Slot Antenna Prachi

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An antenna is a circuit element that provides a transition form (a guided wave ) on a transmission line to a free space wave and it provides for the collection of electromagnetic energy.

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SLOT ANTENNA •The slot antenna was invented in 1938 by Alan Blumlein. •A slot antenna consists of a metal surface, usually a flat plate, with a hole or slot cut out. •The shape and size of the slot, as well as the driving frequency, determine s the radiation distribution pattern. •The slot antenna is popular because they can be cut out of whatever surface they are to be mounted on and have radiation patterns that are roughly Omni directional. •The polarization of the slot antenna is linear.

SLOTTED-CYLINDER ANTENNA 3

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Babinet's Principle can be used to find complementary impedances. It states (in optics) that when a field behind a screen with an opening is added to the field of a complementary structure (that is a shape covering the screen hole), then the sum is equal to the field where there is no screen. If we take two such complementary screens and perform line integrals over identical paths to compute the impedance of each, we obtain the result

ZѕZс=η²/4 

Complementary Screens

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2-D RADIATION PATTERN

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Horizontal Radiation Patterns

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WAVEGUIDE SLOT ANTENNA Waveguide slot antennas are often used as Omni directional microwave antennas.  Unique features of these antennas are horizontal polarization and Omni-directional gain around the azimuth.  They are also simple, rugged, and fairly easy to build. 

Cross section of a slotted waveguide antenna from a marine radar set

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APPLICATIONS :  Slot antennas are widely used in radar antennas.

 Slot Antennas are used in fast-moving vehicles.  Particularly used in microwave region (>1GHz).  Slot antennas are often used at UHF and microwave

frequencies instead of line antennas when greater control of the radiation pattern is required.  And are often found in standard desktop microwave sources used for research purposes. 9

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