Efficient mode scheduling for airborne E-scan radars

Using Electronic scanning (E-scan) radars it is possible to employ multichannel processing algorithms such as STAP to suppress clutter. A further significant advantage of E-Scan radars is the rapid look-back capability for simultaneous Search and Track operation. A great deal of experience and know-how on radar mode scheduling exists for Mechanical scanning (M-scan) radars. This should be used in combination with the new range of capabilities for E-scan radars. For both Air-to-Air and Air-to-Ground operation, E-scan radar multichannel processing can greatly improve present mode performance. Currently, for Air-to-Air operational modes, HPRF waveforms are used to detect targets in nose-on aspect. Tangential or rear aspect targets often disappear in the mainlobe or sidelobe clutter echoes. In these circumstances, airborne radars usually switch to MPRF modes to exploit the all-aspect capability of these modes. However, one disadvantage of MPRF modes is their reduced detection range as well as the requirement for a guard antenna. For E-scan radars it is also possible to use STAP processing algorithms for clutter suppression. For Air-to-Ground operational modes, LPRF waveforms can detect ground targets with velocities in antenna boresight direction exceeding a minimum detectable velocity that depends on the clutter Doppler extension. Using E-scan radars, the antenna beamwidth is dependent on the beam look direction. For off-boresight angles, this has the effect that the Doppler width of the mainlobe clutter is wider compared to that for M-scan radars. In this case too, STAP processing with E-scan radars can help to suppress clutter and to detect ground targets below the minimum detectable velocity given by conventional processing. The purpose of this paper is to highlight the possibility of detecting both Air-to-Air and Air-to-Ground targets with the most suitable waveform. For example, for closing Air-to-Air targets, the use of HPRF waveforms provides the greatest detect- - ion range and obviates the need for a guard antenna, while the use of STAP with multi channel processing provides better performance when the air target is in tangential or rear aspect. First, when an E-scan instead of a M-Scan radar is used, the differences in clutter returns for HPRF waveforms are highlighted. Then, depending on targets velocity and aspect angle, conditions are defined for which the radar can use a HPRF or MPRF waveform or for when STAP processing is necessary so as not to lose the target.