Source: http://www.ss-pub.org/wp-content/uploads/2015/03/3-BCR-E20140906-02.pdf

Patch Antennas

There are three layers to a patch antenna from bottom to top: the ground plane, substrate with a dielectric constant value, and a conducting patch.

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How Patch Antennas Work

Patch antennas work because of fringing fields created between the conducting patch and the ground plane. Fringing fields are the effect of radiation travelling from the conducting patch to the ground plane through the air and substrate, allowing the patch antenna to radiate.

  1. Current flowing through the feed line reaches the patch antenna and generates electromagnetic waves in the substrate.
  2. Electromagnetic waves are reflected by the edge of the patch since the thickness of the patch is small. Waves long the width of the patch create radiation, waves along length eliminate each other.
  3. Max and min electric fields continuously change polarization (sides of the patch) based on the RF signal phase. The electric field is zero at the patch center, max or positive on one side and min or negative on the other.
  4. Electric fields extending beyond patch edges cause patch to radiate. These field extensions are called fringing fields.

Designing a Patch Antenna

When designing a patch antenna, the length and width of the conducting patch is determined by the desired resonant frequency and the dielectric constant of the substrate.

Conducting Patch Width

The width of the conducting patch is given as:

Effective Refractive Index