Gain Enhancement of Millimeter-Wave On-Chip Antenna Through an Additively Manufactured Functional Package

Abstract

The antenna-on-chip (AoC) presents an excellent solution for applications requiring higher integration levels and lower cost; however, its radiation performance is poor due to the inherent lossy Si substrate in conventional complementary metal–oxide–semiconductor (CMOS) processes. It is well known that every chip requires a package to protect it from the environment; however, this package does not provide any functionality, despite adding to the cost and required space. In this article, we propose a functional package that has been designed to enhance the gain of the AoC. A 71 GHz coplanar waveguide (CPW)-fed on-chip monopole antenna, driven by a voltage-controlled oscillator (VCO) and frequency doubler, was realized in the standard 0.18 $\mu \text{m}$ CMOS technology. As a first step to enhance its gain, the AoC was designed on top of an artificial magnetic conductor (AMC) surface. Further gain enhancement was achieved by transforming the chip package into a combination of a superstrate layer and a Fresnel lens, qualifying this as a system-on-package (SoP). The package has been realized through additive manufacturing to maintain the low-cost aspect. Overall, the measured gain of the packaged AoC is 6.8 dBi, which has been enhanced by ~20 dBs compared to the unpackaged antenna without an AMC layer.