Grid Array Antennas With Subarrays and Multiple Feeds for 60-GHz Radios

A grid array antenna is presented in this paper with sub grid arrays and multiple feed points, showing enhanced radiation characteristics and sufficient design flexibility. For instance, the grid array antenna can be easily designed as a linearly- or circularly-polarized, unbalanced or balanced antenna. A design example is given for a linearly-polarized unbalanced grid array antenna in Ferro A6M low temperature co-fired ceramic technology for 60-GHz radios to operate from 57 to 66 GHz (≈ 14.6% at 61.5 GHz ). It consists of 4 sub grid arrays and 4 feed points that are connected to a single-ended 50-Ω source by a quarter-wave matched T-junction network. The simulated results indicate that the grid array antenna has the maximum gain of 17.7 dBi at 59 GHz , an impedance bandwidth (|S₁₁| ≤ -10 dB) nearly from 56 to 67.5 GHz (or 18.7%), a 3-dB gain bandwidth from 55.4 to 66 GHz (or 17.2%), and a vertical beam bandwidth in the broadside direction from 57 to 66 GHz (14.6%). The measured results are compared with the simulated ones. Discrepancies and their causes are identified with a tolerance analysis on the fabrication process.

I. Introduction

The atmospheric absorption factor and abundantly available spectrum resources have made the 60-GHz band attractive for short-range and high-speed wireless communications [1]. The recent advances in CMOS have enabled single-chip solutions of 60-GHz radios, paving the way for the 60-GHz band being explored for commercial applications [2], [3]. For the 60-GHz market to flourish, however, cheap antennas are required, not only low-cost IC chipsets [4]–[8]. Also, high-gain antennas are needed, due to low transmit power (10 mW), large propagation loss (68 dB at 1 m), and high data rate Gbps [9]. Planar array antennas on standard low temperature co-fired ceramic (LTCC) and printed circuit board (PCB) processes are found suitable for 60-GHz integrated radios for their high gain and low profile. For example, a patch array antenna [10] fed by a T-junction network on an LTCC substrate achieved the maximum gain of 14.1 dBi with 4×4 radiating elements at 61 GHz and a slot array antenna [11] based on the substrate integrated waveguide in a PCB substrate attained the maximum gain of 22 dBi with 12×12 radiating elements at 60.5 GHz.