频控阵雷达动态点状波束合成

频控阵(Frequency diverse array, FDA)雷达通过在每个阵元辐射信号上附加一个微小频差，实现依赖于距离和角度的波束方向图合成。由于在距离角度维的缠绕和时变特性导致其波束指向难以控制。针对该问题，本文重点研究了FDA雷达发射波束时变特性和点状波束合成。首先，分析了线性频率增量FDA发射波束的时变性和空间扫描特性；其次，构建了时间调制对数频率增量和多载频频率增量FDA雷达信号模型，其中，对数频率增量方式合成的点状波束旁瓣较高，而多载频方式合成的点状波束具有较大的动态范围；接着，详细研究了时间调制信号模型中频率增量项时间变量与传播项时间变量的关系，若两者相同则通过抵消消除波束时变特性，然而，两者具有不同的物理意义，频率增量项中的时间变量仅与波形产生时刻相关，当电磁信号产生并在空间传播后，其频率将不再发生变化，传播项时间变量与电磁波的传播特性有关，是变化的量，因此两者不能相互抵消。最后，对脉冲对数频率增量和脉冲多载频频率增量模式下的发射波束进行了仿真，验证了对时间调制FDA雷达波束分析的正确性，并得出两种模式下可以合成动态前向传播的点状发射波束，且多载频模式具有较低的波束旁瓣。

Dynamic Point Transmit Beam Forming of Frequency Diverse Array Radar

Frequency diverse array (FDA) radar applies a small frequency offset between the adjacent elements to synthesize a range-angle-dependent beam pattern. It is difficult to control the beam steering for the coupled time-variant beam pattern. For the problem, the time-variant characteristic and point beam forming of FDA radar are mainly studied in the paper. Firstly, the characteristic of transmit beam pattern of FDA using linearly increasing frequency increment is analyzed. Secondly, the signal models of FDA using logarithmically frequency increments (log-FDA) and multicarrier frequency increments (multi-FDA) are constructed, where the muti-FDA transmit beam pattern has lower sidelobes. Then, the relationship between the time variable of the frequency increase term and the time variable of the propagation term in the two time modulated signal models is studied in detail. If both of them are the same, the time-varying characteristics of the transmit beam pattern can be eliminated by the two time variables offset. However, they have different physical meanings. When the electromagnetic signal is generated and propagated in space, the time variable in the frequency increase term will not change, whereas thetime variable of the propagation term in the propagation process is related to the propagation characteristics of the electromagnetic wave, which is a variable quantity, so the two time variables can not offset each other. Finally, simulation results verify the correctness of the transmit beam pattern analysis of time modulated FDA radar, and demonstrate that the spot transmit beampattern with dynamic forward propagation can be synthesized usinglog-FDA and multi-FDA, where the beam pattern of the multi-FDA has lower sidelobes.