Radar Transmit Spectrum Sharing Techniques Development

C-RACAS (AN/ZPY-9) integrated onto MQ-4C Triton, satisfies FAA requirements to Detect and Avoid non-cooperative traffic using an Air-To-Air Radar in the National Air Space as well as provide safety for Due Regard operation. It must coexist with other friendly radar systems operating in the same frequency band.  While AN/ZPY-9 has robust signal processing protection from received interfering pulses, this study addresses transmit spectrum sharing techniques that provide deconfliction of interference for coexistence with friendly radars. AN/ZPY-9’s operates between 5.35 and 5.46 GHz which is protected against other radars and Unlicensed National Information Infrastructure devices.  In this frequency band stations in the radiolocation service shall not cause harmful interference to, nor claim protection from, radar systems. Practically, there are numerous legacy radars in this band that cannot be changed to adhere to this note when the AN/ZPY-9 is deployed. Consequently, DO-366 Phase 1 MOPS Para 2.2.4  and RTCA recommendation to ICAO  require DAA radars, such as AN/ZPY-9, to have Dynamic Frequency Selection (DFS) which provides for DAA radar switching automatically between frequency channels, within the band, in the presence of interference from another radar. The 5.35 to 5.46 GHz band is currently utilized by many different types of radars.  The DoD specifically uses this band for a wide variety of ground based, shipborne, and airborne radars. By far, the most prevalent of these are surface based radars.  Some military radars have both narrow-band and wide-band waveforms which sometimes fall within the AN/ZPY-9 operating band.  DFS techniques are appropriate to address the narrowband friendly radar emissions per DO-366. Dynamic Frequency Vacate (DFV) was introduced in Phase 1 to address the deconfliction of broadband waveforms, from the military radars, with the waveforms of the AN/ZPY-9.  DFV monitors the spectrum for short duration broad-band emissions, within the AN/ZPY-9 operating frequency range, and provides a quick response to suspend radar transmission until the conflict ceases. These suspensions of transmission events will usually only last a few hundred milliseconds. The research focus of the proposed Phase II effort is to further develop and mature, as well as demonstrate, Dynamic Frequency Selection (DFS) and Dynamic Frequency Vacate (DFV) transmit spectrum sharing techniques to support transition of the AN/ZPY-9 to SDD.  These spectrum sharing capabilities are critical for the increased operating air space volume of the AN/ZPY-9, while Triton is operating in the proximity of Friendly Ground Radars (FRG) and to directly mitigate potential program-level risks.  The secondary research focus is to support the development of High Gain ESM (HGESM) for future addition of upgraded capabilities to the same AN/ZPY-9 system. The HGESM effort is being led by Azure Summit and detailed in their Phase 2 proposal submittal under the same topic.