Microstrip or patch antennas are becoming increasingly useful because they can be printed directly onto a circuit board.Increasing the height also increases the efficiency of the antenna. The height of the substrate h also controls the bandwidth, increasing the height increases the bandwidth. The fringing fields around the antenna can help explain why the microstrip. Allows for use of different substrates to optimize Higher bandwidth is possible since probe inductance isĮliminated (allowing for a thick substrate), and also a Feed-line radiation is isolated from patch radiation Might be too large (e.g., when using high permittivity) Can allow for a match even with high edge impedances, where a notch Can allow for higher bandwidth (no probe inductance, so Less line radiation compared to microstrip feed For deep notches, patch current and radiation pattern may show distortion Significant line radiation for thicker substrates Significant probe inductance for thicker substrates (limits Significant probe (feed) radiation for thicker substrates Easy to obtain input match by adjusting feed position Directly compatible with coaxial cables The feeding methods are illustrated for a rectangular patch,īut the principles apply for circular and other shapes as well. The substrate is so thin that it can be bent to “conform” to the surface. Cannot handle extremely large amounts of power (dielectric breakdown).Ģ-D 8X8 corporate-fed array 4 8 corporate-fed / series-fed array Only used at microwave frequencies and above (the substrate becomes too Efficiency is limited byĬonductor and dielectric losses*, and by surface-wave loss**. Efficiency may be lower than with other antennas. Thickness and inversely proportional to the substrate permittivity. Bandwidth is roughly proportional to the substrate Low bandwidth (but can be improved by a variety of techniques). Easy to use in an array to increase the directivity. Patterns are somewhat hemispherical, with a moderate directivity Easy to incorporate with other microstrip circuit elements and Easy to feed (coaxial cable, microstrip line, etc.). Easy to fabricate (use etching and photolithography). Low profile (can even be “conformal,” i.e. (a) Top View of Patch Antenna (b) Side View of Microstrip Antenna The patch may be in a variety of shapes, but rectangular and circular are the most common. It usually consists of a metal “patch” on top of a grounded dielectric substrate. Received: March 3, 2010. One of the most useful antennas at microwave frequencies (f > 1 GHz).
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