International Symposium on Antennas and Propagation
Design of Circularly Polarized Patch Antennas with Coaxial Feed through a Silicon Chip
KimHuey Koh, Takuichi Hirano, Jiro Hirokawa, Makoto Ando,
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In late years, semiconductor devices have increasing demands for smaller size and more functionality as the radiator. In order to meet these demands, 60 GHz millimeter wave antenna integrated in silicon CMOS chip has very attractive features that offer massive available bandwidth and high-speed. A bottleneck of the antenna design is that the substrate thickness is too thin (~10 μm) to realize high efficiency and/or wide bandwidth. So, the antenna structure on the back side of silicon CMOS chip with a thick resin (~200 μm) had been proposed by the authors . A dipole antenna on the backside of a 60 GHz silicon CMOS chip has been investigated . The dipole antenna is on thick resin with about 200 μm to achieve high radiation efficiency and bandwidth on the backside of a 5mm square silicon CMOS chip in 60 GHz band. The dipole antenna is connected through via hole to the RF circuit layer on the opposite side of the same CMOS chip. The antenna was fabricated on the resin and the reflection, the gain and the radiation pattern were measured by using the waveguide aperture feeder which is not realistic. In this paper, the coaxial feeder through the resin on the backside of chip is designed for a circularly polarized 2x2 patch antenna array for monopulse operation as shown in Fig.1. The challenge here is that not only four radiating element but also their coaxial feeders should be accommodated in a very small and limited space of the 5mm square chip. The monopulse operation gives a simple method to find the direction of arrival, and the circular polarization dispenses with polarization adjustment between transmission and received antennas. Sequentially rotated arrangements  for the 2x2 array element are used, as shown in Fig. 1 (b) to gather via holes near the center of the chip. The sequentially rotated arrays arranged with quadrature phase excitation of 0°, 90°, 180°, 270° would be achieve by using the RF circuitry on the backside of the chip.