Dual Grid Array Antennas in a Thin-Profile Package for Flip-Chip Interconnection to Highly Integrated 60-GHz Radios

We examine the current development of highly integrated 60-GHz radios with an interest in antenna-circuit interfaces. We design and analyze grid array antennas with special attention to the differential feeding and the patterned ground plane. More importantly, we integrate two grid array antennas in a package; propose the way of assembling it to the system printed circuit board; and demonstrate a total solution of low cost and thin profile to highly integrated 60-GHz radios. We show that the package in low temperature cofired ceramic (LTCC) technology measures only 13×13×0.575 mm³ ; can carry a 60-GHz radio die of current and future sizes with flip-chip bonding; and achieves good antenna performance in the 60-GHz band with maximum gain of 13.5 and 14.5 dBi for the single-ended and differential antennas, respectively.

I. Introduction

Traditional commercialized 60-GHz radios have been designed as an assembly of several microwave monolithic integrated circuits (MMICs) in gallium arsenide (GaAs) semiconductor technology. They have been used for Gigabit Ethernet (1.25 Gb/s) bridges between local area networks [1], [2]. Recently, integrated transmitter (Tx) and receiver (Rx) MMICs in 0.15- GaAs pHEMT and mHEMT processes have been realized to support data rates of several Gb/s for 60-GHz short-range applications [3], [4]. However, the 60-GHz radios in GaAs MMICs are expensive and bulky. In order for 60-GHz radios to have mass deployment and meet consumer marketplace requirements, the cost and size of any solution must be low and compact. That implies silicon, not GaAs as the better technology choice. In fact, designs towards low-cost highly integrated 60-GHz radios have been realized in silicon technologies. For example, Floyd, et al. have demonstrated a 60-GHz Tx and Rx chipset in a 0.13- silicon-germanium (SiGe) technology [5] and Tanomura, et al. in a 90-nm complementary metal oxide semiconductor (CMOS) technology [6]. An examination of the above works and many other reported 60-GHz highly integrated radios in SiGe and CMOS reveals that two types of antenna-circuit interfaces as shown in Fig. 1 can be identified in the current two-chip solutions. The first type features the 50- single-end and the second type the 100- differential antenna-circuit interfaces. For the first type, the 60-GHz on-chip input/output pads are designed as the ground-signal-ground (GSG) pads; while for the second type as the ground-signal-ground-signal-ground (GSGSG) pads. The GSG pads are bonded to an off-chip but in-package single-end antenna; while the GSGSG pads a differential antenna with either flip-chip or wire-bonding techniques [7]–[10]. Fig. 1.

Illustration of the (a-b) single-end and (c-d) differential antenna-circuit interface in current highly integrated 60-GHz radios.