UWB RADAR IMAGING SYSTEM WITH TWO- ELEMENT RECEIVING ARRAY ANTENNA

Transcription

1 UWB RADAR IMAGING SYSTEM WITH TWO- ELEMENT RECEIVING ARRAY ANTENNA A.O. Boryssenko 1) & D.H. Schaubert 2) University of Massachusetts Amherst MA USA 1) 2) In Cooperation with Diascarb & Ratio (both in Kiev, Ukraine) 1

2 Highlights UWB Radar Trough-Wall Vision Advances in Hardware and Antennas Matlab for Radar Control and Processing Radar Scene Imaging in 1D & 2D in Matlab 2D Scene Imaging with UWB Array (Time-Domain Focusing) 2

3 General Idea Behind Operational Principle 1 A-Scan Presentation of the Received Data Operational scene Signal: without background compensation Notebook: -Control -Processing -Imaging Basic UWBR Hardware Signal: with background compensation Tx, Rx & Antennas On Tripod 3

4 2-Rx 1-Rx Trough-Wall Vision UWB Radar - 1 UWBR Hardware Windows compatible sound card for DAC & Serial (RS231) port for control Stereoacoustic = Stereo-Imaging 4

5 Novel UWB Antenna:: Geometrical MoM Model & Simulated Input Impedance Nice 50-Ω bandwidth! Direct termination to 50-Ω coax no balun! 5

6 Novel UWB Antenna:: Simulated Radiation Pattern in GHz GHz GHz E-plane H-plane Good gain and front-to-back ratio! 6

7 Radar Control, Signal Processing and Data Imaging Using Matlab 2 Byte Command Word (through serial port) CONTROL.COM_PORT=1; % 1 / 2 CONTROL.Start=1; %1 CONTROL.GM=4; % <3 digit> Maximum gain factor for AGC CONTROL.G0=0; % <3 digit> Initial gain factor CONTROL.RESERVE_HIGH=1; Controlling of ADC for Sound Card through Matlab ADC.SamplePerScan=700; %722; ADC.ScanShift=-100/2; ADC.NumberOfScans=10; ADC.SampleRate=44100; ADC.BitsPerSample=16;. Processing Specifications for Signal Processing in Matlab PROCESS.AmplitudeNorm=1; PROCESS.ScanStack=1; PROCESS.BckgRemove='NO'; %'YES'/'NO' PROCESS.SkipScans=50; Image Plot Options Radar Hardware Control Start / Stop Range / Range Window Time-Varying Gain, etc. Data Acquisition Scattered Waveforms are downconverted from UHF/Microwave GHz to Audio Frequencies ~ khz that can be digitized using a standard compute audio card (very chip and good ADC!) Signal Processing & Data Imaging A lot of such options in Matlab but a number of smart tricks is required to perform this in nearly real-time mode 1-D A-Scan (oscilloscope mode) 2-D B-Scan (wavelets, dense,..) 2-D Stereoscopic View For this prototype all control/processing/imaging software is written in Matlab! 7

8 1-D (A-Scan) Imaging = Oscilloscope Mode Background Removing Mode Regular Mode All is quite A target is invisible? A target is moving & becomes visible Tx-Rx Direct Coupling Target 8

9 2-D (B-Scan) Imaging = Stacked Waveforms Regular Mode A target is stationary Background Removing Mode A target is moving Imaging Technique similar to those Used for Ground Penetrating Radars (GPR) 9

10 2D Scene Imaging in Matlab: Stereoscopic View Time-Domain Focusing Ranging and Angular Tracking Image Pixel Map A Naive Time-Domain Focusing Technique: 1. Equalize time delay to focus on a image pixel 2. Compute inter-channel windowed correlation s1 (2), ij ( t) = S1(2) ( t D0 c Di, j1(2) c) I = W t) s ( t) s ( t) dt i, j TW ( 1, ij 2, ij 10

11 2D Scene Stereoscopic Imaging: How it woks? Simulated Measured Target Mark The target mark is widespread in azimuth = More sophisticated time-domain beam-forming is required! E.g., a similar problem is solved in stereoacoustic But Matlab cannot handle this in real time 11

12 2D Scene Stereoscopic Imaging: Why is the Target Mark so Wide Spread? Rx-2 Rx-1 Because of a small base, viz. the distance between Tx & Rx, the signals in the Rx channels are slightly mutually shifted in time that causes the wide spread mark. 12

13 Directions of Potential Future Efforts More Elements in UWB Arrays Two-Plane & Dual-Polarization Image focusing, More sophisticated Time-Domain Focusing Techniques Fast DSP Signal Processing Fast ADC instead of slow Sound Card Antenna Adaptations to Media Interfaces Tracking and Recognition of Complex Scenes Feedbacks and Propositions are very welcome 13