Research
Target Distance Direct Determination from QPSK Mapped OFDM Modified Radar Signal
Time shift of the target reflected signal in radar system can be calculated directly from modified QPSK mapped OFDM signal. It makes possible to determine target distance from radar station. When time shift respecting to phase delay depends on OFDM subcarrier number, modified OFDM signal prevents that dependence and lets system to decide the phase delay directly from QPSK-OFDM signal rotation angle of constellation points. Additionally, proposed system requires low computing resources as the entire calculation process could be done during a single OFDM symbol.
Doppler Shift Extraction from QPSK Mapped OFDM Signal Constellation
Doppler effect gives a frequency offset on received OFDM signal in radar system. That offset can be seen as a distortion and rotation of reflected signals QPSK mapping vectors. It is possible to determine moving target velocity by estimating expected value of the distorted signal and then calculating the rotated angle. A mathematical relationship between Doppler frequency shift and rotated angle of QPSK mapping vectors was obtained. The recommended systems will require less computing resources, because Doppler frequency shift calculation could be done during one OFDM symbol.
