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Outline for ECE 6341 at UH


Outline for ECE 6341 at UH

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This 32 page Class Notes was uploaded by an elite notetaker on Friday February 6, 2015. The Class Notes belongs to a course at University of Houston taught by a professor in Fall. Since its upload, it has received 15 views.

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Date Created: 02/06/15
Outline Introduction gt Introduction to 1D periodic microstrip leakywave antennas LWAs gt Broadside scanning and openstopband OSB problems 058 Mitigation technique gt Doublestub technique OSB Suppression technique Metamaterial Design gt CLRH Design 058 Suppression technique recent new Conventional Designs gt A new periodic LWA with a Ushaped stub gt A new periodic LWA with an impedance transformer Introduction iD Periodic Printed LWAsr 1D Periodic Printed LWAs B road 5 id e z Backward Forward 29 Air F a n gt v I G rou n cl Combline structure source Side View sketch OpenStopband OSB Region At broadside stopband null point 27 1871180 O Olko P Freespace radiation region Frequency A kop 7z 1 p Bound region Brillouin zone OpenStopband OSB Region At broadside gt The traveling leaky wave turns into a standing wave a shortcircuit at the ends of the unit cell for the combline structure gt The attenuation constant drops sharply to zero gt The Bloch impedance becomes pure imaginary gt The input match becomes poor gt The beamwidth changes rapidly near broadside dropping to zero at broadside for an infinite structure Example Combline Structure 1GHZJ A Frequency range near broadSIde Microstrip w 06 mm h1676rnn 8 102 Example cont Bloch Impedance Frequency range Hz Q near broadside quot12 Q 200 150 I00 50 Stopband null point OSB Mitigation Technique DoubleStub Method mwmwwwmwmmwwwwww A Historically this is the first method that was used to reduce the OSB JR James and PS Hall Microstrip Antennas and Arrays part 2 New array design technique IEE J Microwave Optics and Antennas 1977 Double Stub P Two identical stubs per unit cell Key idea The two reflected waves cancel out At broadside 27239 27239 3 1 30 9 gt p 80 g gt Results Double Stub 3235Li b same stub dimensions 21 265 fGHZ as 255 25 us 39 005 006 0M 92 0 411 4 n was 01 Even though the openstopband region has been reduced we are far from the ideal beahavior DoubleStub Optimization The distance dhas been optimized with a periodic MoM code m 1 quotI l dp 0225 I a L dpo225 39 E i 355 I 0 mp 14 10 39 i fGHZ a To1p r1l4 quot 1 5 lb I l I 39 A 9 255 I 39 I III 39 M ins um um am a c1 cas n 006 01 It does not appear to be possible to completely eliminate the openstopband region OSB Suppression Technique Metamaterial CLRH LeakyWave Antenna This structure is a quasiuniform structure that radiates from the n O harmonic L Liu C Caloz and T Itoh Dominant Mode LeakyWave Antenna with BackfiretoEndfire Scanning Capability Electron Lett vol 38 pp 1414 1416 Nov 2002 G V Eleftheriades A K lyer and P C Kremer Planar Negative Refractive Index Media using Periodically Loaded Transmission Lines IEEE Trans Microwave Theory Tee1 vol 50 pp 2702 2712 Dec 2002 Metamaterial CLRHTL LWA Artificial transmission line ATL Planar realization LR 0L Zsh S6 Z LL T CR l p l Balanced gt The series and shunt branches condition resonate at the same frequency The stub length S is varied to optimize the structure CRLH LWA ATL Analysis Ansoft Designer 21 Zz EEw Equivalent Tnetwork A Approximate analysis Propagation wavenumber Characteristic impedance 1 yaj steZsh Z0 ZseZsh 7 CLRH LWA ATL Analysis Propagation constant 05 I I I 1 I 44 46 48 KGHa Anso De gner ATLanaWsB Characteristic impedance Q 01 300 I I ock0 Re Im 250 i 008 200 i 006 ii I 150 quot39 quot gt n l I I 004 39I 3939 100 2 E 3939 002 0 O i i 4 42 44 46 48 5 fGHZ l 165mm i168mm i170mm 100 50 50 100 CLRH LWA FullWave Solution 1 012 Bk ock 01 008 006 004 002 f GHz The fullwave results show that a further optimization is necessary CLRH LWA Optimization by FullWave Solution k ock l3 0 ATL 01 MOM 008 The fullwave MoM solution predicts an optimum stub 005 length of 16 mm compared with 168 mm predicted by ATL theory 004 002 4 42 44 46 48 5 fGHz CLRH LWA Finite Structure A finite structure formed by 42 cells is simulated with Ansoft Designer using a voltage source at the input end fGHz Gain dBi 430 129 446 131 460 135 15 dBi 1O 1O 6O OSB Suppression Technique Novel UShaped LWA This LWA radiates from the n 1 harmonic not a metamaterial LWA This structure showed for the first time that the open stopband could be eliminated in a LWA that radiates from the 1 harmonic S Paulotto P Baccarelli F Frezza and D R Jackson A Microstrip Periodic LeakyWave Antenna Optimized for Broadside Radiation IEEE APS Symp Honolulu Hawaii June 2007 UStub LWA The design uses a and The thickness 139 of the end cap is varied in the optimization study UStub LWA AquotL Analysis 1llku propagation wave number alku Raga Characteristic impedance Ilmzn M V 005 an on 04 i one so so 0 am 40 40 u 0 unis m u 04 Funquot j am an m 415 onus w w 0 o o 5 4unnuhumsml r o a 5 u u u a I39GH new l3905mm Ansoft Designer 139 055mm l39 06mm UStub LWA FullWave Analysis 04 I I HR I I 02 a Phase gt 0 constant 2 Leakage constant 04 06 413 1 I I a I a a2 5A 55 as 9 Hana 004 002 055 nun 050 nun The fullwave MoM solution predicts an optimum endcap thickness of 050 mm instead of 055 mm predicted by ATL theory UStub LWA Finite Structure 192 cm Gap source periods ii i MiMiiMiL Pom Ansoft Designer GaindBi f Gain dB 141 142 141 141 140 Perfectly equalized gain 30 I I I I I I I 80 60 4O 2O 0 2O 4O 60 80 9 OSB Suppression Technique Impedance Transformer Design This LWA radiates from the n 1 harmonic not a metamaterial LWA This design was discovered after the Ustub design S Paulotto P Baccarelli F Frezza and D R Jackson A Novel Technique to Eliminate the Open Stopband in 1D Periodic Printed LeakyWave Antennas Proc EuCAP Edinburgh Scotland Nov 2007 QuarterWave Transformer Design OSB Suppression Technique Assume that at broadside the input impedance looking to the right at point A is Z0 the unit cell is matched to the impedance of the main line B C D Z 39Z k d Z 2 Zon R 20 ZOT 20R Z0 Z Z0 st tanke d1 Results Optmized Design substrate W d1 L1 ne 1 ma1n 39l1ne 06 2 102 1 0676 mm W mm L 11 071 mm stub 5 WT 1 wll 1 17mm w o1mm Line 2 transformer T T WT 049 mm 17 74 mm I 51209776 mm 512 Phase and attenuation constants Bloch impedance Q 393 006 200 l 200 1 01160 Re Im n 005 150 i 100 004 39 m 100 0 002 50 A100 001 I ass as a 1 215 no 0 200 25 255 25 265 27 27 5 23 quot0quot GHZ Gain Pattern Near Broadside Note Gain accounts for directivity and input mismatch f2675GHZ a 9quotva Finite structure 32 cells 32 x 4mm 128 mm Simulated with Ansoft Designer Conclusions It has been shown how openstopband effects impair broadside scanning in 1D periodic printed LWAs Metamaterial Design 71 0 gt The CLRH metamaterial LWA can eliminate the open stopband but fullwave optimization is necessary in order to achieve this Conventional Designs 71 1 gt A doublestub mitigation technique reduces but does not completely remove the openstopband problem gt A new Ushaped stub design can eliminate the open stopband gt A new quarterwave transformer design can eliminate the open stopband ackup Viewgraphs QuarterWave Transformer Design Procedure Usually 2 or 3 iterations The broadside frequencyf0 can be estimated through the Brillouin diagram of the unperturbed microstrip line Using a commercial software Z1 in is extracted atfo considering a unit cell with Z0 as load The length of the delay line all is determined to obtain a real input impedance R The quarterwave transformer is designed to match Z0 to the impedance R The dispersion behavior of the initial desing is determined by using a fullwave analysis The broadside frequency usually differs from the one predicted at step 1 Steps 15 are repeated until the actual broadside frequency is the same that assumed in the design Some finetuning using a fullwave solver is done to optimize the structure and to obtain a complete suppression of the open stopband USNCURSI National Radio Science Meeting Boulder CO January 36 2008 Techniques for Scanning Through Broadside with Periodic LeakyWave Antennas Simone Paulotto Paolo Baccareli Fabrizio Frezza and David R JacksonM Electronic Engr Dept La Sapienza University of Rome Italy MDept of ECE University of Houston TX APIENRZA


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