IFAs of all types are ground-plane based antennas, meaning that the size and shape of the local ground plane and the relatively close spacing of the ground plane to the antenna element are both an integral part of the antenna design. IFAs should always be placed on the edge of a ground plane, like the edge of a PCB, or on top of a planar ground plane surface. An IFA should never be completely surrounded by ground planes and other conducting surfaces. IFAs and PIFAs are considered “psuedo-omni” antennas, meaning there is no predominant direction of radiation. These antennas radiate in both orthogonal polarizations, depending on the direction.
If the IFA structure is disconnected from ground and fed from one end, it can be considered a meandered-line antenna. This type of antenna is similar in performance and capability to the standard IFA and is mentioned only for reference. In some single-band cases, a meandered-line antenna can be smaller than the corresponding IFA.
Microstrip Patch Antenna
The microstrip patch antenna is another common low-profile antenna. The patch antenna requires a ground plane beneath it and can exist much closer to the local
Antenna Fundamentals – Technical Brief