antenna-theory.com

[mamdomia]

Hi,

I am confused about patch antennas and microstrip transmission lines. Why does the patch antenna radiate and the microstrip does not? In one note in the website it says due to the fringing fields the patch radiates. Aren't there fringing field for microstrip TL as well? I would really appreciate some explanation.

[bigSteve]

You should draw yourself a picture and label the fringing fields and it will be clear.

In the case of a transmission line, the fringing fields are perpendicular to the direction of power, and are equal on both sides of the transmission line. They therefore cancel each other, don't reinforce and therefore don't radiate.

For the patch antenna, the fringing fields are along the long edge of the patch, which are also in the direction of travel of the power down the transmission line. Further, since they are separated by a half-wavelength they reinforce each other, giving rise to the radiation.


http://www.antenna-theory.com/antennas/patches/antenna.php