Antenna is a spatial filter. It favors signal coming from a certain direction while rejecting signals from other directions depending on its gain pattern.

Rajnish Kumar is right, for a directional antenna, but a filtering antenna is also an antenna which is designed to not receive at a designed frequency, frequencies or band of frequencies, or to only receive at some frequencies. This can also be done by adding a filter after the antenna, but it may be cheaper and simpler to build the filter into the design of the antenna. All antennas do have a limited bandwidth anyway, so do act as frequency filters to some extent, as well as directional filters, if they are directional - some antennas are not directional.

It is usual to filter the signal received by an antenna, but extra filtering may be needed if there is a strong interfering signal at a frequency close to the antenna's operating band.

Generally speaking, it is an antenna that reduces the cross-band mutual coupling between the closely spaced elements operating at different frequency bands.

The idea is that for various reasons, you want to integrate the design of a discrete antenna and a discrete filter in one combined structure, usually because this allows for better coupling, smaller geometry and less losses between the two elements, depending on your specific implementation.

A common type of filtering antenna is replacing the last stage of an open loop resonator bandpass filter directly with a patch,

Adrian K. Stavrakis , Malcolm White and Rajnish Kumar ,

I truly appreciate your responses to my inquiry. Thank you very much for the guidance.

A filtering antenna also known as Filtenna is a kind of multifunctional device consisting of a filter integrated with an antenna which simplifies the complexity of the wireless communication system and reduces the interconnection losses