The nonstationarity of interferences and array errors may bring fatal degradation to the interference cancellation performance of an adaptive beamformer. Covariance matrix tapering (CMT) can produce wide troughs in receiving pattern and becomes a promising solution. However, not only the full adaption methods but also the robust sidelobe canceller widen all nulls symmetrically to the original directions of arrival (DOAs) with the same width. In fact, in most cases, the adaptive pattern does not need symmetrical and equivalent-width nulls since it is of little possibility that different interference poses the same nonstationarity. To cover the worst nonstationarity, traditional CMT methods need to produce a widest null and will suffer a waste of degrees of freedom (DOFs). In this paper, a flexible method for null widening is proposed which can produce wide null with different desired width and asymmetry. The asymmetry is developed from the spatial asymmetrical interference cluster, and the unequal null width is produced by disturbing different interference space with different tapering matrix. Computer simulation result corroborate the feasibility and merits of the proposed method.

Nonstationary interference, generated by time-varying propagation paths or relative motions between the receiving array and jamming sources, is a serious problem faced with radar and wireless communication systems. To solve this problem, null widening has been proposed and proven to be able to achieve reliable performance. However, most existing methods were proposed for full-array or dimension-reduced beamformer. Little literature discusses its application on sidelobe canceller, a useful technique in real system. In this paper, a computationally efficient null widening method for sidelobe canceller is proposed. This method is a covariance matrix taper-based method which puts fictitious interferences into snapshots to widen the sharp null. The proposed method can achieve satisfactory performance and needs less computation costs than existing methods. Detailed derivations and simulation results show its effectiveness.

Beam hopping technology is considered to provide a high level of flexible resource allocation to manage uneven traffic requests in multi-beam high throughput satellite systems. Conventional beam hopping resource allocation methods assume constant rainfall attenuation. Different from conventional methods, by employing genetic algorithm this paper studies dynamic beam hopping time slots allocation under the effect of time-varying rain attenuation. Firstly, a beam hopping system model as well as rain attenuation time series based on Dirac lognormal distribution are provided. On this basis, the dynamic allocation method by employing genetic algorithm is proposed to obtain both quantity and arrangement of time slots allocated for each beam. Simulation results show that, compared with conventional methods, the proposed algorithm can dynamically adjust time slots allocation to meet the non-uniform traffic requirements of each beam under the effect of time-varying rain attenuation and effectively improve system performance.

In this letter, we propose a new movable antenna (MA) enabled symbiotic radio (SR) system that leverages the movement of MAs to maximize both the primary and secondary rates, thereby promoting their mutualism. Specifically, the primary transmitter (PT) equipped with MAs utilizes a maximum ratio transmission (MRT) beamforming scheme to ensure the highest primary rate at the primary user (PU). Concurrently, the backscatter device (BD) establishes the secondary transmission by overlaying onto the primary signal. The utilization of MAs aims to enhance the secondary rate by optimizing the positions of MAs to improve the beam gain at the BD. Accordingly, the beam gains for both MA and fixed-position antenna (FPA) scenarios are analyzed, confirming the effectiveness of the MA scheme in achieving the highest primary and secondary rates. Numerical results verity the superiority of our proposed MA enabled scheme.

In this study, the authors consider a two‐stage constant false alarm rate (TS‐CFAR) detection problem in a distributed multiple‐input–multiple‐output radar. This study is motivated by the fact that the clutter plus noise power and the signal to clutter plus noise ratio may be both unknown in practice. Two TS‐CFAR detectors are proposed, that is, TS generalised likelihood ratio test detector and TS adaptive matched filter detector. Each of the proposed detectors has two thresholds: the first one called local threshold controls the communication rate and the second one called global threshold adjusts the global probability of false alarm. It is proved that both of the proposed detectors have CFAR property. Numerical results illustrate that the two proposed detectors have good detection performance at a low communication rate.

Deception jamming poses a fatal threat to the radar performance, and its jamming performance has been greatly improved through networking. However, available deception electronic counter‐countermeasure (ECCM) methods are mostly developed in the scenario of a single jamming source. Therefore, it is of great importance to develop deception ECCM methods that can counter multiple jammers. This work proposes a deception jamming discrimination method applicable to multiple jammer sources in distributed multiple‐radar system, based on the correlation coefficient between different target‐received signal vectors. The false targets generated by one jammer are highly correlated, while a radar target is uncorrelated with either other radar targets or false targets. For the estimated correlation coefficient, the Fisher z‐transformation is applied to determine the correlation between targets with the Z‐test. Since the jammer usually generates multiple false targets at once to enhance its deceptions, a target can be judged as a false target when multiple targets are highly correlated with it; otherwise a radar target is declared. More importantly, compared with existing methods, no prior information is required here. Simulation results corroborate the feasibility of the proposed discrimination method and its performance due to the influence of jamming‐to‐noise ratio. The spatial correlation of radar targets and geometry conditions are covered.