE Conf. on Geoscience and Remote Sensing 2006, 403 (2006).
Slide17Remember this?
time
time
intermediate
frequency (IF)
frequency
Slide18Compensation algorithm
collected non-linear deramped data
transmitted non-linearties removal
range deskew
non-linearities compensation
linear deramped data
time
time
time
time
Slide19Implementation
deskew filter
“Peek”
“Meta”
“Burgos-Garcia”
“Peek”
“Meta”
“Burgos-Garcia”
phase error
Slide20
Sinusoidal phase error (low frequency)
Parameter
Value
Unit10GHz50MHz500μs15km0.1Rad4kHz
Parameter
Value
Unit
10
GHz
50
MHz
500
μ
s
15
km
0.1
Rad
4
kHz
Slide21Sinusoidal phase error (high frequency)
Parameter
Value
Unit10GHz50MHz500μs15km0.1Rad63kHz
Parameter
Value
Unit
10
GHz
50
MHz
500
μ
s
15
km
0.1
Rad
63
kHz
Slide22Cubic phase error
Parameter
ValueUnit10GHz50MHz500μs15km4 × 1011Hz/s2
ParameterValueUnit10GHz50MHz500μs15km4 × 1011Hz/s2
Slide23Quartic phase error
Parameter
ValueUnit10GHz50MHz500μs15km4 × 1011Hz/s2
ParameterValueUnit10GHz50MHz500μs15km4 × 1011Hz/s2
Slide24FCMW in optics
Swept-Source Optical Coherence TomographyCompensation algorithm not in the literature!
3
D image of a frog tadpole using a
Thorlabs
OCS1300SS OCT microscope system.
Slide25Conclusions
Phase quantization effects in digital chirp synthesizers have negligible effect on performance
Frequency sweep nonlinearity can be compensated by digital post-processing of the beat signal
Algorithm is also applicable to optics, but not mentioned in optics literature
Slide26Thank you for your attention!
Questions?
Slide27Extra slides
Slide28Effect on Doppler processing
Systematic phase errors have negligible effect on Doppler processing
Sinusoidal phase error, 3 cycles per sweep, amplitude 0.1 radian
Sinusoidal phase error, 3.1 cycles per sweep, amplitude 0.1 radian
Slide29Spectrum of the complex exponential
‘signal’
‘replicas’
Slide30
Spectrum of the analytic signal
‘signal replica’
‘main’ signal
‘image replica’
Slide31Observed beat signal
‘signal
×
image replica’
‘signal
×
signal replica’
‘image replica
×
image replica’
‘signal
×
signal’
Slide32Slide33Slide34Slide35Today's Top Docs
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