Solving the Spectrum Crisis: Intelligent, Reconfigurable Microwave Transmitter Amplifiers for Cognitive Radar

In 2009, the U.S. Federal Communications Commission (FCC) chair, Julius Genachowski, warned of a looming spectrum crisis [1]. Issues such as a 2010 saga involving satellite communications interfering with the global positioning system (GPS)have reminded us that spectrum is becoming an ever-precious commodity. With wireless broadband technologies evolving at a rate that will outgrow the available spectrum, the U.S. government has acted to try to "stop the bleeding." President Barack Obama\´s National Broadband Plan of 2010 [2] mandates that 500-MHz of spectrum be reallocated for wireless broadband applications. However, the continued surge in wireless spectrum users shows that even this spectrum will be used quickly and that a new paradigm is needed. Many have suggested that dynamic spectrum access (DSA), where spectrum is assigned in real time, will be the sharing protocol of the future, and that future spectrum users will be required to be frequency-flexible and cognitive. Radar systems are spectrum users that, in their present form, will have difficulty operating in this future environment because of their fixed operating frequencies, high power, and tendency to leak power into neighboring bands and interfere with other users. In 2011, National Telecommunications and Information Administration (NTIA) Chief of Staff Thomas Power stated, "The community and policy makers must begin to understand the challenges and constraints that currently exist for radar" [3]. The last three years have witnessed an upshot of radar spectrum conferences and meetings, many organized by the NTIA and the Department of Defense\´s (DoD\´s) Joint Spectrum Center. Our interest has been stimulated through encountering this issue in military radars, and in participating as speakers and panelist in many of these meetings, including a 2011 NTIA meeting for radar and communications experts to converse about coexistence challenges. However, the DoD, the FCC, and the NTIA still have not developed- any technically sound solutions to achieve spectrum sharing between radar and communications. Wireless broadband expansion is not going away. The cry to radar operators is clear: radar systems must change how they operate.