A high powered radar interference mitigation technique for communications signal recovery with fpga implementation
[Technical Report, Master's Thesis]
Naval Postgraduate School
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In this thesis, we investigate the demodulation of a communications signal that is interfered with by a high-powered radar signal. We choose quaternary phase-shift keying QPSK modulation for illustration. The radar phase offset is initially assumed to be fixed. Later, a practical phase sequence is added to the phase offset. A least-squares estimator LSE is used to estimate the amplitude and fixed-phase offset of the interfering radar signal to be used for interference cancellation. Then, we utilize a maximum-likelihood detection MLD receiver. We show that the QPSK symbol error ratio SER improvement in the radar interference depends on collection time. The variance of the estimate increases as the QPSK signal-to-noise ratio SNR increases. The increase in variance affects SER. SER results approach the ideal with increasing collection times. For the case where the phase offset includes a phase sequence, the original LSE technique is modified. Later, a system is created in Simulink and converted to hardware-description language HDL. The SER performance of the HDL implementation in hardware is compared to those of the signal model. SER performance is somewhat degraded in the hardware implementation.
- Active and Passive Radar Detection and Equipment