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Slot Antenna basics | Impedance of Slot Antenna

This page covers basics of slot antenna. It mentions features of slot antenna. The equation for impedance of slot antenna is also mentioned.

Definition: The antenna which is formed by constructing slot in metallic surface is known as slot antenna. This antenna will have opening either in conducting sheet of metal or in the walls of waveguide. This type of antenna is excited either by coaxial cable or by waveguide with suitable coupling.

Key features of slot antenna

slot antenna

The figure-1 depicts slot antenna of rectangular type. This slot antenna type will have slot of length equal to λ/2 and will have width much less than λ/2. As shown, the excitation is done from distance of 0.05λ from one end of slot using coaxial cable.

Following are the key features of slot antenna:
• The slot can be circular, rectangular or of anyother shape and size.
• As slots are omni-directional, it will radiate from both sides.
• Array of slots are used to have higher gain and higher directivity.
• Electric field in the slot is like sinusoidal waveform.

Slot Antenna Impedance Equation

Following is the slot antenna impedance equation:
Zs = [ ηo2 / (4* Zd) ]
ηo = 120*π Ohm
Zd = Impedance of complementary dipole = Rd + j*Xd
Where, Rd = Real Part and Xd = Reactive Part

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