Linearly polarized and circularly polarized Arrays in LTCC Technology for 60GHz Radios

Abstract

Designs towards low-cost highly-integrated 60GHz transceivers have been carried out using the multi-layer low temperature cofired ceramic (LTCC) based System-in-Package (SiP) technology [1]. 60GHz antenna designs are also shifting from conventional discrete designs to Antenna-in-Package solutions [2,3]. In this paper we present two antennas for 60GHz radios in Ferro A6 LTCC package with a relative dielectric constant of e r = 5.9. The two antennas are fed by stripline (SL) structures. This makes the antenna performance less sensitive to the surrounding package- and PCB-level dielectric and metal layers. These structures also decouple the design of the antenna from the exact physical properties of the package, simplifying simulation and modeling complexity. The two antennas have different polarization characteristics. One antenna is circularly polarized (CP), which is realized by an aperture-coupled 2×4 patch array with a sequential rotation scheme. With this scheme, wide axial ratio (AR) and impedance bandwidth are achieved. The other antenna is linearly polarized (LP), which is realized by a grid array antenna. This type of antenna is particularly suitable for fabrication in LTCC with rectangular meshes of microstrip lines for radiation. It also avoids the complicated feeding network associated with the commonly used patch array antenna. In view of wireless access applications, the CP property is very desirable for 60GHz antennas [4]. This is because the LP antenna requires the transmitting and receiving antenna to be rotated properly to achieve polarization matching. Using the CP antenna, this problem can be eliminated. In this paper, we not only present the design of two antennas but also the measurement to show the wireless access advantage of the CP patch array over the LP grid array antenna.