Ka‐band 1‐W PHEMT MMIC power amplifiers on 2mil‐thick GaAs substrates

Abstract

ABSTRACT:A fully matched Ka-band INTRODUCTIONLow cost, light weight, high yield, and good reliability are key issues for the successful development of missile seekers, electronic warfare, smart munitions, and commercial point-to-point communication applications. With the maturing of pseudomorphic highelectron-mobility transistor (PHEMT) technology, monolithic millimeter-wave integrated circuit (MMIC) high-power amplifiers (HPAs) can offer all the above benefits. These PHEMT MMIC HPAs have also generated considerable interest in the electronicpower community in recent years. On the other hand, the demand for broadband-data distribution has increased significantly. As lower frequency bands become saturated, communication providers are now focusing on the Ka band for next-generation terrestrial systems, such as satellite communication systems, wireless local area networks (LANs), local multipoint distribution system (LMDS), personal communications network links, and digital radio. As a result, research activities in Ka-Band HPAs have also increased significantly in recent years [1][2][3][4][5]. Ka-band terrestrial systems require HPAs with compact size and high reliability. These HPAs also need to be mass producible in order to reduce the cost. Although traveling-wave tube amplifiers (TWTAs) can be used in Ka-band terrestrial systems, solid-state power amplifiers (SSPAs) are less expensive, smaller in size, lighter in weight, and more reliable. Indeed, the performances of GaAs-based PHEMT microwave monolithic integrated HPAs have been drastically improved in the past decade. In fact, GaAs-based PHEMTs have already been extensively used as SSPAs in Ka-band terrestrial systems. As the performances of GaAs-based PHEMTs are further improved, these devices will continue to offer significant performance enhancements for applications in satellite and ground-based communication systems. To reduce the production cost of Ka-band HPAs, we can use lumped-element matching circuits to miniaturize the size of GaAs-based MMIC chips. On the other hand, we can use multistage configurations to achieve large output power. However, the circuit complexity increases significantly as the number of amplifier stages increases. It should be noted, however, that conventional GaAs-based PHEMTs have been fabricated on 4-mil-thick GaAs substrates [6 -8]. Recent development of the 2-mil-thick GaAs PHEMT fabrication technology has made it possible to pack more power within the same device periphery and to provide a lower production cost without sacrificing the device performance. This article describes the design, fabrication, and testing of Ka-band HPAs using lumped-element matching circuits and 2-mil-thick GaAs PHEMT fabrication technology. The proposed two-stage AlGaAs/InGaAs/GaAs PHEMT MMIC [9,10] HPA delivers a 1-W output and a linear power gain larger than 10 dB in the frequency range between 30 and 37 GHz. This amplifier is designed to fully match 50⍀ input and output impedances without any external circuit. Figure 1 shows the designed tw...