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Waveform diversity, which can be used to resolve range ambiguity and suppress range folded clutter in pulse-Doppler radar system, has attracted an increasing amount of attention in recent years. Especially for high pulse repetition frequency (PRF), the range folded clutter severely impacts the detection of small targets with long range and low speed. Using diverse waveforms, pulses of the transmitted sequence of radar are agile. It is possible to construct corresponding matched filters (MFs) to suppress the range folded clutter. However, the performance greatly depends on the cross-correlation among pulses of the transmitted sequence. In this paper, diverse nonlinear frequency modulation (NLFM) waveforms, the spectra of which are based on different window functions, are designed to construct a signal library, and positive and negative frequency modulation rate are both considered. Then, a Min-Max algorithm is proposed for sequentially selecting NLFM waveforms from the signal library to generate an optimal transmitted sequence. Pulse-to-pulse random initial phases are also added to each pulse of the sequence to further improve the irrelevance among pulses. Moreover, to eliminate the range sidelobe modulation (RSM) effect in Doppler processing, a cyclic algorithm for designing joint mismatched filters (JMMFs) with finite impulse response (FIR) is provided. Simulations show that the optimized pulse-agile sequence based on NLFM waveforms yields satisfactory performance on the ambiguity function, and range folded clutter can be effectively suppressed.

The phase-derived velocity measurement (PDVM) method based on range profiles cross-correlation (RPCC) can achieve high precision velocity estimation of Doppler centroid for complex targets, and the PDVM satisfied the precision requirements of envelope alignment and phase adjustment for ISAR imaging, that is, the PDVM method can be employed to attain target translational reconstruction. On this basis, this paper proposes an interferometric inverse synthetic aperture radar (InISAR) imaging method based on translational reconstruction. This method can obtain high-quality ISAR images by compensating the translational velocity at the target's Doppler centroid of different channel echoes. Moreover, the translational reconstruction also indirectly achieved image registration. Compared with the traditional approaches, the proposed method is not only suitable for low signal-to-noise ratio (SNR), but also simple to implement. Furthermore, it can better ensure the coherence between different channels of ISAR images, that is, the InISAR imaging results with higher precision can be obtained. The correctness and robustness of the proposed method are verified by the measured data of civil aircraft.

The target micro-motion features contain unique structural information and motion information, which can be utilized as an important basis for target recognition. At present, the main constraints of micro-motion feature extraction for high-speed targets include that the translational compensation is inaccurate, the scattering points are difficult to distinguish, the micro-motion amplitude is small, the data rate is not high enough, and so forth. The phase-derived velocity measurement (PDVM) method based on wideband radar has phase-magnitude velocity measurement precision, which can accurately reconstruct the target motion while ensuring high data rate, and meet the micro-motion measurement requirements of high-speed targets. In this paper, a PDVM method for high-speed targets based on wideband direct sampling LFM radar is proposed. The high-precision velocity measurement performance and micro-motion measurement capability of the proposed method are verified by simulation.

This paper presents a high-precision position finding method for short baseline radar system based on phase-derived range and angle measurement. Multiple baselines are utilized to measure the azimuth and elevation angle based on phased-derived angle measurement method, while the target range is measured based on phased-derived range measurement. The phase-derived range and angle measurement has much higher accuracy than envelope-based methods, thus can achieve high-precision position finding. The performance of the proposed method is verified by simulation and ejection ball experiment.

A novel ISAR (inverse synthetic aperture radar) motion compensation approach in conjunction with the phase-derived velocity measurement (PDVM) technique to extract micro-motion feature is presented in this paper. In order to obtain high quality ISAR image, the accurate velocity information provided by PDVM is utilized for target motion compensation. By analyzing proper amount of adjacent Doppler cells around the prominent scatterer in the ISAR image, the impact of other scatterers is effectively reduced for micro-motion extraction. Experiments based on radar measured data are performed to show the effectiveness of the proposed method.