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ECE 563 & TCOM 590 Microwave Engineering. Planar Transmission Lines: Striplines and Microstrips October 14, 2004. Planar Transmission Lines. Parallel Plate Waveguide. Surface Waves on a Grounded Dielectric Slab. 0. x. 0 r. z. //////////////////////////////////////.
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ECE 563 & TCOM 590Microwave Engineering Planar Transmission Lines: Striplines and Microstrips October 14, 2004
Surface Waves on a Grounded Dielectric Slab 0 x 0r z //////////////////////////////////////
Stripline Triplate transmission line
Stripline Advantage (compared to parallel plates) • transverse fields remain in the vicinity of the center conductor between 2 grounded planes • 2 conductor line, no lower frequency cutoff: down to f=0 , up to cutoff of first TE mode. • Miniaturization
Stripline • Compared to coax or waveguide • Advantage if Gunn diodes or mixer diodes to be apart of circuit design. • Advantage, large bandwidth, mini-size • Disadvantage- lack of isolation, lower power handling • Dominant mode - TEM
Microstrip Lines w t ////////// h ////////////////////// • Popular • fabricated by photolithographic processes • easily integrated with other passive and active microwave devices • convenient, economical; therefore, widespread use • Problem • radiation and undesired modes by lines at discontinuities
Microstrip w t h
Effects to Dampen Signal Propagation along a Microstrip • Signal heats conductor through Ohmic Losses • Signal heats substrate which is not lossless • Signal leaks away as radiation
Microwave Transmission Notes on striplines and microstrips • less bulky than waveguides • no need for welding and brazing • planar circuits - 2 dimensional universe • but high field concentration • limits power • breakdown • heating center condition • Open structure - radiates
Microwave Advances • High Speed Circiuts • MMIC’s - Monolithic Integrated Circuits • High speed & high frequency • Photonics • Lightwave Techniques • fiber optics • image processing • high speed • Considerable Interaction • distribution of analog microwave signals via high speed fiber - optic links • optically controlled microwave devices & circuits
Microwave Advances • Fiber-optic cables to route microwave signals • reduce size and weight • large bandwidth • immunity to interference • crosstalk isolation • potentially smaller transmission losses • applications • feeds for phased array antennas • delay lines, cable TV signal signal distribution
Millimeter Wave Monolithic Integrated Circuits (MIMIC) • Affordable, reliable, reproducible wave and millimeter wave components • frequency • tests up to 40 GHz • pulse power goal S-band (3 GHz) to 75 GHz • Materials Research • GaAs • High electron mobility transistors (HEMT’s) • CAD • MHDL-Microwave Hardware Descriptive Language