Characterization of Dielectric Materials using Ring Resonators

Transcription

1 Technical Advisory Board demonstration Characterization of Dielectric Materials using Ring Resonators Gregory J. Mazzaro Kelly D. Sherbondy Gregory D. Smith Russell W. Harris Anders J. Sullivan Army Research Laboratory 800 Powder Mill Rd Adelphi, MD May 10, 011 4:15 pm 04/3D01 Presentation Overview Motivations Dielectric Characterization at Radio Frequencies Reflectometry, Scatterometry, Ring Resonators Ring Resonator Technique & Demonstration Basic Operation and r Calculation Higher Resonances: Wideband Measurement Compact Design using Meander Lines Recent Measurements & Summary 600-MHz ring resonator, E-field

2 Presentation Overview Motivations Dielectric Characterization at Radio Frequencies Reflectometry, Scatterometry, Ring Resonators Ring Resonator Technique & Demonstration Basic Operation and r Calculation Higher Resonances: Wideband Measurement Compact Design using Meander Lines Recent Measurements & Summary 600-MHz ring resonator, E-field 3 Find IEDs/UXOs/Mines Sense through the wall distance (m) Motivations received power (db/sm) Synchronous Impulse Reconstruction (SIRE) radar transmit antennas (CPU inside) receiver array distance (m) received power (db/sm) Main concerns: Roadside, in-road (buried), hidden/ obscured threats IEDs, landmines, enemies hiding inside buildings evaluate ultra-wideband (UWB) ground-penetrating radar (GPR) technology for concealed target detection 4

3 Motivations EM properties of materials affect UWB radar target detection. Dielectric constant ( r ) indicates wave transmission, reflection, loss. To predict performance, we need to know/estimate r of our environment. soil, r 10 cm plastic mine 3 cm 1.5 cm k inc mine dielectric = (3.1, ) simulated UHF HH simulated UHF HH Yuma soil, 5% H O r = (3.6,0.1) Target Clutter Yuma soil, 15% H O r = (1.0,0.68) Clutter 10 db Target radar cross-section & penetration change with r Motivations Dielectric constant varies greatly between soil types (e.g. sand, loam, clay), terrain (vegetative, mountainous), and moisture content. We want to measure r for many samples. We prefer a portable system for in-situ measurements. Yuma, AZ In addition to soils, we want to measure explosives, simulants, building materials. We prefer a measurement method that won t disturb/destroy our samples. We need to measure r at enough frequencies to cover our operating band (currently 300 MHz to 3 GHz). 6

4 Presentation Overview Motivations Dielectric Characterization at Radio Frequencies Reflectometry, Scatterometry, Ring Resonators Ring Resonator Technique & Demonstration Basic Operation and r Calculation Higher Resonances: Wideband Measurement Compact Design using Meander Lines Recent Measurements & Summary 600-MHz ring resonator, E-field 7 RF Methods for Measuring 1 Reflectometry Pulser Oscilloscope V refl / V in 0 TDR waveform 0-1 time Soil Fourier Transform Stainless steel transmission line c L fl S 11 f l frequency Scatterometry can t insert probes into solid samples; need to bring pulser & oscilloscope Source Detector V i 1 V r Vr V cos sin r1 i r r1 i cos sin i r1 i r r1 i RF source i Soil r Power meter 8 far-field measurement; requires large sample at RF 10 cm to1 m

5 Methods for Measuring : Work at ARL Permittivity Measurement Software, VNA, PC, and Soil Coaxial Transmission Line Our original work: -- the coaxial line gave us consistent, repeatable values for r 0 eff 0 c f ln X X 1 L T S S S S T X 1 S11 S1 S11 Figure of ARL-TR-4780, U.S. Army Research Laboratory (ARL) Very High Frequency (VHF)/Ultra High Frequency (UHF) Permittivity Measurement Software: Data Capture and Reduction by Gregory D. Smith need to bring sample back to lab (i.e. disturb it) before measurement 9 Ring-Resonator Technique A ring in air has a resonant frequency f u and quality factor Q u. air vs. lossy dielectric f u,q u f l,q l (ground plane underneath) f u l,q ul A ring loaded by a dielectric sample has a lower resonance f l and a lower quality factor Q l. These changes give us r. resonator on top of sample: sample is undisturbed Ring-resonator concept: 10 (Air vs. Sand Demo) K. Sarabandi and E. S. Li, Microstrip Ring Resonator f or Soil Moisture Measurements, IEEE Trans. on Geoscience and Remote Sensing, Vol. 35, No. 5, Sept

6 Presentation Overview Motivations Dielectric Characterization at Radio Frequencies Reflectometry, Scatterometry, Ring Resonators Ring Resonator Technique & Demonstration Basic Operation and r Calculation Higher Resonances: Wideband Measurement Compact Design using Meander Lines Recent Measurements & Summary 600-MHz ring resonator, E-field 11 Ring-Resonator Technique Re{ r } vs. shift Im{ r } vs. Q Re r r Im Im r tan Re r greater shift higher Re{ r }; wider resonance higher Im{ r } (Sand & Water Demo) 1

7 Higher-Order Resonant Modes If the ring resonates at f 0, it will resonate at f 0, 3f 0, 4f 0, 5f 0, 600 MHz 1. GHz One ring can be used to make measurements at multiple frequencies. We don t need to fabricate a resonator for every measurement frequency. 600-MHz ring resonator, electric field magnitude 1.8 GHz.4 GHz 13 (Wideband Demo) Compact Design using Meander Lines The volume of sample necessary for measurement may be reduced if the area of the ring is reduced. 900 MHz 1.5 GHz 1. GHz meander the microstrip, maintain circumference of ring, reduce the size of the sample 600 MHz 350 MHz traditional design 350 MHz 300 MHz 550 MHz 400 MHz 350-MHz ring: 6.5-in diameter, without meandering.5-in diameter, with meandering MHz meander-line design

8 Measurement System laptop w/ LAN, Matlab (only necessary for real-time r calculation) Agilent FieldFox N993AN handheld vector network analyzer V out V in 1 resonator sample 15 portable wideband in-contact with sample, but won t disturb sample non-destructive ( < 1 mw power ) quick calculation (Matlab GUI Demo) Presentation Overview Motivations Dielectric Characterization at Radio Frequencies Reflectometry, Scatterometry, Ring Resonators Ring Resonator Technique & Demonstration Basic Operation and r Calculation Higher Resonances: Wideband Measurement Compact Design using Meander Lines Recent Measurements & Summary 600-MHz ring resonator, E-field 16

9 Measurements: Sand, with Moisture Yuma soil samples water dielectric constant content Duke U ARL 0.0%.8.4.5%.9 5.0% % % Measurements: RTV Rubber 18

10 Summary The ring-resonator technique enables measurement of r in-situ, without disturbing the dielectric sample. r may be determined at frequencies down to 50 MHz using a.5 -diameter meander-line ring. Our r data will be used to model the detection of concealed targets by UWB radar and predict target detection performance. 10 cm mine 3 cm 1.5 cm soil, r 19