This paper describes a concept of the circulating codes covering the whole class of the space-time codes. The circulating codes do not narrow the radiated pattern of the antenna array, thus providing a wide angular coverage, possibly tunable. In turn, the beam-forming on transmit is achievable by means of the signal processing in one (or each) receiver channel. The modelling results demonstrate the efficiency of the circulating codes based on their multidimensional ambiguity functions.
This paper describes an analytical model of the full-polarimetric sea surface scattering and Doppler signature. The model combines the small-slope-approximation theory (at the second order) with a weak nonlinear sea surface representation. Such a model is used to examine the variation of the Doppler central frequency/bandwidth and of the normalized radar cross section as function of wind speed and direction. The results suggest that the model can be a valuable tool for the accurate observation of sea surface currents.
A global signal processing chain for detection and localisation of moving human targets using a multistatic ultrawideband radar system with widely separated receiving antennas is proposed. The design options for the system are presented and justified, and the required signal processing steps are summarised. Special attention is then devoted to the critical issue of target association. A slow-time feature, video time density function, is proposed to associate target responses in different receiver channels. Video time density function is extracted from range-Doppler video sequences for each target. It indicates the slow-time evolution characteristic of the moving human targets, and thus is invariant to radar observation angles (provided that the target can be detected). Auction algorithm-based global nearest neighbour approach is extended to the measurement-to-measurement association between receivers. The decentralised tracking approach proposed is experimentally verified on measured data.
This study presents a simple yet ingenious transmit diversity technique (so-called hybrid codes) for phased array radar. Its main property is the capability of digital beamforming on transmit just like with a set of orthogonal signals employed by coherent multiple-input-multiple-output radar and simplicity (only one waveform has to be generated in time). The performance of the hybrid codes is examined by analysing the transmit ambiguity functions containing beampatterns and range profile for all angular directions of interest.
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