The smart antenna is one of the most promising
techniques for improving communication quality in mobile communications
systems. It is usually categorised as either a switched-beam
or an adaptive array antenna [1].
Researches on switched-beam antenna were proposed [2-4].
However, in addition to the ability to switch beam, low-profile and compact antenna structure is desirable.
Monopole elements were applied in [2], thus resulting in the lack of
low-profile structure. While a linear array of five-element patch
antennas was introduced [SI, relatively more space was occupied.
A phased array antenna was developed in [4].
The 3 dB hybrid couplers
were necessary, but this requirement made antenna feeding complicated
and the antenna structure non-compact. In this Letter we
propose a simple and compact switched-beam antenna made up of a
single centre-fed square patch antenna and PIN diodes used as RF
switches to switch the beam of the antenna