Co-registered Vibrometry & Imaging: A Combined Synthetic-Aperture Radar & Fractional-Fourier Transform Approach University of New Mexico FY2008 University Project. May 2009 NCMR Technology Review. PI & Presenter: Majeed Hayat. Project Information.
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
Co-registered Vibrometry & Imaging: A Combined Synthetic-Aperture Radar & Fractional-Fourier Transform ApproachUniversity of New MexicoFY2008University Project
May 2009NCMR Technology Review
PI & Presenter: Majeed Hayat
UNM Faculty:
Prof. Majeed Hayat (ECE, 15%)
Prof. Balu Santhanam (ECE,15%)
Prof. Walter Gerstle (CIVIL Engr,15%)
Sandia collaborators: Tom Atwood and Toby Townsend (10%)
Graduate students:
Qi Wang (50%)
Srikanth Narravula (50%)
Tong Xia (50)%
Tom Baltis (25)%
Post Doc: Matt Pepin (DOE funded)
The returned signal after this step is:
A/D
LPF
Quadrature term
Step 3: Inverse Fourier transform in each dimension creates an image
j
900
Resolution is limited by the bandwidth of the sent chirped microwave pulse and the size of the synthetic aperture
LPF
In-phase term
Background: 2-D SAR process
Step 1: Deramp quadrature demodulation removes the u-chirp
Step 2: Aperture compression and range compensation remove v-chirp
Previous Work: Non-stationary case
Analysis of Discrete Vibrating Points
The discrete fractional Fourier transform (DFRFT) has the capability to concentrate linear chirps in few coefficients
MA-CDFRFT
Return echo
quadratic demodulation
& low-pass filtering (A/D)
MA-CDFRFT
Read out the positions of peaks
Compute the central frequencies,
and chirp rates
Compute positions, and velocities
Co-registration with
traditional SAR imagery
Vibrating Targets
Est. position: FRFT/FT (actual)
Est. reflectivity (actual)
Est. velocity (actual)
Target1
-39.4/-28.5 (-37.5)
0.78 (0.9)
945 (1000)
Target2
1.27/6.5 (0)
0.42 (0.5)
472 (500)
Target3
37.5/37.5 (37.5)
0.48 (0.5)
0 (0)
New Work: 2-D Non-stationary case
Model for Discrete Vibrating Points
Cross-Range
Vibrating Target
ϴ
Range
0
Changing aperture splits vibration into two sin waves
Complex amplitudes estimate vibration direction ᶿ
Fit of V(t) cos envelope also estimates direction ᶿ
Multi-Look
How to calculate at multiple look angles
By taking two looks with different squint angles, the average energy ratio these two looks is
The vibration direction can be resolved this way using multiple look angles and fitting the expected change in energy over the different squint angles to resolve the vibration direction
Results:
Return echo
quadratic demodulation
& low-pass filtering (A/D)
MA-CDFRFT
Read out the positions of peaks
Compute the frequencies, chirp
rates, positions, and velocities
Estimate vibration frequencies
and directions
Form SAR image and overlay
vibration information
Multiple looks to measure
and refine vibration direction
(¼ 0.8-1).
Monica Madrid (Ph.D. student)and Jamesina Simpson (Assistant Professor)
Electrical and Computer Engineering Department, University of New Mexico
Leveraging DOE Funding
(~ 2,000 FDTD-related publications/year as of 2006, 27 commercial/proprietary FDTD software vendors)
[1] A. Buerkle, K. Sarabandi, “Analysis of acousto-electromagnetic wave interaction using sheet boundary conditions and the finite-difference time-domain method,” IEEE TAP, 55(7), 2007.
[2] A. Buerkle, K. Sarabandi, “Analysis of acousto-electromagnetic wave interaction using the finite-difference time-domain method,” IEEE TAP, 56(8), 2008.
frictionless tube (A, L)
k1
k2
m1
m2
gas (B, ρ, A)
vibrating mass
x
L
Modeling Vibrations and Physical Structures- Tests simulate theoretical model
- A speaker simulates the vibrating mass m1
- An aluminum disk and two steel beams simulate the spring- mass system response
- Matlab code controls the vibration frequency generating a sinusoidal excitation with well-controlled frequencies
Acceleration Amplitude (m/s2)
Forcing Frequencies (Hz)
Structural Acoustics Experiment
Pressure transducer
measures the pressure of a sound excitation.
A steel box will simulate a room
The speaker (inside the box) generates harmonic forces causing the box to vibrate. The transducer will measure the pressure of the sound, an accelerometer attached to the box will measure the acceleration of the walls
Summary of Effort against Objectives
Summary of Effort against Objectives