Communication systems at microwave and millimetre wave regimes require compact broadband
high gain antenna devices for a variety of applications, ranging from simple telemetry antennas to
sophisticated radar systems. High performance can usually be achieved by fabricating the antenna
device onto a substrate with low dielectric constant or recently through micromachining techniques.
This thesis presents the design, fabrication, assembly and characterisation of microstrip and CPW
fed micromachined aperture coupled single and stacked patch antenna devices. It was found that
the micromachining approach can be employed to achieve a low dielectric constant region under the
patch which results in suppression of surface waves and hence increasing radiation efficiency and
bandwidth. A micromachining method that employs photolithography and metal deposition
techniques was developed to produce high efficiency antenna devices. The method is compatible
with integration of CMOS chips and filters onto a common substrate. Micromachined polymer rims
(SU8 photoresist) was used to create millimetre thick air gaps between the patch and the substrate.
The effect of the substrate materials and the dimensions of the SU8 polymer rims on the
performance of the antenna devices were studied by numerical simulation using Ansoft HFSS
electromagnetic field simulation package. The antenna structures were fabricated in layers and
assembled by bonding the micromachined polymer spacers together. Low cost materials like SU8,
polyimide and liquid crystal polymer films were used for fabrication and assembly of the antenna
devices. A perfect patch antenna device is introduced by replacing the substrate of a conventional
patch antenna device with air in order to compare with the micromachined antenna devices. The
best antenna parameters for a perfect patch antenna device with air as a substrate medium are ~20%
for bandwidth and 9.75 dBi for antenna gain with a radiation efficiency of 99.8%. In comparison,
the best antenna gain for the simple micromachined patch antenna device was determined to be ~8.6
dBi. The bandwidth was ~20 % for a microstrip fed device with a single patch; it was ~40 % for
stacked patch devices. The best bandwidth and gain of 6.58 GHz (50.5%) and 11.2 dBi were
obtained for a micromachined sub-array antenna device. The simulation results show that the
efficiency of the antenna devices is above 95 %. Finally, a novel high gain planar antenna using a
frequency selective surface (FSS) was studied for operation at ~60 GHz frequency. The simulation
results show that the novel antenna device has a substantial directivity of around 25 dBi that is
required for the emerging WLAN communications at the 60 GHz frequency band
