Integrated Active Antenna Arrays for Millimeter Wave Wireless Communications

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9979282PozarWhile the vast majority of commercial wireless systems deployed to date are characterized by the use of frequencies below 2 GHz and the use of low-gain antennas, many of the proposed high-speed wireless data networks of the future will use millimeter wave frequencies and high gain antennas. Examples include point-to-point radios operating at 23 and 38 GHz (largely used for cellular and PCS base station backhaul traffic), local multi-point distribution systems (LMDS) operating at 28 GHz, and ground terminals operating at 20 and 30 GHz for the Celestri and Teledesic low-earth orbit (LEO) satellite systems. Although micro-strip antenna technology has matured considerably over the last 15 years, a persistent problem has been the fact that micro-strip feed line losses increase exponentially with antenna size and with frequency, so that it is impossible to construct an efficient high-gain micro-strip array at millimeter wave frequencies using a coplanar micro-strip feed network. The research plan described here proposes to address this and related fundamental problems associated with millimeter wave wireless systems by studying the integration of as much of the critical antenna and front-end microwave electronics as possible. We will make use of recent advances in silicon machining, wafer bonding and polymer films to create structures that were not possible just a few years ago. In addition, by considering the antenna and RF electronics as a whole unit, we will be able to greatly reduce cost by focusing on processing only the component characteristics that are necessary for high efficiency arrays.A three-year research effort is proposed to carry out experimental and theoretical investigations of millimeter wave antennas and RF front-end circuitry for future wireless data networks and systems. Both monolithic and semi-hybrid approaches will be studied. One component of the research involves the development of HBT power amplifiers with specific geometry, configuration, and characteristics that will be favorable for monolithic integration with micro-strip antenna elements on GaAs substrates to minimize feed losses at millimeter wave frequencies. Using state-of-the-art MOCVD techniques, we will develop optimum HBT structures with sufficient gain in the millimeter wave regime without the requirement of nano-fabrication technology. In fabrication of the HBTs, we will collaborate with researchers at the Raytheon Advanced Device Center where state-of-the-art millimeter wave devices and integrated circuits are presently being developed. We will work with Raytheon researchers on the device design (both epitaxial structure and layout), process sequences, and specific process steps. We believe their experience and expertise will significantly enhance and accelerate our development of HBT technology for this program. Graduate students involved will also benefit greatly from this interaction with our industrial partners.***