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Intelligent RF Front-Ends (IRFFE)
During the last two decades, maturation of monolithic microwave/millimeter wave monolithic integrated circuits (MMIC) technology has been the focus of many DoD efforts enabling many of the current generation of military and commercial RF sensors and communication capabilities. Today's typical MMICs include active devices (field effect transistors (FET) or bipolar transistor), capacitors (metal-insulator-metal), thin film resistors, inductors, via hole grounding, and air bridges all integrated on a single semi-insulating (usually GaAs) substrate. Typically, the ultimate component performance is fixed by the design of the "static" input/output impedance matching networks. This approach was first implemented several decades ago and has become the method of choice in today's RF component industry. One of the disadvantages of using conventional MMIC technology is the inability to tune components after fabrication, limiting the ability of the system to adapt and accommodate new functionalities.
The ability of MMICs to intelligently tune or adapt in real time to a situation or to the environment is highly desirable. Such an ability in MMICs could open the door for new opportunities in RF sensing and communication enabling a new class of system architectures with unprecedented performance, agility, and multifunctionality. From a technological standpoint, a compelling reason to pursue the proposed concept is that recent advances in micro-electro-mechanical devices (MEMS), nano-scale analog/digital complementary metal oxide semiconductor (CMOS) technology, and heterogeneous integration techniques allow us to achieve a new class of high performance, compact, and low cost-to-manufacture RF/analog microsystems.
The objective of this effort is to develop and demonstrate revolutionary concepts in devices, fabrication processes, component architectures, and integration technologies to produce highly adaptable, highly integrated analog microwave and or millimeter-wave circuits and components. An Intelligent RF Front-End microsystem is defined as a passive and/or active, highly integrated RF/analog component with the ability to self-assess and adapt itself to meet changing functional requirements or environmental conditions (adjust its performance in real time), by automatically self-tuning its impedance-matching networks. This adaptability characteristic will allow extension of the operational performance of the component to the intrinsic semiconductor device limits.
Communications, radars, and electronic warfare systems tend to have application-specific RF front ends that are carefully tuned by hand to produce optimum performance over a fairly narrow operating condition. Change the application and we build a different system with different components. And, of course, vibration, temperature variation, and aging all eat away at performance.
DARPA's Intelligent Radio Frequency Front Ends (IRFFE) program aims to change this by creating early examples of strategic microsystems: in this case, smart RF components enabling autoadaptive, reconfigurable RF systems that sense their internal and external environments and automatically match impedances and biases through the subsystem, enabling unprecedented agility for diverse DoD radar and communication system applications. It also offers significant cost savings over the entire system life cycle by simplifying system design, reducing maintenance and inventory, and extending the operational lifetime.
IRFFE technology will increase manufacturing yields by giving components the capacity for self-compensation, providing high performance despite fabrication variations. Self-compensation, automated reconfigurability, and exploiting commercial technology are new ways to cut a path to high-performance autoadaptive systems from cheap components.