Antenna-In-Package Forges Interconnection At 60 GHz

TO ENABLE VERY-HIGH-DATA-RATE applications, the IEEE 802.15.3c standards group is defining specifications for 60-GHz radios that use only a few gigahertz of unlicensed spectrum. Typically, those radios have been designed by assembling several monolithic microwave integrated circuits (MMICs) in gallium-arsenide (GaAs) semiconductor technology. Yet a recently proposed antenna, which targets highly integrated 60-GHz radios, is specifically designed to exhibit capacitive input impedance that complements low-cost wirebonding packaging and assembly techniques. It was developed by Y.P. Zhang and M. Sun from Nanyang Technological University, K.M. Chua and L.L. Wai from Singapore Institute of Manufacturing Technology, and Duixian Liu from the IBM T.J. Watson Research Center.

At millimeter-wave frequencies, one challenge is the realization of a low-loss interconnection between a radio chip and antenna using a wirebonding technique. Although this antenna-inpackage (AiP) design may provide an answer, it also invites the risk of the antenna coupling to the radio chip. In the worst-case scenario, in which no guard ring and pattern grounded shield are used for the inductor and the distance between the inductor and antenna is the shortest allowed by the on-chip layout rule, coupling from the in-package antenna to the on-chip inductor was lower than 27.5 dB at 60 GHz.

The quasi-cavity-backed, guard-ring-detected, substrate-material-modulated slot antenna is implemented in a thin cavity-down, ceramic-ballgrid- array (CBGA) package in low-temperatureco- fired-ceramic (LTCC) technology. It offers an impedance bandwidth of 59 to 65 GHz with 94 percent estimated efficiency. See "Antenna-in- Package Design for Wirebond Interconnection to Highly Integrated 60-GHz Radios," IEEE Transactions On Antennas And Propagation, October 2009, p. 2842.

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