Electrically Small, High-gain, Multi-band Antennas using
Compact Yagi and Artificial Magnetic Conductor (AMC) Ground
A compact antenna package using an
electrically small Yagi antenna and a small Artificial
Magnetic Conductor (AMC) ground plane with multi-band and
high gain characteristics has been developed [25,26]. A
preliminary antenna design is first simulated with a closely
spaced Yagi antenna over an electromagnetic band-gap (EBG)
ground plane (Fig. 1a). The closely spaced Yagi is composed
of two elements including a driver and a director. The
driver is folded to step up the low radiation resistance due
to the close spacing between the driver and the director.
The total height from the top of the EBG ground plane to the
director of the Yagi is 0.03λ.
Two resonances (see Fig. 1b) are attained and each band
shows high gain. The first resonance is due to the driver of
the Yagi over the EBG ground plane. This resonant frequency
is similar to the case when only the driver of the Yagi is
placed over the same EBG ground plane (driver mode).
Furthermore, the second resonance is created due to the Yagi
antenna itself (Yagi mode). The gains at the dipole mode and
the Yagi mode are 7.84dB and 8.75dB, respectively. The
separation of these two bands can be altered easily by
tuning the closely spaced Yagi antenna. In order to realize
a truly small antenna package together with the Yagi and the
ground plane, a miniaturized Yagi over a small AMC ground
plane will be designed. The expected design will be placed
in a small cylinder volume, while maintaining multi-band and
high gain characteristics. All designs will be optimized by
using the Genetic Algorithm (GA).
Tasks and deliverables
Optimized designs based on gain, matching, and
bandwidth using the Genetic Algorithms to design the
electrically small Yagi and the AMC ground plane.
Simulation & measured results with variety of
antenna shapes over the small AMC ground plane.
Prototypes of the optimized design.
|Fig. 1a. Prototype
of the compact Yagi antenna over the EBG ground
||Fig. 1b. Measured
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