Compared to traditional phased-array radar, multiple-input multiple-output (MIMO) radar can transmit multiple probing signals that are correlated or uncorrelated with each other. An interesting current research topic in MIMO radar is the frequency diversity MIMO (f-MIMO) radar. The frequency between two adjacent transmitted signals of f-MIMO radar are not identical but stepped uniformly at the same time. In this paper, a f-MIMO radar array processing model is developed. It is shown that the f-MIMO radar array processing can form a range-dimension beam, so it has the ability to distinguish targets in different ranges. The range resolution of array processing is derived, and then, the virtual array aperture of f-MIMO radar is also investigated.Index Terms-frequency diversity MIMO radar; rangdimension beam; virtual array aperture.

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Regenerative chatter can easily occur in the milling process of thin-walled workpiece due to the inherently low stiffness. This article aims to predict the stability of thin-walled workpiece in the milling process with a complete dynamic model. First, multiple structural modes of thin-walled workpiece are taken into consideration, and a complete dynamic model of thin-walled workpiece milling system is developed. Then, a numerical integration method is used to achieve the stability lobe diagrams of the milling system and identify the chatter frequency. Besides, the major structural mode, which is responsible for the occurrence of thin-walled workpiece chatter in the milling process, is predicted. A series of milling tests concerning a general cantilever plate are conducted, and the test results agree well with the predicted results, which shows the effectiveness of the proposed method. Finally, the effects of milling tool and structural modes on milling stability are discussed separately, which could provide theoretical basis for the dynamic modeling of thin-walled workpiece in milling process.