Development of SARbased UWB SeeThroughWall Radar Yunqiang Yang

Development of SAR-based UWB See-Through-Wall Radar Yunqiang Yang Song Lin Alex Zhang Department of Electrical and Computer Engineering University of Tennessee, Knoxville

Outline q q q Background Information Electromagnetic/Antenna Aspects UWB Components Design/DAQ Aspects Imaging Processing Aspects See-Thru-Wall Experiment Future Work

See-Thru-Wall Goals q provide dismounted and remote users with the capability to detect, locate and “see” personnel with concealed weapons/explosives behind obstructions from a standoff distance Tactical Operation q Increased force protection and survivability of soldier in during operations, combat search and rescue, and hostage recovery operations. q Provide initial information on building layout and enemy personnel locations Search Operation

Why Microwave UWB Radar? ¡ ¡ ¡ ¡ ¡ Optical Quality Images at Microwave Frequencies Active System – Day and Night Imaging Adverse Weather Long Stand-off Ability (fine resolution imaging independent of range) Both Broad and Spot Coverage Coherent Imaging Bi-static and Multi-static Configurations (transmitter separate from receiver provides stealth) Penetration of Materials and Particulates (frequency dependent) Detection of Ground Moving Target

Microwave Imaging ¡ Good scene recognition ¡Advantages l. Day/night, all weather l. Penetration (e. g. buildings) ¡ Poor object recognition ¡Disadvantages l. Non-literal imagery

Imaging Fundamentals ¡ Optical Images l. Angle vs. ¡ Microwave Images l. Range vs. Angle Range Angle Crossrang e

Optical Quality at Radar Frequency

Interior Image of Mannequin Photograph Mannequin Only Mannequin Behind Wall

Resolution vs. Frequency

What controls the resolution of these systems? q Downrange resolution is solely based on bandwidth in conventional RADAR (i. e. CW, FMCW) q UWB range resolution is based on the pulse width q meanwhile cross range timing resolution in a single antenna setup is a function of the antenna beamwidth (θ), where R is range q Multiple element or SAR system cross range resolution is a function of their effective aperture (L) and wavelength (λ)

See-Through Wall Radar Prototype RF Transceiver DAC/Control Image Processing Wall Radar Rage: 20 m Radar PRF: 5 MHz Pulse Width: 0. 5 ns Center Frequency: 10 GHz Hand-held portable/Ground Vehicle-Based System

Electromagnetic/Antenna Aspects of the System q Wave-propagation through the wall, and characterization of various Walls: Dielectric Constant, conductivity, attenuation Loss q Efficient EM modeling of scattering from objects inside a room q Wall parameter effects q Role of polarization in image enhancement q Low-profile printed antennas/arrays for the system

UWB Transceiver Design and Data Acquisition Aspects q UWB components design: power amplifier, low noise amplifier, power divider, SP 16 T switch, mixer, pulse generator. q Sampling of UWB signal: equivalent time sampling technique

Image Processing Issues q Improve two-dimensional imaging resolution q Reduce antenna size q Mitigate the effects of the wall q Imaging quality depends on: Bandwidth, Baseline range, Wall distortions, Wall uniformity, Wall absorption, Positioning errors

RF Attenuation in Different Wall Materials v N. C. Currie, D. D. Ferris, and al, “New law enforcement application of millimeter wave radar”, SPIE Vol. 3066, pp 2 -10, 1997

Propagation Modeling q Frequency domain measurement q VNA for insertion transfer function. Advanced Design System (ADS) models

UWB Antenna Consideration o Wide band-width o Good impedance match o Minimum waveform ringing o Minimum pulse dispersion o Small size o Low cost

Types of UWB Antennas q Tapered slot: q TEM horn: q Bow-tie: Two dimensional microstrip Most commonly used Relatively high input impedance Requires a matching balun q Resister loaded dipole Low gain and low efficiency q Discone: High performance, Difficult to manufacture 3 -D structure q Bicone: High performance, Difficult to manufacture 3 -D structure q Log-periodic: Dispersive q Spiral: Dispersive

Antipodal Vivaldi Antenna q Developed by Gibson in 1979 q Wide band performance q Fabricated on dielectric substrates q Great potential to low cost and weight q Small size Tapered flares on different layers Dimension: 2. 15 cm x 5. 52 cm Substrate: Roger 4003 C, 10 mil-thick

Vivaldi Sub-array q q 16 Element sub-array Dim: 18 cm x 40 cm Wilkinson power divider Element spacing: 2. 15 cm 7. 5 GHz – 12. 5 GHz

Pattern: Simulation Versus Measurement @ 10 GHz Measurement: 13 d. B Gain, 4° Beamwidth Simulation: 15 d. B Gain, 3° Beamwidth

Measured Radiation Pattern E Plane H Plane

Transmitter/Receiver Structure 1 2 3 4 16 . . . . Switch

System Block Diagram

UWB See-Through-Wall Imaging Radar Simulation (in ADS)

UWB_Sub. Harmonic_Mixer ¡ ¡ Why Sub. Harmonic_Mixer? 1. Easy to implement in a PCB technology using coplanar lines. 2. LO frequency can be lowered 3. Provides very high isolation between the RF port , LO port and IF port. Specially the RF and LO have more than 40 d. B isolation in the 8 -12 GHz frequency range.

UWB_Sub. Harmonic_Mixer Simulation

Harmonic Mixer Frequency Range, RF: 8 - 12 GHz Frequency Range, LO: 8 - 12 GHz Frequency Range, IF: 0. 1 - 2. 5 GHz Conversion loss <13 d. B RF to LO isolation > 45 d. B RF to IF isolation > 45 d. B LO to IF isolation > 45 d. B IP 3 (Input) 14 d. Bm LO input power : 7 d. Bm

Parallel-Feedback Dielectric-Resonator Oscillator ¡ ¡ Why DRO? DROs are attractive microwave sources because of their high Q, low phase noise, good output power and their high stability versus temperature. They represent a good compromise of costs, size, and performance compared to alternative signal sources such as cavity oscillators, microstrip oscillators or multiplied crystal oscillators. The parallel-feedback with BJT DRO can achieve the highest performance in some frequency range.

DRO Simulation

DRO Oscillator Operating Frequency Range: 9. 9 -10. 1 GHz Phase noise: -95 d. Bc @ 10 KHz -120 d. Bc @ 1 MHz Output power: Temperature stability: +/- 1 MHz 7 d. Bm Harmonics: -40 d. Bc min Spurious: - 80 d. Bc min

Narrow Band Low Noise Amplifier Freq range: 9. 9 -10. 1 GHz Gain: >11. 5 d. B Gain Flatness: +/- 0. 5 d. B Noise figure: 1. 2 d. B P 1 d. B: 16 d. Bm IP 3 out: 24 d. Bm

UWB Power Amplifier Freq range: 2 -18 GHz Gain: >12 d. B Gain Flatness: +/- 0. 5 d. B Psat: 26 d. Bm P 1 d. B: 25 d. Bm IP 3 out: 27 d. Bm

UWB System Topology

SP 16 T With Antenna Array

SP 16 T Using SPDT in Series Hittite SPDT (SMT) DC - 14. 0 GHz

SP 4 T Measurements Frequency Range: 7 to 13 GHz IL: - 4 d. B with flatness: +/-1 d. B Isolation : <- 40 d. B

Test Fixture Design Top Side Bottom Side

RF Layout Frequency Range: 9 to 13 GHz IL: - 8 d. B with flatness: +/-2 d. B Isolation : <-45 d. B Switching Time: < 50 ns

Driver Logic

Pulse Generator

Simulation & Measurement Results of Pulse Generator

Pulse Width: Adjustable 400 ps - 1 ns Rise Time: 50 ps Fall Time: 50 ps Bandwidth: up to 2 GHz

Solutions for DAQ System Oscilloscope: for experimental system PCI Digitizer: for ground vehicle based system UWB Sampler: for handheld portable model ADC Chip: for handheld portable model

See-Trough-Wall Radar Experiment

Measurements without Wall

Measurements with Drywall

Targets Location 20 cm X 24 cm 12 cm X 24 cm

Top View -- Hallway Geometry and UWB Radar Setup Concrete Wall 9. 30 m Radar Position Side Wall 2. 85 m Door 1 Door 2 1. 02 m Metal-covered Door Targets

Non-through-Wall Image Side Wall Door 2 Gas Tank Door 1 Cylindrical Target

Image of Water Cup ----- Position 1 Side Wall Door 2 Door 1 Water Cup 10 cm X 12 cm

Image of Water Cup ----- Position 2 Side Wall Door 2 Door 1 Water Cup 10 cm X 12 cm

CFDTD Simulation

Side View z x 120 cm y Free space gap 6 cm CFDTD Simulation Parameters Mesh Size Nx = 330, Ny = 430, Nz = 330 Cell Size dx = dy = dz = 1. 0 cm Time resolution dt = 19. 15 ps Local point source Drywall boards thickness = 2 cm Epson=2. 4, Sigma=0. 003 Concrete @ f = 2 GHz Epson=7. 0, Sigma=0. 005 240 cm

Current simulation Problems At f=2 GHz l=15 cm requiring step size of 1 cm. To increase Mesh Resolution, we needed higher frequency Operation i. e. more mesh points. Currently with a 4 -processor server it requires 5 hours @ 2 GHz -at 4 GHz, it is anticipated 5 x 23 hours !!! -at 8 GHz it will be 5 x 26 hours.

Top View Z = 120 cm z 16 y 30 cm conducting cubic box at (x=70 cm, y=195 cm, z=120 cm) x 250 cm 16 -Element receiver array 12 cm 55 cm Local point source 30 cm conducting cubic box at (x=145 cm, y=355 cm, z=120 cm) 1 350 cm

Radiated UWB Pulse Baseband signal is Gaussian with 0. 8 GHz bandwidth Carrier is 2 GHz Sine Wave.

Recorded Response at 16 Receivers Direct Transmission from source to receivers Reflection from 1 st Target Reflection from 2 nd Target (m) Without Gating

Direct Transmission from Source to Receivers 12 cm: Receiver Spacing (m) Direct Coupling Due to the Isotropic Point Source

Reflection from Targets Reflection from 1 st Target Gating Direct Transmission Reflection from 2 nd Target Reflection from far wall (m) After Gating of receivers response due to direct coupling

Extracted I/Q Channel I Channel 1 st Target Q Channel (m) 2 nd Target Far wall

Image Recovered from Simulation Data 30 cm conducting cubic box at (x=145 cm, y=350 cm, z=120 cm) 16 30 cm conducting cubic box at (x=70 cm, y=195 cm, z=120 cm)

Future Work Digital Signal Processing

Comparison of 2 -D Spectral Estimation Techniques for Imaging Synthetic Point Scatterers Image-Domain TCR is 13 d. B True Points PML Estimates Taylor – 35 d. B n = 5 Sinc MUSIC EV RRMVM TKARLP (2 quad) SVA ASR TKARLP (all pred) 2 Super SVA, Taylor 2 Super SVA, SVA MVM ARLP (2 quad) Pisarenko Relative d. B scale Note: S. R. De. Graaf, “SAR Imaging…, ” IEEE T-IP, Vol. 7, No. 5, 1998 – 60 d. B