A New Nested MIMO Array with Increased Degrees of Freedom and Hole-free Difference Coarray

We propose a new antenna array design approach for multiple input and multiple output (MIMO) radar, which has closed-form expressions for the sensor locations and the number of achievable degrees of freedom (DOF). This new approach utilizes the nested array as transmitting and receiving arrays. We employ the difference coarray of the sum coarray (DCSC) of the MIMO radar to obtain more DOF for direction of arrival (DOA) estimation. Via properly designing the inter-element spacings of the transmitting and receiving arrays, we can obtain a hole-free DCSC. The characteristics of array geometries are analyzed and the optimal numbers of sensors in transmitting/receiving antenna arrays are derived when given the total number of physical sensors. Simulations are conducted to demonstrate the advantages of the proposed array in the number of DOF, the number of resolvable sources and the DOA estimation performance over the Coprime MIMO array.