A Low-Power Radar Imaging System

Transcription

1 EM Group A Low-Power Radar Imaging System BY GREGORY L. CHARVAT

2 Introduction Through lossy dielectric slab imaging has been receiving much attention recently Current research is very diverse; using various types of frequencies, radar architectures, imaging algorithms, and antenna systems: MMW radiometers, CW doppler at 900 MHz and 2.4 GHz, pulsed doppler at 5.8 GHz, Noise, stepped frequency CW, UWB impulse at 10 GHz, UWB impulse between 1-3 GHz Most of this work has been focused on UWB impulse operating at in the 1-3 GHz band, with antennas placed directly up against the slab small spatially diverse antenna arrays, facilitate the use of various types of beamforming algorithms Using specialized beam forming algorithms to eliminate Snell s effects of the slab on the antenna array Reasons for this are solid, and have to do with range gating out the flash from the slab, and noise power budgeting Stepped frequency, FMCW, or CW doppler have been avoided because flash from slab limits system dynamic range

3 A different approach to through slab radar imaging In this dissertation a different approach was chosen: A modified FMCW radar architecture, a hardware range gate without the use of time domain electronic switches or pulsing of IF Preserves/increases receiver sensitivity, and eliminates flash from the slab Largest S-band array for through-slab imaging ever developed Provides high resolution data System operates at stand-off range Uses an airborne SAR imaging algorithm, producing near real-time imagery of what is behind that slab Objects as small as coke cans have been tracked in near real-time. Objects as small as 6 inch tall 3/8 inch diameter rods have been located behind a slab

4 Overview of Presentation Fundamentals of RADAR Synthetic Aperture Radar (SAR) imaging Through-slab Imaging Geometry Development of a slab and cylinder SAR imaging model Analysis of theoretical results Development of the high sensitivity range gated FMCW radar architecture S-band rail SAR through slab imaging system S-band rail SAR measured results, comparison to model X-band front end, comparison of imaging results to previous direct conversion FMCW radar S-band antenna array and near real-time SAR imaging, free-space and through slab Discussion and future work

5 Fundamentals of RAdio Direction And Range (RADAR) A transmitter sends out a pulse of radio frequency (RF) energy. Pulse of radio waves goes out to an unknown object (target) at some distance from the transmitter. Pulse hits target, and reflects off target (like shining a flashlight at something in the night, reflection occurs). Reflected pulse travels back towards the transmitter, where, placed next to that transmitter is a receiver. The reflected pulse is detected by the receiver. This pulse takes time to make a round trip. Pulse travels at the speed of light. So, we time this pulse like a stop watch, using our receiver as the start/stop and an oscilloscope as the time indicator

6 -THE A-SCOPE INDICATES RANGE TO TARGET ON AN OSCILLOSCOPE SCREEN -USES A DIRECTIONAL RADAR ANTENNA -THE OPERATOR MOVES THE ANTENNA MANUALLY TO GET BEARING -SCOPE INDICATES RANGE -IMAGE OF THE TARGET SCENE IS DRAWN BY HAND THE A-SCOPE INDICATING RANGE TO TARGET ON AN OSCILLOSCOPE SCREEN

7 -TARGET SCENE IS IMAGED BY ACQUIRING A-SCOPE DATA USING A ROTATING NARROW BEAMWIDTH ANTENNA -THIS A-SCOPE DATA IS DISPLAYED ON A POLAR INTENSITY PLOT A MODERN DAY PPI SCOPE RADAR: PLAN POSITION INDICATOR (PPI) AN IMAGE IS FORMED BY AUTOMATICALLY ROTATING A NARROW BEAMWIDTH ANTENNA

8 -SAR IN GENERAL: A RADAR SYSTEM TRAVERSES A KNOWN PATH ACQUIRING NUMEROUS RANGE PROFILES (A-SCOPE DATA) WHICH ARE THEN APPLIED TO AN IMAGE FORMATION ALGORITHM RESULTING IN A HIGH RESOLUTION RADAR IMAGE EQUIVALENT TO A VERY LARGE REAL APERTURE. -TYPICAL APPLICATION: AIRBORNE SAR RECONNAISSANCE IMAGING. -APPLICATION DISCUSSED IN THIS PRESENTATION: SMALL APERTURE SAR. PRODUCE HIGH RESOLUTION IMAGERY ON A SMALL SCALE USING A SMALL RADAR MOUNTED ON A 1D LINEAR RAIL: APPLY A SAR IMAGING ALGORITHM TO RANGE PROFILE DATA RESULTING IN HIGH RESOLUTION IMAGERY. AIRBORNE SAR: MOST COMMON APPLICATION (IMAGE FROM SANDIA NATIONAL LABORATORY, ALBUQUERQUE INTERNATIONAL AIRPORT AT KU BAND). SYNTHETIC APERTURE RADAR (SAR) IMAGING ACQUIRING RANGE PROFILES (A-SCOPE DATA) AT KNOWN RADAR LOCATIONS

9 SAR Imaging Small radar sensor is mounted on a mechanized linear rail Rail SAR data is acquired using a chirped radar system, which produces data in frequency domain Range profiles are acquired at evenly spaced increments down the length of the rail Wide beamwidth antenna is used, so that the radar acquires overlapping range profiles Resulting chirped data is saved as a 2D data matrix: s ( x n, ω(t) )

10 The Range Migration Algorithm (RMA) The RMA follows these four processing steps: 1. Cross range Fourier transform. 2. Matched filter. 3. Stolt interpolation. 4. Inverse Fourier transform into resulting image. This will be shown by example: assuming a chirped radar from 2-4 GHz, a single point scatter represented by the equation: s ( x n, ω(t) ) = a t e j2ω(t) (x n x t ) 2 +y 2 t where the return amplitude of the point scatterer is: a t = 1 and the position (in feet) of the point scatterer: (x t, y t ) = (0, 10)

11 The RMA cross range DFT of point scatterer results in: s ( k x, ω(t) ) k r = ω(t)/c a simple change of notation for convenience by substituting: results in: s(k x, k r ) multiply this by the matched filter: resulting in: s mf (k x, k r ) = e jr s k 2 r k 2 x s matched (k x, k r ) = s mf (k x, k r ) s ( k x, k r ) Stolt interpolate the down range data by the relation: k y = k 2 r k 2 x truncate a rectangular region full of data perform a 2D IDFT on the truncated data resulting in the image domain: S(X, Y )

12 STEP-BY-STEP RMA SHOWING THE SIGNAL HISTORY OF EACH STEP

13 Through-Slab Imaging Geometry Rail SAR is located at some standoff distance form the slab Slab has lossy dielectric properties Some target is located behind the slab

14 Through-Slab Imaging Geometry PERMITTIVITY OF THE SLAB ɛ r = 5 CONDUCTIVITY OF THE SLAB:

15 2D PEC cylinder model E s = ẑe o n=0 ( j) n J n (k o a) ε n H(2) n (k o ρ) cos nφ (k o a) H (2) n ε n = { 1 for n = 0 2 for n 0 T M Z INCIDENT PLANE WAVE SIMULATED RAIL SAR IMAGE OF A 6 INCH DIAMETER CYLINDER

16 Lossy dielectric slab model using wave matrices φ i (n) = cos 1 [ d 3 ( L 2 + x(n)) 2 + (r1 (n) + r 2 (n)) 2 ] r 1 (n) = d 1 cos φ i (n) r 3 (n) = d 3 d 1 d cos φ i (n) c 1 (n) = E o e jk or 1 (n) E s (n) = b 1 (n)e jk or 1 (n) Z(n) = (ɛr + cos φ i (n) σ jωɛ o ) sin 2 φ i (n)

17 Lossy dielectric slab model using wave matrices [ c1 b 1 ] = 1 T 1 T 2 [ e jθ i R 1 e jθ i R 1 e jθ i e jθ i ] [ 1 R2 R 2 1 ] [ c3 b 3 ] R 1 (n) = Z(n) 1 Z(n) + 1 T 1 (n) = 1 + R 1 (n) R 2 (n) = 1 Z(n) Z(n) + 1 T 2 (n) = 1 + R 2 (n) c 3 (n) = c 1 (n)t 1 (n)t 2 (n) e jθ(n) + R 1 (n)r 2 (n)e jθ(n) + Γ ( R 2 (n)e jθ(n) + R 1 (n)e jθ(n))

18 Lossy dielectric slab model using wave matrices b 1 (n) = [ c 3 (n) R 1 (n)e jθ(n) + R 2 (n)e jθ(n) T 1 (n)t 2 (n) (R +Γ 1 (n)r 2 (n)e jθ(n) + e jθ(n))] θ(n) = k o d (ɛr + σ jωɛ o ) sin 2 φ i (n) b 3 (n) = Γc 3 (n) Γ = REFLECTION REFLECTION COEFFICIENT OF RADAR TARGET

19 Lossy dielectric slab model using wave matrices Γ = 0 IN THIS CASE, WILL BE CHANGED TO THE CYLINDER SCATTERING SOLUTION LATER SLAB 20 FEET DOWNRANGE

20 Lossy dielectric slab and PEC cylinder model SUBSTITUTE A PHASE SHIFTED SCATTERED CYLINDER SOLUTION IN TO THE PREVIOUS WAVE MATRIX RESULT: Γ(n) = e j2k or 3 (n) ( j) i J i (k o a) ε i H(2) (k i o ρ) cos nφ (k o a) i=0 H (2) i ε n = { 1 for n = 0 2 for n 0

21 Lossy dielectric slab and PEC cylinder model WALL AT 20 FT, 6 IN DIAMETER CYLINDER AT 30 FT, CENTERED ON RAIL

22 Lossy dielectric slab and PEC cylinder model s targets ( xn, ω(t) ) = s scene ( xn, ω(t) ) s back ( xn, ω(t) ) s back ( xn, ω(t) ) = dielectric slab model s scene ( xn, ω(t) ) = dielectric slab and cylinder model SAR IMAGE OF THEORETICAL CYLINDER BEHIND A LOSSY SLAB USING COHERENT BACKGROUND SUBTRACTION:

23 THEORETICAL RANGE PROFILES TAKEN AT NORMAL INCIDENCE OF A 6 INCH DIAMETER CYLINDER BEHIND A 4 INCH THICK SLAB SLAB 20 FT DOWNRANGE CYLINDER 30 FT DOWNRANGE LOSSY SLAB NO SLAB GEOMETRY LOSSLESS SLAB ANALYSIS OF THEORETICAL RESULTS RANGE PROFILES

24 FREE-SPACE BEHIND 4 INCH LOSSY SLAB ANALYSIS OF THEORETICAL RESULTS 6 INCH DIAMETER CYLINDER IN FREE SPACE AND BEHIND A 4 INCH THICK LOSSY SLAB

25 FREE-SPACE BEHIND 4 INCH LOSSLESS SLAB ANALYSIS OF THEORETICAL RESULTS 6 INCH DIAMETER CYLINDER IN FREE SPACE AND BEHIND A 4 INCH THICK LOSSLESS SLAB

26 FREE-SPACE BEHIND 12 INCH LOSSY SLAB ANALYSIS OF THEORETICAL RESULTS 6 INCH DIAMETER CYLINDER IN FREE SPACE AND BEHIND A 12 INCH THICK LOSSY SLAB

27 FREE-SPACE BEHIND 12 INCH LOSSLESS SLAB ANALYSIS OF THEORETICAL RESULTS 6 INCH DIAMETER CYLINDER IN FREE SPACE AND BEHIND A 12 INCH THICK LOSSLESS SLAB

28 Analysis of theoretical results: offset imagery

29 FREE-SPACE BEHIND 4 INCH LOSSY SLAB ANALYSIS OF THEORETICAL RESULTS OFFSET 6 INCH DIAMETER CYLINDER IN FREE SPACE AND BEHIND A 4 INCH THICK LOSSY SLAB

30 FREE-SPACE BEHIND 4 INCH LOSSLESS SLAB ANALYSIS OF THEORETICAL RESULTS OFFSET 6 INCH DIAMETER CYLINDER IN FREE SPACE AND BEHIND A 4 INCH THICK LOSSLESS SLAB

31 FREE-SPACE BEHIND 12 INCH LOSSY SLAB ANALYSIS OF THEORETICAL RESULTS OFFSET 6 INCH DIAMETER CYLINDER IN FREE SPACE AND BEHIND A 12 INCH THICK LOSSY SLAB

32 FREE-SPACE BEHIND 12 INCH LOSSLESS SLAB ANALYSIS OF THEORETICAL RESULTS OFFSET 6 INCH DIAMETER CYLINDER IN FREE SPACE AND BEHIND A 4 INCH THICK LOSSLESS SLAB

33 Analysis of theoretical results: radar design guidelines range gate to attenuate or eliminate flash off of the slab sensitive receiver, for overcoming slab attenuation RMA has shown in simulation to be effective when the radar is placed at a stand-off range, no need to try to account for the slab in the algorithm

34 Range gating and receiver sensitivity MDS dbm = log 10 B n + NF ASSUME: NF = 3.3 db B n = 1/T = 25 MHz B n = 1/T = 50 MHz SENSITIVITY: dbm THEORETICAL SENSITIVITY: dbm THEORETICAL

35 High sensitivity range gated FMCW radar architecture BF O(t) = cos ( 2πf BF O t ) LO(t) = cos ( 2π( c r t)t ) T X(t) = LO(t) BF O(t) T X(t) = cos ( 2π( c r t)t + 2πf BF O t ) + cos ( 2π( c r t)t 2πf BF O t ) RX(t) = cos ( 2π( c r t)(t t delay ) + 2πf BF O (t t delay ) ) + cos ( 2π( c r t)(t t delay ) 2πf BF O (t t delay ) )

36 High sensitivity range gated FMCW radar architecture IF (t) = LO(t) RX(t) IF (t) = cos ( 2π( c r t)(t t delay ) + 2πf BF O (t t delay ) + 2π( c r t)t ) + cos ( 2π( c r t)(t t delay ) + 2πf BF O (t t delay ) 2π( c r t)t ) + cos ( 2π( c r t)(t t delay ) 2πf BF O (t t delay ) + 2π( c r t)t ) + cos ( 2π( c r t)(t t delay ) 2πf BF O (t t delay ) 2π( c r t)t ) IF PORT ON MXR2 CAN NOT OUTPUT MICROWAVE FREQUENCIES, SO THE HIGH FREQUENCY TERMS DROP OUT: IF (t) = cos ( 2π( c r t)(t t delay ) + 2πf BF O (t t delay ) 2π( c r t)t ) + cos ( 2π( c r t)(t t delay ) 2πf BF O (t t delay ) 2π( c r t)t )

37 High sensitivity range gated FMCW radar architecture [ IF (t) = cos [ + cos ] 2π( c r t)t delay + 2πf BF O (t t delay ) ] 2π( c r t)t delay 2πf BF O (t t delay ) AMP1 IS AN HF AMPLIFIER, SO IT DOES NOT PASS DC, THUS: IF (t) = cos ( 2π(f BF O c r t delay )t ) + cos ( 2π(f BF O + c r t delay )t )

38 High sensitivity range gated FMCW radar architecture THE IF IS FED THROUGH FL1, WHICH IS A HI-Q COMMUNICATIONS FILTER (SUCH AS A CRYSTAL FILTER). OSC1 IS SET TO A FREQUENCY SUCH THAT: f BF O BW 2 + f c WHICH CAUSES THE OUTPUT OF FL1 TO FILTER OUT ONE OF THE SIDEBANDS FROM THE IF, RESULTING IN: F IL(t) = { ( cos 2π(fBF O c r t delay )t ) if BW 2 + f c < f BF O c r t delay < BW 2 + f c 0 for all other values SINCE THIS IS AN FMCW RADAR, AND RANGE TO TARGET IS IN THE FORM OF BEAT FREQUENCY TONES, FL1 EFFECTIVELY BECOMES A HARDWARE RANGE GATE

39 High sensitivity range gated FMCW radar architecture THE OUTPUT OF FL1 IS THEN CONVERTED DOWN TO BASE BAND VIA MXR3 AND OSC1: V ideo(t) = BF O(t) F IL(t) VIDEO AMP1 IS AN ACTIVE LPF, SO THE HIGH FREQUENCY TERMS DROP OUT, LEAVING A HIGH-Q BAND LIMITED BASE-BAND VIDEO. BAND LIMITING IN FMCW RADAR RESULTS IN RANGE GATING (ONLY LETTING IN A CERTAIN BANDWIDTH OF BEAT TONES): V ideo(t) = { ( cos 2πcr t delay t ) if BW 2 + f c f BF O < c r t delay < BW 2 + f c f BF O 0 for all other values FRONT END IS FAIRLY ROBUST, LEAVING THE IF TO PREVENT DIGITIZER SATURATION. THIS IS A VERY EFFECTIVE RANGE GATE, AND WILL BE SHOWN IN THE RESULTING IMAGERY. RANGE GATE IS ADJUSTABLE, SIMPLY INCREASE THE FREQUENCY OF OSC1 TO PUSH RANGE GATE FURTHER DOWN RANGE. CHANGING THE BANDWIDTH OF FL1 CHANGES THE LENGTH OF RANGE GATE

40 High sensitivity range gated FMCW radar architecture FURTHERMORE: THE NARROW BAND HI-Q IF FILTER FL1 REDUCES THE EFFECTIVE NOISE BANDWIDTH OF THE RECEIVER, GREATLY INCREASING SENSITIVITY. A TYPICAL CRYSTAL FILTER HAS THE FOLLOWING SPECS: f c = 10.7 MHz BW = 7.5 KHz WHICH WOULD WOULD PROVIDE A THEORETICAL RECEIVER SENSITIVITY OF dbm FOR A CHIRP RATE OF c r = Hz/Sec THIS WOULD PROVIDE AN EFFECTIVE RANGE GATE OF APPROXIMATELY ns

41 S-Band Rail SAR A B C D E A B C D E 1D Linear Rail FL11 1 PC 1 1 IF Input FL6 AMP3 Out to ATTN2 1 A 1 FL12 1 B RS232 1 SEL1 SEL2 A M B IF input from RX front end 1 C ATTN1 D PCI Bus 2 2 PCI6014 NIDAQ Card Motor Controller Beat Frequency Oscillator BFO Output 2 E Xtal Filter Mux2 FL C Input from ATTN2 Out to ATTN3 Output to radar IF A Input from radar IF B 1 2 ATTN2 Video Input to Digitizer AI0 pin 1 FL7 3 F 3 CLPR1 AMP5 FL10 MXR CTR0 pin FL8 1 E LO Output to Power Splitter Yig 1 N Ramp Oscillator Generator 4 4 SEL3 Xtal Filter Mux1 FL9 SEL4 4 3 VideoAmp1 2 BFO Input D 4 Output to radar IF C 2 Input from BFO CLPR1 D BFO output to transmitter front end I 3 3 ATTN3 A B C D E Video Output 4 Video Output 4 G F A B C D A B C D E A B C D E A B C D E 1 1 A B C D E L 2 LO Output to RX Front End DELAY1 ANT FL5 FL4 LNA1 FL3 RX in 1 1 K K 2 Receive Ant Connection 2 to Rx in ANT1 2 MXR1 AMP1 FL2 TX Out 2 2 CLPR2 1 H H 1 MXR2 FL1 AMP2 To TX Out RF Input from Yig Oscillator LO Output to TX Front End SPLTR1 N 1 1-3dB J LO in IF Out db Out 3 BFO in LO in 3 I J 2 L M A B C D E 4 4 A B C D E A B C D E

42 S-Band Rail SAR CAL PROCEDURE: ( ) ( ) s pole ω(t) scalback ω(t) ( ) ( ) ( ) s cal ω(t) = spole ω(t) scalback ω(t) ( ) s caltheory ω(t) = e j2k r R pole ( ) ( ) s caltheory ω(t) s calfactor ω(t) = ( ) s cal ω(t)

43 S-BAND RAIL SAR RADAR IN ACTION

44 FREE SPACE IMAGERY, TRANSMIT POWER APPROX. 10 dbm 6 INCH SIMULATED CYLINDER 12 INCH MEASURED CYLINDER 6 INCH MEASURED CYLINDER M RADIUS SPHERE 6 INCH TALL 3/8 INCH DIAMETER RODS FREE-SPACE S-BAND IMAGERY CYLINDER IMAGERY: THEORETICAL COMPARED TO MEASURED, AND OTHERS

45 6 INCH SIMULATED CYLINDER M RADIUS SPHERE AT 100 pico-watts RODS AT 10 nano-watts 6 INCH MEASURED CYLINDER, 100 pico-watts RODS AT 100 pico-watts RODS AT 5 pico-watts FREE-SPACE S-BAND IMAGERY LOW POWER CYLINDER IMAGERY: THEORETICAL COMPARED TO MEASURED, AND OTHERS

46 S-BAND RAIL SAR THROUGH SLAB IMAGING EXPERIMENTAL SETUP

47 simulated 6 in cylinder simulated 12 in cylinder m radius sphere behind slab measured 6 in cylinder measured 12 in cylinder 12 oz soda cans behind slab S-BAND RAIL SAR THROUGH SLAB IMAGERY MEASURED COMPARED TO THEORETICAL

48 6 INCH CYLINDER, ZOOMED OUT THREE 6 INCH TALL, 3/8 INCH RODS S-BAND RAIL SAR: THROUGH SLAB IMAGERY VARIOUS TARGETS

49 X-Band front end A B C D E Attenuator ATTN5 Or Thru O O P P O P BFO In MXR4 AMP6 CIRC3 2 2 CLPR3 I ANT3 CLPR4 ATTN4 ATTN6 CIRC db Out CIRC2 DELAY2 3 3 ANT4 FL14 AMP7 MXR5 LNA2 1 Yig Oscillator LO Input 2 IF Out 4 N 4 M A B C D E GHz, plugs directly into existing IF

50 X-BAND FRONT END PLUGS DIRECTLY INTO EXISTING IF, MOUNTS ON EXISTING RAIL SYSTEM

51 pushpins 10 nano-watts pushpins 10 milli-watts F14 model pushpins 100 nano-watts pushpins on a direct conversion system F14 model on an direct conversion system X-BAND IMAGERY COMPARISON FULL POWER AND LOW POWER IMAGERY COMPARED TO DIRECT CONVERSION SYSTEM

52 VERY LITTLE DOWNRANGE CLUTTER NOTICEABLE DOWNRANGE CLUTTER X-BAND RAIL SAR COMPARISON RANGE GATE IN OPERATION

53 S-Band Antenna Array Receive Elements 2.00 ANT14 ANT15 ANT16 ANT17 ANT18 ANT19 ANT20 ANT21 44 Evenly Spaced Phase Centers Evenly Spaced Transmit Elements 5.75 ANT1 ANT2 ANT3 ANT4 ANT5 ANT6 ANT7 ANT8 ANT9 ANT10 ANT11 ANT12 ANT Copper 0.14 inch Diameter Mounting Holes Antenna Feed FR4 Dielectric Copper 22.00

54 A B C D E S-Band Antenna Array 1 PC 1 32 Bit Hex Code Out to Array Switch Matrix PCI Bus 2 2 PCI6014 NIDAQ Card PCI Bus PCI-6509 NIDAQ Card Beat Frequency Oscillator 32 Lines of DIO BFO Output 2 3 E Video Input to Digitizer AI0 pin 1 3 F 3 CTR0 pin LO Output to Power Splitter Yig 1 N Ramp Oscillator Generator 4 4 A B C D E A A B B C C D D E E ANT21 ANT20 ANT19 ANT18 ANT17 ANT16 ANT15 ANT ANT1 ANT13 ANT12 ANT11 ANT10 ANT9 ANT8 ANT7 ANT6 ANT5 ANT4 ANT3 ANT2 1 1 LNA1 LNA2 SW7 LNA3 LNA RFout3 RFout2 2 RFout3 RFout2 2 RFout4 RFout1 RFout4 RFout C5 C5 P2,4 P2,0 Mini-Circuits Mini-Circuits 6 2 P2,1 ZX60- C3 P2,5 ZX60- C3 6013E-S E-S+ 3 C4 P2,2 C4 P2,6 8 4 RFin C6 P2,3 RFin C6 P2,7 1 1 LNA5 LNA6 SW6 LNA7 LNA8 SW4 SW3 SW RFout3 RFout2 RFout3 RFout2 RFout3 RFout2 RFout4 RFout1 RFout4 RFout1 RFout4 RFout P1,4 5 P1,0 9 C5 C5 C5 P0,4 Mini-Circuits Mini-Circuits Mini-Circuits 2 2 P1,5 6 C3 P1,1 1 ZX60- C3 ZX60- ZX60- C3 P0, E-S+ 3 P1,6 6013E-S+ 7 C4 C4 P1,2 6013E-S+ 2 C4 P0,6 4 8 RFin C6 P1,7 RFin C6 P1,3 3 RFin C6 P0, K 4 A B RF2 Com SW5 Mini-Circuits ZSDR-230 C TTL RF1 9 P3,0 D Out to S-band Receiver Front End RX in Port E RFout3 RFout2 7 RFin C6 P0,3 CLPR1 Input from S-band 1 Front End TX Out 4 1 H 4 A B SW1 RFout4 5 RFout1 2 C5 Mini-Circuits ZX60- C3 6013E-S+ C4 C P0,0 P0,1 P0,2 D -10 db Out 2 E

55 THE S-BAND ANTENNA ARRAY HIGH SPEED ARRAY, CAPABLE OF DISPLAYING 1 SAR IMAGE EVERY 1.9 SECONDS

56 S-Band Antenna Array ARRAY CAL PROCEDURE: ( ) ( ) s pole xn, ω(t) s calback xn, ω(t) ( ) ( ) ( ) s cal xn, ω(t) = s pole xn, ω(t) s calback xn, ω(t) ( ) s caltheory xn, ω(t) = e j2k rr pole R pole = x 2 n + ( ) 2 ( ) ( ) s calfactor xn, ω(t) = s caltheory xn, ω(t) ( ) s cal xn, ω(t)

57 simulated 6 inch cylinder simulated 12 inch cylinder measured 6 inch cylinder measured 12 inch cylinder S-BAND ARRAY FREE-SPACE IMAGERY COMPARISON OF MEASURED TO THEORETICAL

58 6 inch tall rods 2 inch tall nails 3 inch tall nails 1.25 inch tall nails S-BAND ARRAY FREE-SPACE IMAGERY IMAGERY OF SMALL OBJECTS F14 model, 1:38 scale

59 simulated 6 inch cylinder simulated 12 inch cylinder measured 6 inch cylinder measured 12 inch cylinder S-BAND ARRAY THROUGH-SLAB IMAGERY COMPARISON OF MEASURED TO THEORETICAL

60 S-Band Array: Near Real-Time Imagery of a 6 Inch Cylinder in Free-Space

61 S-Band Array: Near Real-Time Imagery of a 12 oz Soda Can in Free-Space

62 S-Band Array: Near Real-Time Imagery of a 6 inch Diameter Cylinder Behind a Lossy Slab

63 S-Band Array: Near Real-Time Imagery of a 12 oz Soda Can Behind a Lossy Slab

64 Discussion and Future Work In this dissertation a different approach was chosen: A modified FMCW radar architecture, a hardware range gate without the use of time domain electronic switches or pulsing of IF Largest S-band array for through-slab imaging ever developed System operates at stand-off range Uses an airborne SAR imaging algorithm, producing near real-time imagery of what is behind that slab Objects as small as coke cans have been tracked in near real-time. Future work includes: Periodic structure modeling, with multiple layers and air gaps Trying the modified FMCW design on other applications Increasing array speed, 5-10 frames per second this is done by upgrades: data acquisition antenna array IF, increase of bandwidth Faster YIG, or possibly switch to DDS