An Investigation of Higher-order Mode Microstrip Antennas for 60 GHz Short-range Wireless Communications

Description

Oxygen absorption of millimeter-wave at 60 GHz limits its applications to short-range and inter-satellite communications. However, its absolute bandwidth ranging from 3.5 GHz in Australia to 7 GHz in Japan and North America and to 9 GHz in China and Europe makes millimeter-wave communications at 60 GHz a viable technology for high-throughput wireless communications at gigabits per second. This license-free frequency band is ideally suited for personal area networks (PANs), wireless high definition multimedia interface (HDMI) and wireless point-to-point telecommunications backhauls, especially in indoor and intravehicular environments for the first two applications.Toshiba has realized a 60GHz 90 nm CMOS transmitter/receiver chip in which a loop antenna has been integrated in the package. The IBM chip employs 0.13 μm SiGe technology in which the antenna is a dipole. At 60 GHz, the length of the dipole is less than 1 mm and monolithic integration of passive and active millimeter-wave components on the same substrate becomes feasible. However, there are circumstances that this off-the-shelves antenna in package (AIP) may not be usable due to the form factor of the applications or specific performance requirements. Because of their minute size, tailor-made 60 GHz antennas necessitate expensive fabrication process. Alternate solutions, suitable for Hong Kong-based electronics manufacturing services (EMS) providers, renowned for their ingenuity in providing low-cost, high-quality adaptation of the original designs of their international clients, are needed to maintain their competitive edge in this emerging market.The 60 GHz antenna in AIP operates at its fundamental mode. To increase its size for easier fabrication, the researchers can design the antenna to operate at its higher-order mode. There are two factors hindering the popular use of higher-order mode antennas. Firstly, the antenna will have multiple beams and thus a lower gain. Secondly, the absolute bandwidth may not be sufficient for the intended applications of IEEE 802.15.3c. Even for the high-order mode antenna, its overall size should still be kept small to meet the small form-factor required for wireless local area network (WLAN) or Wireless PAN (WPAN). Furthermore, there are studies showing that circular polarization (CP) antennas can reduce the multipath effects in line-of-sight (LOS) environments in the 60 GHz band and therefore, investigation of highorder mode CP antennas is also warranted.In this project, the researchers propose to design high-order mode antennas at 60 GHz band to mitigate the expensive fabrication cost. Size reduction techniques will be employed to limit the overall size of the antennas. The multiple beam characteristic of the higher-order mode will be eliminated using their patent-pending differential feed technology. The bandwidth of the high-order mode antenna will be enhanced using capacitive and inductive cancellation technique. Wideband CP antenna will then be designed using the designed linear polarized antenna elements.Based on their preliminary results, the researchers strongly believe that the proposed 60 GHz band antennas operating at high-order mode would provide a low-cost alternative to AIP that have both scientific and commercial impact.