Guest Editorial

Abstract

T HE ACTIVE (or solid state) phased array [also referred to as active electronically scanned arrays (AESAs)] is currently the work horse for the majority of sensors for high-end RF systems. The evolution of RF packaging/device technologies and architectures continues to mold their capabilities and affordability for the user communities. The U.S. Government is by far the largest sponsor and user, especially the Department of Defense (DoD); however, the Department of Homeland Security (DHS), Department of Commerce (DoC), the Department of Transportation (DoT), and the commercial wireless industry also recognize their utility beyond traditional defense missions. Opportunities to integrate weather and air-traffic surveillance into a single radar and provide increased channel capacity via multiple beams for wireless communications are all enabled by phased arrays.Looking at the evolution of phased arrays from the early 1970s to today, we see a dramatic increase in capability enabled by key technology developments in microwave monolithic integrated circuits (MMICs), packaging, and interconnects. The early focus was at the HF to UHF frequency bands, but today, designs are prolific from -through -band and extend into the millimeter band thanks to the advances in GaAs, silicon, and mixed-signal devices to the microwave and millimeter-wave bands. These developments enable architectures that provide cost/performance trades with scalability and modularity that are now more easily integrated into a wider variety of platforms and applications.The production of AESAs for many military applications and some high-end commercial applications (e.g., Iridium) began in earnest in the early 1990s. Packaging of the microwave electronic circuitry in most cases required hermetically sealed modules and together with the corresponding interconnects, thermal control, etc. dictated the weight and volume of the AESAs. Today's AESAs have evolved to lighter, denser packages, some with hermetic packages and some exploiting alternative environmental protection technologies. This evolution along with technology improvements in MMICs, interconnects, thermal control, etc. have realized 50% savings in both weight and cost.There are many challenges driving the development of the next generation of radar, communications, and electronic warfare phased arrays. The ground-and surface-based applications must meet a broad range of requirements, from simple low-power radars for weather, surveillance, and communications to high-power radars for ship and missile defense. The airborne applications are additionally challenged by the weight, volume, and sometimes the radar cross section (e.g., low RCS for stealth) constraints of the platform. A common challenge across all of the applications, however, is affordability, thus they have traditionally been limited to systems and platforms where the benefits could justify their higher price tag. The maturation of RF panel AESA technology is now beginning to change the cost-benefit paradigm.The industry began investing...

Switchable and tunable triple-channel bandpass filter

“…To meet the external Q value of the three channels, especially to broaden the reconfigurable ranges of the channels, the switchable and tunable triple-channel bandpass filter proposed in this paper adopts the varactor C t4 feed at the port. Figure 7 shows the theoretical external Q values required in the tunable ranges of three channels and the actual external Q values extracted under different C t4 values from formula (11). When C t4 becomes smaller or the frequency becomes larger, the external Q value of each channel becomes larger.…”

“…In Refs. [10][11][12], a compact dual-channel reconfigurable filter is designed by using a dual-mode resonator loaded with varactors. In Ref.…”

“…Although in Refs. [7][8][9][10][11][12][13] the dualchannel reconfigurable filters have been implemented, there is no channel selection function, and the two channels can work only at the same time. In Refs.…”