Ionosphere effect estimation in micro-Doppler signature extraction for P-band radar targets

Micro-motion depicts the special feature of the target, which is an important basis for target recognition. As for early warning radar, P-band radar has longer range, thus the warning time can be nearly 20 minutes advanced by using it, which can contribute to the detection and identification of the targets. Works have been done in estimating micro-motion parameters on P-band, however, one of the problems is that the ionospheric effects are always neglected. P-band echoes of the ballistic missile will be inevitably affected by the ionosphere during its flight, which will lead to propagation delay of the signal. This paper focuses on the parameter estimation of the micro-motion target on P-band, and proposing a correction method of the ionospheric effects for micro-motion frequency extracting based on Multicarrier Modulated (MCM) radar signal. In order to eliminate the ionospheric effects, we firstly analyze the change of total electron content (TEC) according to the missile trajectory. Then multiple carriers are applied to deduce the propagation delay of the ionosphere based on radar echo model, propagation delay caused by the micro-motion and the ionosphere are separated. After that, micro-motion frequency can be obtained by using Fourier transformation on the uncontaminated spectrum. Finally, simulation results verify the effectiveness of the proposed algorithm. Compared with the ionosphere correction algorithm for P-band synthetic aperture radar (SAR) imaging based on double frequency measurement (DFM) method, the root-mean-square-error (RMSE) of the ionosphere in MCM method is one-fifth on average of that in DFM method. When the carrier frequencies are 430 MHz and 455 MHz, the accuracy of the estimated micro-motion frequency reaches up to 95.0% as the SNR of the signal is 17 dB.