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Rectangular Patch Antenna

Rectangular Patch Antenna

Rectangular Patch Antenna

I came across this when reading Antenna Theory 3/e by C. A. Balanis. He says a rectangular patch antenna can be represented by two radiating slots, separated by half-wavelength. Each slot is represented with a parallel equivalent admttance. If the admittance of the second slot is transformed over half-wavelength to the location of first slot, then susceptances of the two slots have opposite signs. Adding the two susceptances makes the total input susceptance equal to zero.

I am confused about this: if you transform an admittance over half-wavelength long transmission line, wouldn't the admittance be unchanged? Essentially, the impedance rotates a full circle on the Smith Chart. But Balanis says the susceptance would acquire a negative sign.

I hope someone here could resolve my question. Thanks.

RE: Rectangular Patch Antenna

A full circle on the Smith chart is 180 degrees of phase.  Thus a perfect inversion (cos(pi) = -1).  


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