Biomedical Engineering Reference
In-Depth Information
Fig. 2 The properties of
atmospheric absorption of
electromagnetic waves [ 4 ]
transmitter power for portable devices, a gain of
15 dBi is usually required for 60-
GHz indoor WLAN applications. Hence, the use of antenna arrays with high-gain is
anticipated.
Low-temperature co-fired ceramic (LTCC) multilayer technology enables inte-
gration of passive components including antennas in a single package. Compared
with the multilayer print circuit board (PCB) technology, the LTCC technology is
capable of realizing blind, buried and through vias and air cavities in the substrate
easily [ 6 ]. The LTCC technology is also allowed to mount active devices or in-
tegrated circuit on/in them to achieve a new option to integrate an antenna array
in a chip package. Several LTCC materials can be selected. Ferro A6 is one kind
of LTCC material suitable for 60-GHz antenna array design, due to its excellent
high frequency characteristic. Based on the Ferro A6 material, LTCC technologies
can realize functional packages and antennas for applications in the 60-GHz band.
The LTCC process has been regarded the promising technology of achieving light
weight, compactness, easy integration, and excellent high frequency performance
for 60-GHz wireless communication applications.
Considering the wide 15 % bandwidth (for 9 GHz world wide band coverage) and
more than 15 dBi gain requirements, the antenna arrays based on LTCC technology
have many challenges for 60-GHz wireless short-range communications. Due to the
high permittivity of the LTCC substrate, the bandwidth of antenna arrays is limited.
Hence, the choice of the array element becomes more significant for 60-GHz antenna
array design. A variety of array elements, such as patch, dipole, slot, and others have
been used as the element in the 60-GHz LTCC antenna array designs. Also some
methods about broadening bandwidth of the LTCC antennas have been reported,
such as using aperture coupled patch, U-slot patch, L-probe patch, stacked patch,
and off-center dipole, etc. [ 7 - 13 ]. For the antenna arrays, the feeding network is
crucial to develop the antenna arrays. A parallel, series, or combined feed is used
to produce the necessary amplitude and phase distribution for an array element.
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