Another way to achieve orthogonality of MIMO radar wave- forms is FDMA, where the signals transmitted by different antennas are modulated onto different carrier frequencies. This approach suffers from several limitations. First, due to the linear relationship between the carrier frequency and the index of antenna element, a strong range azimuth coupling occurs when using the classic virtual uniform linear array (ULA) configuration , , . To resolve this aliasing, the authors in  use random carrier frequencies, which creates high sidelobe level. These may be mitigated by increasing the number of transmit antennas, which in turn increases system complexity. The second drawback of FDMA is that the range resolution is limited to a single waveform’s bandwidth, rather than the overall transmit bandwidth , . To increase range resolution, the authors of ,  use an inter-pulse stepped frequency waveform (SFW), utilizing the total bandwidth over the slow time , . However, SFW leads to range-Doppler coupling  and the pulse repetition frequency (PRF) increases proportionally to the number of steps increasing range ambiguities , .
Baca lebih lanjut
Baca lebih lajut