Abstract
As technology continues to evolve and the size of electronics becomes small, so does the size of
Radio Frequency (RF) transceivers. Wireless systems require antennas in order to be able transmit
and receive information in an efficient manner. In most cases these communication/RF systems
operate over a wide frequency band or over multiple frequency bands. Current RF systems which
communicate at multiple bands use wideband or multiband antennas to reduce the total number of
antennas in RF systems. However, the big problem with wideband and multiband antennas such as
dual band antennas is the inconsistent radiation patterns across the desired frequencies. This means
that even though the antenna might be well matched impedance-wise, the antenna doesn’t retain its
radiation pattern characteristics throughout all the desired frequencies.
This dissertation presents the design, realization and measurement of a planar dual band antenna with
consistent antenna parameters and performance for wireless communications. The antenna is
omnidirectional and is operational in the WIFI/WiMAX bands of 2.4-2.5GHz and 5-6GHz and provides
consistent performance throughout the bands of interest.
The proposed antenna is designed on Rogers 4003C with a dielectric constant of 3.55 and a substrate
thickness of 0.8mm. The antenna is realized by having two Vivaldi antennas (which is a wideband
directional antenna) in a back-to-back configuration. This configuration provides an omnidirectional
pattern and a wide radiation pattern bandwidth. The proposed antenna displays simulated and measured
results of a VSWR of <2:1 in the bands of interest, gain of above 1.5dBi for the 2.4-2.5GHz band and
4dBi in the 5-6GHz. The simulated and measured radiation patterns show that the patterns are
omnidirectional with azimuth 2D polar plot showing at worst a gain variation of 5dB, which is good
performance.
The prototype is designed and simulated using the 3D EM simulation software FEKO and the
gain and radiation patterns are measured inside a tapered anechoic chamber. The final prototype
shows a size of 40mm by 54mm, which is relatively small for a 2.4GHz antenna as usually a normal
2.4GHz antenna will be at least 62.5mm (half-wave dipole) in size for it to work properly. The
proposed antenna satisfies the requirements.
Keywords: VSWR(Voltage Standing Wave Ratio), impedance, gain, radiation patterns.