A waveform design technique for range and Doppler ambiguity mitigation

Space Based Radars (SBR) have been considered for a number of civilian and military missions. Most recently, SBR concepts are being developed to have the platform operate in multiple modes, i.e., as a synthetic aperture radar (SAR) and as a moving target indication (MTI) radar for both slow surface moving targets (SMTI) and fast moving airborne targets (AMTI). This set of requirements can be dealt with by a properly designed antenna. Launch vehicle considerations, however, may impose restrictions on the size of the antenna needed to perform the mission requirements. Due to the collection geometries involved, there may be instances where these restrictions will result in degradation of the radar product due to either range or Doppler ambiguities. In order to overcome these difficulties, transmit waveform diversity can be used to pre-condition the waveform to counter this problem. An approach has been developed that considers a combination of techniques, using both inter- and intrapulse modulation, orthogonal waveforms, non-traditional pulse compression and a priori knowledge of the collection geometry to enhance both SAR and MTI performance.