  This paper proposes a novel and compact nonreciprocal filtering antenna based
on temporal modulation. The device is composed of a third order filtering
section integrated into a Yagi-Uda planar printed antenna. Strong
nonreciprocity in transmission and reception is achieved at the same operation
frequency by time-modulating the resonators of the filtering section. These
resonators are implemented as quarter wavelength microstrip lines terminated
with varactors located on the ground plane. Such plane is also employed as a
reflector for the Yagi-Uda antenna and to host the coplanar waveguides that
feed low-frequency signals to the varactors, thus leading to a very compact
design. A prototype is manufactured and successfully tested at 2.4 GHz, showing
isolation greater than 20 dB between transmission and reception modes in both
E- and H- planes for all directions in space and a gain drop of only 3.5 dB
compared to a reference antenna. The proposed devices can easily be integrated
with other electronic circuits and may find exciting applications in
communication, radar, and sensing systems.
