| dc.description.abstract | The work described in this thesis aimed to design radiation pattern reconfigurable
(RPR) antenna that is capable to combat propagation scenarios such as fading,
interference and shadowing with its ability to steer the beam towards a desired
direction. Patch type RPR antennas suffer from major drawback of achieving beam tilt
angle with respect to broadside due the finite ground plane behind the radiating element.
The maximum tilt angle achieved is 30° by the existing patch RPR antennas without the
implementation of actual RF switches. In this thesis, thorough investigation on parasitic
patch array antenna with actual RF switches is conducted with two types of RF PIN
diodes, namely BAR50-02V and HPND-4005. Taconic substrate is chosen to design the
antennas since it offers low tangent loss. The mutual coupling and Yagi-Uda principles
are adopted to design the three-element parasitic patch array antenna with the two types
of RF PIN diodes. BAR50-02V is adopted to design Low Isolation Loss Parasitic Patch
Array Antenna (LILPPA). A novel installation of RF PIN diodes in patch antenna is
introduced, where the BAR50-02V diodes are embedded inside the substrate of the
antenna. Due to low isolation loss (ISO), LILPPA with BAR50-02V PIN diode only
achieves maximum tilt angle of 23°. HPND-4005 PIN diode is adopted for the design of
High Isolation Loss Parasitic Patch Array Antenna (HILPPA). HPND-4005 PIN diode
offers high ISO at 5.8 GHz frequency, thus it helps HILPPA to achieve maximum tilt
angle of 30°. In both designs, only four RF PIN diodes are used. Next, Broadly
Steerable Parasitic Patch Array (BSPPA) antenna is proposed and it uses HPND-4005
PIN diode, since the diode yields superior performance with HILPPA antenna in terms
of beam tilt angle. BSPPA antenna able to improve the beam tilt angle to 50° by
adopting techniques of adding parasitic element, increasing the number of switches and
reducing the ground plane with respect to the broadside. BSPPA antenna is able to work
in two modes where in the first mode it is capable of steering the directive beam
patterns towards five directions, -50°, -30°, 0°, +30°, +50° in H-plane. In the latter
mode, BSPPA is able to shape the beam pattern from narrow beam to broadside beam.
HPND-4005 PIN diodes require high reverse bias voltage at OFF state. The problem
arises if the antenna is connected to the I/O ports of control devices such as
microcontroller or microprocessor since they operate at 5V and 0V for High and Low
operation. To solve this, an exclusive electronic switching network is developed to
perform the switching of HPND-4005 PIN diodes. All three antennas developed in this
work have high gain of greater than 6 dBi and common operational bandwidth of
greater than 100 MHz. With this characteristics, the proposed antenna could be a
promising candidate in latest wireless communication system such as WIFI and
WiMAX. | en_US |
