Microstrip Antennas for 60 GHz Band Application

The next generation of mobile networks will exploit frequencies above 5 GHz and will use a wide available bandwidth for high speed data communication. At the time of writing this thesis work is ongoing to launch into the market a communication system operating between 25 GHz and 30 GHz. Following news about 40 GHz spectrum acquisition by telecommunication companies, it will be the next in turn. At the same time there is a continued interest on frequencies around 60 GHz, with potential applications not limited by mobile networks. The main reason for this development is that there is about 7 GHz of available unlicensed bandwidth around the world due to the electromagnetic waves absorption peak in the atmosphere.
This dissertation is devoted to microstrip antenna design at 60 GHz band.
The main challenge addressed in the thesis is a wideband antenna design with
high directivity and efficiency to overcome the free space propagation loss and
atmosphere attenuation. In addition, the presented antennas are suitable for
a reliable fabrication and have small thickness, which might be critical for the
antenna integration. A single antenna and an array antenna are designed and
manufactured. A wideband high gain antenna and an array design on a ceramic
substrate, which is suitable for multilayer fabrication and system integration is
presented in Paper I. A novel gridded parasitic patch microstrip antenna design
and fabrication on a polytetrauoroethylene substrate is presented in Paper II. A
comparison with similar conventional antenna designs is provided showing better characteristics for the designed antenna. During the antenna measurements the effect of surface waves propagation was identified. To suppress this unwanted radiation an electromagnetic band-gap structure around the antenna is designed and manufactured, the results are presented in Paper III. Two array antenna configurations for the gridded parasitic patch antenna are presented in Paper IV.
The second topic of the dissertation is an investigation of reconfigurability
of a gridded parasitic patch antenna pattern. The principles using switches and
varactors implementation are discussed in Paper II. The results of the proof-of concept fabrication using narrow metal strips imitating switch connection are
presented in Paper V. An implementation using Schottky diodes as switches is
presented in Section 5 of the introduction part of the thesis.
The third topic of the dissertation is an antenna integration with a power
amplier using bond wires. In Section 6 of the introduction part a planar antenna
array integration with the injection locked power amplifier is presented. In Paper VI the same antenna is integrated with a two-stage power amplifier. Simulated and measured results are presented.