microstrip antennas overview

Microstrip antennas - Overview of Microstrip Antennas David R Jackson Dept of ECE University of Houston Overview of Microstrip Antennas Also

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Overview of Microstrip Antennas David R. Jackson Dept. of ECE University of Houston
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Overview of Microstrip Antennas Also called “patch antennas” • One of the most useful antennas at microwave frequencies ( f > 1 GHz). • It consists of a metal “patch” on top of a grounded dielectric substrate. • The patch may be in a variety of shapes, but rectangular and circular are the most common.
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History of Microstrip Antennas • Invented by Bob Munson in 1972. • Became popular starting in the 1970s. R. E. Munson, “Microstrip Phased Array Antennas,” Proc. of Twenty- Second Symp. on USAF Antenna Research and Development Program, October 1972. R. E. Munson, “Conformal Microstrip Antennas and Microstrip Phased Arrays,” IEEE Trans. Antennas Propagat., vol. AP-22, no. 1 (January 1974): 74–78.
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Typical Applications single element array (Photos courtesy of Dr. Rodney B. Waterhouse)
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Typical Applications (cont.) Microstrip Antenna Integrated into a System: HIC Antenna Base-Station for 28-43 GHz filter MPA diplexer LNA PD K-connector DC supply Micro-D connector microstrip antenna fiber input with collimating lens (Photo courtesy of Dr. Rodney B. Waterhouse)
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Geometry of Rectangular Patch x y h L W Note: L is the resonant dimension. The width W is usually chosen to be larger than L (to get higher bandwidth). However, usually W < 2 L . W = 1.5 L is typical.
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Geometry of Rectangular Patch (cont.) view showing coaxial feed x y L W feed at ( x 0 , y 0 ) Feed along the centerline is the most common (minimizes higher-order modes and cross-pol) x
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Advantages of Microstrip Antennas • Low profile (can even be “conformal”). • Easy to fabricate (use etching and phototlithography). • Easy to feed (coaxial cable, microstrip line, etc.) . • Easy to use in an array or incorporate with other microstrip circuit elements. • Patterns are somewhat hemispherical, with a moderate directivity (about 6-8 dB is typical).
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Disadvantages of Microstrip Antennas ¾ Low bandwidth (but can be improved by a variety of techniques). Bandwidths of a few percent are typical. ¾ Efficiency may be lower than with other antennas. Efficiency is limited by conductor and dielectric losses*, and by surface-wave loss**. * Conductor and dielectric losses become more severe for thinner substrates. ** Surface-wave losses become more severe for thicker substrates (unless air or foam is used).
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Basic Principles of Operation ± The patch acts approximately as a resonant cavity (short circuit walls on top and bottom, open-circuit walls on the sides). ± In a cavity, only certain modes are allowed to exist, at different resonant frequencies. ± If the antenna is excited at a resonant frequency, a strong field is set up inside the cavity, and a strong current on the (bottom) surface of the patch. This produces significant radiation (a good antenna).
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Thin Substrate Approximation On patch and ground plane, 0 t E = ( ) ˆ , z E zE x y = Inside the patch cavity, because of the thin substrate, the electric field vector is approximately independent of z .
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This note was uploaded on 09/09/2010 for the course ECE 4436 taught by Professor Staff during the Spring '08 term at University of Houston.

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Microstrip antennas - Overview of Microstrip Antennas David R Jackson Dept of ECE University of Houston Overview of Microstrip Antennas Also

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